Dual-head gamma camera coincidence imaging in pancreatic cancer.

OBJECTIVE: To assess the usefulness of dual-head camera imaging with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) in the identification of malignant pancreatic lesions. MATERIAL AND METHODS: Fifteen (15) patients with pancreatic masses (7 females and 8 males, mean age 52 10 years) have been studied prospectively. After a 12-hour fasting patients received 120 MBq of FDG and were imaged in a dual-head camera equipped with coincidence detection. The final diagnosis was obtained by histology (biopsy or surgery in 13 patients) or follow-up (in 2 patients). RESULTS: Nine patients showed FDG uptake, all had pancreatic cancer proven on histological examination. Six patients had no tracer uptake: two had chronic pancreatitis, 1 had insulinoma, 1 had gastrinoma and two had pancreatic adenocarcinoma. Overall sensitivity was 69%, specificity was 100% and accuracy was 73%. CONCLUSION: Dual-head camera FDG images seem potentially useful in the characterization of the nature of pancreatic lesions. However, a negative study does not rule out malignancy in this patient population.

Detection of the viable myocardium. A perfusion scintigraphic study, before and after coronary bypass surgery in myocardial infarction patients.

OBJECTIVE: To compare single-photon-emission computed tomography (SPECT) imaging scans using 201Tl and 99mTc-MIBI in detection of viable myocardium, in regions compromised by infarction. METHODS: Thirty-two (59.3 +/- 9.8 years old and 87% male) myocardial infarction patients were studied. All had Q waves on the ECG and left ventricle ejection fraction of < 50%. They underwent coronary and left ventricle angiographies and SPECT before (including 201Tl reinjection) and after coronary artery bypass surgery (CABG). Improvement in perfusion observed after surgery was considered the gold standard for myocardial viability. RESULTS: Among 102 studied regions of the heart, there were 40 (39.2%) areas of transient perfusion defects in the conventional protocol with 201Tl and 52 (51.0%) after reinjection. Therefore, 12/62 (19.4%) more viable regions were identified by reinjection. Using 99mTc-MIBI, only 14 (13.7%) regions with transient defects were identified, all of which were seen also in 201Tl protocols. After surgery, 49 of a total of 93 regions analyzed (52.7%) were viable. Sensitivity, specificity, accuracy, positive and negative prediction values were, respectively, 201Tl SPECT scans--65.3%, 90.9%, 77.4%, 88.9% and 70.2%, reinjection protocol with 201Tl scans--81.5%, 81.8%, 81.7%, 83.3% and 80.0%, 99mTc-MIBI SPECT scans--20.4%, 90.9%, 53.8%, 71.4% and 50.6%. Logistic regression demonstrated that the reinjection protocol with 201Tl was the best predictor of viability (P < 0.001). CONCLUSION: Our data suggest the election of 201Tl for viability studies, especially when using the reinjection protocol.

Plasma clearance and biodistribution of oxidatively modified 99mTc-Beta-VLDL in rabbits

The biodistribution and removal from plasma (measured as fractional clerance rate, FCR, per hour) of native and oxidatively modified (99m)technetium-labeled Beta-very low density lipoprotein ((99m)Tc-Beta-VLDL)) were investigated in hypercholesterolemic (HC) and control (C) three-month old New Zealand rabbits. The intracellular accumulation of Beta-VLDL labeled with (99m)Tc was studied in vitro in THP-1 cells and monocyte-derived macrophages isolated from rabbits. After intravenous injection into C rabbits, copper-oxidized Beta-VLDL ((99m)Tc-ox-Beta-VLDL)) was cleared from the circulation faster (0.362 + 0.070/h) than native Beta-VLDL ((99m)Tc-nat-Beta-VLDL, 0.241 + 0.070/h)). In contrast, the FCR of (99m)Tc-ox-Beta-VLDL in HC rabbits was lower (0.100 + 0.048/h) than that of (99m)Tc-nat-Beta-VLDL (0.163 + 0.043/h). The hepatic uptake of radiolabeled lipoproteins was lower in HC rabbits (0.114 + 0.071 percent injected dose/g tissue for (99m)Tc-nat-Beta-VLDL and 0.116 + 0.057 percent injected dose/g tissue for (99m) Tc-ox-Beta-VLDL) than in C rabbits (0.301 + 0.113 percent injected dose/g tissue for (99m)Tc-nat-Beta-VLDL and 0.305 + 0.149 percent injected dose/g tissue for ((99m)Tc-ox-Beta-VLDL). The uptake of (99m)Tc-nat-Beta-VLDL and (99m)Tc-ox-Beta-VLDL by atherosclerotic aorta lesions isolated from HC rabbits ((99m)Tc-nat-Beta-VLDL:0.033 + 0.012 percent injected dose/g tissue and (99m)Tc-ox-Beta-VLDL: 0.039 + 0.017 percent injected dose/g tissue) was higher in comparison to that of non-atherosclerotic aortas from C rabbits (99m)Tc-nat-Beta-VLDL: 0.023 + 0.010 percent injected dose/g tissue and (99m)Tc-ox-Beta VLDL: 0.019 + 0.010 percent injected dose/g tissue). However, (99m) Tc-nat-Beta-VLDL and (99m)Tc-ox-Beta-VLDL were taken up by atherosclerotic lesions at similar rates. In vitro studies showed that both monocyte-derived macrophages isolated from rabbits and THP-1 macrophages significantly internalized more (99m)Tc-ox-Beta-VLDL than (99m)Tc-nat-Beta-VLDL. These results indicate that in cholesterol-fed rabbits (99m)Tc-ox-Beta-VLDL is slowly cleared from plasma and accumulates in atherosclerotic lesions. However, although the extent of in vitro uptake of (99m)Tc-ox-Beta-VLDL by macrophages was high, the in vivo accumulation of this radiolabeled lipoprotein by atherosclerotic lesions did not differ from that of (99m)Tc-nat-Beta-VLDL.

Gallium-67 lung imaging and pulmonary clearence of 99mTc-DTPA aerosol in patients with amiodarone pneumonitis

The aim of this study was to compare gallium-67 citrate lung imaging with the pulmonary clearance of 99mTc-DTPA (technetium 99m diethylenetriaminepentaacetic acid) in 9 patients with amiodarone pneumonitis (8 males and 1 female, aged 58 to 76 years). The diagnosis of amiodarone pneumonitis was based on clinical and radiological grounds in all patients, and histological changes in seven. The mean values for the effective half-life of the pulmonary clearance of 99mTc-DTPA aerosol were below the normal range in all 9 patients, and lower than the values obtained previously for patients on a long-term amiodarone regimen without side effects. Positive gallium-67 accumulation was demonstrated in 7 of the 9 patients. Two patients had negative gallium-67 imaging and increased alveolar-capillary 99mTc-DTPA clearance; with corticosteroid therapy and discontinuation of amiodarone, their radiological changes and clearance became normal within 120 days. In conclusion, when compared to gallium-67 lung imaging, the 99mTc-DTPA aerosol clearance is more advantageous because it is a much faster test than the gallium scan. This is essential for those patients suspected of amiodarone pneumonitis who need specific therapy as soon as possible. Moreover, the 99mTc-DTPA aerosol clearance test appears to be a more useful diagnostic tool because it is positive even in those patients who have normal gallium-67 lung imaging.

Slow coronary run-off in patients with angina pectoris: clinical significance and thallium-201 scintigraphic study

To determine whether or not slow coronary flow (SF) depends on hemodynamic variables, we studied 17 patients (15 men, mean age = 47.8 years) with SF at coronariography. Exercise thallium-201 myocardial scintigraphy revealed perfusion abnormalities in 13 (76.4 per cent) patients. We then selected 89 individuais submitted to cinecoronariography for comparison: 15 were normal and 74 had heart disease. The coronary flow velocity was evaluated by the number of heart beats (HB) needed for coronary artery dye filling. The patients in the SF group had normal hemodynamic variables which were significantly different from those of patients with heart disease (P = 0.001). Patients with heart disease needed no more than 4 HB to fill their arteries, in contrast to 6.88 ñ 1.68 (5 to 11) in the SF group (P<0.OOO1). Thus, in our patients with myocardial scintigraphy suggesting ischemia, SF was found to be an event which did not depend on hemodynamic factors.

Clinical and left ventricular function outcomes up to five years after dynamic cardiomyoplasty.

Improvement in congestive heart failure and left ventricular function after dynamic cardiomyoplasty has been reported in patients with severe cardiomyopathies, but the long-term effects of this procedure remain unclear. In this investigation 31 patients undergoing cardiomyoplasty for treatment of idiopathic dilated cardiomyopathy were annually investigated with radionuclide scintigraphy, Doppler echocardiography, and right-sided heart catheterization. They were in New York Heart Association functional class III or IV before the operation. No hospital deaths occurred, but one patient with progressive heart failure required urgent heart transplantation 42 days after cardiomyoplasty. The other patients were followed up from 6 to 70 months (mean 25.6 months) and 12 patients died at late follow-up. Actuarial survivals were 86% at 1 year, 61.4% at 2 years, and 42.5% at 3 to 5 years of follow-up. Multivariate analysis of factors influencing outcome showed that long-term survival was significantly affected by preoperative functional class and pulmonary vascular resistance. Functional class improved from 3.2 +/- 0.4 to 1.7 +/- 0.7 in the surviving patients (p < 0.01). Furthermore, left ventricular ejection fraction improved from 19.8% +/- 3% to 23.9% +/- 7.2% (p < 0.01), and significant changes in stroke index, arterial pressure, pulmonary wedge pressure, and left ventricular stroke work index were also found at 6 months of follow-up. In the late postoperative period, the left ventricular ejection fraction tended to decrease and returned to preoperative levels at 5 years, whereas hemodynamic variables did not change significantly. Thus, despite the tendency of the left ventricular ejection fraction to decrease at late follow-up, the long-term course of these patients seems to be characterized by the maintenance of hemodynamic improvement. However, long-term survival after cardiomyoplasty is limited by the severity of the patient's condition before the operation.

Plasma kinetics and biodistribution of a lipid emulsion resembling low-density lipoprotein in patients with acute leukemia.

Low-density lipoprotein (LDL) could be used as a carrier of chemotherapeutic agents to neoplastic cells that overexpress LDL receptors (rLDL), but LDL is difficult to obtain and handle. Recently, it was observed that a protein-free emulsion resembling the lipid portion of LDL (LDE) behave like native LDL when injected into the bloodstream. In this study, the evidence that LDE is taken up by rLDL was expanded by comparing LDL and LDE plasma decay curves in rabbits and by competition experiments with lymphocytes. To verify whether LDE could be removed from the plasma by neoplastic cells with increased rLDL, LDE labeled with 14Ccholesteryl ester was injected into 14 patients with acute myeloid leukemia (AML) and into 7 with acute lymphocytic leukemia (ALL). In AML rLDL expression is increased but in ALL it is normal. LDE plasma fractional clearance rate (FCR, in h-1) was calculated from the remaining radioactivity measured in plasma samples collected during 24 h following injection. LDE FCR was 3-fold greater in AML than in ALL patients 0.192 +/- 0.210 (SD) and 0.066 +/- 0.033 h-1, respectively, P < 0.035. When LDE injection was repeated in 9 AML patients in hematological remission, LDE FCR diminished 66% compared to the pretreatment values (from 0.192 +/- 0.210 to 0.065 +/- 0.038 h-1, P < 0.02), so that it could be estimated that nearly 66% of the emulsion was taken up by AML cells and only 34% by the normal tissues. As expected, LDE FCR was unchanged in 4 patients with ALL in hematological remission (0.069 +/- 0.044 h-1). Gamma camera images obtained 6 h after the injection of 99mTc-label LDE into one patient with ALL showed biodistribution similar to that of LDL. In one AML patient LDE was comparatively more concentrated over the areas corresponding to the bone marrow infiltrated by AML cells. Our results indicate that LDE FCR is increased in a disease known to contain malignant cells that overexpress rLDL, suggesting that LDE is taken up by malignant cells with increased rLDL.

Correlation between gallium-67 imaging and endomyocardial biopsy in children with severe dilated cardiomyopathy.

Fourty-four patients (aged 10 months to 15 years) were assessed in a double-blind study to observe the correlation between myocardial uptake of 67-gallium and endomyocardial biopsy in the detection of moderate to severe myocardial inflammation. The sensitivity and specificity of gallium-67 imaging were 87 and 81%, respectively. Based on these findings, immunosuppressive therapy can be assigned to children with dilated cardiomyopathy and positive myocardial uptake, since moderate and severe myocardial inflammation may be detected by this non-invasive method.