PET/CT in prostate cancer: non-choline radiopharmaceuticals.

In this brief review, the major potential clinical applications of 18F-FDG, 11C-acetate, 18F-FDHT, 18F-FLT, 18F-FMAU, and anti-18F-FACBC in the imaging evaluation of men with prostate cancer are discussed. 18F-FDG has a limited role in primary diagnosis and staging but it may be able to reflect tumour aggressiveness, detect sites of recurrence in some men with high serum PSA after biochemical failure and assess response to chemo- and hormonal treatment in metastatic disease. 11C-acetate has been investigated for intra-prostatic primary tumour detection and staging as well as for re-staging in case of biochemical relapse with results that are overall similar to those with 18F- and 11C-labeled choline. 18F-FDHT targets the androgen receptor and may be particularly useful in the assessment of the pharmacodynamics of the androgen signalling pathway. PET in conjunction with 18F-FLT or 18F-FMAU that track the thymidine salvage pathway of DNA synthesis has also been investigated for imaging cellular proliferation in prostate cancer. Initial experience with the radiolabeled synthetic amino acid, anti-18F-FACBC, which displays slow urinary excretion has been encouraging but further studies will be needed to decipher its exact role in the imaging management of men with prostate cancer.

Electrocardiographic characterization of embryonic zebrafish.

The zebrafish (Danio rerio) has emerged as one of the primary experimental models of developmental cardiovascular research. Recent progress in flow visualization techniques along with the existing genetic map of the species has made zebrafish amenable to a variety of experiments relating cardiac developmental structure and function. One essential tool in establishing the proper functioning of the heart is the electrocardiogram (ECG). This study presents a methodology whereby the ECGs of embryonic zebrafish could be used in assessing the electrophysiological consequences of genetically-, mechanically-, or pharmacokinetically-induced cardiac perturbations. Five day post-fertilization (dpf) embryos produced repeating bimodal ECGs with clearly distinguished atrial (P) and ventricular (R) depolarization waves. P-R intervals along with P-P intervals are cited.

Diagnostic role of [F-18]-FDG positron emission tomography in restaging renal cell carcinoma.

AIMS: To retrospectively assess the diagnostic utility of positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) in restaging renal cell carcinoma. MATERIALS AND METHODS: We performed whole-body PET scans (45 minutes after intravenous injection of 10 - 15 mCi FDG) for restaging 25 patients (18 male, 7 female, 42 - 81 years old) with known or suspected metastatic renal cell carcinoma. Prior treatments included immunotherapy (n = 1), nephrectomy (n = 16), nephrectomy followed by chemotherapy (n = 3), by radiation therapy (n = 1), and by combined chemoradiation therapy (n = 4). Contrast-enhanced chest, abdomen and pelvis CT studies were available for all patients. Diagnostic validation was by histological sampling (n = 2) and clinical and imaging follow-up for up to 1 year (n = 23). RESULTS: PET was concordant with the findings of CT in 18 patients (3 TN, 15 TP). PET was discordant with CT in 7 patients (28% of total). PET was falsely negative in 6 of these patients and did not demonstrate hypermetabolism in pulmonary (n = 4), mediastinal (n = 2), adrenal (n = 1) and lytic osseous (n = 2) metastatic lesions. PET was falsely positive in the remaining 1 patient in the discordant group with lumbar facet arthropathy. The diagnostic performance of PET in detection of recurrent and metastatic renal cell carcinoma revealed a sensitivity of 71%, specificity of 75%, accuracy of 72%, negative predictive value of 33% and positive predictive value of 94%. CONCLUSIONS: FDG PET demonstrates modest accuracy in the diagnostic imaging evaluation of patients with suspected or known metastatic renal cell carcinoma. A negative study may not exclude disease while a positive study is suspicious for malignancy.

Evaluation of recurrent gastric malignancy with [F-18]-FDG positron emission tomography.

AIM: We retrospectively assessed the use of [(18)F] fluorodeoxyglucose positron emission tomography (FDG PET) in the evaluation of recurrent disease in patients with history of gastric malignancy. MATERIALS AND METHODS: Eighteen patients were referred for FDG PET for evaluation of recurrent gastric cancer. Prior treatments included total (n = 4) or partial gastrectomy (n = 14) followed by chemotherapy alone (n = 7) or combined chemoradiation therapy (n = 2). The interval between the most recent treatment and PET ranged from 3 months to 2 years. Correlative diagnostic data were available in 16 patients and were all obtained within 3 months of the PET study. Validation was by clinical or imaging follow-up (2-45 months) in 16 patients and histology in two patients. RESULTS: PET was concordant with computed tomography (CT) in 12 patients (5 TP, 6 TN, 1 FN). In one patient with negative imaging studies, an incidental finding of left obstructive uropathy was determined to be due to metastatic ureteral stricture. Discordant imaging findings were present in four patients (22% of total). PET-detected diffuse metastatic lesions in three of these patients with rising serum tumour markers while other imaging studies were negative. Additional chemotherapy was initiated in these three patients (17% of total) based on PET localization of disease. PET and a gastric anastomosis biopsy were negative in another patient with positive CT. The remaining two patients without correlative imaging studies died shortly after positive PET studies with presumed recurrent cancer. CONCLUSION: FDG PET may be useful in the evaluation of recurrent gastric cancer, and can localize the disease when CT is non-diagnostic. Imaging evaluation with PET may also impact on the clinical management of patients with recurrent gastric cancer.

Evaluation of pancreatic carcinoma with FDG PET.

BACKGROUND: To assess the diagnostic usefulness and clinical impact of positron emission tomography with [F-18]fluorodeoxyglucose (FDG PET) on the management of patients with known or suspected pancreatic carcinoma. METHODS: Attenuation-corrected FDG PET was performed in 20 patients (12 male, eight female) with pancreatic carcinoma at the time of initial diagnosis (n = 7), for tumor surveillance after Whipple surgery (n = 11), and for reevaluation after chemoradiation therapy (n = 2). Visual analysis of PET images were correlated with the results of abdominal computed tomography (CT) and carbohydrate antigen (CA) 19-9 serum tumor marker level that were obtained within 1 month of the PET study. Diagnostic validation was by histology in nine patients and by clinical or radiologic follow-up (5-48 months) in 11 patients. Changes in therapeutic management that were prompted by PET were tabulated. RESULTS: PET was concordant with the findings of abdominal CT in 14 patients (13 true positive, 1 true negative). PET detected clinically unsuspected lung lesions, confirmed subsequently by a chest CT, in one of these 14 patients. PET was discordant with CT in six patients. PET detected tumor recurrence in three patients in this group (15% of total) with nondiagnostic CT findings and elevated CA 19-9 serology. In two of these three patients, chemotherapy with gemcitabine was initiated based on PET localization of disease. Tumor was confirmed in the remaining one of the three patients at autopsy shortly after the PET study. FDG localization in a displaced loop of bowel resulted in an apparent false-positive hepatic lesion in one of six patients in the discordant group. PET underestimated the extent of metastatic disease in the remaining two of six patients due to hyperglycemia. CONCLUSION: In patients with suspected pancreatic carcinoma at the time of initial presentation, PET is complementary to abdominal CT and allows detection of unsuspected distant metastases. In patients with suspected recurrent pancreatic carcinoma, based on elevated or rising CA 19-9 serology, PET can localize the disease when abdominal CT is nondiagnostic as a result of posttherapy anatomic alteration. Imaging evaluation with PET may impact the clinical management of patients with pancreatic carcinoma.

Non-visualization of sentinel lymph node in patients with breast cancer.

Histological evaluation of the first draining lymph node (sentinel node) in the axilla of patients with breast cancer has dramatically altered the surgical approach to these patients, with sparing of the axilla if no tumour cells are identified. In a fraction of patients imaged after peri-tumoural injection of the breast, there is no visualization of the sentinel node. We retrospectively analysed the status of patients whose nodes were visualized and of patients whose nodes failed to visualize, to define the variables associated with non-visualization of the sentinel node. Seventy-four breast cancer patients were imaged following peri-tumoural injection of filtered 99Tc(m)-sulfur colloid, immediately and up to 5.5 h post-injection. The scintigraphic data were analysed with reference to the patient's age, histology, grade, site and size of tumour, previous diagnostic procedure and time interval to scan, using univariate analysis and a logistic regression model. A sentinel node was visualized in 53 of 74 women (72%). Comparison of patients with non-visualized versus visualized sentinel nodes disclosed no statistically significant univariate relation to age of the patients (P = 0.10), size of tumour (P = 0.46), site (P = 0.26), histology [invasive ductal carcinoma in 16 of 20 (80%) non-visualized cases, and in 43 of 53 (81%) visualized patients], prior excision biopsy (P = 0.36) and time interval to surgery (P = 0.29). Tumour grade was the only significant variable on univariate analysis (P = 0.03), though multivariate analysis showed that none of the independent parameters were statistically significant. In 39 patients with an upper outer quadrant tumour, the location of the sentinel node was not limited to the axilla and even crossed the midline of the breast. Our results show that none of the independent variables is associated with non-visualization of sentinel lymph node on preoperative lymphoscintigraphy of patients with breast cancer, though the tumour grade may have contributed to non-visualization of this node. The non-axillary drainage from upper outer quadrant tumours suggests the routine use of lymphoscintigraphy prior to axillary dissection.

Medical imaging in microgravity.

Microgravity environment induces significant pathophysiological changes in humans. As long-term space habitation and interplanetary missions become commonplace in the next century, researchers and imaging specialists must embrace the unique challenges of microgravity research in developing innovative uses of imaging technology. Microgravity results in cephalad fluid shift, loss of electrolytes, loss of muscle and bone mass, anemia, reduced immune response, variability in gastric emptying and hepatic metabolism, increased bowel transit, and development of space motion sickness. Medical imaging is uniquely capable of assessing all of these physiologic adaptations to weightlessness. The imaging information will also aid in identifying those changes which are potentially beneficial and those which are harmful to humans living in space. Interventions may then be employed to capitalize on the benefits and prevent the harmful effects. This article reviews the physiological adaptations to weightlessness and outlines ways in which medical imaging techniques may provide insight into these adaptations.

The effect of fluorine-18 fluorodeoxyglucose positron emission tomography on the management of cutaneous malignant melanoma.

PURPOSE: To assess the effect of positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) on the treatment of patients with cutaneous malignant melanoma. MATERIALS AND METHODS: We retrospectively reviewed the medical records of 38 patients with newly diagnosed (n = 25) and recurrent (n = 13) cutaneous melanoma who were referred for evaluation with FDG PET imaging at our institution. We compared the PET findings with computed tomography (CT), which was available in 21 (55%) patients, and tabulated the changes in the diagnostic evaluation and therapeutic management that were prompted by PET during a follow-up period of 10 to 36 months. RESULTS: Compared with PET, the extent of disease was underestimated by CT in 5 (13%) patients. Planned surgical resection of metastases was canceled in two of these patients. In another patient, surveillance PET detected an unsuspected hypermetabolic abdominal mass that was noted on a subsequent CT to arise from the small bowel. The mass was found to be jejunal metastatic melanoma at the time of resection. Overall, PET influenced surgical management in 3 (8%) patients, but it did not affect the wait-and-watch strategy or decision to initiate immunotherapy in the others. CONCLUSIONS: FDG PET contributes important information not provided by CT and has a substantial effect on the clinical management of patients with malignant melanoma.

2. Diagnostic Utility of FDG-PET in the Clinical Management of Patients with Suspected Recurrent Pancreatic Carcinoma after Whipple Procedure.

Purpose: We evaluated the usefulness of FDG-PET in the assessment of patients with suspected pancreatic carcinoma who have previously undergone a Whipple procedure.Methods and Materials: Attenuation-corrected FDG-PET was performed in 11 patients (5 males, 6 females, age range 52-76 years), with suspected recurrent pancreatic carcinoma after Whipple procedure. Recurrence was suspected based on clinical, laboratory (CA19-9 serum tumor marker level), or abdominal CT findings. Diagnostic validation was by histology in 2 patients and radiologic or clinical follow-up (5 to 48 months) in 9 patients. Changes in therapeutic management that were prompted by PET were tabulated.Results: PET was concordant with the findings of abdominal CT in 7 patients (6 true-positive, 1 true-negative). PET detected unsuspected lung lesions in 1 of these patients that was subsequently confirmed by a chest CT. PET was discordant with abdominal CT in 4 patients. PET detected tumor recurrence in 3 of 4 patients in this group (27% of total) who had non-diagnostic CT and elevated CA19-9 serology. Chemotherapy was initiated in 2 of these 3 patients (18% of total), while the other patient died shortly after the PET study from pneumonia and recurrent tumor was confirmed at autopsy. The remaining 1 of 4 patients in the discordant group had a false-positive PET study due to relatively high FDG localization in a displaced loop of bowel.Conclusion: PET is useful in localizing the tumor in post-Whipple patients with suspected recurrent pancreatic carcinoma and can impact their clinical management.

Comparison of fluorine-18 deoxyglucose and O-15 water PET in temporal lobe epilepsy.

This study reports a comparison of Fluorine-18 deoxyglucose positron emission tomography (FDG-PET) and O-15 water (H2(15)O) PET with regard to lateralization of the seizure focus in patients with complex partial epilepsy. The analysis of 35 patients who had an anterior temporal lobectomy for medically intractable seizures indicated that FDG- and H2(15)O-PET were highly correlated in demonstrating the epileptic focus. FDG- and H2(15)O-PET showed significant asymmetries in 83% and 77% of cases respectively. The lateralization with visual analysis of MRI was found to be lower than both FDG and blood flow imaging. Ictal electroencephalography (EEG) lateralizations were concordant with sites of blood flow and FDG-PET abnormalities. Thirty-three patients (94%) were seizure-free or improved significantly after surgery. In conclusion, blood flow PET yielded similar results compared to FDG-PET and can be a valuable modality in preoperative evaluation of patients with temporal lobe epilepsy.

Effect of atropine and sincalide on the intestinal uptake of F-18 fluorodeoxyglucose.

PURPOSE: Variable diffuse intestinal uptake of F-18 fluorodeoxyglucose (FDG) is commonly seen in patients undergoing positron emission tomography (PET) imaging. Diffuse high uptake can obscure a lesion, whereas occasional high focal uptake can mimic a lesion. The cause of intestinal FDG uptake and the parameters that influence the level of uptake are unknown. METHODS: We hypothesized that intestinal FDG uptake may result from smooth muscle peristalsis. We tested our hypothesis by comparing FDG uptake at baseline and after administration of two drugs (atropine and sincalide) that are known to affect intestinal motility. We performed FDG PET scans in random order in five healthy male volunteers without medication, after intramuscular administration of atropine, and after intravenous administration of sincalide. RESULTS: Qualitative comparison of the images before and after both medications did not show any significant difference in the level of intestinal FDG uptake. CONCLUSIONS: We conclude that intestinal FDG uptake is probably not caused by peristalsis. Mucosal uptake may be an alternative explanation.

SPECT and PET in the evaluation of coronary artery disease.

Cardiac positron emission tomography (PET) is an accurate method for assessing myocardial perfusion and metabolism in the evaluation of coronary heart disease. PET allows more accurate detection of myocardial ischemia than single photon emission tomography (SPECT). In addition, PET has higher spatial resolution and allows attenuation correction and the quantification of various physiologic parameters. PET with 2-(fluorine-18) fluoro-2-deoxy-D-glucose is considered the standard of reference for predicting improvement in regional or global left ventricular function after revascularization by identifying hibernating viable myocardium that shows diminished perfusion and preserved metabolism. Other less commonly used clinical applications of cardiac PET include assessment of myocardial oxygen consumption and fatty acid metabolism. The use of PET in myocardial imaging is expected to increase in the near future with the regional distribution of positron-emitting radiotracers and the emergence of relatively low-cost PET systems.

Annular pancreas in adults: imaging features in seven patients.

BACKGROUND: Annular pancreas is a rare congenital abnormality that may be associated with variable degrees of duodenal obstruction. This diagnosis is often overlooked in adult patients who present with symptoms suggestive of duodenal obstruction. Imaging evaluation aids in establishing the diagnosis. We evaluated the imaging findings in seven adult patients with known annular pancreas. METHODS: Seven adult patients with abdominal symptoms had evaluation with one or more of the following imaging studies: upper gastrointestinal (UGI) series, computed tomography (CT), and endoscopic retrograde cholangiopancreatography (ERCP). All patients underwent subsequent laparotomy as a part of routine care. Surgical and imaging findings were correlated in each patient. RESULTS: UGI series is suitable for demonstrating different degrees of duodenal narrowing at the level of pancreatic annulus. Contrast-enhanced abdominal CT is useful in visualizing directly the complete or partial annular pancreatic tissue. ERCP is particularly useful in visualizing the annulus duct coursing around the duodenum. CONCLUSIONS: Imaging plays a pivotal role in the diagnosis of annular pancreas in adult patients avoiding surgery for confirmation with its associated cost and risks.

Evaluation of suspected recurrent papillary thyroid carcinoma with [18F]fluorodeoxyglucose positron emission tomography.

We evaluated 10 patients with suspected recurrent papillary thyroid cancer using [18F]fluorodeoxyglucose positron emission tomography (FDG PET). Prior therapy included total (n = 8) or subtotal (n = 2) thyroidectomy, radiation therapy (n = 2) and radioiodine ablation (n = 2). All patients had an 131I scan and one or more of the following imaging studies: 99Tcm-sestamibi scan. 111In-octreotide scan, sonography (US), computed tomography (CT) and magnetic resonance imaging (MRI). Both the PET and 131I scans were negative in four patients. The PET and 131I scan results were discordant in six patients. Of the six discordant cases, five had true-positive PET scans and false-negative 131I studies. Three of these patients underwent neck lymph node dissection that showed positive histology for metastatic papillary carcinoma. Another patient had fine-needle aspiration (FNA) of a parapharyngeal mass that was also positive for papillary carcinoma. One patient was treated with radiation to the thyroid surgical bed based on an elevated serum thyroglobulin and a positive PET finding. Tumour response with a decrease in the size of the lesion was documented by a follow-up MRI scan. The remaining patient had a presumed false-positive PET scan, since a difficult hypocellular FNA of a small palpable lymph node was negative for tumour. We conclude that FDG PET is useful in the evaluation of patients with suspected recurrent papillary thyroid cancer when the 131I scan is negative.

Effect of radionuclide renograms on treatment of patients with spinal cord injuries.

OBJECTIVE: Urinary tract problems stemming from neurologic dysfunction are a major cause of morbidity in patients with spinal cord injury. Radionuclide renograms have been used to monitor renal function in these patients. However, the effect of renographic results on the treatment of patients has not been studied. A retrospective study was done to determine the effect of radionuclide renography on the diagnostic evaluation and therapeutic treatment of patients with spinal cord injury. MATERIALS AND METHODS: The records of 199 patients with spinal cord injuries were reviewed. A decline in effective renal plasma flow of 20% or more, a low effective renal plasma flow for age, and abnormal tracer time-activity curves were correlated with diagnostic procedures and therapeutic interventions. Diagnostic procedures included renal sonography, CT, excretory urography, and urodynamics. Therapeutic interventions included changes in medication, changes in bladder management, and surgery. RESULTS: Patients with abnormal findings on renograms underwent more diagnostic procedures and therapeutic interventions. A significant correlation was found between abnormal tracer time-activity curves and use of excretory urography. A decline in effective renal plasma flow was the best predictor of therapeutic intervention. CONCLUSION: Radionuclide renograms influence the diagnostic evaluation and therapeutic treatment of patients with spinal cord injury.

False-negative fluorine-18-FDG PET in metastatic carcinoid.

Carcinoid tumors have high numbers of somatostatin receptors that allow scintigraphic imaging with the radiolabeled somatostatin analog octreotide. Experience, however, with PET using 2-[18F]fluoro-2-deoxy-D-glucose (18FDG) in carcinoid is very limited. In two prior studies which investigated the utility of 18FDG-PET in cancer detection, three patients with small, solitary, indolent carcinoid tumors had false-negative results. We report a case where 18FDG-PET imaging was false-negative in a patient with known metastatic carcinoid and a positive octreotide scan.