Technical Parameters of In Vivo Red Blood Cell Labeling with Technetium-99m

The in vivo labeling of red blood cells (RBC) using sequential injections of stannous pyrophosphate and 99mTc-pertech- netate has resulted in excellent blood pool images since it was initiated in our laboratory in 1975. Recently certain technical parameters of the procedure have been further researched and clarified. The optimum RBC labeling has been obtained by using 1.43 mg “cold” Sn-PYP/1000 ml blood and a 30-minute lag time prior to pertechnetate injection (15-20 mCi). The binding of 99mTc to RBCs is not instantaneous, but requires several minutes for completion. The “secondary” RBC labeling effect of additional pertechnetate, added after the initial in vivo labeling, demonstrates an initial rapid fall in the labeling efficiency as a function of time followed by a more gradual decrease; the level of baseline (spontaneous) RBC labeling is achieved approximately 8 days after an initial in vivo labeling. Monitoring in vivo RBC labeling over several hours indicates that more than 90 % of the initial activity was still in the vascular blood pool at 4 hours, bound to RBCs.

Viewing the functional consequences of traumatic brain injury by using brain SPECT

High-resolution brain SPECT is increasingly benefiting from improved image processing software and multiple complementary display capabilities. This enables detailed functional mapping of the disturbances in relative perfusion occurring after TBI. The patient population consisted of 26 cases (ages 8-61 years)between 3 months and 6 years after traumatic brain injury.A very strong case can be made for the routine use of Brain SPECT in TBI. Indeed it can provide a detailed evaluation of multiple functional consequences after TBI and is thus capable of supplementing the clinical evaluation and tailoring the therapeutic strategies needed. In so doing it also provides significant additional information beyond that available from MRI/CT. The critical factor for Brain SPECT's clinical relevance is a carefully designed technical protocol, including displays which should enable a comprehensive description of the patterns found, in a user friendly mode.

Incorporation of SPECT imaging in a longitudinal cognitive rehabilitation therapy programme

In this clinical study, five consecutive referrals to a cognitive rehabilitation therapy (CRT) programme were followed in a longitudinal protocol involving a resting SPECT and neuropsychological evaluation at pre-treatment, post-treatment, and post non-treatment intervals. All clients had acquired brain injury and initially demonstrated neuropsychological deficits and various degrees of hypoperfusion on SPECT. Statistical Parametric Mapping (SPM) was used to evaluate change in successive SPECT images. Following CRT, all clients were able to return to productive employment or schooling. Examination of the neuropsychological testing results revealed significant improvement in performance following CRT which were generally maintained during the non-treatment period. SPM analysis of the SPECT data revealed that, in a majority of cases, most of the significant increases in relative cerebral blood flow redistribution were seen during the treatment period, rather than the non-treatment period. The results suggest that, even in individuals who are more than 2 years post-brain damage, relative increases in rCBF can be demonstrated following individualized CRT and that most of these changes can be related to improvements on neuropsychological tests.

Visual form of Alzheimer's disease and its response to anticholinesterase therapy

In a 60-year-old woman with the visual variant of Alzheimer's disease, single photon emission computed tomography abnormalities were most marked in the parieto-occipital regions of the brain. After treatment with donepezil, improvement is noted on neuropsychological testing and on brain SPECT, including increased perfusion (metabolism) in the occipital lobes.

Comparison between factor analysis of dynamic structures and Fourier analysis in detection of segmental wall motion abnormalities: a clinical evaluation

To evaluate Factor Analysis of Dynamic Structures (FADS) versus or in association with other methods, a protocol was set up including as 'gold standard' investigation the left ventricular angiography (LVA) and processing by Fourier Analysis (FA), and FADS with different variants. To refine the diagnosis of Regional Wall Motion Abnormalities (RWMA), processing was done on a sectorial basis for more accurate spatial localization and functional description. 53 patients were studied (8 normal, 45 with coronary artery disease). FADS gave better results than FA on a sectorial basis. Total agreement between FADS and LVA was obtained in 208/265 (78%), while FA was in agreement with LVA in only 167/265 segments (63%). Globally, FADS was significantly better than FA (Z-test: p < 0.05). When only the diagnosis of maximal abnormality was considered, FA and FADS are statistically equivalent. The superiority of FADS vs FA is more obvious in the diagnosis of hypokinesia. Most FA discrepancies corresponded to underestimation of WMA.

Comparison of electrocardiography and thallium-201 myocardial scintigraphy for the detection of ergonovine-induced coronary artery spasm: angiographic correlation

This study was performed to determine the sensitivity of thallium imaging vs ECG monitoring for detecting coronary artery spasm noninvasively following intravenous ergonovine administration as compared to simultaneous coronary angiography. Thirty-two patients with insignificant coronary artery disease and chest pain underwent 12-lead ECG monitoring, thallium imaging, and coronary arteriography following the administration of 0.05, 0.1, 0.2, and 0.3 mg of ergonovine given 5 minutes apart or until chest pain occurred. One minute following the last dose of ergonovine, 2.5 mCi of thallium-201 was injected intravenously, and a final ECG was recorded and repeat coronary arteriography performed. Within 10 minutes following the injection of thallium, imaging was performed in the 40-degree and 70-degree left anterior oblique and anterior projections. The ECG, thallium study, and coronary arteriogram were read blindly and results were compared. The ECG, angiogram, and thallium study were read as positive if the following occurred, respectively: greater than or equal to 1 mm ST segment elevation, depression, or T wave reversal; greater than 50% vessel narrowing,; and reversible perfusion defect. Five patients were excluded from analysis because of either catheter-induced spasm, suboptimal thallium studies, or protocol violations. Of the 27 patients included for analysis, six had chest pain, five had a positive angiogram, five had a positive thallium study, and one had a positive ECG. The sensitivity of thallium vs ECG monitoring was 80% vs 25%, and the accuracy was 92% vs 80%. We conclude that thallium imaging greatly increases the noninvasive detection of ergonovine-induced coronary spasm as compared with the ECG with no loss of accuracy.

Sequential regional phase mapping of radionuclide gated biventriculograms in patients with sustained ventricular tachycardia: close correlation with electrophysiologic characteristics

Radionuclide (RNA) gated studies were performed during sinus rhythm and during spontaneous or induced sustained ventricular tachycardia (VT) in six patients with clinical VT. Fourier analysis of time-activity variation was used to calculate a RNA phase value for each pixel in the image. Color coding of each pixel according to its calculated phase resulted in a RNA phase map of the ventricles. The following results were considered to be consistent with the known electrophysiology of VT: (1) the phase map correlated with QRS morphology and axis in most but not all tachycardias; (2) earliest phase usually demonstrated the VT origin to be at the border of the ventricular wall motion abnormality; (3) endocardial mapping (available in one patient) showed close correlation with RNA phase mapping; (4) in three patients with ischemic heart disease, VT with left bundle branch block (LBBB) pattern had earliest LV phase along the septum; and (5) for one patient imaged during two different VT morphologies, the tachycardias had earliest phase at different borders of the same wall motion abnormality with differing progression of phase across the ventricles. RNA phase mapping of VT is feasible and appears to provide data consistent with the electrophysiology of this arrhythmia.

Assessment of left ventricular function by radionuclide angiography during induced supraventricular tachycardia

Electrocardiographically synchronized radionuclide angiography was performed before, during and after induced paroxysmal supraventricular tachycardia in 13 patients. Data were acquired with a computer-interfaced Anger camera in a left anterior oblique projection. No data were acquired during tachycardia until tachycardia had been sustained for 1 minute. Patients ranged in age from 20 to 64 years (mean +/- standard deviation 42 +/- 14.5). Three patients had organic heart disease and 10 did not. Baseline and tachycardia heart rates (beats/min) were 59 to 99 (73 +/- 11) versus 141 to 228 (157 +/- 22). Baseline and tachycardia left ventricular measurements (mean +/- standard error) were as follows: ejection fraction 64 +/- 2 versus 62 +/- 4 percent (not significant), ejection rate 3.0 +/- 0.1 versus 4.3 +/- 0.4 mean ventricular counts/s (p less than 0.001), normalized end-diastolic counts 72.7 +/- 7.8 versus 48.7 +/- 6.7 X 10(3) counts (p less than 0.001), normalized stroke counts 37.1 +/- 3.4 versus 23.3 +/- 2.7 X 10(3) counts (p less than 0.001) and normalized count cardiac output 2,717.5 +/- 273.0 versus 3,620.2 +/- 403.7 X 10(3) counts/min (p less than 0.005). Although ejection fraction for the whole group did not change significantly, it decreased during tachycardia by 5 percentage points or more in five patients. These were the three patients with heart disease and the two normal patients with the fastest heart rate during tachycardia (228 and 214 beats/min, respectively). In summary, paroxysmal supraventricular tachycardia was characterized by a marked decrease in left ventricular end-diastolic and stroke volumes but increased ejection rate and cardiac output without significant change in ejection fraction. Heart disease or rapid heart rate during tachycardia appeared to have a deleterious effect on ejection fraction.

Radionuclide regurgitant index: value and limitations

The radionuclide regurgitant index, defined as left ventricular/right ventricular stroke counts obtained from gated equilibrium studies, has been reported to predict the presence and severity of left-sided valve regurgitation. This study evaluated the radionuclide regurgitant index in 100 patients in whom left-sided valve regurgitation was angiographically graded (0 to 4+) with regard to most severe mitral or aortic regurgitation. Regurgitation was graded 0 in 44 of the 100 patients, 1+ in 22, 2+ in 8, 3+ in 6 and 4+ in 20. The radionuclide regurgitant index was 0.9 to 1.5 in 51 patients, 1.6 to 2.4 in 23 and 2.5 to 12.0 in 26. The mean radionuclide regurgitant index was 1.34 in the group with no regurgitation and 1.60 in those with 1+, 2.01 in those with 2+, 2.80 in those with 3+ and 3.85 in those with 4+ regurgitation. There was a significant difference (p less than 0.05) in the radionuclide regurgitant index between patients with no regurgitation and each group with regurgitation and between groups with regurgitation separated by two or more grades of angiographic regurgitation. Twelve patients had a discordant radionuclide regurgitant index; their index either predicted clinically significant or severe regurgitation when they had no or trivial regurgitation, or predicted no or trivial regurgitation when they had clinically significant regurgitation. Eight of 10 patients with a left ventricular ejection fraction of less than 0.30 had a discordant index (p less than 0.0005). All three patients with mitral valve prolapse associated with frequent ventricular extrasystoles had a discordant index (p less than 0.0005).