Genitourinary System泌尿系统

Genitourinary System,Radioisotope imaging of the genitourinary tract has become an invaluable asset to clinicians in the evaluation of renal parenchymal and urologic abnormalities. The unique combination of functional and anatomic assessment provided by nuclear imaging makes it the diagnostic test of choice in many situations.,1 Renogram,The principal of renogram is that metabolites and useless materials first filtrated by golmeruli or secreted by renal tubules and then passed outside the body. 131I-OIH is a urinary excretory substance and can be secreted by renal tubules after injection into the body. The renogram is a time-activity curve obtained during the transit, secretion and excretory route of 131I-OIH through the kidney formed renogram.,In general, patients must drink 500 ml water 15 min before test for maintenance of a steady state of urine flow. When 131I-OIH 5-10 Ci is injected into vein as a bolus, the radioactivity over the both kidneys is recorded by scintillation probe or detector as long as 20 min, then time-activity curve (renogram) is obtained.,The normal curve involves three phases:The first phase (phase a) is called rapidly rising vascular phase. Normally, it lasts only 30 sec. The second phase (phase b) is called functional phase, it rises slowly and lasts 3 min. The slope and height of phase b reflects the velocity and amount of 131I-OIH, accumulating in the kidney. The third phase (phase c) is excretory phase, which slowly descends and lasts 15 min.,The efficiency of uptake is reflected of uptake is reflected by the slope of the ascending portion of the time-activity curve and by the time at which the peak counts or TMAX are reached. The rate of disappearance of the tracer from the kidney is an important indication of tubular function an is expressed by T1/2 .The normal value is showed in Table 1.,Nomal values of renogram,Left/min Right/minTmax 3.240.72 3.451.13T1/2 4.941.8 5.062.27,There are several types of abnormal curve indicating different diseases respectively.,1.1 Acute rising type Phase a is normal, phase b is continued uprising, but phase c is disappeared. In this condition, it means urinary obstruction.,1.2 High level prolonged type Phase a is normal too, and phase b rises gradually. This curve always occurs in urinary obstruction with renal insufficiency.,1.3 Parabola typeThe curve rises slowly, gradually falls Tmax prolongs. It suggests the patients suffer from mild renal insufficiency.,1.4 Low level prolonged type Height of a phase is lowered, while phase b and c merged each other. It indicates severe renal injury.,1.5 Low level descending type The curve shows significant low phase a with gradual down slope, without phase b and c. Such patients usually have nonfunctional kidney.,1.6 Stepwise drop typePhase a and b are normal, but phase c drops step by step. It is seen in spasmodic ureter.,1.7 Unilateral small kidneyIt markedly narrowed compared with the normal renogram, but its shape is normal and three phases exists. Such patients usually have unilateral renal artery stenosis or small congenital kidney.,The renogram is very useful. It can screen for the diagnosis of renovascular hypertension, investigate uropathy such as stone, diagnose acute anuria, monitor the therapeutic effect of renal disease, and monitor renal function in renal transplant.,2 Dynamic Renal Imaging,Dynamic renal imaging contains renal artery perfusion imaging and cortical function phase.,2.1 Radiopharmaceuticals,The use of tracers, which are taken up and excreted by the kidney, allows the estimation of renal perfusion, divided, drainage and assessment of the lower urinary tract.,Diagram of the nephron showing GFR agents such as 99mTc-DTPA,51Cr-EDTA and 125I-iothalamate filtered at the glomerular level. While 99mTc-MAG3, 123I- or 131I-hippurate are filtered, their predominant method of renal excretion is by tubular secretion at the level of the proximal convoluted tubule. 99mTc-DMSA and 99mTc-glucoheptonate become fixed within the renal tubules. 99mTc-glucoheptonate is also filtered and secreted by the nephron.,2.1.1 99mTc-MAG (Mercaptoacetyltriglycine) The typical dose of MAG3, in adults is 10 mCi (370 MBq). MAG3 is cleared almost exclusively by tubular secretion. 98% is secreted in the proximal tubule and only 2% of the agent is filtered at the glomerulus.,The extraction fraction of MAG3 is between 40 and 50% and the average renal clearance is between 340 ml/min and 400 ml/min, which is much higher than the normal GFR (125 ml/min).,2.1.2 99mTc-DTPA (Diethylenetriamine-pentacetic Acid)The typical dose of 99mTc-DTPA in adults is 5-10 mCi. For children the dose is 0.1 mCi/kg, minimum dose 0.5 mCi. The agent can be used to evaluate renal perfusion, glomerular filtration, and for renal and urinary tract imaging. DTPA is cleared entirely by glomerular filtration (similar to insulin or IV contrast dye).,The patient should be well hydrated prior to the study. For adults, 300-500 ml of clear fluids should be taken in the hour prior to the hour prior to the study (unless clinically contra-indicated).,2.2 Image Acquisition,All images are usually obtained from the posterior. If there is a pelvic kidney, this is best assessed with an anterior position of the camera.,For most purpose, a 20-second frame rate is adequate. If deconvolution analysis of transit times is being performed, then a 10-second frame rate is required. For first-pass studies 1 frame/second for 30 or 40 seconds is required.,The normal time for a dynamic study is 20 minutes (minimum 15 minutes). If delayed frusemide (furosemide) is being administered, then at least 15-minute study at a 20-second frame rate is required.,Abdomens aorta,Left kidney,Right kidney,Normal renal perfusion imaging and renogramby 99mTc-DTPA,Abnormal renal perfusion imaging,theleftkidney disappear (posterior),Normal renal functional imaging and renogram by 99mTc-DTPA,Abnormal renal functional imaging,The left renal pelvis show marked dilation and radioactivity is detained.,Bothkidneys have radioactive concentrate continuously, but the bladder has no radioactivity.,post,2.3 Glomerular Filtration,The plasma volume (ml) filtrated through the glomerulus per minute is called glomerular filtration (GFR). GFR is expressed as a clearance value, that is, a parameter of renal function determined from the clearance of a compound from the blood by the kidney. The measurement of GFR is regarded as one of the most valuable assessments of renal function.,GFR, in a healthy person, is 80-100 ml/min, and is decreasing with age. In early stage of diabetes, GFR can increase. But during renal insufficiency, such as in late stage of diabetes, the 3rd stage of hypertension, azotemia, or uremia, GFR will decrease.,2.4 Effective Renal Plasma Flow,Clearance of the plasma volume (ml) per minute during the first pass of the injected material through the kidney is called effective renal plasma flow (ERPF). ERPF is a parameter of the renal tubular function.,Normal value of ERPF is over 450 ml/min, and is also decreasing with age. In acute and chronic nephritis, ERPF will decrease, paralleling with the changes of renogram. ERPF can monitor therapeutic effect and rejection of transplant kidney.,3 Renal Cortical Scintigraphy,3.1 Radiopharmaceuticals99mTc-DMSA (2,3dimercaptosuccinic acid): The typical dose in adults is 5 mCi (minimum dose 300-350 Ci). For children the dose is 0.05 mCi/kg ,minimum dose 0.3 mCi. 99mTc-DMSA is used for high resolution imaging of the renal cortex. The agent is slowly cleared from the blood as a result of its binding to sulfhydryl groups in proximal renal tubules.,3.2 Image Acquisition Supine and the patient should be as close to the camera face as possible. Image acquisition should start 2-4 hours post injection. Posterior image of both kidneys are obtained for a total of 300,000-500,000 counts. Both left and right posterior oblique images should be obtained each for approximate 150,000-200,000 counts.,Normal renal cortical scintigraphy,Both kidney have many radioactive defect area,4 Clinical Use,4.1 Evaluation of renal cortical functionDynamic renal imaging is better than X-ray intravenous pyelography (IVP) in high sensitivity, non-invasive, and safety.,Case 1: male, 53 years old, suffered from left flank intermittent pain for 1 year. A: IVP - left kidney is invisible.B: 99mTc-DTPA scintigraphy left kidney has some radioactive uptake and excretion.,Case 2: female, 48 years old, suffered from left renal tuberculosis.,Case 3: male, 56 years old, suffered from backache and haematuria(bloodin urine) for 2 years. The effect of two months of treatment was evaluated compared with before.,4.2 Renal Artery Stenosis Renal artery stenosis may be recognized by its effect on the inflow into and subsequent reduced function of the affected kidney. This is enhanced by prior administration of angiotensin converting enzyme inhibitor (ACEI).,The technique is useful not only for screening, but also for monitoring the effect of revascularization surgery. Functional results of renal artery stenosis are shown by changes in size or function, rather than the anatomical lesions shown by conventional imaging,