Liver and Spleen Imaging PDF

Liver and Spleen Imaging Anatomy and Physiology PAGE 121 ​ Liver Location: Located on the right side, underneath the ribs and directly below the diaphragm. ​ Liver Composition: Composed of two cell types: RE cells (Kupffer cells) and hepatocytes. ​ Liver Size: The largest solid...

Liver and Spleen Imaging Anatomy and Physiology PAGE 121 ​ Liver Location: Located on the right side, underneath the ribs and directly below the diaphragm. ​ Liver Composition: Composed of two cell types: RE cells (Kupffer cells) and hepatocytes. ​ Liver Size: The largest solid organ in the body. ​ Function of RE Cells: Responsible for phagocytosis, ingesting particulate matter like bacteria. ​ Location of RE Cells: Primarily found in the liver (80%), with smaller amounts in the spleen, bone marrow, and lymph system. ​ Liver Blood Supply: Receives oxygenated blood from the hepatic artery and nutrient-rich blood from the hepatic portal vein. Clinical Indications PAGE 121 ​ Determination of the size, configuration, and position of either the liver or the spleen ​ Detection of tumors, hematomas, cysts, abscesses, and trauma ​ Evaluation of functional liver diseases, such as cirrhosis and hepatitis Radiopharmaceutical PAGE 121 ​ Technetium-99m sulfur colloid is used for liver/spleen imaging. The colloid is engulfed by RE cells, which distribute it uniformly throughout the liver. ​ Dose: 10 mCi ​ MOA: IV ​ MOL: Phagocytosis ​ Biodistribution: Patient Preparation PAGE 121-122 ​ NO SPECIAL PATIENT PREPARATION IS REQUIRED FOR LIVER/SPLEEN IMAGING. Patient History ​ Patient diagnosis ​ Serum bilirubin level ​ Liver enzyme levels (SGOT, SGPT) ​ Serum alkaline phosphatase ​ Total serum protein levels (including globulin and albumin) ​ Urine bilirubin level ​ Previous abdominal surgery Imaging Priority: Perform liver/spleen imaging before GI tract studies using barium or contrast agents. Reason for Priority: Contrast agents can cause artifacts on nuclear medicine images. Flow Imaging PAGE 122 ​ Flow Study Positioning: Patient should be positioned under the camera before tracer administration. ​ Flow Study Purpose: To demonstrate the vascularity of defects visible on static images. Static Imaging PAGE 122 ​ Imaging Time: Static imaging begins after 10-15 minutes for tracer localization. ​ Standard Views: Anterior, posterior, right lateral, left lateral, right anterior oblique, left anterior oblique, right posterior oblique, and left posterior oblique projections. ​ Additional Image: Anterior image with a reference marker along the right costal margin for liver size and location assessment. SPECT Imaging PAGE 122 ​ SPECT Imaging Purpose: To better assess the size, location, and depth of liver and/or spleen abnormalities. ​ SPECT Imaging Benefits: Aids in assessing abnormalities, distinguishing between artifacts and true lesions, and detecting lesions not visible on planar images. Imaging Findings PAGE 122 Tc99m-Sulfur Colloid Distribution: Primarily localized in the liver (85%), followed by the spleen (10%), with minimal presence in the bone marrow. Liver Location and Variations: Typically situated above the right costal margin, exhibiting diverse shapes, including the enlarged Reidel’s lobe. Spleen Location and Visualization: Located in the left upper quadrant above the left costal margin, best visualized on the posterior view due to its posterior positioning. Artifact Sources: Heart, right kidney, porta hepatis, and gallbladder can distort the liver’s shape. Artifact Differentiation: SPECT imaging or additional planar views can help distinguish artifacts from true defects. Liver Displacement Causes: Emphysema, subphrenic abscess, or an enlarged left hepatic lobe can cause liver displacement. Tumor/Cyst/Abscess Appearance: Single or multiple areas of decreased or absent tracer uptake. Diffuse Liver Disease Appearance: Decreased or uneven tracer distribution throughout the liver. Severe Diffuse Liver Disease Appearance: Colloid shift, bone marrow visualization, and increased spleen tracer concentration. Technical Considerations PAGE 122  ​ Imaging Time: Imaging too soon after injection of Tc99m-sulfur colloid may result in cardiac blood-pool activity being seen on the from the blood by the Kupffer cells. ​ Attenuation Artifacts Source: Residual barium in the GI tract, particularly in the hepatic and splenic flexures. ​ Attenuation Artifacts Impact: May appear as artifacts. ​ Other Artifact Source: Female breast tissue overlying the superior portion of the liver’s right lobe. ​ Imaging Priority: Liver/spleen imaging should be performed before radiographic procedures using any contrast. ​ Breast Shadow Artifacts: Can be eliminated by positioning the breast out of the way. ​ Skin Fold Artifacts: Can be alleviated by imaging obese patients in an upright position. ​ Respiration Artifacts: Can be decreased by imaging patients in an upright position. Hepatobiliary Imaging Anatomy and Physiology PAGE 123 ​ Biliary Tract Components: Canaliculi, right and left hepatic ducts, common hepatic duct, cystic duct, common bile duct, and sphincter of Oddi. ​ Bile Flow: Bile flows from canaliculi to hepatic ducts, then to the common hepatic duct, and finally to the duodenum through the sphincter of Oddi. ​ Gallbladder Function: Stores bile when the sphincter of Oddi is contracted, releasing it into the duodenum for digestion. ​ Bile Function: Emulsifies fats, stimulates peristalsis, and enhances fatty acid absorption. ​ Bile Production: Produced by erythrocyte breakdown and hepatocyte metabolism. ​ Bile Secretion Stimulation: Cholecystokinin (CCK) stimulates the gallbladder to secrete bile when fatty foods enter the duodenum. Clinical Indications PAGE 124 ​ Evaluation of patients experiencing upper abdominal pain is needed to rule out cystic duct obstruction (acute cholecystitis). ​ Hepatobiliary imaging can help differentiate the cause of jaundice by ruling out obstruction of the biliary tract. ​ Such imaging can also delineate bile drainage and reflux following surgery. ​ Cold defects visualized on Tc99m-sulfur colloid images may be normal or abnormal variations of the biliary system.  ​ Pediatric applications include the detection of cho-ledochal cysts, biliary atresia, or other congenital abnormalities of the biliary tree. Radiopharmaceuticals PAGE 124 ​ Radiopharmaceutical Agents: Mebrofenin, disofenin, and lidofenin are commercially available Tc-labeled derivatives of iminodiacetic acids (IDA) used for hepatobiliary imaging. ​ Drug Distribution: After intravenous administration, these compounds are extracted from the blood by hepatocytes and transported into the canaliculi along with the bile. ​ Bile Flow Tracking: The IDA compounds follow the path of bile flow, allowing visualization of the biliary system. ​ Factors Affecting Tracer Uptake: Chemical structure of the IDA compound, hepatic blood flow, hepatocyte viability, and bilirubin level. ​ Bilirubin Impact: Elevated bilirubin levels can reduce tracer uptake, potentially requiring higher dosages. ​ Dosage Determination: Adult dosage of 99mTc-IDA (2-8 mCi) is influenced by serum bilirubin levels. Patient Preparation PAGE 124 1.​ Bile flowing into the gallbladder indicates cystic duct obstruction is ruled out. 2.​ Narcotics, sedatives, and other drugs relaxing the sphincter of Oddi should be discontinued before hepatobiliary imaging. 3.​ Morphine or other opiates increasing sphincter muscle tone can promote gallbladder filling. 4.​ Patient should fast 2-4 hr before tracer, but not fast more than 24 hr. 5.​ Reason for Fasting: To prevent the gallbladder from emptying the tracer after a fatty meal. Imaging PAGE 124 ​ Imaging Procedure: Imaging starts after tracer administration, using a scintillation camera with a low-energy collimator. ​ Patient Positioning: Patient lies on their back, allowing visualization of the liver, biliary tract, and small intestine in a single image. ​ Image Acquisition: Sequential 5-minute images are taken for 45-60 minutes. ​ Initial Projections: Anterior oblique or right lateral projections after the first hour for bowel activity and organ visualization. ​ Delayed Imaging: Obtain delayed images up to 24 hours if the gallbladder or bile ducts are not visualized initially. ​ Delayed Views for Intestinal Tracer: Obtain delayed views of the abdomen if the gallbladder and common bile duct are visualized but no tracer is seen in the small intestine. Sincalide (Kinevac) PAGE 124  ​ Sincalide Usage: Used in hepatobiliary imaging to empty the gallbladder before injecting radioactive tracer. ​ Sincalide Administration: 0.01-0.02 g/kg intravenously over 3-5 minutes, 30-60 minutes before tracer injection. ​ Sincalide Indication: Patients who have fasted for prolonged periods or are on hyperalimentation. ​ Sincalide Administration Time: Typically given 60 minutes after tracer administration to visualize the gallbladder and determine gallbladder ejection fraction (GBEF). ​ Sincalide Effect on Gallbladder: Empties the gallbladder and can be administered before and after tracer administration to calculate GBEF. ​ Sincalide and Morphine Interaction: Sincalide should not be given after morphine sulfate administration due to potential counteraction and falsely low GBEF results. ​ Gallbladder Emptying Time: Normally begins 2 minutes after sincalide administration and continues for approximately 11 minutes. ​ Image Acquisition: Images are acquired for approximately 30 minutes after sincalide infusion at a frame rate of 1-2 frames/minute. ​ Normal GBEF Value: A GBEF of at least 35% is usually considered normal, while a GBEF of less than 35% is indicative of acalculous cholecystitis. Contraindications ​ Patients with hypersensitivity or intestinal obstruction. ​ Common Side Effects: Nausea, abdominal pain, urge to defecate, dizziness, and flushing. ​ Side Effect Duration: Usually brief, lasting only a few minutes. Gallbladder Ejection Fraction Formula (𝑚𝑎𝑥 𝐺𝐵 𝑐𝑜𝑢𝑛𝑡𝑠 − 𝑏𝑘𝑔 − (𝑚𝑖𝑛 𝐺𝐵 𝑐𝑜𝑢𝑛𝑡𝑠 − 𝑏𝑘𝑔) 𝐺𝐵𝐸𝐹% = 𝑚𝑎𝑥 𝐺𝐵 𝑐𝑜𝑢𝑛𝑡𝑠 − 𝑏𝑘𝑔 × 100 Morphine Sulfate (Astranorph, Duramorph) PAGE 125 ​ Morphine Administration: Administered intravenously if the gallbladder is not visualized within 40-60 minutes after tracer administration. ​ Morphine’s Effect: Causes contraction of the sphincter of Oddi, increasing pressure in the bile ducts and forcing tracer into the gallbladder. ​ Nonvisualization After Morphine: Increases the likelihood of acute cholecystitis. ​ Morphine Dose: 0.04-0.1 mg/kg administered intravenously over 2-3 min.  ​ Imaging Duration: Continued for approximately 30 min after morphine administration. ​ Contraindications: Premature neonates, respiratory depression, morphine allergy, or acute pancreatitis. Phenobarbital (Luminal) PAGE 125 ​ Aids in differentiating biliary atresia from other causes of neonatal jaundice. ​ Phenobarbital Administration: Pretreatment at 5 mg/kg/day for 3-5 days before a hepatobiliary study. ​ Test Interpretation: Tracer excretion into the bowel within 24 hours indicates nonobstructive jaundice, while its absence suggests biliary atresia. ​ Contraindications: Patients with known allergies to barbiturates and/or respiratory depression. ​ Adverse Effects: Respiratory depression, drowsiness, hyper-excitability in children, rash, nausea, and vomiting. Image Findings PAGE 125-126 Tracer Uptake Time ​ Hepatocytes: several minutes ​ hepatic ducts and gallbladder: 15-30 minutes ​ gallbladder: 45-60 minutes ​ small intestine: 30 minutes. Less than 35% GBEF: May indicate acalculous cholecystitis. Nonvisualization of gallbladder: Indicates cystic duct obstruction (acute cholecystitis). Delayed visualization of gallbladder: May be seen in patients with chronic cholecystitis. Possible Cause of Small Intestine Issue: Common bile duct obstruction. Possible Cause of Bile Presence Outside Biliary System: Bile leak. Technical Considerations PAGE 126 ​ Prolonged Fasting Impact: Prolonged fasting or hyperalimentation can cause nonvisualization of the gallbladder due to thick, viscous bile buildup. ​ Elevated Bilirubin Effect: High bilirubin levels can delay tracer clearance by hepatocytes, leading to kidney excretion and potential identification on lateral and oblique views. Liver Hemangioma ​ Tumor Type: Cavernous hemangiomas are the most common benign tumors of the liver. ​ Diagnosis: Tc99m-labeled red blood cell (RBC) imaging is used to differentiate benign tumors from malignant liver carcinomas. Radiopharmaceutical PAGE 126 ​ RBC Labeling Methods: In vivo, in vitro, and modified in vivo/in vitro.  ​ Preferred Method: In vitro labeling due to high labeling efficiency. Imaging PAGE 127 ​ Imaging Procedure: 99mTc-RBC imaging of the liver involves three phases: flow study, immediate blood pool images, and delayed imaging. ​ Tracer Administration: 20 to 25 mCi (740-925 MBq) of labeled RBCs are administered. ​ Imaging Modality: SPECT imaging is preferred for its sensitivity in detecting small hemangiomas. Image Findings PAGE 127 ​ Decreased or normal perfusion on flow study, increased uptake on delayed images. ​ Diagnostic Accuracy: 99Tc-labeled RBC imaging has a nearly 100% positive predictive value for hemangioma detection. Technical Considerations Patient Preparation ​ No special preparation is required. Contrast Material Interference: Patients should wait several days after abdominal CT or radiographic procedures using contrast material before undergoing “Tc99m-labeled RBC liver imaging. Meckel’s Diverticulum ​ Definition: An outpouching of the intestine, usually located in the distal ileum, and is a remnant of an embryonic duct. ​ Prevalence: Found in 2% of the population, but only 25% of these individuals ever display symptoms. ​ Imaging: Most commonly performed in children. ​ Diverticulum Composition: Ectopic gastric mucosa lining secretes hydrochloric acid and pepsin. ​ Potential Complications: Ulceration of adjacent intestine due to gastric mucosa secretions, leading to GI bleeding and lower abdominal pain. ​ Diagnostic Aid: 99m Tc-pertechnetate can localize the diverticulum in patients with unexplained GI bleeding. Patient Preparation PAGE 127 1.​ Fast for at least 2 hours and avoid laxatives, contrast agents, and potassium perchlorate for 3-4 days before imaging. 2.​ Drug Administration for Enhanced Visualization: Pentagastrin (subcutaneously 15-20 minutes before tracer) or cimetidine (orally or intravenously 1 hour before imaging) can be used. 3.​ Pentagastrin dosage is 6 ug/kg, cimetidine dosage is 300 mg four times a day for adults, 20 mg/kg/day for children, and 10-20 mg/kg/day for neonates.  4.​ Glucagon’s Effect on GI Tract: Relaxes smooth muscle, slowing down peristalsis and allowing pertechnetate to remain stationary. 5.​ Glucagon Administration: 50 micrograms per kilogram administered intravenously 10 minutes after Tc-pertechnetate injection. 6.​ Adverse Effects of Glucagon: Nausea, vomiting, and allergic reactions in hypersensitive patients. Imaging PAGE 127 ​ Patient Positioning: Supine position with the area between the xiphoid and symphysis pubis centered in the camera’s field of view. ​ Imaging Protocol: Static images acquired every 30-60 seconds for 30-60 minutes after Tc-pertechnetate administration. ​ Localization Techniques: Additional views (obliques, laterals, posterior, postvoid) can be used for precise localization of increased activity. Image Findings PAGE 128 ​ Meckel’s Diverticulum Visualization: A Meckel’s diverticulum containing functioning gastric mucosa is typically visualized 10-15 minutes after injection. ​ Location: It is usually seen in the right lower quadrant of the abdomen, but can appear anywhere in the abdomen. ​ Comparison: A negative scan is shown for comparison. Technical Considerations ​ False-negative results: Failure to image the entire abdominal area, insufficient gastric mucosa, or pertechnetate removal by bowel secretions. ​ False-positive results: Most often caused by other pathologies. ​ Importance of complete imaging: Failure to image the entire abdominal area can lead to false-negative results. GI Bleeding ​ GI Bleeding Detection: Can be accomplished with Tc99m-sulfur colloid or Tc99m-labeled RBCs. ​ Sulfur Colloid Usage: Best for active bleeding, but may obscure bleeding in the right upper quadrant due to liver uptake. ​ Labeled RBCs Usage: Better for intermittent bleeding due to their long blood pool retention time, allowing delayed imaging. Imaging PAGE 128 ​ Patient Positioning: Supine position with the abdomen centered in the field of view. ​ Image Acquisition: Rapid sequential images acquired during tracer administration, followed by short static images at intervals for up to 60-90 minutes.  ​ Dynamic Image Display: Dynamic images should be displayed in cine format for physician review. Image Findings ​ Normal Visualization: Liver, spleen, abdominal vessels, kidneys, bladder, genital organs, and stomach. ​ Bleeding Site Identification: Progressive tracer accumulation in other areas indicates a bleeding site. ​ Early Bleeding Detection: Tc99m-sulfur colloid can demonstrate active bleeding within the first 5 minutes of imaging. Gastroesophageal Reflux Esophageal Reflux Complications: Can lead to esophagitis and dysphagia in adults and failure to thrive and aspiration pneumonia in infants. Diagnostic Method: Gastroesophageal scintigraphy is a sensitive method for detecting reflux. Patient Preparation PAGE 129 1.​ Patients should fast for several hours before imaging. 2.​ Adults receive 150 mL 99Tc-sulfur colloid mixed with orange juice and 150 mL dilute hydrochloric acid orally. Infants receive it mixed with infant formula through a nasogastric tube or baby bottle. 3.​ The entire volume of the tracer mixture must be consumed. Imaging ​ Patient Positioning: Supine position under the scintillation camera with the stomach positioned low to include the esophagus and lung fields. ​ Image Acquisition: Serial images obtained with varying abdominal pressure using an abdominal binder. ​ Delayed Imaging: Delayed lung field images up to 24 hours after tracer administration to detect intermittent reflux. Image findings ​ Esophageal Reflux Confirmation: Presence of radioactivity in the esophagus or lungs. ​ Normal Study Result: No esophageal reflux observed. Technical Considerations ​ Patient Side Effect: The patient may experience emesis (vomiting). ​ Technologist Preparation: The technologist should take steps to minimize possible radioactive contamination before the procedure begins. Gastric Emptying Study Gastric Emptying Rate Disruption: Caused by diseases or surgical procedures, leading to symptoms like nausea, vomiting, weight loss, and abdominal discomfort. Patient Preparation PAGE 129-130 1.​ Patients should fast for at least 4 hours before the study, ideally starting at midnight. 2.​ Patients should be informed about the meal used, eating time (less than 10 minutes), imaging duration, number of images, and activities allowed between images. 3.​ Diabetic Patients’ Preparation: Bring glucose monitors and insulin. 4.​ Maintain good control with blood sugar ideally below 200 mg/dL. 5.​ Monitor glucose levels and adjust morning insulin dose for the prescribed meal. For premenopausal woman: 1.​ Days 1-10 of the menstrual cycle to avoid hormonal effects on gastrointestinal motility. 2.​ Prokinetic agents (metoclopramide, tegaserod, domperidone, erythromycin) and medications that delay gastric emptying (opiates, antispasmodic agents) should be stopped 2 days before testing. 3.​ Medications that affect gastric emptying rate such as atropine, nifedipine,progesterone, octreotide. Standard Meal Preparation PAGE 130 1.​ 118 mL of liquid egg whites, two slices of toasted white bread, 30 g of jam or jelly, and 120 mL of water. 2.​ Mix 0.5-1 mCi of Tc-99m sulfur colloid into the liquid egg whites, cook until firm, toast the bread, and spread with jelly. 3.​ Eat it as a sandwich or separately. Imaging Procedure PAGE 130 ​ Patients are positioned supine under a scintillation camera after eating a recommended meal. ​ Initial Imaging: Anterior and posterior planar images (or a single left anterior oblique image) are obtained for 1 minute immediately after meal ingestion. ​ Subsequent Imaging: Repeated images are obtained in the same projection(s) for 1 minute at hourly intervals for up to 4 hours. ​ Static Imaging Protocol: Static images acquired at 15-minute intervals for gastric emptying retention/emptying time calculation. ​ Dynamic Imaging Importance: Necessary for accurate calculation of emptying halftime from a time-activity curve. ​ Image Diagnosticity: Static images are not considered diagnostic. Genitourinary System ​ Renal Imaging Purpose: Evaluate kidney structure, location, and function. ​ Renal Imaging Advantages: Safe, easy to perform, and causes minimal discomfort. Anatomy and Physiology PAGE 134 ​ Kidney Location: Retroperitoneal organs between the 12th thoracic and 4th lumbar vertebrae. ​ Kidney Position: The right kidney is positioned slightly lower than the left due to the liver. ​ Blood Supply: The kidneys receive blood from the right and left renal arteries, which branch off the descending aorta. ​ Blood Drainage: The kidneys drain blood into the inferior vena cava via the renal veins. ​ Nephron Function: Microscopic functional units of the kidney, filtering waste and excess fluid from the blood. Indications PAGE 135 Functional imaging: ​ Relative blood flow and renal function. ​ Obstructive uropathy. ​ Renal transplant function. ​ Renal function of potential kidney donors. ​ Renovascular hypertension. Static Renal Imaging may be useful in: ​ Evaluating renal trauma. ​ Congenital abnormalities, tumors and cysts. ​ Patients allergic to contrast media. Contraindication PAGE 135 ​ Patients with transient contrast-induced acute tubular necrosis after a renal arteriogram. ​ Precaution: Wait several days after the arteriogram before performing the radionuclide renal study. Radiopharmaceuticals PAGE 136 Technetium-99m (99mTc)-Pentetate (DTPA) ​ A radiopharmaceutical used to assess glomerular filtration and relative blood flow to each kidney. ​ Cleared by glomerular filtration with minimal binding to the renal parenchyma. ​ Clinical Application: Useful in demonstrating glomerular filtration capabilities and relative blood flow to each kidney. 99mTc-Mertiatide (MAG3) ​ Excretion: Excreted by the kidneys via tubular secretion. ​ Clearance: High first-pass extraction fraction and rapid plasma clearance. ​ Medical Application: Used to assess effective renal plasma flow (ERPF). 99MTC-Succimer(DMSA)  ​ Binds to tubules in the renal cortex, with 50% bound within 2 hours of administration. ​ Succimer Imaging: Useful for imaging space-occupying lesions (cysts or tumors) or gross renal anatomy due to its long retention in the renal parenchyma. Patient preparation PAGE 136 1.​ Explain the procedure to the patient. 2.​ Previous abdominal surgery, particularly to the kidneys. 3.​ Patient’s blood pressure. 4.​ Laboratory Values for Renal Function: Creatinine, urea, and nitrogen are metabolic waste products that the kidneys normally remove from the circulation. 5.​ Elevated Levels Indication: Elevated blood urea nitrogen and creatinine levels may indicate poor renal function. Renal perfusion Imaging Acquisition PAGE 136 1.​ Position the patient supine with the kidneys centered over the detector to obtain a posterior projection. 2.​ Administered 10-15 mCi IV Bolus 3.​ Obtain sequential images every 2 sec for 30-60 sec. 4.​ Obtain a blood pool image immediately after the flow acquisition. Normal Findings page 136 ​ Radiopharmaceutical Distribution: The radiopharmaceutical bolus perfuses each kidney in a vascular blush, arriving at approximately the same time and with equal intensity. ​ Tracer Concentration and Disappearance: The concentration and disappearance of the tracer depend on the agent used, with pentetate showing a gradual increase due to glomerular filtration. ​ Agent-Specific Excretion Patterns: Tc-mertiatide is promptly taken up by the kidneys and excreted into the collecting system and bladder, while succimer accumulates gradually in the tubular cells with minimal excretion in the urine. Abnormal Findings ​ Vascular Tumors and arteriovenous malformations(AVMs): Appear as areas of increased activity in the flow sequence. ​ Cysts and Avascular Tumors: Show as areas of decreased activity in the flow sequence. Renal Function Imaging (Renogram) Radiopharmaceuticals ​ 99mTc-mertiatide(MAG3) ​ 99mTc-pentetate.(DTPA) ​ Renal Function Assessment: Generates a time-activity curve (renogram) to demonstrate renal function. Acquisition ​ Position the patient either prone or supine to obtain a posterior projection over the kidneys. For a renal transplant, ensure the patient is supine with the detector positioned over the iliac fossa, where the kidney is situated. ​ Intravenously administer the tracer. ​ Acquire a dynamic flow study (refer to the section on renal perfusion imaging). Obtain sequential 30 to 60-second images immediately after the flow measurement for a total of 20 to 30 minutes. All images are saved on a computer for subsequent processing. ​ If tracer activity persists in the renal pelvis or ureteropelvic junction after the initial acquisition, administer furosemide (Lasix) to rule out ureteral obstruction. (Refer to the section on diuresis renography for further details.) Normal Renogram Findings ​ Prompt tracer uptake, peak activity at 3-5 minutes, gradual decrease as tracer is excreted, renal pelvis and bladder activity visible by 3-6 minutes. ​ Renogram Phases ➔​ Vascular phase (tracer arrival) ➔​ secretory phase (tracer concentration in kidneys) ➔​ excretory phase (tracer excretion). Abnormal Renogram Findings PAGE 137 ​ Abnormalities typically appear in the second and third phases of the activity curve. ​ Obstruction Indication: An upslope without a subsequent fall in activity suggests renal tubule obstruction, preventing excretion. ​ Poor Renal Function: A below-normal activity curve throughout the renogram indicates poor renal function. Diuresis Renography ​ Purpose of Diuresis Renography: To rule out urinary tract obstruction by observing the washout of residual tracer activity. Procedure: Furosemide is administered intravenously to increase urine production, and imaging is continued for approximately 20 minutes. Patient Preparation 1.​ Patients should be well-hydrated. 2.​ Patients should have an empty bladder, and not be anuric or dehydrated. 3.​ Patients who are unable to void voluntarily should be catherized. Drug Interaction: ​ Increased bladder pressure may diminish the effect of furosemide. Contraindication: ​ Furosemide is contraindicated in anuric and/or dehydrated patients. Post-surgical Precaution: ​ Extreme care must be taken when using furosemide in patients who have just undergone urologic surgery. Data Acquisition: Same as renal function study. ​ Furosemide Dosage: 20-40 mg for adults, 0.5-1 mg/kg for pediatric patients. ​ Imaging Procedure: Furosemide injected slowly over 1-2 min, imaging continued for approximately 20 min. Quantitative Renal Studies page 138 ​ Provide numerical values to evaluate tubular and glomerular function. ​ Applications of Quantitative Studies: Useful in monitoring the progression of various renal pathologies. ​ Methodologies for Quantitative Studies: Based on either blood sampling for tracer clearance estimation or camera-based methods to measure tracer accumulation. Effective Renal Plasma Flow page 138 ​ ERPF Measurement: ERPF is a measure of renal tubular function, typically performed after administering 99mTc-mertiatide. ​ ERPF Definition: ERPF is the volume of plasma that flows through the kidneys per minute. ​ ERPF Measurement History: Renal plasma flow was first measured using PAH, a non-radioactive substance. ​ ERPF Estimation Methods: Imaging and computer data processing, blood and urine sample collection. ​ Normal ERPF Value: 500-600 ml/min, but varies with age and gender. Glomerular Filtration Rate page 138 ​ GFR Measurement: 99mTc-pentetate is used to determine GFR due to its renal uptake being proportional to GFR. ​ GFR Calculation Methods: Single blood sample or imaging with computer data processing. ​ Normal GFR Value: 125 mL/min, but varies with age and gender. Renal Imaging with ACE Inhibitors page 138-139 ​ RAS Impact on GFR: RAS decreases filtration pressure and GFR due to reduced perfusion pressure. ​ Renin release from the juxtaglomerular apparatus compensates for RAS by increasing angiotensin II, which constricts the efferent arteriole and maintains filtration pressure.  ​ Angiotensin II Role: Angiotensin II, converted from angiotensin I by ACE, constricts the efferent arteriole, restoring filtration pressure and GFR. ​ ACE Inhibitors’ Role in Diagnosis: Help diagnose renovascular hypertension caused by RAS by revealing abnormal GFR despite normal baseline renograms. ​ Mechanism of Action: Block angiotensin I to angiotensin II conversion, leading to decreased glomerular filtration pressure and abnormally low GFR. ​ Impact on Renal Perfusion: May present as normal or increased due to decreased vascular resistance. ​ GFR Agent Uptake: May be decreased initially but prolonged retention occurs due to decreased GFR. ​ Abnormal Renogram Indication: High likelihood of renovascular hypertension due to RAS. ​ Pre-study Preparation: Patients should discontinue ACE inhibitor therapy for 3-7 days, remain well-hydrated, and void before the procedure. ​ Baseline Measurement: Baseline sitting and standing blood pressures and heart rate should be recorded before ACE inhibitor administration. ​ Post-infusion Monitoring: Blood pressure and pulse should be monitored every 10-15 minutes during the infusion, and the patient should not be released until their standing blood pressure returns to at least 70% of the baseline reading. ​ Commonly Used ACE Inhibitors: Captopril (Capoten) and enalaprilat (Vasotec IV). ​ Captopril and Enalaprilat Dosage: 25-50 mg orally, crushed and dissolved in water for enhanced absorption. ​ Captopril Administration Time: 60 minutes after administration to coincide with peak blood levels. ​ Enalaprilat Dosage and Administration: 40 mg/kg in 10 mL of normal saline, administered intravenously over 3-5 minutes. ​ Administration Time: Inject the renal tracer at least 15 minutes after enalaprilat administration is complete. ​ Adverse Effects: Orthostatic hypotension, dizziness, chest pain, headache, dry cough, electrolyte disturbances, fatigue, abdominal pain, vomiting, and diarrhea. Static Renal Imaging page 139 ​ Imaging Agent: Tc99m-succimer (1-6 mCi [37-222 MBq]) ​ Imaging Purpose: Visualize renal cortical outline, size, shape, and contour for quantification of viable renal parenchyma. ​ Imaging Procedure: Posterior projection with left and right posterior oblique images, acquired 2-3 hours after the flow study. Normal Findings ​ Smooth renal contour with equal tracer accumulation and uniform distribution. Abnormal Renal Findings ​ Congenital abnormalities like horseshoe kidney, ectopic kidneys, and kidney absence. ​ Horseshoe Kidney: Located anteriorly in the pelvis due to failed separation during fetal development. Radionuclide Cystography ​ Procedure Purpose: Evaluate vesicoureteral reflux. ​ Most commonly use in children. ​ Vesicoureteral reflux is a condition where urine flows back from the bladder to the ureters. ​ Cause: Often caused by a congenital malformation of the ureters’ connection to the bladder. ​ Complication: Can lead to recurrent urinary tract infections and potential kidney damage. Acquisition Radionuclide Cystography Methods ​ Two methods: indirect and direct. ➔​ Indirect Method: Involves intravenous administration of a functional renal agent, followed by imaging during voiding to observe reflux. The more commonly used direct method involves the following steps: 1. Have the patient void before the study begins. 2. Catheterize the patient. 3. Connect the catheter to a bottle of normal saline that has been infused with 1 mCi (37 MBq) of “Tc-pertechnetate.” 4. Position the patient supine on the imaging table, ensuring that the upper portion of the bladder is within the lower part of the field of view. 5. Obtain multiple sequential images as the bladder is gradually filled with the radioactive saline solution. 6. Discontinue the saline infusion once the bladder capacity is reached. Obtain a posterior prevoid image that captures the entire bladder and the upper urinary tracts. 7. Obtain voiding images by positioning the patient in the seated position and placing the camera against the patient’s back. Remove the catheter and encourage the patient to void into a bed pan or urinal. 8. Obtain a post-void image that includes the entire bladder and the upper urinary tracts. Image Findings ​ Normal Exam: Increasing bladder activity without reflux into the ureters. ​ Abnormal Exam: Ureteral reflux, especially during urination, with reflux increasing as the study progresses.  ​ Quantitative Information: Reflux bladder volume and the volume of reflux into the kidney can be calculated. Testicular Imaging ​ Purpose of Testicular Imaging: To differentiate acute torsion of the spermatic cord and epididymitis. ​ Acute Torsion of the Spermatic Cord: Often spontaneous, occurs in young men, and presents with acute pain. ​ Importance of Differentiation: Torsion requires immediate treatment, while epididymitis does not. ​ Patient Positioning: Patient lies on their back with penis taped to pubic bone and scrotum supported for camera access. ​ Testes Positioning: Testes should be positioned symmetrically in the lower center of the imaging field. ​ Imaging Procedure: Dynamic images are taken at 2-3 second intervals after 99mTc-pertechnetate injection, followed by static images. Table 13.1 Page 141 Scans Radiopharmaceutical Dose MOA Imaging time post-tracer Renal tubular Tc99m-Succimer(DTPA) 2-6 mCi IV 2-3 hr binding Captopril Tc99m-Mertiatide 5-10 mCi; low IV Flow-serial images for 30 Renography dose:high dose min is 1 mCi ERPF Tc99m--Mertiatide(MAG3) 5-10 mCi IV Flow-serial images for 30 min GFR Tc99m-Pentetate(DTPA) 5-15 mCi IV Flow-serial images for 30 min Testicular Tc99m-Pertechnetate 5-20 mCi IV Flow followed by static imaging images, delay images may be needed Indirect Tc99m-Pentetate(DTPA) or 3-10 mCi IV Flow image while voiding Cystography Tc99m--Mertiatide(MAG3) Direct Tc99m-SC or 1 mCi Via Flow during filling and Cysrography Tc99m-Pertechnetate urinar voiding y cathe ter