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We developed a clinical score (CS) at Vanderbilt Ingram Cancer Center (VICC) that we hoped would predict outcomes for patients with progressive well-differentiated neuroendocrine tumors (NETs) receiving therapy with Lutetium-177 (177Lu)-DOTATATE. Patients under consideration for 177Lu-DOTATATE between March 1, 2016 and March 17, 2020 at VICC were assigned a CS prospectively. The CS included 5 categories: available treatments for tumor type outside of 177Lu-DOTATATE, prior systemic treatments, patient symptoms, tumor burden in critical organs and presence of peritoneal carcinomatosis. The primary outcome of the analysis was progression-free survival (PFS). To evaluate the effect of the CS on PFS, a multivariable Cox regression analysis was performed adjusting for tumor grade, primary tumor location, and the interaction between 177Lu-DOTATATE doses received (zero, 1–2, 3–4) and CS. A total of 91 patients and 31 patients received 3–4 doses and zero doses of 177Lu-DOTATATE, respectively. On multivariable analysis, in patients treated with 3–4 doses of 177Lu-DOTATATE, for each 1-point increase in CS, the estimated hazard ratio (HR) for PFS was 2.0 (95% CI 1.61–2.48). On multivariable analysis, in patients who received zero doses of 177Lu-DOTATATE, for each 1-point increase in CS, the estimated HR for PFS was 1.22 (95% CI 0.91–1.65). Among patients treated with 3–4 doses of 177Lu-DOTATATE, those with lower CS experienced improved PFS with the treatment compared to patients with higher CS. This PFS difference, based upon CS, was not observed in patients who did not receive 177Lu-DOTATATE, suggesting the predictive utility of the score.

Purpose To measure the SUVs in the tail of the pancreas compared with normal liver parenchyma and somatostatin receptor-positive lesions. Materials and methods Ga-DOTATATE PET/low mAs CT of 35 patients were reviewed. Results There was no significant difference (P = 0.59) between the SUVaverage of normal liver and the SUVpeak of normal tail. Five patients had uptake in the tail slightly above that of normal liver that were interpreted equivocally. In one of these patients with Ga-DOTATATE uptake in a peripancreatic lymph node, proven neuroendocrine tumor underwent a distal pancreatectomy and pathologic examination revealed islet cell hyperplasia. Conclusions Ga-DOTATATE uptake in the tail of the pancreas above that of normal liver indicates a somatostatin receptor-avid lesion. Uptake in the tail of the pancreas equal to the liver can be normal. Patients with uptake equivalent to the liver should undergo further anatomical imaging before procedural intervention.

4109 Background: Questions remain regarding when to sequence PRRT and how to categorize pts being considered for the treatment (tx). We previously developed a CS (comprised of 5 categories: available non-PRRT tx for tumor type, prior systemic tx, pt symptoms, tumor burden in critical organs and peritoneal carcinomatosis presence) at Vanderbilt Ingram Cancer Center (VICC) for pts being considered for PRRT to help answer these questions and demonstrated the score to be associated with progression-free survival (PFS) in pts receiving PRRT. Herein, we present the performance of the CS in a validation cohort (VC) and combined cohort (CC). Methods: Our original cohort (OC) included pts with progressive WD NETs (N = 122) under consideration for PRRT between 3/1/2016-3/17/2020 at VICC while our VC included pts under consideration for PRRT (N = 126) between 1/25/2017-11/18/2019 at Ochsner Medical Center (OMC) (N = 51), Markey Cancer Center (MCC) (N = 51) and Rush Medical Center (RMC) (N = 24). All pts in the OC were prospectively scored while pts in the VC were scored retrospectively, with the CS-assigning investigator blinded to patient outcomes. The primary outcome PFS, was estimated by the Kaplan‐Meier method; a Cox proportional‐hazards model adjusting for primary tumor site, tumor grade and number of PRRT doses administered (0, 1-2 or 3-4) was used to analyze effect of CS. Overall survival (OS) was a key secondary outcome. Results: In our VC, on multivariable (MV) analysis, for each 2-point increase in CS, the hazard ratio (HR) for PFS was 2.58 (95% confidence interval (CI) 1.62-4.11). On MV analysis, for each 2-point increase in CS, the HR for OS was 3.89 (95% CI 1.8-4.83). We combined the OC and VC for this analysis in order to increase the predictive power of our originally developed Cox proportional-hazards models. In our CC, of the 248 total pts, median pt age, CS and number of prior tx were 63.3 years, 4 (range 0-8) and 1 (range 0-7), respectively. The most represented primary tumor sites were small intestinal (N = 136), pancreatic (N = 58), unknown primary (N = 26) and lung (N = 14). A total of 140, 82 and 26 pts received 3-4, 0 or 1-2 doses of PRRT, respectively. On MV analysis, for each 2-point increase in CS, the HR for PFS was 2.52 (95% CI 1.90-3.35). On MV analysis, for each 2-point increase in CS, the HR for OS was 3.48 (95% CI 2.33-5.18). No interaction between PRRT doses administered and CS was observed. Conclusions: Increases in CS were strongly associated with worsening PFS and OS in our VC and CC, validating findings from our OC. Although we cannot determine whether the CS specifically predicts PRRT response or is prognostic based upon these data, it is the first presented clinical metric which can categorize pts with WD NETs under consideration for PRRT and estimate anticipated benefit from PRRT for pts.

363 Background: Despite the benefit of PRRT for patients with WD NETs, questions remain regarding sequencing and optimal patient selection for the treatment. We developed a CS at Vanderbilt Ingram Cancer Center (VICC) that we hoped would predict outcomes for patients with WD NETs receiving PRRT. Methods: Patients with progressive WD NETs (N = 146) under consideration for PRRT with Lu 177-dotatate between 3/1/2016-3/17/2020 at VICC (N = 122) and Rush Medical Center (RMC) (N = 24) were scored. The CS included 5 categories: available non-PRRT treatments for tumor type, prior systemic treatments, patient symptoms, tumor burden in critical organs and peritoneal carcinomatosis presence. All categories were scored from 0-2 except the peritoneal carcinomatosis category which was scored from 0-1; scoring criteria were determined by the VICC NET tumor board. All patients at VICC were prospectively scored, while patients from RMC were scored retrospectively with the investigator blinded to patient outcomes. The primary outcome, progression-free survival (PFS) was estimated by the Kaplan‐Meier method; a Cox proportional‐hazards model adjusting primary tumor site, tumor grade and number of PRRT doses administered (none, 1-2 doses or 3-4 doses) was used to analyze effect of CS. Results: Median patient age was 62.7 while median CS was 5 (range 1-8); the most common primary tumor sites were small intestinal (N = 81) and pancreatic (N = 37). A total of 101 patients and 31 patients received 3-4 doses and no doses of PRRT, respectively. On multivariable analysis, in patients treated with 3-4 doses of PRRT, for each 2-point increase in CS, the estimated hazard ratio (HR) for PFS was 3.26 (95% confidence interval (CI) 2.05-5.19). On multivariable analysis, in patients who received no doses of PRRT, for each 2-point increase in CS, the estimated HR for PFS was 1.37 (95% CI .78-2.41). Conclusions: Among patients treated with 3-4 doses PRRT, those with lower CS had better PFS with the treatment compared to patients with higher CS. This PFS difference, based upon CS, was not observed in patients who did not receive PRRT, suggesting the predictive utility of the CS for patients with WD NETs receiving PRRT with Lu 177-dotatate. Though the CS needs to be validated, it is the first of its kind reported.

Our purpose was to evaluate the safety and efficacy of (68)Ga-DOTATATE PET/CT compared with (111)In-pentetreotide imaging for diagnosis, staging, and restaging of pulmonary and gastroenteropancreatic neuroendocrine tumors.(68)Ga-DOTATATE PET/CT and (111)In-pentetreotide scans were obtained for 78 of 97 consecutively enrolled patients with known or suspected pulmonary or gastroenteropancreatic neuroendocrine tumors. Safety and toxicity were measured by comparing vital signs, serum chemistry values, or acquisition-related medical complications before and after (68)Ga-DOTATATE injection. Added value was determined by changes in treatment plan when (68)Ga-DOTATATE PET/CT results were added to all prior imaging, including (111)In-pentetreotide. Interobserver reproducibility of (68)Ga-DOTATATE PET/CT scan interpretation was measured between blinded and nonblinded interpreters.(68)Ga-DOTATATE PET/CT and (111)In-pentetreotide scans were significantly different in impact on treatment (P0.001). (68)Ga-DOTATATE PET/CT combined with CT or liver MRI changed care in 28 of 78 (36%) patients. Interobserver agreement between blinded and nonblinded interpreters was high. No participant had a trial-related event requiring treatment. Mild, transient events were tachycardia in 1, alanine transaminase elevation in 1, and hyperglycemia in 2 participants. No clinically significant arrhythmias occurred. (68)Ga-DOTATATE PET/CT correctly identified 3 patients for peptide-receptor radiotherapy incorrectly classified by (111)In-pentetreotide.(68)Ga-DOTATATE PET/CT was equivalent or superior to (111)In-pentetreotide imaging in all 78 patients. No adverse events requiring treatment were observed. (68)Ga-DOTATATE PET/CT changed treatment in 36% of participants. Given the lack of significant toxicity, lower radiation exposure, and improved accuracy compared with (111)In-pentetreotide, (68)Ga-DOTATATE imaging should be used instead of (111)In-pentetreotide imaging where available.

Objectives: We examined Ki-67 heterogeneity within single and between synchronous liver metastases of small intestine neuroendocrine tumors. Methods: There were 27 patients (10 men and 17 women) with two or more liver metastases. The Ki-67 index was used to classify the tumors into World Health Organization grade 1, 2, or 3. The association between Ki-67 heterogeneity and tumor size of liver metastases was analyzed. Correlation of tumor grade with patient survival was also evaluated. Results: Primary tumors from 20 patients were graded, including 17 grade 1 and three grade 2. A total of 188 liver metastases were resected, including 122 (65%) grade 1, 47 (25%) grade 2, and 19 (10%) grade 3. The highest tumor grade was grade 1 in 10 (37%), grade 2 in nine (33%), and grade 3 in eight (30%) patients. Patients with one or more grade 3 liver lesions had a shorter progression-free survival compared with those with grade 1/2 tumors ( P < .001). A positive association was found between tumor size and Ki-67 index ( P = .04), as well as between tumor size and intratumoral Ki-67 heterogeneity ( P < .001). Conclusions: Intratumoral and intertumoral Ki-67 heterogeneity is common and positively correlated with tumor size. The presence of one or more grade 3 liver lesions predicts a worse prognosis.

A 39-year-old man presented with new onset of sinus congestion, shortness of breath, and diaphoresis. His laboratory tests were notable for hypercalcemia and lactic acidosis. A CT scan of the head demonstrated mild paranasal disease. CT scan of the chest, abdomen, and pelvis demonstrated omental caking with lymphadenopathy and a thickened loop of bowel in the left upper quadrant suggestive of lymphoma. All abdominal lesions seen in the CT were intensely F-FDG avid with diffuse uptake in the bone marrow. There was markedly decreased F-FDG uptake in both the brain and liver. Histopathology was positive for Burkitt lymphoma.

This study described and validated a new solid-state single-photon γ-camera and compared it with a conventional-SPECT Anger camera. The compact new camera uses a unique method for localizing γ-photon information with a bank of 9 solid-state detector columns with tungsten collimators that rotate independently. Methods: Several phantom studies were performed comparing the new technology with conventional-SPECT technology. These included measurements of line sources and single- and dual-radionuclide studies of a torso phantom. Simulations were also performed using a cardiothoracic phantom. Furthermore, 18 patients were scanned with both the new camera and a conventional-SPECT camera. Results: The new camera had a count sensitivity that was 10 times higher than that of the conventional camera and a compensated spatial resolution that was moderately better. Dual-radionuclide studies using a phantom show the further potential of the new camera for a 2-tracer simultaneous acquisition. Two-minute clinical studies with the new camera and 11-min studies with the conventional camera qualitatively showed good-to-excellent image quality and improved myocardial edge definition for the new camera. Conclusion: These initial performance characteristics of a new solid-state single-photon γ-camera offer great promise for clinical dynamic SPECT protocols, with important implications for applications in nuclear cardiology and molecular imaging.

Objectives: The purpose of this work was done to evaluate the value of including the brain in the field of view of a whole-body 2-deoxy-2-[ 18 F] fluoro-D-glucose positron emission tomography (FDG-PET) study of patients referred for the evaluation of body malignancies. Methods: A total of 1026 consecutive patients were included in this work. The primary diagnoses were the following: lung (n = 253), colorectal (n = 148), head and neck (n = 61), lymphoma (n = 249), melanoma (n = 84), and others (n = 231). Whole-body FDG images including the brain were acquired with a dedicated PET tomograph (GE advance, General Electronic Medical Systems, Milwaukee, WI) one hour after the intravenous administration of 10 mCi of FDG. Two experienced nuclear medicine physicians interpreted the images. Positive findings in the brain or the skull were correlated with other imaging studies and clinical follow-up. Results: Abnormal findings were detected in 3.9% (40/1026) of the patients. Among the 40 abnormal focal lesions, 29 patients had a known history of cerebral disease, cerebrovascular or metastatic disease in most patients. Of the 11 patients without a prior history of cerebral disease, four patients had increased focal FDG uptake suggestive of metastases. Among these, two were proven clinically, one was proven to be a skull base metastasis on MRI, and the other had negative clinical follow-up, but only of two months duration. The other seven patients had a decreased focal FDG uptake most consistent with infarct, one was proven clinically, and the other six had a negative clinical follow-up (mean of 6.3 months, range 1–10), but had multiple risk factors for cerebrovascular disease. Conclusions: We conclude that FDG-PET screening for cerebral lesions in patients with body malignancy has little clinical impact. Unsuspected cerebral or skull metastases were detected in 0.4% (4/1026) of the patients. (Mol Imag Biol 2002;4:359–362)

Purpose : To demonstrate the feasibility of incorporating gamma camera-based positron emission tomography (GC-PET) nuclear medicine molecular imaging into inverse conformal radiotherapy treatment planning using commercially available hardware and software. Materials and methods : Anatomical X-ray computed tomography (X-ray CT) and GC-PET imaging of the base of the tongue region were performed on a hybrid nuclear medicine—X-ray CT scanner (General Electric Millennium VG Hawkeye, Milwaukee, WI). Patient positioning included a carbon composite flat-table insert and Aquaplast™ U-frame head immobilization mask. Both anatomical and molecular images were acquired and then transferred to the treatment planning and dose calculation workstations via a Local Area Network (LAN). GC-PET molecular information was registered with the anatomy using a four-point external registration technique. A five-field conformal inverse treatment plan, which targets radiation dose to the GC-PET-defined lesion, was then developed using the Varian SomaVision™, CadPlan™ and Helios™ treatment planning modules. Results : The radiation dose distribution was made to conform to the tumor region, as indicated by the area of increased flouro-2-deoxyglucose (FDG) uptake in the GC-PET image, using the inverse treatment planning technique. Conclusions : Information from molecular imaging techniques such as GC-PET may be incorporated into the inverse treatment planning process using the combined molecular and anatomical imaging methods, and commercially available hardware and software.

The rapid advances in imaging technologies are a challenge for nuclear medicine physicians, radiologists, and clinicians who must integrate these technologies for optimal patient care and outcome at minimal cost. Multiple indications for functional imaging using F-18-fluorodeoxyglucose (FDG) are now well accepted in the field of oncology, including differentiation of benign from malignant lesions, staging malignant lesions, detection of malignant recurrence, and monitoring therapy. The use of FDG imaging was first shown using dedicated positron emission tomography (PET) with multiple full rings of bismuth germanate detectors. Most manufacturers now have available hybrid gamma cameras capable of imaging conventional single-photon emitters, as well as positron emitters such as FDG. This new technology was developed to make FDG imaging more widely accessible, first using single photon emission computed tomography (SPECT) with high-energy collimators, and then using dualhead coincidence (DHC) detection with multihead gamma cameras that improved spatial resolution. Most hybrid gamma cameras are now equipped with thicker NaI(TI) crystals to improve sensitivity. Technical developments are still evolving with correction for attenuation and new iterative reconstruction algorithms to improve the quality of the images. Users need to be familiar with the rapid developments of the technology as well as its limitations. Currently, one model of hybrid gamma camera is equipped with an integrated x-ray transmission system for attenuation correction, anatomic mapping, and image fusion. This powerful tool has promising clinical applications including intensity-modulated radiation therapy.

Study objective The purpose of this study was to evaluate the accuracy of positron emission tomography (PET) using F-18-fluorodeoxyglucose (FDG) in differentiating benign from malignant pulmonary lesions both in patients with and without a history of prior malignancy. Design Forty-eight consecutive patients with pulmonary lesions suspicious for malignancy underwent FDG-PET scanning. Group 1 included 27 patients without and group 2 included 21 patients with a history of malignancy. Pathologic proof of diagnosis was obtained for 32 patients and 16 patients were followed up clinically and radiographically for at least 6 months. The standard uptake ratio (SUR) and the lesion to background (L/B) ratio were determined in 45 patients. Setting Vanderbilt University Medical Center. Results In group 1, the average SUR and L/B ratio for malignant lesions (n=14) were 8.9 ±4.9 and 20.6 ± 14.2, respectively. For benign lesions (n=12), the average SUR was 3.3±3.2 and L/B ratio was 5.2±5.5. In group 2, the average SUR and L/B ratio for malignant lesions were not significantly different from group 1. Using either a SUR greater than 2.5 or L/B ratio greater than 5 as an cutoff level to differentiate benign and malignant lesions, the sensitivity and negative predictive value in both groups were 100%. There were five false-positive studies in group 1 and one in group 2, including tuberculosis (n=2), a granulomatous lesion (n=l), an inflammatory lesion (n=l), a schwannoma (n=l), and a fibrous mesothelioma (n=l). The overall accuracy was 88%, 81% in group 1, and 95% in group 2. Conclusion FDG-PET can identify malignant pulmonary lesions both in patients without and with a history of prior malignancy with a high sensitivity and negative predictive value for lesions greater than 1 cm (100% in this study). High FDG uptake by some inflammatory processes and benign tumors may cause false-positive results. Semiquantitative evaluation using SUR or L/B ratio provides similar accuracy.

Background Accurate detection of recurrent colorectal carcinoma remains a clinical challenge. Positron emission tomography (PET) using 18 F-fluorodeoxyglucose ( 18 FDG) is an imaging technique that allows direct evaluation of cellular metabolism. 18 F-fluorodeoxyglucose PET was compared to computed tomography (CT) and CT portography for staging metastatic colorectal carcinoma. Patients and methods Twenty-four patients previously treated for colorectal carcinoma who had suspected recurrence to the liver underwent an 18 FDG PET scan of the entire body. All patients had either a CT scan of the abdomen (n = 17), a CT portogram (n = 18), or both (n = 11). The final diagnosis was obtained by tissue pathology in 19 patients and clinical follow-up in 5 patients. Results A total of 60 suspicious lesions were identified. Of the 55 intrahepatic lesions, 39 were malignant and 16 were benign. Of the 5 extrahepatic lesions, 4 were malignant. The 18 FDG PET imaging had a higher accuracy (93%) than CT and CT portography (both 76%) in detecting metastatic disease to the liver, and detected unsuspected extrahepatic recurrence in 4 patients. Although the sensitivity of 18 FDG PET (90%) was slightly lower than that of CT portography (97%), the specificity was much higher (100% versus 9%), including postsurgical sites. 18 FDG PET altered surgical plans in 6 (25%) of 24 patients. Conclusions 18 FDG PET is extremely useful in staging patients with suspected metastatic colorectal carcinoma to the liver.

Compared with other imaging modalities and clinical investigation, the 111In-pentetreotide scan identified additional metastatic disease sites in 12 carcinoid patients and 2 occult primaries, and influenced the therapeutic outcome in 36 patients [29 carcinoids, 2 atypical carcinoids, 3 cancers of unknown primaries (CUPs) and 2 medullary thyroid carcinomas (MCTs)]. No adverse reactions were noted. Somatostatin receptors were detected in 59/60 carcinoid patients, 3/4 atypical carcinoid patients, 0/2 MCT patients, and 0/3 cases of CUP. Somatostatin receptor presence is underestimated in some patients using standard hormonal response criteria rather than scintigraphy. 18 patients with metastatic carcinoids who underwent 111In-pentetreotide scanning were all somatostatin receptor positive. Their mean (+/- SE) 5-hydroxyindoleacetic acid (5-HIAA) suppression with octreotide therapy was -53% (+/- 6%). 8 patients had50% and 10 had50% 5-HIAA suppression (ranges: -4 to -47% and -58 to -94%, respectively). To investigate the effect of somatostatin analogues on survival, 90 consecutive cases of carcinoid syndrome patients treated during the somatostatin analogue era were reviewed. Survival according to primary site was 12.01, 18.29 and 6.05 years (overall median 12.01 years) for patients with foregut, midgut and unknown primaries, respectively. The difference from historical controls is substantial (67 vs. 18% 5-year survival), although our series is neither prospective nor randomised. The heterogeneity in patient and tumour response to somatostatin analogue therapy is discussed.

Objectives.This study sought to develop a dual-isotope single-acquisition single-photon emission computed tomographic (SPECT) protocol using a multihead SPECT camera equipped with an ultra-high energy collimator to evaluate rest metabolism/stress perfusion simultaneously with fluorine-18 (F-18) deoxyglucose/technetium-99m (Tc-99m) 2-hexakis-2-methoxy-2-methylpropyl isonitrile (MIBI).Background.The most accurate and logistic method of identifying injured but viable myocardium remains a diagnostic challenge.Methods.Sixty-five patients were given 25 to 50 g of glucose and, after ∼60 min, an injection of 370 MBq (10 mCi) of F-18 fluorodeoxyglucose. After a 35-min distribution phase, patients underwent exercise or pharmacologic stress followed by administration of 925 MBq (25 mCi) of Tc-99m MIBI. Five patients underwent F-18 fluorodeoxyglucose positron emission tomography before dualisotope SPECT.Results.With a window of 20% for both photopeaks and a technetium-99m/fluorine-18 concentration of 3.2: 1, the “spillover” from fluorine-18 into the technetium-99m window is 70% was used as the criterion for a diagnosis of coronary artery disease, dual-isotope SPECT had a sensitivity of 100%, specificity of 88%, positive predictive value of 93%, negative predictive value of 100% and an accuracy of 96%.Conclusions.Dual-isotope SPECT may provide an alternative, accurate, cost-effective method to nitrogen-13 ammonia/F-18 fluorodeoxyglucose positron emission tomography or thallium-201 reinjection for identifying injured or dysfunctional but viable myocardium.

Carney's triad, a rare disorder affecting young females, is characterized by the presence of at least two of the three following neoplasms: gastric epithelioid leiomyosarcoma, extra-adrenal paraganglioma, and pulmonary chondroma. Diagnosis and follow-up evaluation of cases of Carney's triad may require an approach that uses a combination of modalities, including magnetic resonance imaging (MRI), metaiodobenzyl-guanidine (MIBG) I 131 scintigraphy, and computed tomography. MRI is as effective as MIBG scintigraphy in detecting functioning paragangliomas. In the evaluation of suspected cases of Carney's triad in which there is clinical and biochemical evidence of a paraganglioma, MRI is the modality of choice for screening and follow-up. We report a case of gastric leiomyosarcoma and extra-adrenal paraganglioma in a young woman whose initial presentation was at 7 years of age. To our knowledge, this is the earliest presentation of this disorder.

We have shown that positron emission scintigraphy detects changes in the uptake of 18-F 2-deoxyglucose and 13-N ammonia by the acutely rejecting myocardium in a nonworking model of heterotopic heart transplantation in the rat. We developed a new working model of heterotopic heart transplantation to determine the possible relevance of these changes to clinical transplantation. Moderate aortic valvular regurgitation was produced allowing the heterotopic left ventricle to fill and eject. Rejecting allografts and nonrejecting isografts (controls) were studied 4 days after transplantation. Histologically, isografts were normal and all allografts showed mild acute rejection. Decay-corrected uptakes of 18-F 2-deoxyglucose and 13-N ammonia reflect glucose metabolism and blood flow, respectively. Values are presented as percent of injected dose per gram of tissue. Uptake of 18-F 2-deoxyglucose was higher in rejecting allografts compared with nonrejecting isografts (3.0 +/- 1.8 versus 1.1 +/- 0.4; p = 0.024). Ammonia uptake was elevated in allografts compared with isografts (2.2 +/- 0.5 versus 1.3 +/- 0.5; p = 0.023). Uptakes of 18-F 2-deoxyglucose and 13-N ammonia are higher in mildly rejecting allografts, implying increased glucose utilization and blood flow during acute rejection. These data support our earlier findings of changes in myocardial metabolism in the absence of diminishing blood flow in acutely rejecting hearts. This model may lead to a better understanding of the physiology and metabolism of acute rejection.

Thyroid imaging has evolved from early radionuclide rectilinear thyroid scanning to the recently developed technique of single photon emission computed tomography. At the same time, x-ray fluorescent scanning, ultrasound, computed tomography, magnetic resonance imaging, and positron emission tomography have improved identification of the thyroid gland. The appropriate use and relative roles of these imaging modalities in the investigation of patients with thyroid disease are discussed.

Positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG) has been used to evaluate cardiac glucose utilization in different cardiac diseases, including hypertrophic cardiomyopathy, acute ischemic syndromes (infarction and unstable angina), and chronic ischemic left ventricular (LV) dysfunction. Most studies have evaluated patients with ischemic cardiomyopathy with the aim of assessing myocardial viability. Currently, the only clinically accepted application of cardiac FDG imaging is the assessment of viability in this subset of patients. Using FDG imaging for the assessment of viability makes prediction of improvement of LV function, heart failure symptoms, and long-term prognosis after revascularization possible. In the 1980s, FDG imaging could only be performed with PET equipment, but with the introduction of 511 keV collimators in the 1990s, FDG imaging is now feasible with single photon emission computed tomography (SPECT).

The thyroid is a bilobed structure evolving from the fourth and fifth branchial pouches. It is initially attached to the ventral floor of the pharynx by the thyroglossal duct. Thyroid tissue may be found anywhere between the base of the tongue and the retrosternal anterior mediastinum (Figure 13.1). The fetal thyroid gland begins to concentrate iodine and synthesize thyroid hormones by approximately 10.5 weeks, which is pertinent when the administration of 131I to fertile women is contemplated. The two ellipsoid lobes of the adult thyroid are joined by a thin isthmus. Each lobe is approximately 2 cm in thickness and width and averages 4–4.5 cm in length. The thyroid gland, averaging approximately 20 grams in weight, resides in theneck at the level of the cricoid cartilage. A pyramidal lobe is present in approximately 30–50%, arising from either the isthmus or the superomedial aspect of either lobe; it undergoes progressive atrophy in adulthood but may be prominent in patients with Graves’ disease. Although the right lobe tends to be somewhat larger than the left lobe, there is a great deal of variability in both size and shape of the normal gland. 13.1.2 Physiology

The purpose of the study was to determine the diagnostic impact of 131I-SPECT/CT imaging compared with conventional scintigraphic evaluation in the follow-up of patients with thyroid carcinoma. Seventy-one patients with thyroid carcinoma underwent concurrent 131I-SPECT/CT, using an integrated imaging system, at various stages of their disease in order to evaluate foci of uptake detected on planar whole-body images. SPECT/CT imaging had an incremental diagnostic value in 57% (41/71) of patients. Uptake in the neck was evaluated in 61 patients, and SPECT/CT imaging in this region had an incremental diagnostic value in 27% of the whole patient population (19/71). Low-resolution integrated CT images allowed for the precise characterization of equivocal neck lesions on planar imaging in 14/17 patients and changed the assessment of the lesion location in five patients as compared with planar studies. Thirty-six patients underwent SPECT/CT for evaluation of foci of uptake distant from the neck. SPECT/CT imaging improved characterization of equivocal foci of uptake as definitely benign in 13% (9/71) of patients. Precise localization of malignant lesions to the skeleton was possible in 17% (12/71) and to the lungs versus the mediastinum in 6% (5/71) of patients. Integrated 131I-SPECT/CT was found to have an additional value over planar imaging in patients with thyroid cancer for correct characterization of equivocal tracer uptake seen on planar imaging as well as for precise localization of malignant lesions in the neck, chest, and skeleton. SPECT/CT optimized the localization of 131I uptake to lymph node metastases versus remnant thyroid tissue, to lung versus mediastinal metastases, and to the skeleton. It also had a further clinical impact on patient management by influencing referral for 131I treatment, tailoring of the administered radioiodine dose, and/or the addition of surgery or external radiation therapy when indicated.

1. History of Instrument Development.- 2. Physics of Positron Imaging.- 3. FDG Production and Distribution.- 4. Clinical Applications for the Central Nervous System.- 5. Cardiac Applications for FDG Imaging with PET and SPECT.- 6. Clinical Applications in Oncology: 6.1. Normal Distribution of FDG. 6.2. Head and Neck Carcinoma. 6.3. Lung Carcinoma. 6.4. Breast Carcinoma. 6.5. Colorectal Carcinoma. 6.6. Other Gastrointestinal Tumors. 6.7. Genitourinary Tumors. 6.8. Lymphoma and Hodgkin's Disease. 6.9. Melanoma. 6.10. Miscellaneous.

Doses of radiation from medical imaging procedures including fluoroscopy, computed tomography (CT), and nuclear medicine procedures can be substantial in certain groups of patients for whom the likelihood of repetitive studies is high. Today, there is increasing concern that multiple imaging

To compare lesion detectability on 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomographic (PET) images obtained with a dual-head coincidence (DHC) gamma camera equipped with an integrated x-ray tube-based transmission system (a) with images reconstructed with filtered back projection (FBP) and those reconstructed with an iterative reconstruction algorithm based on coincidence-ordered subsets expectation maximization (COSEM), (b) with images reconstructed without and with attenuation correction (AC), and (c) with images reconstructed without and with image fusion for anatomic mapping.Thirty-five patients known or suspected to have malignancy underwent initial imaging with a dedicated positron emission tomography (PET) unit after injection of 10 mCi (370 MBq) of FDG. Transmission computed tomographic (CT) scans and FDG emission images were then obtained with the DHC camera. The proportion of lesions detected on the various sets of FDG DHC images was determined by using FDG PET as the standard of reference. Imaging findings were correlated with those from histologic examination and clinical follow-up, in consultation with the respective referring physicians.FDG PET depicted 78 lesions, 29 of which were equal to or less than 1.5 cm in diameter. FDG DHC depicted 52 of the 78 (67%), 59 of 78 (76%), and 61 of the 78 (78%) lesions, respectively, when image reconstruction was performed with FBP without AC, COSEM without AC, and both COSEM and AC. The detection rate of lesions 1.5 cm or smaller was better with COSEM and AC than with FBP (55% vs 34%, respectively). In addition, COSEM and AC allowed more confidence in the interpretation. None of these differences, however, were significant. Fusion of CT scans and FDG DHC images obtained with COSEM and AC allowed localization of lesions to the skeleton in three patients and to the liver versus adjacent bowel in three patients. Image fusion was especially helpful for localizing lesions in the neck in five patients. Anatomic mapping on fusion images was clinically relevant in 11 patients (31%).The COSEM reconstruction algorithm should replace FBP when available. Functional anatomic mapping improved lesion localization in one-third of the patients studied.

Shankar Vallabhajosula Berlin, Germany: Springer-Verlag, 2009, 371 pages, $179 Molecular Imaging: Radiopharmaceuticals for PET and SPECT is a well-written compendium of chapters that cover a wide range of topics regarding the use of radiopharmaceuticals in SPECT and PET. Dr. Vallabhajosula has

The assessment of myocardial viability has become an important aspect of the diagnostic and prognostic work-up of patients with ischemic cardiomyopathy. Although revascularization may be considered in patients with extensive viable myocardium, patients with predominantly scar tissue should be treated medically or evaluated for heart transplantation. Among the many viability tests, noninvasive assessment of cardiac glucose use (as a marker of viable tissue) with F18-fluorodeoxyglucose (FDG) is considered the most accurate technique to detect viable myocardium. Cardiac FDG uptake has traditionally been imaged with positron emission tomography (PET). Clinical studies have shown that FDG-PET can accurately identify patients with viable myocardium that are likely to benefit from revascularization procedures, in terms of improvement of left ventricular (LV) function, alleviation of heart failure symptoms, and improvement of long-term prognosis. However, the restricted availability of PET equipment cannot meet the increasing demand for viability studies. As a consequence, much effort has been invested over the past years in the development of 511-keV collimators, enabling FDG imaging with single-photon emission computed tomography (SPECT). Because SPECT cameras are widely available, this approach may allow a more widespread use of FDG for the assessment of myocardial viability. Initial studies have directly compared FDG-SPECT with FDG-PET and consistently reported a good agreement for the assessment of myocardial viability between these 2 techniques. Additional studies have shown that FDG-SPECT can also predict improvement of LV function and heart failure symptoms after revascularization. Finally, recent developments, including coincidence imaging and attenuation correction, may further optimize cardiac FDG imaging (for the assessment of viability) without PET systems.

Objective To assess the accuracy and clinical impact of 18 fluorodeoxy-glucose-positron emission tomography ( 18 FDG-PET) on the management of patients with suspected primary or recurrent pancreatic adenocarcinoma, and to assess the utility of 18 FDG-PET in grading tumor response to neoadjuvant chemoradiation. Background Data The diagnosis, staging, and treatment of pancreatic cancer remain difficult. Small primary tumors and hepatic metastases are often not well visualized by computed tomographic scanning (CT), resulting in a high incidence of nontherapeutic celiotomy and the frequent need for blind resection. In addition, the distinction between local recurrence and nonspecific postoperative changes after resection can be difficult to ascertain on standard anatomic imaging. 18 FDG-PET is a new imaging technique that takes advantage of increased glucose metabolism by tumor cells and may improve the diagnostic accuracy of preoperative studies for pancreatic adenocarcinoma. Methods Eighty-one 18 FDG-PET scans were obtained in 70 patients undergoing evaluation for suspected primary or recurrent pancreatic adenocarcinoma. Of this group, 65 underwent evaluation for suspected primary pancreatic cancer. Nine patients underwent 18 FDG-PET imaging before and after neoadjuvant chemoradiation, and in eight patients 18 FDG-PET scans were performed for possible recurrent adenocarcinoma after resection. The 18 FDG-PET images were analyzed visually and semiquantitatively using the standard uptake ratio (SUR). The sensitivity and specificity of 18 FDG-PET and CT were determined for evaluation of the preoperative diagnosis of primary pancreatic carcinoma, and the impact of 18 FDG-PET on patient management was retrospectively assessed. Results Among the 65 patients evaluated for primary tumor, 52 had proven pancreatic adenocarcinoma and 13 had benign lesions. 18 FDG-PET had a higher sensitivity and specificity than CT in correctly diagnosing pancreatic carcinoma (92% and 85% vs. 65% and 62%). Eighteen patients (28%) had indeterminate or unrecognized pancreatic masses on CT clarified with 18 FDG-PET. Seven patients (11%) had indeterminate or unrecognized metastatic disease clarified with 18 FDG-PET. Overall, 18 FDG-PET suggested potential alterations in clinical management in 28/65 patients (43%) with suspected primary pancreatic adenocarcinoma. Of the nine patients undergoing 18 FDG-PET imaging before and after neoadjuvant chemoradiation, four had evidence of tumor regression by PET, three showed stable disease, and two showed tumor progression. CT was unable to detect any response to neoadjuvant therapy in this group. Eight patients had 18 FDG-PET scans to evaluate suspected recurrent disease after resection. Four were noted to have new regions of 18 FDG-uptake in the resection bed; four had evidence of new hepatic metastases. All proved to have metastatic pancreatic adenocarcinoma. Conclusions These data confirm that 18 FDG-PET is useful in the evaluation of patients with suspected primary or recurrent pancreatic carcinoma, 18 FDG-PET is more sensitive and specific than CT in the detection of small primary tumors and in the clarification of hepatic and distant metastases. 18 FDG-PET was also of benefit in assessing response to neoadjuvant chemoradiation. Although 18 FDG-PET cannot replace CT in defining local tumor resectability, the application of 18 FDG-PET in addition to CT may alter clinical management in a significant fraction of patients with suspected pancreatic cancer.

The purpose of this study was to compare the diagnostic accuracy of fluorine-18 fluorodeoxyglucose (FDG) images obtained with (a) a dual-head coincidence gamma camera (DHC) equipped with 5/8-inch-thick NaI(Tl) crystals and parallel slit collimators and (b) a dedicated positron emission tomograph (PET) in a series of 28 patients with known or suspected malignancies. Twenty-eight patients with known or suspected malignancies underwent whole-body FDG PET imaging (Siemens, ECAT 933) after injection of approximately 10 mCi of 18F-FDG. FDG DHC images were then acquired for 30 min over the regions of interest using a dual-head gamma camera (VariCam, Elscint). The images were reconstructed in the normal mode, using photopeak/photopeak, photopeak/Compton, and Compton/photopeak coincidence events. FDG PET imaging found 45 lesions ranging in size from 1 cm to 7 cm in 28 patients. FDG DHC imaging detected 35/45 (78%) of these lesions. Among the ten lesions not seen with FDG DHC imaging, eight were less than 1.5 cm in size, and two were located centrally within the abdomen suffering from marked attenuation effects. The lesions were classified into three categories: thorax (n=24), liver (n=12), and extrahepatic abdominal (n=9). FDG DHC imaging identified 100% of lesions above 1.5 cm in the thorax group and 78% of those below 1.5 cm, for an overall total of 83%. FDG DHC imaging identified 100% of lesions above 1.5 cm, in the liver and 43% of lesions below 1.5 cm, for an overall total of 67%. FDG DHC imaging identified 78% of lesions above 1.5 cm in the extrahepatic abdominal group. There were no lesions below 1.5 cm in this group. FDG coincidence imaging using a dual-head gamma camera detected 90% of lesions greater than 1.5 cm. These data suggest that DHC imaging can be used clinically in well-defined diagnostic situations to differentiate benign from malignant lesions.

IanBoiskin,1 Martin P.SandIer,1 Arthur C.Fleischer,1 andWilliam A.NylanderThenumber ofpancreas transplantations performed inselected patients withseverediabetes mellitushasincreasedinrecent years.Technical complications aftersurgery arerelativelycommon andremainamajorobstacle tothesuccessoftheprocedure. According toHantoandSutherland [1],acutevenousthrombosis isthesecondmostcommon causeofgraftlossandusuallyoccurs inthefirstweekaftertrans-plantation. Successful thrombectomy hasnotbeenaccom-plished inanypatient; infarction occurs immediately afterthrombosis, andthediagnosis isnotmadeearlyenough toallowrevascularization.Perfusion scintigraphy isasensitive, albeitnonspecific in-dicatorofabnormal perfusion inthetransplanted organ[2].Ifthegraftisnotvisualized, arteriography isnecessary andistheprocedure ofchoiceforfurtherevaluation. Theabsenceofbloodflowisthought tosignifyvascular thrombosis andwarrants theremoval oftheallograft [i].Inarecentcase[3]inwhichduplex Doppler sonographywasusedincorrelation withtheradionuclide perfusion study,earlydiagnosis ofallograft renalveinthrombosis wasre-ported. Surgical correction wasdoneimmediately, andthetransplanted kidneywassalvaged.Wedescribe acaseinwhich,usingthesametwoproce-dures, wediagnosed anacute venous thrombosis inanallograft pancreas transplant.

Background In most malignant cells, the relatively low level of glucose-6-phosphatase leads to accumulation and trapping of [18F]fluorodeoxyglucose (FDG) intracellularly, allowing the visualization of increased uptake compared with normal cells. Objectives To assess the value of FDG positron emission tomography (PET) to differentiate benign from malignant hepatic lesions and to determine in which types of hepatic tumors PET can help evaluate stage, monitor response to therapy, and detect recurrence. Design Prospective blinded-comparison clinical cohort study. Setting Tertiary care university hospital and clinic. Patients One hundred ten consecutive referred patients with hepatic lesions 1 cm or larger on screening computed tomographic (CT) images who were seen for evaluation and potential resection underwent PET imaging. There were 60 men and 50 women with a mean (±SD) age of 59 ± 14 years. Follow-up was 100%. Interventions A PET scan using static imaging was performed on all patients. The PET scan imaging and biopsy, surgery, or both were performed, providing pathological samples within 2 months of PET imaging. All PET images were correlated with CT scan to localize the lesion. However, PET investigators were unaware of any previous interpretation of the CT scan. Main Outcome Measures Visual interpretation, lesion-to-normal liver background (L/B) ratio of radioactivity, and standard uptake value (SUV) were correlated with pathological diagnosis. Results All (100%) liver metastases from adenocarcinoma and sarcoma primaries in 66 patients and all cholangiocarcinomas in 8 patients had increased uptake values, L/B ratios greater than 2, and an SUV greater than 3.5. Hepatocellular carcinoma had increased FDG uptake in 16 of 23 patients and poor uptake in 7 patients. All benign hepatic lesions (n = 23), including adenoma and fibronodular hyperplasia, had poor uptake, an L/B ratio of less than 2, and an SUV less than 3.5, except for 1 of 3 abscesses that had definite uptake. Conclusions The PET technique using FDG static imaging was useful to differentiate malignant from benign lesions in the liver. Limitations include false-positive results in a minority of abscesses and false-negative results in a minority of hepatocellular carcinoma. The PET technique was useful in tumor staging and detection of recurrence, as well as monitoring response to therapy for all adenocarcinomas and sarcomas and most hepatocellular carcinomas. Therefore, pretherapy PET imaging is recommended to help assess new hepatic lesions.

The myocardial uptake of fluorine-18 fluorodeoxyglucose (FDG) has emerged as the most sensitive and specific technique for the assessment of myocardial viability. With the development of FDG single-photon emission tomography (SPET) and dual head coincidence imaging, a hindrance to the widespread clinical use of FDG cardiac imaging is the complexity of the preinjection glucose loading necessary for obtaining interpretable myocardial FDG scans. In a population of 209 patients undergoing dual-isotope single acquisition (DISA) FDG/sestamibi (MIBI) SPET, we describe the improvements in both image quality and time efficiency using a new short, simple glucose/insulin/potassium (GIK) infusion protocol prior to FDG injection as compared to a conventional oral glucose loading protocol. DISA FDG/MIBI SPET scans were performed in 111 nondiabetic patients after oral loading with 50 g of glucose (group 1). Ninety-eight consecutive nondiabetic patients were subsequently scanned following preparation with a fixed-concentration GIK infusion administered at a standardized rate (group 2). A three-point grading scale was used to assess image quality. The time to FDG injection following glucose administration was significantly shorter for the group 2 patients (39.9+/-15.6 min; range 20-105 min) than for the group 1 patients (99.5+/-30.3 min; range 56-270 min) (P0.0001), representing a 1-h decrease in patient preparation time. More of the group 1 patients (n=30; 27%) required supplemental intravenous boluses of regular insulin than did the group 2 patients (n=13; 13%) (P0.02). There were more excellent and good quality graded images using the GIK method (group 2) than the more traditional oral loading protocol (group 1) (P0.02). Nine of 111 scans (8%) in group 1 were uninterpretable, whereas only one of 98 scans (1%) in group 2 was uninterpretable. Standardized infusion of a fixed concentration of GIK prior to FDG administration and continued during myocardial FDG uptake is an effective yet simple method of obtaining consistently good to excellent quality FDG SPET cardiac scans. It is preferable to conventional oral glucose loading due to decreased patient preparation time and improved image quality. The technique is safe and should improve both the clinical use and the cost-effectiveness of FDG SPET imaging for the identification of injured but viable myocardium.

A dual-head scintillation camera has been adapted for high-energy (511-keV) imaging by extending the useful energy range and linearity maps to 560 keV, implementing high-energy sensitivity maps, and developing high-energy collimators. High-energy parallel-hole collimators have inferior spatial resolution and sensitivity relative to the low-energy, high-resolution collimators commonly in use. With high-energy parallel-hole collimators, phantom studies show that the limit for detectability of "hot" lesions is 1.5 cm and 1.3 cm in diameter or larger for 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) uptake ratios of 5:1 and 10:1, respectively, if one assumes adequate counting statistics. Dual-isotope, single-acquisition techniques for using technetium-99m methoxy isobutyl isonitrile and FDG have been developed and proved useful in identification of ischemic but viable myocardium. High-energy fan-beam collimators have superior spatial resolution but inferior sensitivity relative to low-energy, high-resolution collimators. Metabolic images of the brain obtained with FDG demonstrate spatial resolution comparable with that of positron emission tomography, but such studies are often limited by inadequate counting statistics.

The identification of hibernating myocardium in patients with poor ventricular function has become increasingly important as investigators demonstrate an improvement in ventricular performance in patients with injured but viable myocardium who undergo surgical revascularization. Modifications of 201Tl redistribution protocols and rest/stress 99mTc-labeled hexakis-2-methoxy-2-methyl propylisonitrile perfusion studies continue to underestimate myocardial viability compared with resting 18F-labeled fluorodeoxyglucose (18FDG) positron emission tomography. The combined data from multiple investigators suggest that 18FDG single-photon emission computed tomography used in combination with cardiac perfusion agents, either sequentially or with simultaneous dual-isotope acquisition, may provide an acceptable alternative to positron emission tomographic imaging for the detection of hibernating myocardium.

To compare single photon emission computed tomography (SPECT) with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) and positron emission tomography (PET) with FDG to evaluate malignancies.PET and SPECT, with fluorine-18 sodium fluoride, were performed sequentially in a cylindric phantom that contained different size spheres with activity ratios of 5:1, 10:1, and 15:1. PET and SPECT were also performed in 24 patients with known or suspected malignancies.Sensitivities of PET and SPECT were 2,238 cpm/microCi (82.8 cpm/MBq) and 129 cpm/microCi (4.8 cpm/MBq), respectively (reconstructed spatial resolution, 7 and 17 mm, respectively [13-cm radius of rotation]). In the phantom studies, lesions of 1.5 and 1.3 cm or more in diameter were detected with a ratio of 5:1 and 10:1, respectively, and an information density of 150 counts per square centimeter. At FDG PET, 46 hypermetabolic lesions consistent with tumor were depicted in patients; at FDG SPECT, 36 (78%) were depicted. Sensitivity of FDG SPECT was 92% for detection of malignancies 1.8 cm or more in diameter seen at FDG PET.Findings at FDG SPECT can help differentiate benign from malignant lesions.

A radionuclide cerebral blood flow study demonstrated normal flow in the face of clinical and electrical brain death in a patient who had a ventricular drain. After the drain became obstructed and was removed, a further radionuclide study demonstrated no flow, confirming the role of the drain in the earlier false-negative studies.

Thirty-three patients with biopsy-proven lung cancer and a total of 150 lesions diagnosed by conventional staging procedures were imaged using a Tc-99m labeled monoclonal Fab fragment of an IgG2B murine monoclonal antibody (MoAb) (NR-LU-10, NeoRx Corporation). Immunoscintigraphy demonstrated 100% of primary and 78% of metastatic lesions. MoAb imaging detected 88% of lesions in 12 small cell lung cancer (SCLC) patients and 77% of lesions in 21 non-small cell lung cancer (NSCLC) patients. Based on initial evaluation by other methods, 29 sites of MoAb activity were not associated with evidence of disease. Eleven of these were subsequently shown to represent sites of metastases; 18 remain unconfirmed. Four of ten patients studied with limited NSCLC had eight unsuspected lesions on MoAb imaging. Confirmation of unsuspected lesions in two patients altered initial clinical staging, and surgical therapy was abandoned. This study demonstrates that Tc-99m labeled NR-LU-10 can accurately stage patients with lung cancer.

Positron emission tomography has recently been used to evaluate ischemic heart disease through changes in myocardial blood flow and carbohydrate metabolism. Positron-emitting tracers were evaluated for their ability to detect acute allograft rejection after heterotopic cardiac transplantation in the rat. Sham-operated controls, nonrejecting isografts, and rejecting allografts were evaluated. Decay-corrected uptake of 13NH3 and 18F 2-fluoro 2-deoxyglucose (FDG) reflects blood flow and glucose flux, respectively. Histologic examination of rejecting allografts documented mild rejection at 4 days and severe acute rejection by 8 days. All isografts were free from rejection. Uptake of FDG is greater in rejecting allografts than in nonrejecting isografts during both severe rejection (2.4% +/- 0.8% versus 0.7% +/- 0.4%; p less than 0.02) and mild rejection (2.1% +/- 0.6% versus 0.4% +/- 0.1%; p less than 0.02). Uptake of NH3 in severely rejected grafts is reduced compared with nonrejecting grafts (0.6% +/- 0.3% versus 1.7% +/- 1.1%; p less than 0.02). There is no difference in NH3 uptake during mild rejection (1.8% +/- 0.7% versus 1.3% +/- 0.3%; p greater than 0.05). Uptake of FDG and NH3 in native hearts of animals from all experimental groups is not significantly different from that in sham-operated controls. Glucose may be a preferred metabolic substrate during rejection. Our data support a humoral mechanism for substrate preference during transplant rejection and a potential diagnostic role for positron emission tomography.

Alterations of right ventricular (RV) size and shape are common in both congenital and acquired cardiopulmonary disease. Noninvasive quantification of RV mass could enhance the assessment of various hemodynamic overloads in such patients, as well as response to treatment. Left ventricular mass can be estimated using magnetic resonance imagery, 1–3 echocardiography, 4 x-ray transmission computed tomography, 5 single photon emission computed tomography 6 and contrast ventriculography. 7 RV mass has been estimated invasively in a single report 8 and a single abstract has been published measuring RV mass by x-ray transmission computed tomography. 9 Gated magnetic resonance imagery provides excellent detail of cardiac anatomy 10–12 through the use of orthogonal planes, as well as angled views that simulate echocardiographic imaging planes. This study evaluates magnetic resonance estimation RV mass in vitro.

An ultra high energy collimator for the Apex Helix (Elscint) was designed and fabricated with acceptable specifications for imaging both 99m Tc and 18 F. Five patients (59.4 ± 11.5 years, 4 males/l female) with a left ventricular ejection fraction of l 35% were studied to assess the ability of identifying hibernating myocardium using dual isotope, single acquisition (SOIA) SPECT with 99m Tc-MIBI/ 18 FDG. Patients were loaded with 25–50 grams of oral glucose and after approximately 60 minutes injected with 25 mCi of 99m Tc-MIBI and 10 mCi of 18 FDG. After a 35-minute distribution phase, they underwent 18 FDG-PET followed immediately by SDIA-SPECT (30 min acquisitionl. There was excellent correlation between the 18 FDG-PET/ 18 FDG-SPECT images. The study identified 2 patients with matched (MA) defects and 2 with mismatched (MM) (hibernating myocardium) defects. One patient had both a MM and a MA defect. Eighteen different patients (56.7 ± 12.2 years, 11 males/7 females) were studied using a rest (10 mCi 18 FDG)/stress (25 mCi 99m Tc-MIBI) SOIA-SPECT protocol to identify both acute on chronic and chronic myocardial ischemia. After oral glucose loading and myocardial distribution of 18 FDG patients underwent exercise or pharmacological stress followed by administration of 99m Tc–MIBI. Patients were imaged 15–30 minutes later with SDIA-SPECT. In the patients studied there were 16 MA defects, 12 MM defects and 2 normal studies. Eight of the 18 patients studied underwent cardiac catheterization with no false positive results. Conclusion Simultaneous dual isotope acquisition-SPECT using 18 FDG/ 99m Tc–MIBI may provide an alternative, accurate, cost-effective method com-pared to 13 NH 3 / 18 FDG or 201 TI reinjection to identify both acute on chronic myocardial ischemia and hibernating myocardium.