VIVAMED - oddelenie nukleárnej medicíny

  • Vivamed - oddelenie nukleárnej medicíny
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Examination principle

In in vivo examination, an appropriate chemical with a bound radionuclide, the so-called radiopharmaceutical (RAP), is applied into the body. This substance enters the metabolism and is distributed into the organism in line with the pharmacokinetics of a particular radiopharmaceutical. Nuclear medicine uses various types of radiopharmaceuticals with affinity for example to kidneys, bones, lungs, thyroid, heart, liver, some inflammatory or tumorous tissues, for which the given substance is an indicator. The rate of local accumulation depends on the intensity of local metabolic and functional processes in organs and tissues and potential failures may be localised and quantified (analyses of curves, accumulation ratios, sizes ...). This enables non-invasive examination of physiological, biochemical, and pathological processes in the body. RAP applied into the body emits the gamma radiation which is only partially absorbed in the body. This penetrating gamma radiation passes through tissues out of the organism and is subsequently detected by devices with a scintillation detector located near the body, facilitating thus obtaining a planar or a spatial image (SPECT - Single Photon Emission Computer Tomography - using a gamma camera).

 

Scintigraphy examinations belong to imaging methods used in medical diagnostics, divided into static and dynamic, depending on the procedure type. Static (localisation) examinations are carried out in certain intervals (minutes, hours, days) after the RAP is applied, whereas a selected area of interest is scanned for a certain period of time (they serve mainly for the visualisation of shapes, sizes, locations, and functions of scanned organs and detection of focal processes, i.e. anomalies in shapes, sizes, and locations, as well as the detection of post-inflammatory residual changes and expansive foci), whereas dynamic examinations are carried out immediately after the RAP is applied (a series of gammagraphic images is obtained in certain time intervals, the time curve of RAP passing through a certain organ or body part is obtained). Dynamic methods are used mainly for the evaluation of the function of an examined organ.

 

RAP is eliminated from the body physically (a radioactive substance has a short half-life) and biologically (by excretion).

 

An separate section of nuclear medicine is the therapy of some malign and benign diseases; a radioactive substance – beta emitter, or a combined beta/gamma emitter – is applied in form of a solution near the cells that are to be irradiated. As the beta radiation reaches only a few millimetres in the tissue, all the energy is actually absorbed in the target focus. The therapy that applies the nuclear medicine methods is used for the treatment of differentiated thyroidal carcinoma, thyrotoxicosis, for the palliative treatment of bone metastases, radiation synoviorthesis, and for the therapy of follicular lymphoma by labelled monoclonal antibodies.

Types of examinations

Pneumology

Perfusion lung scintigraphy ( + SPECT) – it is the imaging of the distribution of pulmonary capillary perfusion and the detection of defects of blood flow through the pulmonary bed. RAP is trapped in well perfused areas and, by contrast, it will not get into poorly perfused areas.

 

Ventilation lung scintigraphy - it is the imaging of the distribution of pulmonary alveolar ventilation and the detection of pulmonary ventilation defects. A radiopharmaceutical is applied by inhalation in form of aerosol, using a mask. The examination supplements the perfusion lung scintigraphy and increases the specificity of the examination.

 

Nephrology

Radionuclide renography - this method provides a separated semi-quantitative examination of kidneys with 2 detectors that are attached to the back above the kidney area. The resulting renography curves facilitate the evaluation of the tubular secretion function and of discharge parameters for each kidney separately.


Since 1 January 2012, this method is no longer applied in our centre, as the manufacturer decided to terminate the production of the 131-O-sodium iodohippurate radiopharmaceutical.

 

Dynamic renal scintigraphy - this method facilitates a functional and morphological kidney examination. On the basis of the administered RAP, we monitor the perfusion, filtration and excretion into the tubular system, evaluate discharge parameters and a separated renal function (proportion of the left and the right kidneys in the total function) and the total glomerular filtration rate.

 

Static renal scintigraphy ( + SPECT) - RAP is accumulated and fixed for a certain period of time in the cells of proximal tubes of kidneys, depending on their functional status, which facilitates the imaging of the status of the functional renal parenchyma, evaluation of the localisation, shapes, and sizes of kidneys, calculation of the separated function, and the detection of focal lesions.

 

Dynamic renal scintigraphy with the captopril test - this examination is indicated in patients with hemodynamically significant renal artery stenosis, or of its branch, with probable renovascular hypertension. These examinations are based on the principle of comparing the parameters measured by the dynamic renal gammagraphy, carried out after the ACEI administration (captopril study), and parameters measured in basal conditions (basal study). This examination is carried out twice. The first study carried out is the captopril study. If the captopril study is negative, the probability that a patient has renovascular hypertension is low and the basal study is not necessary. In the case of a pathological finding, the examination is repeated without administration of captopril.

 

Indirect radionuclide cystography - this examination follows after the termination of the dynamic renal scintigraphy. The urinary bladder is filled physiologically. Once it is sufficiently filled up, urination is carried out before a gamma camera detector. The entire urination process is recorded (dynamic study). This method facilitates the detection of VUR, post-void residual urine in the urinary bladder, and the rate of urine flow through the urethra (uroflowmetry).

 

Orthopaedics, traumatology, rheumatology

Whole-body skeletal scintigraphy, 3-phase scintigraphy of a part of the skeleton, SPECT of a part of the skeleton – the imaging of the distribution of osteotropic RAP in the skeleton, increasingly accumulated at locations with high metabolic activity. The examination is of high sensitivity but low specificity.

 

Perfusion scintigraphy of soft tissues - this examination serves for the detection of focal processes in soft tissues (muscles, joints) and for the determination of their metabolic activity. Radioactive pertechnetate (99mTc O4- ) is increasingly accumulated at locations with increased hyperaemia and with increased metabolic activity.

 

Endocrinology

Thyroid scintigraphy – the administered pertechnetate (99mTc O4- ) is accumulated in thyroid gland (TG). Thyroid scintigraphy provides a functional and morphological imaging of TG tissues, evaluates its size, shape, and location; it facilitates the detection of foci with lower accumulation  (cold nodules – cysts, tumours...) or foci with higher RAP accumulation (hot nodules –hyperfunctional tissue).

 

Scintigraphy of parathyroid glands – the RAP, accumulated in parathyroid glands, is concurrently accumulated in thyroid. Subtraction or double-phase scintigraphy is therefore used. In the subtraction method, 99mTc-Myoview is applied initially, after 20 minutes the thyroid is scanned together with parathyroid glands, then the pertechnetate is applied, and after 15 minutes the thyroid is scanned; by the subtraction of images we obtain the image of parathyroid glands (if enlarged); the double-phase scintigraphy uses the information that 99mTc-Myoview is faster discharged from the thyroidal tissue than from the hyperplastic tissue or adenoma of parathyroid glands. Acquisition images are obtained in minute 20-30 and then after approximately 2 hours after the RAP application.

 

Scintigraphy of endocrine and neuroendocrine tumours and tumours coming from the neural tube - the 123I-MIBG/131I-MIBG radiopharmaceutical (noradrenaline analogue) is accumulated in catecholamine secretion granules of neuroendocrine tissues. The examination is indicated in suspected hyperplasia of adrenal medulla, pheochromocytoma/paraganglioma, malign pheochromocytoma, neuroblastoma, medul. thyroid carcinoma and others. To carry out the imaging of GEP tumours with higher density of somatostatin receptors, the 111In-pentetreotid RAP (Octreoscan) is used.

 

Accumulation test of radioactive iodine accumulation in thyroid – the evaluation is focused on the accumulation ability of the rest of the thyroidal tissue after total thyroidectomy prior to the therapy of a differentiated thyroid carcinoma with radioactive iodine; it serves for the calculation of a therapeutic dose of radioactive iodine in the therapy of differentiated thyroid carcinoma. After oral administration of radioactive iodine 131I, the rate of its uptake in thyroid is examined within 48 hours and then compared with the amount of the administered radioactive iodine.

 

Hepatology and gastroenterology

Cholescintigraphy – this examination facilitates the evaluation of the hepatobiliary system, patency of bile ducts, and the gall bladder function; it provides the information on the size, shape, and location of liver, location and size of the gall bladder, and morphology of bile ducts. The administered RAP is absorbed by hepatocytes and the examination is focused on the RAP excretion into bile ducts and the passage through the ductus choledochus to duodenum. To stimulate the gall bladder emptying, fat food is given to a patient during the examination (plain chocolate, cheese). A static image is carried out after 2-4 hours, if required.

 

Static scintigraphy of liver and spleen ( + SPECT) – the administered RAP is absorbed by Kupffer cells in liver (reticuloendothelial system – RES). The RES cells phagocyte the labelled radionuclides. Due to the presence of RES cells also in the spleen we can obtain an image of the liver and the spleen. To assess the changes in size, shape, and distribution of activity, we make 5 projections to evaluate the liver/spleen activity ratio, its duration, cold nodules (hyperplastic nodules, fibrous tissue), sites with increased activity....

 

Scintigraphy of the Meckel's diverticulum – the Meckel's diverticulum is a rather frequent malformation present in approximately 2% of the population. In 20 %, it contains the functional ectopic gastric mucosa that uptakes the 99mTc O4- radiopharmaceutical and may be visualised by the gammagraphy (focal activity increase).

 

Scintigraphy of salivary glands – it is a functional and morphological examination of salivary glands based on their ability to uptake 99mTc O4- from the blood circulation. It is carried out as a dynamic study during which lemon juice is administered orally to stimulate the salivation.  

 

Lymphoscintigraphy

Radioactive colloid, after the intradermal application into the area between the fingers of a lower or an upper extremity, is transported by lymph vessels into tributary lymph nodes, facilitates thus the imaging of the lymph system in the corresponding tributary area (retroperitoneal, auxiliary, cervical, parasternal, or iliopelvic). We make static images in rest and after the load (load: most frequently walking).

 

Phleboscintigraphy

A small amount of RAP is applied into a peripheral vein of the leg dorsum, while constricting the lower extremity above the ankle, under the knee, and in the upper thigh area. The resulting scintigram facilitates mainly the evaluation of the deep venous system. After the next RAP application and subsequent acquisition of a lower extremity, we obtain a scintigram facilitating the evaluation of the peripheral venous system. After the load, we acquire control static images of a lower extremity. Similarly, we can also perform the phlebography of an upper extremity with a single RAP application. If required, perfusion lung scintigraphy can be subsequently carried out, as the same RAP is applied.

 

Tumour diagnostics

Whole-body skeletal scintigraphy, 3-phase scintigraphy of a part of the skeleton, SPECT of a part of the skeleton – imaging of the distribution of osteotropic RAP in the skeleton that is increasingly accumulated at sites with high metabolic activity. This examination is of high sensitivity but low specificity.

 

Scintigraphy of endocrine and neuroendocrine tumours and tumours coming from the neural tube - the 123I-MIBG/131I-MIBG radiopharmaceutical (noradrenaline analogue) is accumulated in catecholamine secretion granules of neuroendocrine tissues. The examination is indicated in suspected hyperplasia of adrenal medulla, pheochromocytoma/paraganglioma, malign pheochromocytoma, neuroblastoma, medul. thyroid carcinoma and others. To carry out the imaging of GEP tumours with higher density of somatostatin receptors, the 111In-pentetreotid RAP (Octreoscan) is used.

 

Tumour scintigraphy with 67Ga-citrate - 67Ga citrate is used in nuclear medicine for its ability to  visualise an inflammatory focus. It is also very helpful in staging, control of therapy efficiency in patients with the Hodgkin’s, non-Hodgkin’s lymphoma and malign melanoma.

 

Accumulation test of radioactive iodine accumulation in thyroid – the evaluation is focused on the accumulation ability of the rest of the thyroidal tissue after total thyroidectomy prior to the therapy of a differentiated thyroid carcinoma with radioactive iodine; it serves for the calculation of a therapeutic dose of radioactive iodine in the therapy of differentiated thyroid carcinoma. After oral administration of radioactive iodine 131I, the rate of its uptake in thyroid is examined within 48 hours and then compared with the amount of the administered radioactive iodine.

 

 

Scintigraphy of the central nervous system

Scintigraphy imaging of dopamine transporters in basal ganglia (striatum) of brain is evaluated using the 123I labelled ioflupane: 123I-FP-CIT (DaTSCAN ©). Prior to the examination, we block the accumulation of free 123I in the thyroid by administering the perchlorate. After the i.v. application of DaTSCAN© (usually 185 MBq), the applied substance is accumulated in striatum for approximately 3-4 hours. The following brain examination by SPECT lasts for about 45 minutes. A patient is lying on their back without a movement. The scintigram is evaluated visually, quantitatively or semi-quantitatively, while using ROI techniques for the area of nucleus caudatus and putamen. The indication is the differential diagnostics of mobility disorders with a deficit (Parkinson’s disease, Parkinsonian syndromes) and without a deficit of dopamine transporters (mainly the essential tremor).

Preparation of patients for the examination

Majority of nuclear medicine examinations do not require any special preparation for the examination. In individual cases, when special preparation is required, a patient is instructed on the method of preparation when making an appointment (most frequently it is an examination that must be carried out on an empty stomach or after proper hydration, after omitting certain group of medications, after the use of laxatives....). These special examination requirements are listed in individual methods performed in our centre.

Contraindication for the examination

Reasons for a contraindication for a nuclear medicine examination may include pregnancy and breastfeeding.

Examinations of pregnant women must be carefully considered, as the radiation burden represents certain risk for an unborn child. The examination is only carried out if the risk of not identifying a correct diagnosis for a pregnant mother outweighs the radiation burden for the foetus.  If the patient is not sure about her pregnancy, the examination should be postponed, in cooperation wit the doctor who sent her to the examination, to a date after the next menstruation or after the delivery.

If a patient is breastfeeding, the breastfeeding must be suspended for 12-24 hours after a nuclear medicine examination. In the case of a RAP with a longer half-life, a patient will be specifically informed about the suspension period.