26. Is it possible to detect malignant neoplasms in the abdominal cavity using radioisotope scanning methods?

Gallium-67 is traditionally considered a nonspecific marker of neoplasms and infectious foci. This isotope is used when a malignant tumor is suspected. This method does not allow determining the stage of tumor development, but it is useful in cases where it is necessary to find out if there have been recurrences of hepatoma, Hodgkin's and non-Hodgkin's lymphomas, since it is quite difficult to distinguish necrosis and cicatricial changes from tumor recurrence during anatomical studies. Difficulties in using this method are due to varying degrees of absorption of the drug by tumors and the release of the drug into the lumen of the colon. The main difficulty lies in differentiating the manifestations of the functional activity of the unchanged intestine from the manifestations of the functional activity of tumor cells. For this, SPECT is used, and studies are carried out within a week (during this time, gallium-67 is removed from the intestinal lumen).
The recently developed 111 In-pentreotide and 131 I-MIBG preparations for imaging of neural crest tumors open up new possibilities for studying these tumors, which are extremely difficult to detect. Scanning with the introduction of 131 I-MIBG, which is an analogue of dopamine, is especially informative as an adjunct to computed tomography and magnetic resonance imaging in the detection of carcinoid tumors, neuroblastomas, paraganglia and pheochromocytoma. Scanning with the introduction of 111 In-octreotide, which is an analog of somatostatin, is also highly sensitive and specific for the detection of neural crest tumors. When using this method, a latent pathology is often detected that is not diagnosed using other imaging methods, often a preliminary diagnosis based on computed tomography and magnetic resonance imaging is confirmed, gastrinoma, glucagonoma, paraganglioma, pheochromocytoma, carcinoid, Hodgkins and non-Hodgkins are diagnosed. lymphomas.
Recently received radiolabeled antibodies 111 In-satumomab. Their use has proved to be extremely effective in examining patients with elevated levels of carcinoembryonic antigen and colon cancer, which is not detected using other methods; patients who have a tumor recurrence; Patients with questionable results during routine testing. Scanning with 111 In-satumomab often reveals hidden diseases. In addition, the data obtained using this method greatly influence the treatment of most patients with primary colon tumors and their recurrences.

This examination method is based on the ability of radioactive isotopes to emit radiation. Now most often they conduct a computer radioisotope study - scintigraphy. First, a radioactive substance is injected into a vein, mouth or inhalation into the patient. Most often, compounds of the short-lived isotope of technetium with various organic substances are used.

Radiation from isotopes is captured by a gamma camera, which is placed above the organ under study. This radiation is converted and transmitted to a computer, on the screen of which an image of the organ is displayed. Modern gamma cameras make it possible to obtain its layer-by-layer "sections". It turns out a color picture, which is clear even to non-professionals. The study is carried out for 10-30 minutes, and all this time the image on the screen changes. Therefore, the doctor has the opportunity to see not only the organ itself, but also to observe its work.

All other isotopic studies are gradually being replaced by scintigraphy. So, scanning, which before the advent of computers was the main method of radioisotope diagnostics, is used less and less today. When scanning, the image of an organ is not displayed on a computer, but on paper in the form of colored shaded lines. But with this method, the image is flat and, moreover, gives little information about the work of the organ. Yes, and scanning delivers certain inconvenience to the patient - it requires him to be completely immobile for thirty to forty minutes.

right on target

With the advent of scintigraphy, radioisotope diagnostics received a second life. This is one of the few methods that detects the disease at an early stage. For example, cancer metastases in the bones are detected by isotopes six months earlier than by x-rays. These six months can cost a person a life.

In some cases, isotopes are generally the only method that can give the doctor information about the state of the diseased organ. With their help, kidney diseases are detected when nothing is determined by ultrasound, microinfarcts of the heart are diagnosed, which are invisible on the ECG and ECHO cardiogram. Sometimes a radioisotope study allows the doctor to "see" a pulmonary embolism that is not visible on an x-ray. Moreover, this method provides information not only about the shape, structure and structure of the organ, but also allows you to assess its functional state, which is extremely important.

If earlier only the kidneys, liver, gallbladder and thyroid gland were examined with the help of isotopes, now the situation has changed. Radioisotope diagnostics is used in almost all areas of medicine, including microsurgery, neurosurgery, and transplantology. In addition, this diagnostic technique allows not only to make and clarify the diagnosis, but also to evaluate the results of treatment, including continuous monitoring of postoperative patients. For example, one cannot do without scintigraphy when preparing a patient for coronary artery bypass grafting. And in the future, it helps to evaluate the effectiveness of the operation. Isotopes detect conditions that threaten human life: myocardial infarction, stroke, pulmonary embolism, traumatic cerebral hemorrhage, bleeding and acute diseases of the abdominal organs. Radioisotope diagnostics helps to distinguish cirrhosis from hepatitis, to see a malignant tumor at the first stage, and to identify signs of rejection of transplanted organs.

Under control

There are almost no contraindications to radioisotope research. For its implementation, an insignificant amount of short-lived and quickly leaving the body isotopes is introduced. The amount of the drug is calculated strictly individually, depending on the weight and height of the patient and on the state of the organ under study. And the doctor necessarily selects a sparing mode of research. And most importantly: radiation exposure during radioisotope research is usually even less than with X-ray. Radioisotope research is so safe that it can be carried out several times a year and combined with x-rays.

In the event of an unforeseen breakdown or accident, the isotope department in any hospital is reliably protected. As a rule, it is located far from the medical departments - on the ground floor or in the basement. The floors, walls and ceilings are very thick and covered with special materials. The stock of radioactive substances is located deep underground in special lead storages. And the preparation of radioisotope preparations is carried out in fume hoods with lead screens.

Constant radiation monitoring is also carried out with the help of numerous counters. The department employs trained personnel who not only determine the level of radiation, but also know what to do in the event of a leak of radioactive substances. In addition to the employees of the department, the level of radiation is controlled by specialists from the SES, Gosatomnadzor, Moskompriroda and the Department of Internal Affairs.

Simplicity and reliability

The patient must adhere to certain rules during a radioisotope study. It all depends on which organ is supposed to be examined, as well as on the age and physical condition of the sick person. So, when examining the heart, the patient should be ready for physical exertion on a bicycle ergometer or on a walking track. The study will be better if it is done on an empty stomach. And, of course, you can not take drugs a few hours before the study.

Before a bone scan, the patient will need to drink plenty of water and urinate frequently. Such washing will help to remove isotopes from the body that have not settled in the bones. When examining the kidneys, you also need to drink plenty of fluids. Scintigraphy of the liver and biliary tract is done on an empty stomach. And the thyroid gland, lungs and brain are examined without any preparation at all.

Radioisotope research can interfere with metal objects caught between the body and the gamma camera. After the introduction of the drug into the body, you must wait until it reaches the desired organ and is distributed in it. During the study itself, the patient should not move, otherwise the result will be distorted.

The simplicity of radioisotope diagnostics makes it possible to examine even extremely severe patients. It is also used in children, starting from the age of three, mainly they examine the kidneys and bones. Although, of course, children require additional training. Before the procedure, they are given a sedative so that during the study they do not spin. But pregnant women do not conduct a radioisotope study. This is due to the fact that the developing fetus is very sensitive to even minimal radiation.

This section of diagnostic methods in modern conditions occupies one of the leading places. First of all, this applies to such a method as scanning (skia - shadow). Its essence lies in the fact that the patient is injected with a radioactive drug that has the ability to concentrate in a particular organ: 131 I and 132 I in the study of the thyroid gland; pyrophosphate labeled with technetium (99 m Tc - pyrophosphate), or radioactive thallium (201 Tl) in the diagnosis of myocardial infarction, a colloidal solution of gold - 198 Au, neohydrin labeled with mercury isotopes - 197 Hg or 203 Hg, in the study of the liver, etc. Then the patient laid on a couch under the detector of the apparatus for scanning (gamma-topograph, or scanner). The detector (scintillation counter of gamma radiation) moves along a certain trajectory over the object of study and perceives radioactive impulses emanating from the organ under study. The counter signals are then converted into various forms of registration (scanograms) using an electronic device. Ultimately, the contours of the organ under study appear on the scan. So, with a focal lesion of the parenchyma of an organ (tumor, cyst, abscess, etc.), foci of rarefaction are determined on the scan; with diffuse parenchymal damage to organs (hypothyroidism, cirrhosis of the liver), a diffuse decrease in the density of the scan is noted.

Scanning allows you to determine the displacement, increase or decrease in the size of the organ, as well as a decrease in its functional activity. Most often, scanning is used to examine the thyroid gland, liver, and kidneys. In recent years, this method has been increasingly used to diagnose myocardial infarction in two methods: 1) myocardial scintigraphy with 99 m Tc - pyrophosphate (pyrophosphate labeled with technetium), which actively accumulates in necrotic myocardium (detection of "hot" foci); 2) myocardial scintigraphy with radioactive 201 Tl, which accumulates only in healthy heart muscle, while necrosis zones look like dark, non-luminous (“cold”) spots against the background of brightly luminous areas of healthy tissues.

Radioisotopes are also widely used in the study of the function of certain organs. At the same time, the rate of absorption, accumulation in any organ and the release of a radioactive isotope from the body are studied. In particular, when studying the function of the thyroid gland, the dynamics of absorption of sodium iodide labeled with 131 I by the thyroid gland and the concentration of protein-bound 131 I in the patient's blood plasma are determined.

To study the excretory function of the kidneys, renoradiography (RRG) is widely used by determining the rate of excretion of hippuran labeled with 131 I.

Radioactive isotopes are also used to study absorption in the small intestine and in studies of other organs.

Ultrasonic research methods

Ultrasound echography (synonyms: echography, echolocation, ultrasound scanning, sonography, etc.) is a diagnostic method based on differences in the reflection of ultrasonic waves passing through tissues and body media with different densities. Ultrasound - acoustic vibrations with a frequency of 2x10 4 - 10 8 Hz, which, due to their high frequency, are no longer perceived by the human ear. The possibility of using ultrasound for diagnostic purposes is due to its ability to propagate in media in a certain direction in the form of a thin concentrated wave beam. At the same time, ultrasonic waves are absorbed and reflected differently by different tissues, depending on the degree of their density. Reflected ultrasonic signals are captured, transformed and transmitted to a reproducing device (oscilloscope) in the form of an image of the structures of the organs under study.

In recent years, the method of ultrasound diagnostics has been further developed and, without exaggeration, has made a real revolution in medicine. It is used in the diagnosis of diseases of almost all organs and systems: heart, liver, gallbladder, pancreas, kidneys, thyroid gland. Any congenital or acquired heart disease is reliably diagnosed by ultrasound echography. The method is used in neurology (study of the brain, ventricles of the brain); ophthalmology (measuring the optical axis of the eye, the magnitude of retinal detachment, determining the location and size of foreign bodies, etc.); in otorhinolaryngology (differential diagnosis of the causes of hearing loss); in obstetrics and gynecology (determining the timing of pregnancy, the condition of the fetus, multiple and ectopic pregnancy, diagnosis of neoplasms of the female genital organs, examination of the mammary glands, etc.); in urology (examination of the bladder, prostate), etc. With the advent of Doppler systems in modern ultrasound devices, it became possible to study the direction of blood flow inside the heart and through the vessels, to detect pathological blood flows in case of defects, to study the kinetics of the valves and muscles of the heart, to conduct a chronometric analysis of the movements of the left and right parts of the heart, which is of particular importance for assessing functional state of the myocardium. Ultrasonic devices with a color image are widely introduced. Under the onslaught of ultrasound research methods, radiological methods are gradually losing their relevance.

Long-term experiments with uranium allowed the French physicist Antoine Henri Becquerel to discover that he was able to emit certain rays that penetrate opaque objects. So about a hundred years ago, the study of radioactivity began.

Substances that emit radioactive rays are called isotopes. And as soon as they learned to register the radiation of isotopes with the help of special sensors, they began to be widely used in medicine.

During the study, the isotope is injected into the patient's body (usually through a vein), then its radiation is recorded using sensors. It signals violations in the work of organs or tissues. If the isotope is chosen correctly, it accumulates only in those organs and tissues that are being studied.

Currently, more than 1000 different radioisotope preparations are used in medicine, but the list is constantly growing. Get medical isotopes in nuclear reactors. The main requirement for these drugs is a short decay period.

The rays emitted by isotopes make it possible to highlight such disturbances in the functioning of organs that cannot be detected in any other way. They are also indispensable in alternative diagnostics, when there are doubts about the nature of the disease. Isotopes are especially important in oncology - since, for example, bone sarcoma can be detected much earlier (three to six months) than x-rays do. Isotopes detect metastases in prostate cancer, have the ability to accumulate in the heart muscle, making it possible to diagnose myocardial infarction, coronary sclerosis, myocardial ischemia, etc.

A radioisotope study reveals abnormalities in the functioning of the lungs, informing the doctor about the obstacles that arise in the path of pulmonary blood flow in tuberculosis, pneumonia, and emphysema. Based on the radiation of isotopes accumulated by the patient's kidneys, the doctor may decide on an urgent operation. Informative radioisotope study and damage to the liver, especially the biliary tract. Isotopes, on the other hand, make it possible to predict with certainty the degeneration of hepatitis into cirrhosis.

The study of the stomach after eating a meal with a small admixture of isotopes provides extremely valuable information about the functioning of the digestive system.

The most modern method of radioisotope diagnostics is scintigraphy - computer radioisotope diagnostics. The radiation of intravenously injected isotopes is recorded by special detectors located at a certain angle, then the information is processed using a computer. The result is not a flat image of a separate organ, as in an x-ray, but a three-dimensional picture. If other imaging methods (radiography, ultrasound) allow us to examine our organs in statics, scintigraphy makes it possible to observe their work. When diagnosing neoplasms of the brain, intracranial inflammatory processes and vascular diseases, physicians in Europe and America resort exclusively to scintigraphy. In our country, as usual, the cost of the equipment hinders the spread of the method.

Patients often ask doctors how safe radioisotope diagnostics are. And this is natural: any medical procedure associated with radioactivity causes, if not fear, then anxiety. Many are also alarmed by the fact that, after injecting a radioactive drug into a vein, the doctor and nurse leave the room. Anxieties are in vain: with a radioisotope study, the patient's radiation dose is 100 times (!) Less than with conventional x-ray diagnostics. Even newborns can carry out such a procedure. Doctors do several such studies per day.

Radioisotope research- what is it, when and how is it carried out?

Such questions have recently been heard more and more often, as this method of diagnosis is becoming increasingly popular.

What is the basis of the method of radioisotope research?

The basis of this method is the ability to emit radioactive isotopes. Computer research using radioactive isotopes is called scintigraphy. A radioactive substance is injected into the patient's vein or mouth by inhalation. The essence of the method is to capture radiation from isotopes with a special gamma camera placed above the diagnosed organ.

The converted radiation pulses are transmitted to a computer, and a three-dimensional model of the organ is displayed on its monitor. With the help of modern equipment, even layered sections of the organ can be obtained. The resulting color picture visibly shows the state of the organ and can be understood even by non-professionals. The study itself lasts 10-30 minutes, during which the image on the computer monitor is constantly changing, which is why the doctor has the opportunity to observe the work of the organ.

Scintigraphy is gradually replacing all other isotope studies. For example, scanning, which was the main method of radioisotope diagnosis, is being used less and less.

Benefits of scintigraphy

Scintigraphy gave radioisotope diagnostics a second life. This method is one of the few that can already detect disease at an early stage. For example, metastases in bone cancer are detected six months earlier than with the help of X-rays, and these six months are sometimes decisive.

High information content of the method- Another undoubted advantage: in some cases, scintigraphy becomes the only method that can provide the most accurate information about the state of the organ. It happens that kidney disease is not detected on ultrasound, but scintigraphy revealed it. Also, using this method, microinfarctions that are invisible on the ECG or ECHO-gram are diagnosed. Moreover, this method informs the doctor not only about the structure, structure and shape of the organ under study, but also allows you to see its functioning.

When is scintigraphy performed?

Previously, with the help of an isotope study, only a condition was diagnosed:

kidneys;
liver;
thyroid gland;
gallbladder.

While now this method is used in all areas of medicine, including microsurgery, neurosurgery and transplantology. Radioisotope diagnostics allows both making an accurate diagnosis and tracking the results of the treatment, including after surgery.

Isotopes can reveal a life-threatening condition:

thromboembolism of the pulmonary artery;
stroke;
acute conditions and bleeding in the abdominal cavity;
they also help distinguish hepatitis from cirrhosis of the liver;
already at the first stage to discern a malignant tumor;
see signs of rejection of the transplanted organ.

Method safety

A negligible amount of isotopes is introduced into the body, which leave the body very quickly without having time to do any harm to it. Therefore, the method has practically no contraindications. Irradiation with this method is even less than X-ray. The number of isotopes is calculated individually, depending on the condition of the organ, as well as the weight and height of the patient.

Preparation and conduct of radioisotope examination of the kidneys. Methods of radioisotope research: diagnostics and scanning How is the study

CHAPTER 75

1. List the main advantages of radioisotope diagnostic methods in comparison with other imaging methods.

In almost every case, radioisotope research methods have one or more advantages over other methods:
1. Obtaining information about the functional state of the body, which cannot be obtained using other methods (or obtaining this information is associated with high economic costs or with a risk to the health of the patient).
2. Ability to clearly contrast(the isotope mainly accumulates in the target organ), despite the low resolution of the method.
3. Relative non-invasiveness radioisotope studies (a radioactive isotope is administered parenterally or orally).

2. What are the main disadvantages of radioisotope studies in comparison with other radiological studies.

1. Resolution of the method (1-2 cm) is lower than the resolution of other imaging methods.
2. Performing a radioisotope scan takes a long time, sometimes 1 hour or even more.
3. Exposure risk significantly higher than with magnetic resonance imaging or ultrasound scanning. However, compared with plain radiography or computed tomography, the risk of radiation exposure to patients using most methods of radioisotope scanning is not greater, and sometimes even less (exceptions are studies with the introduction of leukocytes labeled with gallium-67 or indium-Ill: in these studies, the risk of radiation exposure is 2 -4 times higher than for all other radioisotope studies). In some studies, such as the rate of gastric emptying and the time of passage of food through the esophagus, the risk of radiation exposure is less significant than the risk of radiation exposure in fluoroscopy.
4. Availability of the method is limited, since radioisotope studies require the availability of radiopharmaceuticals, as well as specialists capable of correctly interpreting the results. There are no such drugs and specialists in many treatment and diagnostic centers.

3. What radioisotope studies are the most informative when examining patients with diseases of the gastrointestinal tract?

Radioisotope studies can be used to examine patients with almost any disease of the gastrointestinal tract. However, the improvement and widespread use of endoscopy, manometry, pH monitoring, and other instrumental research methods somewhat limit the scope of radioisotope studies, which are used only in some specific clinical situations.

The use of radioisotope studies for the diagnosis of diseases of the gastrointestinal tract

RESEARCH METHOD	IN WHAT CASES IS IT USED
Cholescintigraphy (visualization of the liver and biliary system)	Acute cholecystitis Biliary dyskinesia Impaired patency of the common bile duct Atresia of the bile ducts Sphincter of Oddi dysfunction Infiltrative neoplasms Leakage of bile into the abdominal cavity
Determination of gastric emptying rate	Quantification of motor activity of the stomach
Assessment of motor activity of the esophagus	Determination of transit time of food through the esophagus Detection and assessment of gastroesophageal reflux Detection of aspiration

RESEARCH METHOD	IN WHAT CASES IS IT USED
Liver/spleen scan	Volumetric lesions of the liver Accessory spleen
Scanning with the introduction of labeled erythrocytes destroyed during heat treatment	Accessory spleen
Scanning with the introduction of gallium	Staging of many malignant tumors Abdominal abscesses
	Neural crest tumors
Scanning with the introduction of 111 In-satumomab	Staging colon tumors
Scanning with the introduction of leukocytes labeled with 111 In	Identification of purulent-infectious foci and abscesses in the abdominal cavity
Scanning with the introduction of leukocytes labeled with 99m Tc-HM-PAO	Determination of the localization of the active inflammatory process in the intestine
Scanning with the introduction of erythrocytes labeled with "Tc	Determination of localization of bleeding in the gastrointestinal tract Identification of liver hemangiomas
Scanning with the introduction of pertechnetate	Identification of Meckel's diverticulum Identification of the unremoved mucous membrane of the antrum of the stomach after its resection
Scanning with the introduction of colloidal sulfur	Determining the location of bleeding in the gastrointestinal tract
Examination of the peritoneal-venous shunt	Study of the functional viability of peritoneal-venous shunts
Assessment of blood flow in the hepatic artery	Examination of the area supplied by the hepatic artery
Schilling test	Vitamin B12 malabsorption

Note. MIBG - t-iodobenzylguanidine; HM-PAO - hexamethylpropyleneamine oxime.

4. How is cholescintigraphy performed (visualization of the biliary system)? What is the normal scintigraphic picture?

The methodology for conducting a standard cholescintigraphic study is practically the same regardless of clinical indications (see question 3). The patient is parenterally injected with preparations of imidodiacetylic acid labeled with technetium-99m. Currently, the most commonly used radiopharmaceuticals are DISHIDA, mebrofenin, and HIDA (hepato-IDA), with the latter name being generic for all of these drugs. Despite the fact that these drugs are metabolized in the same way as bilirubin, they can be used for diagnostic purposes even at very high concentrations of bilirubin in the blood (more than 200 mg / l).
After the injection of the drug, scanning begins. Each individual scan lasts 1 min, and the total duration of the study is 60 min or a little more. Normally, imidodiacetylic acid preparations are rapidly excreted by the liver. When an image of normal intensity is obtained, the activity of the blood pool in the heart weakens rather quickly and is practically not detected already 5 minutes after the injection. Long-term maintenance of blood pool activity and poor absorption of the drug by the liver indicate hepatocellular insufficiency. The left and right hepatic ducts are often, though not always, visualized within 10 minutes of drug administration, and the common bile duct and small intestine within 20 minutes. Usually the gallbladder also becomes visible by this time, and normally its image can persist for 1 hour after the administration of the drug to patients who have not eaten for 4 hours. After 1 hour, the maximum activity of the drug is recorded in the bile ducts, gallbladder and intestine , and the minimum - in the liver (the activity of the drug in the liver may not be determined at all).
If all of the above studies (see question 3) fail to image the organ of interest after 1 hour (for example, the gallbladder in acute cholecystitis, the small intestine in bile duct atresia), it is necessary to repeat the scan within 4 hours. Sometimes after the initial A 60-minute study is administered with syncalide or morphine, and then the study is continued for another 30-60 minutes.

5. How should a patient with acute cholecystitis be prepared for examination? What measures should be taken to shorten the time of the study and increase its reliability?

Traditionally, acute cholecystitis is diagnosed on the basis of insufficient filling of the gallbladder (usually associated with the presence of a cystic duct stone) detected by functional cholescintigraphy at the initial 60-minute study and at a further 4-hour imaging (positive study). All preparatory procedures are performed to ensure that there is no doubt that poor visualization of the gallbladder is a true positive result, as well as to shorten the time of the study, which is sometimes extremely tiring for patients. Since food is a potential long-acting stimulator of endogenous cholecystokinin release and subsequent gallbladder contraction, Patients should abstain from eating for 4 hours before the start of the study; otherwise, the study may give a false positive result. Prolonged fasting contributes to an increase in the viscosity of bile in an unchanged gallbladder, which can make it difficult to fill it with a radiopharmaceutical and cause false positive results. Most clinicians currently use fast-acting cholecystokinin analogs such as syncalide. Syncalide is administered at a dose of 0.01-0.04 μg/kg intravenously for more than 3 minutes 30 minutes before cholescintigraphy, when the patient has been fasting for more than 24 hours, when overeating or in severe disease.
Despite taking all the above measures, the gallbladder may remain unfilled even by the time the 60-minute cholescintigraphic examination is completed. If within 60 minutes the gallbladder is not visualized, but the intestine is well visualized, it is advisable to administer intravenously morphine at a dose of 0.01 mcg/kg; after the introduction of morphine, an additional study should be carried out within 30 minutes. Since morphine causes contraction of the sphincter of Oddi, when it is administered, the pressure in the biliary system increases and the functional obstruction of the cystic duct is resolved. If the image of the gallbladder does not appear after this, there is no longer any point in continuing the study, since it becomes obvious that the patient has acute cholecystitis (see figure). Some physicians believe that the simultaneous administration of syncalide and morphine can lead to perforation of the gangrenous gallbladder, but this complication has not yet been described.

Acute cholecystitis. Examination of the liver and biliary system, started 5 minutes after the injection of 99m Tc-mebrofenin, reflects the rapid uptake of the drug by the liver and its rapid excretion into the common bile duct and small intestine. Note the absence of the gallbladder (the arrow indicates the normal location of the gallbladder). After intravenous administration of 1 mg of morphine, gallbladder filling was not detected with an additional 30-minute imaging. Instead of using the described technique with the introduction of morphine, a 4-hour delayed study can be performed, but this only delays the study, which is not necessary.

6. Should liver and biliary tract scintigraphy be performed in patients with suspected acute cholecystitis?

Scintigraphy of the liver and biliary tract is the most accurate method for diagnosing acute cholecystitis. The sensitivity and specificity of this method are 95 %. However, this method should not be used in all patients suspected of having acute cholecystitis. If, for example, the likelihood of having acute cholecystitis is low (less than 10%), then a positive result in low-risk groups (based on screening) is most likely a false positive. If the probability of having acute cholecystitis is high (greater than 90%), then a negative test result in high-risk groups appears to be a false negative. In examining some patients, such as patients with acalculous cholecystitis or obesity, as well as those with a very severe clinical form of the disease, doctors often receive false positive results, and therefore the results of scintigraphy should only be evaluated in conjunction with ultrasound or computed tomography data.

7. How is cholescintigraphy used to diagnose and treat patients with bile leakage into the abdominal cavity?

The cholescintigraphic method is characterized by high sensitivity and specificity in detecting bile leakage into the abdominal cavity (see figure). Since fluid collections outside the biliary tract often occur after surgery, the specificity of various anatomical studies is low. Cholescintigraphy has a low resolution and therefore does not allow you to accurately determine the localization of the bile outflow zone; endoscopic retrograde cholangiopancreatography (ERCP) may be required to accurately locate the bile leak. A cholescintigraphy may also be used to confirm that a bile leak has been corrected.

Leakage of bile into the abdominal cavity. The patient after percutaneous liver biopsy developed severe pain in the right upper quadrant of the abdomen. Ultrasound scanning did not reveal the cause of these pains. Radioisotope scanning with the introduction of 99mTc-mebrofenin revealed a thin rim of bile along the lower and lateral edges of the liver (large arrow). In this case, early filling of the gallbladder (small arrow) and the absence of bile in the small intestine were noted.

8. On the basis of what signs is obstruction of the common bile duct diagnosed during cholescintigraphy?

Dilated bile ducts on ultrasound scan may be a non-specific finding in patients undergoing biliary surgery, and conversely, acute bile duct obstruction (less than 24 to 48 hours before ultrasound) may not be accompanied by bile duct dilatation. When the common bile duct is obstructed, the gallbladder and small intestine are not visualized during cholescintigraphy, the bile ducts are often not visualized even during a delayed 4-hour study. The sensitivity and specificity of this method in detecting obstruction of the common bile duct is very high (see figure). The results of cholescintigraphy are reliable even at high concentrations of bilirubin. This method can be used to differentiate between mechanical and non-mechanical jaundice.

Blockage of the common bile duct. After injection of a drug that accumulates in the liver and biliary system, the intrahepatic bile ducts and small intestine are not visualized during the 10-minute (A) and 2-hour (B) studies. Ultrasound scans did not reveal dilated bile ducts or stones in the common bile duct, the most common cause of blockage. The appearance of a "hot zone", visualized to the left of the liver, is due to the excretion of the drug in the urine (this is an alternative way to remove the drug from the body)

9. How can sphincter of Oddi dysfunction be detected using cholescintigraphy?

A significant number of patients complain of abdominal pain after cholescintigraphy; The cause of such pain is often dysfunction of the sphincter of Oddi. Performing manometry during ERCP is sufficient to make a diagnosis, but this study is invasive and often entails various complications. Currently, an empirical scintigraphic scale is often used, which allows quantification of bile flow and liver function. It has been proven that there is a close correlation between the results of cholescintigraphy and the results of a manometric study of the sphincter of Oddi.

10. What is the role of cholescintigraphy in the diagnosis of bile duct atresia?

Cholescintigraphy is a rather sensitive and highly specific method, which, with appropriate preparation of the patient, makes it possible to diagnose bile duct atresia. The main symptom of bile duct atresia is the presence of severe hepatitis in newborns. Ultrasound scanning in this case is uninformative: it allows you to detect the expansion of the bile ducts, but with atresia, the expansion of the ducts is usually absent. The main disadvantage of scintigraphy is the high probability of obtaining false positive results due to insufficient bile secretion in severe forms of hepatitis. To eliminate this deficiency, premedication is performed: phenobarbital is administered orally at a dose of 5 mg Dkgxday) for 5 days, which stimulates the secretion of bile. At the same time, the importance of determining the concentration of phenobarbital in the blood serum cannot be underestimated. If the small intestine is visualized on delayed cholescintigraphy, biliary atresia can be ruled out (see figure).

Hepatitis in a newborn with presumed bile duct atresia. In order to confirm this complex diagnosis, the patient is given a drug that enters the liver and biliary system. In this case, after a 5-day course of phenobarbital, the patient was parenterally injected with 99m Tc-mebrofenin. Note that 2 hours after isotope administration, activity of the blood pool in the heart and signs of drug excretion into the gallbladder (B) are determined, which suggests the presence of hepatocellular insufficiency and impaired excretion of the drug, which is mainly excreted in the urine. During the 4-hour study, foci of insignificant activity of the drug (arrows) in the abdominal cavity are determined, which may be due to the ingestion of the drug into the intestine or its excretion in the urine. When conducting a 24-hour study with bladder catheterization, abnormally low activity of the drug is detected in the lower left quadrant of the abdominal cavity (arrow), below and lateral to the liver (L), which indicates that the drug has entered the intestine and excludes bile duct atresia

11. In what cases is it advisable to use cholescintigraphy when examining patients with impaired patency of the gastrointestinal anastomosis?

The adductor (afferent) loop of the intestine is very difficult to examine using fluoroscopy, since it (the adductor loop) has to be filled antegradely with barium suspension. Cholescintigraphy makes it possible to exclude, with a high degree of accuracy, a violation of the patency of the afferent loop of the intestine in the case when the activity of the drug in both the afferent and the outlet loop of the intestine is determined 1 hour after the parenteral administration of the radiopharmacological drug. Violation of the patency of the gastrojejunostomy is diagnosed when the accumulation of a radiopharmacological drug in the afferent loop of the intestine is detected in combination with the entry of this drug into the outlet loop after 2 hours.

12. What is gallbladder dyskinesia? How is a cholescin-tigraphic study of the evacuation function of the gallbladder performed?

A significant number of patients in whom no changes in the gallbladder are detected during clinical and instrumental studies suffer from pain associated with dysfunction of the gallbladder. The severity of symptoms in these patients improves after cholecystectomy. The occurrence of these pains may be based on several yet insufficiently studied pathological conditions, which are usually combined under the general name "biliary dyskinesia". It is believed that the basis of biliary dyskinesia is a violation of the coordination of contractions of the gallbladder and cystic duct. As a result of this violation, pain occurs. It has been established that with biliary dyskinesia, an abnormally small amount of bile is secreted when stimulated with cholecystokinin (syncalide).
After filling the gallbladder, in order to stimulate its contraction, syncalide is administered at a dose of 0.01 μg/kg for 30-45 minutes. The amount of bile excreted by the gallbladder in 30 minutes is the ejection fraction of the gallbladder. This fraction is normally 35-40% of the capacity of the gallbladder. Cholescintigraphy with the introduction of syncalide is a highly informative method that allows you to determine the ejection fraction of the gallbladder and, accordingly, to identify functional disorders.

13. What radioisotope method is used to determine the rate of gastric emptying?

It is possible to determine the rate of evacuation from the stomach of both liquid and solid contents using radioisotope studies. The rate of evacuation of fluid from the stomach is usually determined in children. A solution of colloidal sulfur labeled with technetium-99t is given to a child with milk or during a normal meal. Scanning is performed every 15 minutes for 1 hour, then the half-life of the drug is calculated. In adults, the rate of evacuation of solid food from the stomach is usually determined after an overnight fast. The patient eats scrambled eggs with sulfur labeled with technetium-99t, along with normal food, then in the anterior and posterior projections, scanning is performed every 15 minutes for 1.5 hours, followed by calculation of the percentage of the excreted drug. There are no standard diets, the results of the study depend on the composition of the breakfast. Typically, the patient is offered breakfast, the energy value of which is 300 calories. Breakfast includes scrambled eggs, bread and butter; while gastric emptying is 63% in 1 hour (± 11%).

14. In what clinical situations is it advisable to determine the rate of gastric emptying using radioisotope methods?

FROM symptoms associated with impaired gastric motility are rather non-specific, and X-ray examination using a barium suspension does not allow a quantitative assessment of the rate of gastric emptying; moreover, this study is non-physiological. Methods for determining the rate of gastric emptying are semi-quantitative, which greatly complicates the interpretation of the results. In addition, these techniques are not standardized. However, the determination of gastric emptying rate in certain groups of patients (for example, patients with diabetes mellitus and patients undergoing gastric resection) can be very useful, as this method allows you to find out the origin of non-specific clinical symptoms (see figure).

Picture of normal gastric emptying. A. Initial image in the anterior (A) and posterior (P) projections after the patient has taken colloidal sulfur labeled with "Tc" with scrambled eggs and steak. Accumulation of the drug in the fundus of the stomach (F) in the posterior projection is detected, followed by its entry into the antral part of the stomach (an) B. After 90 minutes, a small amount of the drug remains in the fundus of the stomach, a significant amount of it accumulates in the antrum of the stomach (an), in addition, the accumulation of the drug in the small intestine (S) is detected C. After 84.5 min 50% of the food leaves the stomach (the norm is 35-60% for this food)

15. What radioisotope methods of examination of the esophagus exist and when should they be used?

In clinical practice, three radioisotope methods for examining the esophagus are used: the study of esophageal motility, the study of gastroesophageal reflux, and the detection of pulmonary aspiration.
Study of esophageal motility. While the patient is swallowing water containing colloidal 99m Tc, the doctor is taking a series of sequential images of the esophagus. This study is quite accurate and allows you to quantify the indicators that reflect the functional state of the esophagus. The advantage of X-ray examination using a barium suspension is that it makes it possible to differentiate structural and functional disorders with high accuracy. However, a radioisotope study of esophageal motility has its advantages - it is easy to perform and allows a non-invasive way to evaluate the effectiveness of treatment for disorders of esophageal motility and achalasia.
Examination of gastroesophageal reflux. In this study, a series of sequential images of the esophagus are obtained after the patient drinks orange juice containing colloidal Tc. In this case, the patient's abdomen is compressed with a special inflatable bandage. Although this method is less sensitive than 24-hour esophageal pH monitoring, its sensitivity is higher than the sensitivity of fluoroscopy using barium suspension.This method is useful for screening patients or to evaluate the effectiveness of treatment for already established gastroesophageal reflux. Detection of pulmonary aspiration. This study is an imaging of the chest after injection per os colloidal 99mTc with water. Aspiration is diagnosed by detecting the activity of the drug in the projection of the lungs. Although the sensitivity of this method is rather low, it is still higher than the sensitivity of radiological methods using contrast agents. In addition, the advantage of the radioisotope method is the ease of obtaining a series of consecutive images, which makes it possible to detect intermittent aspiration.

16. What role do radioisotope diagnostic methods play in the examination of patients with large liver masses?

Traditional scanning of the liver and spleen, during which a drug is injected intravenously that is captured by Kupffer cells, or a colloidal solution of sulfur or albumin labeled with 99mTc, can be replaced by ultrasound scanning or computed tomography, since these research methods have a higher resolution and allow assessing the condition of nearby organs and tissues. However, if it is impossible to make an accurate diagnosis, for example, in patients with fatty liver (see figure), it is advisable to perform a radioisotope functional scan.

The study of volumetric education in the liver. A. Computed tomography of the liver using a radiopaque substance revealed diffuse fatty liver and two relatively normal areas (circled) in a patient with colon cancer after treatment with 5-fluorouracil. Differential diagnosis should be made between nodular regeneration and liver metastases. C. When visualizing these pathological lesions in close-up in the anterior projection during cholescintigraphy, metastases appear as light filling defects (arrow). If such defects are not detected, then the detected volumetric formations are regeneration nodes. Focal nodular hyperplasia in traditional radioisotope scanning of the liver and spleen, it looks like an accumulation of "warm" or "hot" foci, since Kupffer cells predominate in the nodes, and looks like an accumulation of "cold" foci during functional cholescintigraphy, since there is an insufficient number of hepatocytes in the nodes. Focal nodular hyperplasia of the liver is characterized by a combination of these features. And vice versa, when liver adenomas, which mainly consist of hepatocytes, the identified masses appear "warm" or "hot" during cholescintigraphy and "cold" during traditional radioisotope scanning of the liver and spleen. This combination is also quite specific. Hepatomas also look "warm" or "cold" (but not "hot") on cholescintigraphy. The cells of the overwhelming majority of hepatomas have a high affinity for gallium-67 and actively accumulate it. This combination can also be considered highly specific, if we do not take into account the rare metastases of various tumors in the liver, which have an affinity for gallium (see table).

Differential diagnosis of volumetric formations of the liver, detected during radioisotope studies

	COLLOID SULFUR LABELED 99mTc	DELAYED IMAGING USED CALLING DRUGS TROPIC TO HEPATOCITES	ERYTHROCYTES LABELED 99mTc	GALLIUM-67
Adenoma	"Cold" lesions or reduced drug accumulation		Norm
Hepatoma	"Cold" spots	Decreased, normal, or increased drug accumulation	Decreased or normal drug accumulation	Normal or increased accumulation of the drug; a significant increase is a characteristic diagnostic sign *
Hemangiomga	"Cold" spots	"Cold" spots	A significant increase in the accumulation of the drug is a characteristic diagnostic sign	"Cold" spots
Metastases	"Cold" spots	"Cold" spots	Normal or slightly reduced accumulation of the drug	Decreased, normal or slightly increased accumulation of the drug
Focal nodular hyperplasia	Normal or increased drug accumulation	Decreased or normal drug accumulation	Norm	Norm

* An exception is liver metastases, which have an affinity for gallium.

17. What methods of radioisotope scanning allow diagnosing liver hemangiomas?

With the help of computed tomography, magnetic resonance imaging and ultrasound scanning, it is not always possible to diagnose liver hemangiomas. Delayed single-photon emission computed tomography (SPECT, three-dimensional scintigraphic imaging, similar in many respects to CT), during which hemangiomas are filled with Tc-labeled red blood cells, is the most sensitive and specific method for diagnosing hemangiomas larger than 2.5 cm (see Fig. The probability of detecting small hemangiomas (less than 1 cm) during SPECT is also very high. This is due to the very high selectivity of drug accumulation in hemangiomas. Delayed SPECT is the method of choice in the diagnosis of liver hemangiomas. However, if hemangiomas are located near blood vessels, it can be difficult distinguish hemangiomas from vessels, in which case other imaging modalities should be used.Rarely, thrombosed hemangiomas and hemangiomas undergoing fibrotic degeneration are also very difficult to detect using SPECT.

Liver hemangioma. A. An ultrasound scan reveals a 3-cm hypoechoic mass, the appearance of which is characteristic of a hemangioma, but not specific enough. C. After 2 hours, during SPECT with the introduction of erythrocytes labeled with 99m Tc, a focus of increased accumulation of the radioisotope in the lower parts of the right lobe of the liver is determined during the reconstruction of sections in the axial and coronal planes (arrows). C. When performing contrast computed tomography, centripetal (afferent) filling of the nodes (arrow) is revealed, which allows confirming the diagnosis established during the study with the introduction of erythrocytes labeled with 99m Tc

18. Is it possible to detect ectopic gastric mucosa using radioisotope scanning methods?

It is the main source of gastrointestinal bleeding in children Meckel's diverticulum almost always contains the lining of the stomach. Since 99m Tc-pertechnetate selectively accumulates in the gastric mucosa, this drug is ideal for localizing sources of bleeding that are very difficult to detect using traditional radiological contrast studies with the introduction of contrast agents. The study includes intravenous administration of pertechnetate to the patient and scanning of the abdominal cavity after 45 minutes. Usually, the ectopic gastric mucosa is visualized simultaneously with the stomach and does not move during the study. The sensitivity of the method for detecting a bleeding Meckel's diverticulum is 85%. To increase the sensitivity of the method, cimetidine (to block the excretion of pertechnetate into the intestinal lumen) and / or glucagon (to suppress gastrointestinal motility and prevent washout of the drug) can be pre-administered to the patient. The same scanning technique can be used to detect unremoved mucous membrane of the antrum of the stomach after surgery for chronic stomach ulcers; in this case, the sensitivity of the method is 73%, and the specificity is 100%.

19. How is the vitamin B12 absorption test (Schilling test) performed and when is it used?

The Schilling test allows you to examine the body's ability to absorb and excrete vitamin B 42. Since there are many causes of vitamin B 12 malabsorption, the study is carried out in stages, at each stage the most likely causes of vitamin B 12 deficiency are identified (or excluded). Although some clinicians in the treatment of patients with vitamin B 12 deficiency do not determine the cause of its development, determining the etiology of the disease is very important for many patients, as comorbidities or disorders that were not expected may be found.

There is no need (and even undesirable) to prescribe to a patient with severe vitamin B 12 deficiency his preparations before the Schilling test. At the first and all subsequent stages of the study, the patient is given regular (not radioisotope-labeled) vitamin B 12, 1 mg intramuscularly to "bind" the corresponding receptors, and 2 hours after that, the patient takes vitamin B 12 labeled with radioactive cobalt with food. The necessary conditions for a successful study are the abstinence of the patient from eating for 3 hours before and after taking a radioactive preparation of vitamin B 12 (to avoid the binding of labeled vitamin B 12 with food) and the collection of all excreted urine within 24-48 hours after the administration of the drug. The concentration of creatinine in the urine and daily diuresis are determined. Decreased creatinine content in the daily volume of urine may indicate improper collection of urine for analysis, which artificially reduces the amount of vitamin B 12 excreted in the urine. In the collected urine, radioactive cobalt is detected. Normally, less than 10% of the dose of radioactive cobalt taken orally is excreted in 24 hours. If the release of the vitamin AT 12 within 24 hours is within the normal range, which indicates its normal absorption in the gastrointestinal tract.
If any pathology is detected at the first stage of the study, they proceed to the second stage. At the second stage of the study, the same actions are performed as at the first, except that, together with a radioactive preparation of vitamin B 12, the patient takes an internal factor. The third stage has several modifications. The choice of modification depends on the etiology of malabsorption of vitamin B 12 assumed on the basis of clinical data (see figure). The detection of normal release of vitamin B 12 at the second stage in the presence of changes detected at the first stage indicates the presence of pernicious anemia.

Algorithm for determining the etiology of vitamin B12 deficiency

20. Can an accessory spleen be detected using radioisotope scanning methods?

The ineffectiveness of splenectomy performed in connection with idiopathic thrombocytopenia may be due to the fact that the patient has an accessory spleen.
Such an undetected accessory spleen may be the cause of abdominal pain. To establish the localization of small areas of the splenic tissue, it is most advisable to perform scanning with the introduction of labeled 99m Ts erythrocytes, which have been subjected to heat treatment, since damaged red blood cells selectively accumulate in the tissue of the spleen. This scanning technique is the method of choice, especially when performing SPECT. However, special heat treatment of erythrocytes can be performed only in specialized laboratories, and therefore this method is not used in every medical and diagnostic center. As a method of primary examination, as a rule, traditional scanning of the liver and spleen is used. If an accessory spleen is found, appropriate therapy is performed (see figure). If an additional spleen is not detected during scanning of the liver and spleen, a study is performed with the introduction of radiolabeled erythrocytes subjected to heat treatment.

Accessory spleen in a patient who underwent splenectomy for idiopathic thrombocytopenic purpura. The extremely high degree of contrast achieved with the introduction of colloidal sulfur labeled with 99m Tc makes it possible to visualize even small areas of the spleen tissue (arrow) and remove them in the future. Shown are images obtained by scanning in the left anterior oblique (LAO) and posterior (PST) projections. If a negative result is obtained during a study with the introduction of colloidal sulfur labeled with radioactive technetium, it is advisable to conduct a high-contrast special study, for example, a scan with the introduction of labeled erythrocytes subjected to heat treatment, which selectively accumulate mainly in the spleen, which allows in most cases to establish the presence of an additional spleen

21. What radioisotope scanning methods can be used to examine patients with inflammatory bowel diseases and abdominal abscesses?

To detect infectious-purulent foci in the abdominal cavity, scanning is used with the introduction of gallium-67, leukocytes labeled with 99m Tc-HMPAO, and leukocytes labeled with indium-111.
Gallium-67 normally secreted into the intestine, a small amount of 99m Tc-HMPAO from leukocytes also enters the intestine; therefore, these drugs are less effective in detecting inflammatory foci in the abdominal cavity. When scanning with the introduction of gallium-67, it may be necessary to perform similar studies during the week to assess intestinal motility. In this case, foci of inflammation in the abdominal cavity can be identified quite clearly. The disadvantages of scanning with the introduction of gallium-67 are offset by the relatively low cost of this study. Despite the large radiation exposure (equivalent to radiation exposure when performing 2-4 computed tomography of the abdominal cavity), this method is used quite often. Studies with the introduction of leukocytes labeled with 99m Tc-HMPAO and 111 In are more expensive and require special equipment.
Scanning with the introduction of leukocytes labeled 111 In, which normally accumulate only in the liver, spleen and bone marrow, is the method of choice when establishing localization purulent-infectious foci in the abdominal cavity in cases where computed tomography, magnetic resonance imaging and ultrasound scanning do not allow a diagnosis. Normally, leukocytes are also absorbed by the liver and spleen, therefore, to obtain a clear picture, an isotope scan is additionally performed with the introduction of colloidal sulfur labeled with "Tc (traditional scan of the liver and spleen). Abscesses of the liver and spleen appear as "cold" foci on conventional scanning of the liver and spleen and the appearance of "hot" foci when scanning with the introduction of leukocytes labeled with 111 In The disadvantage of the method is also the need for a delayed scan after 24 hours to obtain the most reliable picture.Within 1 hour after parenteral administration of leukocytes labeled with 99m Tc-HMPAO, the scan data are clearly correlate with the severity of the inflammatory process. inflammation in the intestine coincides with the localization of these foci, determined during other visualization studies. Therefore, this scanning method can be used for non-invasive monitoring. It is preferable to use 111 In-labeled leukocytes as a radiopharmacological preparation because this method is the most sensitive and its use is associated with the lowest radiation exposure.

22. Is it advisable to use radioisotope scanning methods when placing catheters for arterial perfusion?

Placement of arterial catheters that provide liver perfusion is often difficult due to the inadvertent discovery of undiagnosed systemic shunts, catheter displacement, and the inevitable concomitant perfusion of areas in which it is undesirable to create a high concentration of highly toxic chemotherapeutic drugs. The introduction of macroaggregated albumin (MAA) labeled with 99m Tc into the catheter causes microembolization at the level of arterioles and makes it possible to obtain an image that can be used to judge the area of the perfusion site, especially when using SPECT. Using this technique, it is impossible to obtain reliable results when using a radiopaque substance, since it is rapidly diluted at the level of arterioles.

23. Is it advisable to use radioisotope scanning methods when establishing the localization of the source of gastrointestinal bleeding, or is simpler methods sufficient in this case?

Scanning with the introduction of erythrocytes labeled with 99m Tc, in detecting transient bleeding, is in most cases more sensitive than angiography (see figure). Previously, there was a rule that identification of the source of gastrointestinal bleeding using radioisotope scanning methods should always be performed as a screening method and precede angiography. At present, this rule is not always followed. However, when establishing the localization of the source of bleeding, radioisotope scanning can be useful in many cases. Knowing the advantages and disadvantages of all methods, a specialist can choose the most appropriate study in each case.

Bleeding from the small intestine. After an unsuccessful endoscopic examination against the background of ongoing bleeding, the patient underwent a radioisotope scan with the introduction of Tc-labeled erythrocytes, as a result of which it was possible to detect the source of bleeding, visualized near the spleen (large arrow). small intestine (small arrows) towards the lower right quadrant of the abdomen.These data confirmed that the source of bleeding is in the small intestine.During surgery, the source of bleeding was found to be a low duodenal ulcer.(B - Bladder; AC - ascending colon)

24. What radioisotope scanning methods should be used to identify the source of bleeding from the lower gastrointestinal tract?

It is well known that the localization of the source of acute bleeding from the lower gastrointestinal tract is associated with significant difficulties. An exact determination of the cause of bleeding is often not important for the development of treatment tactics, since treatment in any case involves resection of a section of the colon. Even acute and intense bleeding is often transient and therefore often not detected during angiography; in such cases, bleeding is diagnosed by the presence of blood in the lumen of the intestine, detected during endoscopic examination. It is rather difficult to identify the source of bleeding, localized in the distal parts of the small intestine, inaccessible to the endoscope.
Currently, two methods are used to localize the source of bleeding from the gastrointestinal tract: short-term scanning after injection of colloid labeled with 99m Tc, and long-term scanning after administration of erythrocytes labeled with 99m Tc Despite the theoretical advantages of using a colloid solution with 99m Tc in detecting small bleeding, this method has a limitation characteristic of angiography associated with the residence time of the drug in the bloodstream (several minutes). Scanning with the introduction of erythrocytes labeled with 99m Tc is a more preferable method, since the injected drug remains in the bloodstream for a long time (this time is determined by the half-life of the radioactive isotope), which, during long-term scanning, makes it possible to detect accumulations of radioactive blood in the intestinal lumen.
This technique has become widely used since in vitro technetium-99t-labeled erythrocytes were obtained. Development of a method for obtaining labeled cells in vitro was of great importance, because inadequate labeling of erythrocytes in vivo may be the cause of artifacts associated with the release of red blood cells through the stomach and urine. The patient is injected with radioactively labeled red blood cells, after which a series of sequential computer images is obtained. The study takes 90 minutes or more. When using a computer, the sensitivity of this method in determining the localization of the source of bleeding is higher than when using a kinetoscope.

25. How to assess the functional viability of a peritoneal-venous shunt using radioisotope scanning methods?

When increasing the volume of the abdomen in patients with a peritoneal-venous shunt (LeVeen or Denver), first of all, the functional viability of the shunt should be assessed, since the amount of fluid in the abdominal cavity may increase as a result of a violation of the patency of the shunt. If the shunt is made of X-ray negative material, radiographic examinations cannot be used, and in any case, for such studies, it is necessary to perform shunt catheterization. Since the fluid flows through the shunt in only one direction, it is very difficult to assess the functional viability of the shunt with retrograde administration of a contrast agent. The integrity of the shunt can be assessed with intraperitoneal injection of 99m Tc-MAA followed by a chest scan 30 min later. At the same time, the shunt itself may not be visualized, but the penetration of 99m Tc-MAA into the arterioles of the lungs is determined, which indicates the patency of the shunt.

There are "blind" areas around the liver and spleen This method does not allow to localize the source of transient bleeding without numerous repeated injections

Scanning with the introduction of erythrocytes labeled99m Tc

The most sensitive method in identifying sources of transient bleeding This method allows you to perform several scans during the day

Relatively non-invasive method

The process of labeling erythrocytes is long (20-45 minutes) Repeated scanning does not allow to accurately determine the localization of the source of bleeding, since the blood in the intestinal lumen moves quickly There are "blind" areas around the liver and spleen

Angiography

This method can be used for treatment (administration of vasopressin, Gelfoam)

The method is insensitive if the bleeding is not intense during the administration of the contrast agent Invasive method