Scintigraphy

Scintigraphy is a technique of radioisotope diagnostics that allows obtaining a two-dimensional image of the area under study after the introduction of a radiopharmaceutical (RP) into the body and recording the gamma radiation emitted by it by means of a scintillation chamber. Substances labeled with a gamma-emitting isotope marker are able to selectively accumulate in certain organs and tissues, which makes it possible to detect pathological foci of increased distribution of RP. Static scintigraphy is performed to identify focal lesions. Dynamic scintigraphy is based on recording the passage of a radioactive label through the area under study, therefore it is more informative for assessing the function of an organ. Microdoses of a radioactive pharmaceutical are used for scintigraphy, so the radiation load on the body is minimal.

Scintigraphy (the name is derived from the Latin word scinti – to sparkle and the Greek word grapho – to write, to depict) is a method of radionuclide diagnostics that allows you to explore the visual structure of an object. Scintigraphy is performed using pharmaceutical preparations that have a tropicity to certain organs and emit radiation recorded by a scintillation gamma camera. It is used in the study of bones, myocardium, kidneys, lungs, brain and other organs. It is widely used in the USA and European countries. In America, about 17 million scintigraphs are performed annually.

The first visual study using radio indicators was conducted by Gyorgy de Hevesy in 1911. For the creation of the method, the scientist received the Nobel Prize in medicine. Radionuclide preparations have been used in wide clinical practice since the 50s of the last century, after the development of scanning, radiography and radiometry, allowing to assess the level of drugs in the organ under study, to track their distribution and movement. A little later, a scintillation gamma camera was created, an independent technique called scintigraphy appeared.

Principles of conducting

A radiopharmaceutical drug consisting of two components is injected into the patient’s body: a vector (a compound with a tropicity to a certain organ) and a marker (an isotope emitting gamma rays). Due to the tropicity of the vector, the drug accumulates in the organ under study. At the same time, the marker emits radiation recorded by a gamma camera. The scintillator of the scintigraphy device converts the energy of scattered or absorbed gamma quanta into photons of visible radiation.

Then photomultipliers transform the resulting light flashes into current pulses. The pulses are recorded and processed by a computer. As a result of processing, a two-dimensional image of the three-dimensional object under study is usually created. A similar technology is used when conducting single-photon emmisional computed tomography, only there the object is displayed in volume, and not on a plane (it remains three-dimensional). With intensive accumulation of the drug in some area, a “hot focus” is formed on the scintigrams, with the absence or decrease in accumulation, a “cold” one.

Images obtained during scintigraphy can be static, dynamic or synchronized. Static images are a flat fixed picture, used in the study of the structure of organs. Dynamic images are formed by adding together several static images, used in the study of the function of the liver, kidneys, gallbladder, etc. Synchronized images are created in tomographic mode and are used to study the contractility of the myocardium.

All types of scintigraphy are carried out using radionuclide preparations. The type of drug is determined depending on the tropicity of the vector to a particular organ. Thus, labeled bi- and monophosphate complexes are used in the study of skeletal bones, labeled diethylenetriamine pentacetic acid is used in the study of kidneys, pertechnetate (technetium solution) is used in thyroid scintigraphy, etc. There are special preparations for detecting certain forms of malignant tumors.

In most cases, the radiopharmaceutical is administered intravenously, however, there are exceptions. For example, with static intestinal scintigraphy, the patient takes a drug diluted in water orally. Despite the use of radionuclides, scintigraphy is a safe study. The product does not have a toxic effect on the body. The patient receives a lower radiation dose than during radiography.

Types of research

There are many types of scintigraphy used to detect pathology of various organs and systems. In clinical practice, the following types of studies are most widely used:

• Scintigraphy of skeletal bones
• Scintigraphy of the gastrointestinal tract, including the stomach and esophagus, intestines, pancreas, liver, gallbladder
• Lung scintigraphy
• Kidney and adrenal scintigraphy
• Vascular scintigraphy

Along with the listed methods, the patient may be prescribed scintigraphy of the thyroid gland, parathyroid glands, salivary glands, myocardium, brain, spleen and other organs. There are also special techniques used to detect certain types of tumors, to facilitate subsequent surgical intervention, etc. For example, somatostatin-receptor scintigraphy is used to detect tumors with a large number of somatostatin receptors, and scintigraphy of the signal lymph node is performed to place an isotope label before surgery.

Indications

Scintigraphy is considered as a clarifying study and is usually prescribed at the final stage, after the use of radiography, ultrasound and other diagnostic methods. The purpose of scintigraphy is to assess the topography, shape and size of the organ, to determine the exact localization, structure and functional activity of pathological foci. The technique is used at the stage of clarifying the diagnosis, during differential diagnosis, when drawing up a plan for conservative and surgical treatment and in the process of evaluating the effectiveness of therapeutic measures.

Skeletal bone scintigraphy is performed to assess the structure of bone tissue and identify pathological foci in joints, tubular bones, vertebrae, pelvic bones, sternum, shoulder blades and skull bones. The procedure allows you to detect areas of intensive growth, degeneration or restructuring. Scintigraphy is indicated for suspected metastatic bone lesions in malignant tumors of various localization, rheumatic lesions, degenerative-dystrophic processes, inflammatory changes and difficult-to-diagnose fractures.

Gastrointestinal scintigraphy is performed to study the structure and topography of hollow and parenchymal organs, to determine the functional ability of hollow organs, as well as to assess the nature, size and shape of pathological foci. Various types of static and dynamic scintigraphy are performed for dysphagia, suspected primary and metastatic neoplasms, intestinal obstruction, intestinal bleeding, diffuse liver lesions (cirrhosis, hepatitis), cholelithiasis, as well as after operations on various parts of the gastrointestinal tract.

Lung scintigraphy is performed to assess regional ventilation and pulmonary capillary blood flow. The procedure is prescribed after chest X-ray. The study is indicated for suspected pulmonary embolism, atelectasis, pneumosclerosis, pneumonia, neoplasms, obstructive processes and other pathological conditions.

Scintigraphy of the kidneys and adrenal glands is performed to assess the structure and functional state of the organs located in the retroperitoneal space. Static kidney scintigraphy is prescribed to study the state of the renal parenchyma, localization, size and shape of organs, dynamic – to study the excretory function of the kidneys. Static studies are rarely carried out due to their insufficiently high information content. In many cases, adrenal scintigraphy is also insufficiently informative and is mainly used to detect hormone-producing tumors.

Vascular scintigraphy is used to study the structure and patency of veins and lymphatic vessels. The study can be both static and dynamic. The technique allows you to assess the speed of blood and lymph flow, the condition of blood vessels and lymph nodes. Indications for scintigraphy are lymphostasis and chronic venous insufficiency of various genesis. In addition, the procedure is carried out if lymphogenic metastasis of malignant neoplasms is suspected.

Contraindications

An absolute contraindication to scintigraphy is an allergic reaction to a radiopharmaceutical. The study is not carried out during pregnancy, with a serious condition of the patient and with severe motor anxiety. During lactation, scintigraphy is not contraindicated, however, patients are advised to refrain from breastfeeding for a day after the introduction of a radionuclide substance in order to avoid the drug entering the child’s body. Children’s age is also not considered as a contraindication. When conducting scintigraphy in children, radiopharmaceuticals with a short half-life are used.

Patient preparation

The list of preparatory measures is determined by the type of scintigraphy. Before conducting a study of the bones of the skeleton, it is necessary to refrain from taking bismuth and barium preparations for 4 days. You need to take with you the results of radiography, CT or MRI of bone structures (if available). Before thyroid scintigraphy, you should undergo a thyroid ultrasound, take a hormone test, do not eat seafood for 2 weeks and do not take hormonal drugs for 1 month. Before examining the lungs, you need to do an X-ray or CT scan of the chest organs.

Before examining the kidneys, it is necessary to undergo an ultrasound of the kidneys and drink a glass of water an hour before the procedure. Scintigraphy of the biliary tract is carried out strictly on an empty stomach. The doctor should provide the results of a biochemical blood test, ultrasound of the liver and gallbladder. You need to take a bottle of holosas or another similar drug with you. Liver scintigraphy is performed after liver ultrasound. Before myocardial scintigraphy, it is necessary to refrain from eating, smoking and drinking caffeinated beverages for 4-6 hours. The study is carried out after an ECG.

Methodology of conducting

The duration of scintigraphy ranges from 15-20 minutes to several hours. The longest procedure is the examination of the bones of the skeleton. After administration of the drug, they either wait for 1-3 hours, or take a series of pictures immediately, and then after 3-5 hours. Kidney scintigraphy lasts from 30 minutes to 1 hour, gallbladder – 1-2 hours, thyroid gland – about 20 minutes, lungs – 15-30 minutes. The drug is administered intravenously, less often orally or by inhalation. The patient is asked to lie down on the gamma camera table, scintigraphy is performed and informed that it is necessary to wait to determine if there is a need for additional images. Then the specialist prepares a conclusion and passes it to the attending physician or gives it to the patient.