Jan A. J. Camps

Delayed graft function is characterized by reduced functional mass measured by (99m)Technetium-mercaptoacetyltriglycine renography.

BACKGROUND The mechanism that underlies delayed graft function (DGF) is still poorly defined. Previous studies using tubular function tests have shown that postischemic injury to the renal transplants results in profound impairment of paraimmunohippurate (PAH) extraction through the tubules. METHODS Using (99m)Technetium-mercaptoacetyltriglycine ((99m)Tc-MAG3) renography and tubular function slope (TFS), a study of the tubular uptake of (99m)Tc-MAG3 was undertaken in a prospective study of renal transplant recipients with immediate graft function (IGF) and those with DGF. RESULTS A total of 37 consecutive recipients of a cadaveric graft and 5 kidneys from living donors was evaluated within 48 hours after transplantation and in week 2, months 3 and 6, and 3 years after transplantation. In addition to the protocol scans, recipients with DGF were examined every other day until function was resumed. Repeated measurement two-way analysis of variance and a change point analysis were performed to determine the difference in the follow-up of TFS values between the two groups. Fourteen patients were classified as having DGF and 28 immediate graft function. In the DGF group, the initial TFS value was significantly lower than in the immediate graft function group (0.54 [+/-0.01] and 1.75 [+/-0.16], respectively; P=0.002), a difference that persisted for up to 3 years. Change point analysis revealed that the postischemic tubular excretion improved with time in both groups in the first 3 to 4 weeks, but both groups remained different up to 3 years after transplantation. Multivariate analysis revealed that only the cold ischemic time was an independent risk factor for a low TFS value. After the initial recovery from postischemic injury, the TFS may be used as a marker for functional renal mass. CONCLUSION We propose that the tubular defect in DGF, as defined by (99m)Tc-MAG3 renography, is irreversible and may be a marker of initial graft function.

Assessment of Peripheral Vascular Effects of Antimigraine Drugs in Humans

The vascular beds of the forearm and finger can be used to study the peripheral effects of antimigraine drugs under normal and pathologic circumstances. We have investigated the novel antimigraine drug sumatriptan, a selective agonist for 5HT1 receptors. Its antimigraine effect may be attributed, at least in part, to constriction of cranial arteriovenous anastomoses (AVAs). In assessing the peripheral vascular effects of sumatriptan we used a forearm and finger blood flow model. Forearm blood flow (FBF) is mainly determined by resistance vessels, whereas finger blood flow (FiBF) mainly involves skin vessels, which contain many AVAs. Changes in FBF and FiBF can be assessed using venous occlusion plethysmography. Changes in AVA flow are determined by measuring the patency of the vascular beds of the forearm and hand to well-defined radiolabeled microspheres, which are injected into the brachial artery. We report the effects of sumatriptan on FBF, FiBF and AVA flow when administered into the brachial artery of healthy volunteers, and discuss the peripheral vascular effects of therapeutic doses of sumatriptan when given subcutaneously in migraine patients during and between attacks.

Effects of 5-hydroxytryptamine on Capillary and Arteriovenous Anastomotic Blood Flow in the Human Hand and Forearm and in the Pig Hind Leg

The effects of intraarterially infused serotonin (5-HT) on capillary and arteriovenous anastomotic (AVA) blood flow were investigated in the hand and forearm of 19 healthy volunteers, and in the hind leg of six anesthetized pigs using radioactive microspheres with a diameter of 15 μm. The 5-HT2-receptor antagonist ketanserin was used in an attempt to identify the receptors involved. None of the drugs in the doses used induced systemic hemodynamic effects. Low doses of 5-HT significantly increased forearm blood flow with a maximum response at the dose of 1 ng/kg/min (68 ± 14%, p < 0.05), whereas only at the highest dose of 80ng/kg/min was a net decrease in forearm blood flow measured ( - 28 ± 6%. p < 0.05). Conversely, finger blood flow was not influenced by the lower doses of 5-HT, whereas a major reduction was observed at the highest dose ( - 90 ± 3%). Ketanserin increased both total forearm blood flow and AVA blood flow. The drug blunted the constrictor response to 5-HT in the forearm but only slightly attenuated this response in the finger. The percentage AVA blood flow in the human hand and forearm was not influenced by an infusion of 5-HT at 80 ng/kg/min alone. However, after pretreatment with ketanserin, which itself increased the AVA component, this dose of 5-HT significantly reduced AVA flow. In the pig, total femoral blood flow was not influenced by 5-HT, but AVA blood flow was significantly reduced and capillary skin blood flow increased. It is concluded that in both humans and pigs intraarterially infused 5-HT decreases AVA blood flow but that this effect is seemingly not mediated by 5-HT2 receptors but, as previously reported in the porcine carotid circulation, may involve 5-HT1-like receptors. The fact that low doses of 5-HT did not induce a net vasodilation in the finger is attributed to the relative absence of skeletal muscles and abundance of AVAs in the finger.

Potential of 99mTc-LDLs labeled by two different methods for scintigraphic detection of experimental atherosclerosis in rabbits.

In this study we evaluated two different 99mTc-labeling techniques to produce 99mTc-low density lipoprotein (99mTc-LDL) suitable for the scintigraphic delineation of experimental atherosclerotic lesions. The two methods are 1) a procedure that uses stannous chloride and sodium borohydride (borohydride method) and 2) a procedure that uses sodium dithionite as a reducing agent and that has been successfully applied in previous scintigraphic atherosclerosis detection (dithionite method). 99mTc-LDL produced by either method was injected into New Zealand White rabbits with diet-induced atherosclerotic plaques and in control rabbits. Scintigraphic images were taken 10 minutes (t = 0) and 1, 4, 8, 16, and 24 hours after injection. Clearance of plasma radioactivity was also studied. Stability of the 99mTc-LDL complex in the circulation was examined by size exclusion chromatography of plasma samples. After scintigraphy, the animals were killed, and the biodistribution of radioactivity was determined. The thoracic and abdominal aortas appeared in scintigraphic images to accumulate 99mTc over their entire length with either 99mTc-LDL preparation. The sparse imaging of focal atherosclerosis was found to be due to the fact that the aortas were covered with confluent atherosclerotic lesions. Scintigraphic image analysis showed that 24 hours after injection, the accumulated radioactivity in the abdominal aorta of the atherosclerotic rabbits was 57% and 54%, respectively, of the accumulated radioactivity in the abdominal aorta at t = 0 when the borohydride versus the dithionite method was used. In the control animals this value was 25% for the dithionite method, whereas in the borohydride method the aortas could not be detected in the images at t = 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Short‐Term and Long‐Term Changes of Left Ventricular Volumes During Rate‐Adaptive and Single‐Rate Pacing

SEDNEY, M.L, et al.: Short‐Term and Long‐Term Changes of Left Ventricular Volumes During Rate‐Adaptive and Single‐Rate Pacing To evaluate the adaptation of the heart to exercise during pacing, 15 patients with permanent endocardial pacemakers were studied; nine patients had atrioventricular universal (DDD) pacemakers (Symbios 7005) and six patients had activity detecting rate‐responsive ventricular (WIR) pacemakers (Activitrax 8403). Left ventricular function in each patient during rate variable pacing was compared to ventricular function during VVI single‐rate pacing. End‐systolic and end‐diastolic volume changes during exercise were measured by radionuclide angiography and the amount of volume change was used to assess left ventricular function. Both short‐term (within 4 hours) and long‐term measurements (after at least 4 weeks) were made at rest and at 50% of the maximal exercise capacity in DDD or VVIR mode and were compared with VVI single‐rate pacing. All patients, when changed from DDD or VVIR mode to VVI single‐rate pacing showed a significant increase of the end‐diastolic volume during exercise, which increased even more after long‐term VVI pacing. During long‐term rate variable pacing, there was no increase of the end‐diastolic volume during exercise. DDD or VVIR pacing initially showed a substantial increase of the end‐systolic volume during exercise combined with a decrease of left ventricular ejection fraction, suggesting a decrease of the left ventricular contractility. After 4 weeks, contractility improved both with DDD and VVIR pacing. We conclude that short‐term DDD and VVIR pacing induces a temporary impairment of left ventricular function that improves after 4 weeks, whereas long‐term VVI pacing is associated with left ventricular dilatation even at moderate levels of exercise.

Radioimmunoscintigraphy with melanoma-associated monoclonal antibody fragments in choroidal melanoma

A prospective pilot study on radioimmunoscintigraphy with monoclonal antibody fragments against cutaneous melanoma (MoAb 225.28S) was carried out in 17 patients with a clinical diagnosis of choroidal melanoma. Monoclonal antibodies against melanoma-associated antigen were labeled with 740 mBq99mTc and injected IV; images were made with a gamma camera at 6 h after injection. With a double-pinhole collimator, radioactivity was counted thrice in both eyes at 6 h after injection. In 6 of 16 patients (37.5%), the melanoma could be imaged with the gamma camera. With the double-pinhole collimator, a significantly higher activity was measured in the melanomatous eye in 13 of 16 patients (82.4%). In two patients a false negative result was obtained, and in one patient the difference between the left and right eye was not significant. Considering these results, radioimmunoscintigraphy may be valuable in ocular melanoma diagnostics, but the specificity of MoAb 225.28S needs to be assessed.

A breathing lung phantom for 81mKr lung ventilation studies its use in dosimetry and quality control

The construction of a breathing lung phantom that can be used to measure the amount of radioactive gas in the lungs as well as to determine the absorbed dose is described. For a lung ventilation study that consists of 6 views of 300 kents each, an effective dose equivalent of 50 μSv was calculated. The phantom is also suitable for comparison of different generator systems.

Aspects of performance assessment of whole body imaging systems

Abstract.Regular quality control is one of the cornerstones of nuclear medicine and a prerequisite for adequate diagnostic imaging. Many papers have been published on quality control of planar and tomographic imaging systems. Up to now, however, only minor attention has been given to the assessment of the performance of whole body imaging systems. In this paper we present a comprehensive set of test procedures including acceptance testing and regular quality control. It is not our purpose to present a thorough analysis of the methods and results. The selection of the tests is discussed and the tests are described; some results are presented. In addition action thresholds are proposed. The quality control tests can be applied to systems with either a moving detector or a moving imaging table, and to both detectors with a large field of view and detectors with a small field of view. The tests presented in this paper do not require special phantoms or sources other than those used for quality control of stationary gamma cameras. They can be applied for acceptance testing and for performance testing in a regular quality assurance programme.

Abnormal septal motion after aortic valve replacement for chronic aortic regurgitation: no evidence for myocardial ischaemia by exercise radionuclide angiography

To evaluate interventricular septal motion and left ventricular function after aortic valve replacement for chronic aortic regurgitation, we studied 12 patients at rest and during exercise by radionuclide angiography after a mean of 19 (range 12–36) months after operation (group I). Twenty patients with chronic aortic regurgitation without aortic valve replacement served as controls (group II). None of the patients had coronary artery disease as documented by arteriography. Abnormal interventricular septal motion at rest was seen in 11 patients of group I, of whom 8 showed hypokinesis and 3 akinesis. During exercise, the interventricular septal wall motion improved in 4 patients, worsened in 3 patients and did not change in 5 patients. All patients of group II had normal interventricular septal motion at rest. During exercise, 5 patients showed septal wall hypokinesia together with apical and posterolateral wall motion abnormalities. The left ventricular ejection fraction at rest was 62% ± 20% in group I and 66% ± 8% in group II (not significant). During exercise, the left ventricular ejection fraction was 59% ± 24% in group I and 68% ±13% in group II (not significant). We conclude that abnormal interventricular septal motion at rest is commonly found in patients with aortic valve replacement for chronic aortic regurgitation. During exercise, septal wall motion in the patients with aortic valve replacement shows a variable response from complete normalization to akinesia. These findings are mostly associated with a normal global left ventricular function both at rest and during exercise, which precludes myocardial ischaemia as a primary cause for abnormal septal wall motion after aortic valve replacement.