Journal of nuclear biology and medicine (Turin, Italy : 1991)最新文献

The present study describes extraction fraction and uptake measurements of the [11C]methyl triphenyl phosphonium (11C-MTP), a promising positron emission tomography (PET) agent for cardiac imaging. PET imaging was performed in mongrel dogs. Under physiological flow conditions 11C-MTP uptake reached a maximum within the first 10 minutes after injection and remained constant during the entire observation period of 80 minutes. Over the same time period, the heart/blood ratio was 46-106:1, and the heart/lung ratio 14:1. Following permanent occlusion of the left anterior descending coronary artery, 11C-MTP uptake in the normally perfused myocardium also reached a maximum at 10 minutes after injection, whereas in the infarcted area there was no significant accumulation of 11C-MTP. For a time period of 80 minutes the noninfarcted/infarcted myocardium ratio was 12:1. Extraction was measured in anesthetized dogs with a double isotope method using 99mTc-HSA as the reference tracer. The extraction fraction was 91% at a flow of 69 mL/min/100g. As flow increased to five-fold (342 mL/min/100g) following administration of adenosine, extraction fell to 61%. Following coronary artery occlusion, the 11C-MTP content in the myocardium was highly correlated (r = 0.93, p < 0.01; y = 10.46 + 0.92x) with the microsphere determined regional myocardial blood flow.

Renal transit time and relative renal function are the most commonly used parameters in the study of renal function. In clinical practice the determination of these two parameters is carried out either using the renal retention function or directly from the renogram. This study seeks to compare the values for the transit time and the relative function, as calculated from the renogram and from the renal retention function, in renographic studies using 131I-OIH and 99mTc-MAG3. For both tracers it was found that the estimated renal transit time from the renogram (OIH: 289 +/- 118 s, MAG3: 297 +/- 110 s) generated values that were higher than those obtained from the renal retention function (OIH: 245 +/- 85 s, MAG3: 274 +/- 97 s), with significant differences between the two estimates (p < 0.001). As regards the relative function, there were no significant differences between the estimates obtained from the renogram (58.5 +/- 8.3%) and the renal retention function (59.5 +/- 9.3%) in the case of OIH. For MAG3 the estimate obtained from the renogram (58.3 +/- 6.3%) and from the renal retention function (59.9 +/- 7.1%) were significantly different (p < 0.025).

Synthesis and characterization of a new pentadentate amine-oxime ligand, 3,3,11,11-tetramethyl-7-benzyl-4,7,10-triazatridecane-2,12- dionedioxime is reported. The technetium complexes of this ligand was formed by direct reduction of TcO4- in the presence of the ligand at pH 9. The radiochemical yield of the complex is greater than 95% with 10(-7) M 99TcO4-. The technetium complex formed is a positively charged chelate that elutes as a single peak on a reverse phase HPLC. Biodistribution studies in rats showed an uptake of 1.4% of the injected activity at 15 sec p.i. in heart, but the wash-out was fast. The high radiochemical purity and stability of this 99mTc-chelate indicate that these types of chelates hold potential for development of bifunctional chelating agents (BFCAs).

The effects produced on nuclear perfusion images by exercise-induced changes in the heart and respiration rate and possible transient myocardial stunning are not well understood. In this study we attempted to indirectly evaluate the potential artifacts created by exercise-induced changes in cardiac physiology. Twenty patients with prior myocardial infarction and suspected peri-infarct ischemia were studied by 99mTc-MIBI imaging. Two SPECT perfusion studies were performed after 99mTc-MIBI administration at rest. The first acquisition was carried out 90 minutes after injection of the tracer. Immediately afterwards, the patients underwent a stress test followed by a second acquisition (exercise stress superimposed on rest tracer distribution). A standard stress perfusion scan was also performed 48 hours later. Superimposed exercise stress produced artifactual defects in the resting distribution of the tracer in 15 out of 20 patients (68 of 360 segments). Standard stress images demonstrated concordant defects in 48 of these segments, indicating the concomitant presence of ischemia and stunning. This study indicates that exercise-induced changes in cardiac physiology may result in artifactual perfusion defects in scintigraphic images acquired shortly after the stress.

In 27 patients on periodic haemodialysis, serum levels of alkaline phosphatase (ALP), osteocalcin (BGP), intact parathyroid hormone (PTHi) and its two fragments, terminal COOH (PTH-Cter) and middle molecule (PTH-MM), and procollagen type 1 carboxy-terminal extension peptide (P1CP) were measured. The same patients underwent radiography of the skull and of the hands, ultrasonography of the parathyroids and scintigraphy of the skeleton with 99mTc-MDP. The study was completed by the measurement of aluminium (Al) in the blood and the deferoxamine test (DFO). Two groups of patients emerged, one (group A, n = 14) with PTHi greatly increased (201.07 +/- 109.72 pg/mL) and the other (group B, n = 13) with values within the normal range (32.69 +/- 17.06 pg/mL) (p < 0.001). In group A, ALP, BGP and particularly P1CP were increased with a statistically significant difference compared to group B. Specific radiographic alterations were found in 12 patients of group A; 7 patients also had hypertrophy of the parathyroids. There was no difference in the scintigraphic alterations of the skeleton between the two groups. The authors conclude that it is the association of the high values of PTHi with those of the markers of bone metabolism, the normal level of Al, the negativity of the DFO test and the radiological alterations which together allow the diagnosis of renal osteodystrophy with hyperparathyroidism.

Since myocardial 99mTc-Sestamibi uptake is closely related to coronary blood flow and the tracer does not redistribute, resting perfusion defects may be observed even in viable regions supplied by vessels with severe stenosis. The incidence and the clinical significance of 99mTc-Sestamibi uptake defects at rest were investigated in 60 men with suspected coronary artery disease and no previous myocardial infarction, in a multicenter study. Of 60 patients, 12 showed normal coronary arteries and 48 significant coronary artery disease (> 50% luminal narrowing). Based on the presence or absence of tracer uptake defects at resting planar scans, the patients were divided into Group 1 (27 patients) and Group 2 (33 patients), respectively. A greater incidence of coronary artery disease (100% versus 64%, p < 0.01) and of multivessel disease (70% versus 36%, p < 0.05) was observed in patients of Group 1. All patients underwent dipyridamole (up to 0.84 mg/kg in 10 min) 99mTc-Sestamibi scintigraphy, which more frequently induced transient 99mTc-Sestamibi uptake defects in Group 1 than in Group 2 (85% versus 42%, p < 0.001). A high incidence of resting 99mTc-Sestamibi uptake defects was observed in patients without previous myocardial infarction; this identified a subset of patients with a higher prevalence of coronary artery disease and multivessel involvement and with a greater impairment of the coronary reserve, as evidenced by a dipyridamole test.

Development of a perfusion defect on the 201Tl image from exercise to redistribution is referred to as reverse redistribution, a finding which has been previously associated with several conditions. We describe here two cases in which the reverse-redistribution phenomenon, observed in a routine stress-redistribution thallium-201 scan performed because of chest pain, was considered to be artifactual. Both patients subsequently developed a myocardial infarction in the areas showing the delayed perfusion defect. The potential clinical significance of the reverse-redistribution phenomenon in these two cases is discussed. When observed in patients with typical anginal pain, the reverse redistribution pattern should be considered a potential marker of tissue at risk in a region with previous, otherwise undetected, subendocardial infarction. In such patients the need for coronary angiography should be carefully considered.