Gray-to-white matter ratios of HMPAO in the human brain.

The gray-to-white matter ratio of technetium 99m-hexamethylpropyleneamine oxime (99mTc-HMPAO) in 14 anesthetized patients undergoing partial brain resection for treatment of complex partial seizures. The gray-to-white matter ratio of 99mTc-HMPAO was 1.8:1 (standard deviation 0.6) in the temporal lobe. Many of the biopsied specimens demonstrated histopathological abnormalities.

Preparation of a 99mTc wipe standard for survey instrument calibration in nuclear medicine.

A method was developed for the preparation of a standard source to satisfy the U.S. Nuclear Regulatory Commission requirement for calibration of wipe-assay procedures used in nuclear medicine laboratories. An essential element of this standard was that a locally prepared calibration wipe could be used with thin-window Geiger-Muller detectors that detect 99mTc conversion electrons with high sensitivity. This proposed calibration wipe was evaluated with both a NaI(Tl) well counter and a thin-window Geiger-Muller pancake probe. Average detector sensitivities of 1,540 and 160 counts min-1 per 2000 disintegrations min-1, respectively, were found for 99mTc. An analysis of the errors for each step of the procedure showed most to be less than 3% (95% confidence level). The nuclear medicine dose calibrator, used to assay the activity from which the wipe was prepared, was estimated to contribute a 9% absolute calibration error. Use of the pancake probe contributed a 12% geometry-reproducibility error. The total error associated with the use of the calibration wipe standard to calibrate a typical 99mTc wipe-assay procedure, exclusive of the count-dependent error associated with the number of counts acquired, was found for the NaI(Tl) well counter to be given by a percentage of 2 SD = 10% and for the thin-window Geiger-Muller pancake probe, percentage 2 SD = 16%. Coating of the calibration wipe with an acrylic spray, to prevent it from contaminating instruments during use, was evaluated. This coating was effective while it reduced the detectability of the wipe activity by a negligible degree.

Left ventricular filling in sickle cell anemia.

M-mode echocardiography was performed on 11 normal black subjects and 38 patients with sickle cell anemia while they were at rest to evaluate their left ventricular (LV) systolic and diastolic function. The patients with sickle cell anemia were also evaluated by radionuclide exercise tests and, based on their ejection fraction (EF) response, were separated into 2 groups: a group with a normal EF response to exercise (73 +/- 9%, mean +/- standard deviation) and a group with an abnormal EF response to exercise (53 +/- 9%). Computer-assisted analysis of the M-mode echocardiograms identified abnormalities of diastolic function (impaired left ventricular filling) in patients with sickle cell anemia compared with the normal subjects. The abnormal EF response group had significantly more impaired diastolic function and did less exercise than the normal EF response group. Both groups of patients had a decrease in left ventricular end-diastolic volume during exercise. The patients with sickle cell anemia had abnormalities of systolic and diastolic function on echocardiographic and radionuclide testing. The abnormalities in diastolic and systolic function assumed greater significance at the increased heart rates associated with exercise, accounting for the decrease in left ventricular end-diastolic volume and the abnormal EF response, and contributed to exercise intolerance in patients with sickle cell anemia.

Assessment of cardiac and renal function in children immediately after open-heart surgery: the significance of a reduced radionuclide ejection fraction (postoperative ejection fraction).

Ventricular ejection fractions, calculated from radionuclide studies, and inulin clearance, were determined in 33 infants and children immediately after surgical repair of their congenital or rheumatic heart defects. Of these children, the seven whose surgery did not require a period of ischemic arrest served as controls. The immediate postoperative ejection fractions in the 26 children who did undergo a period of ischemic arrest were significantly less than their preoperative values (P less than or equal to 0.001), but this decline was not observed in the control group. Ejection fraction tended to be depressed, transiently, in children 3-5 h after open-heart surgery. Early postoperative ejection fraction was significantly related to aortic cross-clamp time even when controlling for preoperative ejection fraction (r = 0.74, n = 25, P less than or equal to 0.001). Some striking declines in ejection fraction were observed among children whose aortic cross-clamp time exceeded 42 min. The decline in ejection fraction was transient; late postoperative (greater than 1 week) ejection fraction was not significantly different from preoperative values. Though glomerular filtration rates (GFRs) were often above normal, they were significantly correlated with ejection fraction (r = 0.74, n = 19, P less than or equal to 0.01). The lower GFRs were associated with the lower early postoperative ejection fractions.

Exercise-induced cardiac dysfunction in sickle cell anemia. A radionuclide study.

Cardiac performance was studied by radionuclide angiography at rest and during exercise in 22 adolescents with sickle cell (SC) anemia and the results were compared with those in 12 control subjects. At rest, cardiac contractility was normal; cardiac output and end-diastolic volume were increased. At maximal exercise, heart rate, cardiac output response, and work capacity were reduced; the reduction was related to the degree of anemia. Left ventricular end-diastolic volume decreased with exercise most markedly in patients with ischemic exercise electrocardiograms. An abnormal ejection fraction response to exercise occurred in 4 patients; electrocardiographic signs of ischemia developed in all 4, and wall motion abnormalities in 2. Those patients who had electrocardiographic signs of ischemia had a significantly lower heart rate, ejection fraction, and cardiac output response to exercise, and a lower hematocrit level than subjects with normal results on exercise electrocardiography. The increase in cardiac output was not sufficient to maintain a normal level of exercise. The decrease in end-diastolic volume suggests that diastolic function was abnormal during exercise. Cardiac dysfunction was manifested by an abnormal ejection fraction response, wall motion abnormalities, and incomplete left ventricular filling during exercise.

Thermodilution Qp/Qs: an indicator dilution method.

The pulmonary-to-systemic blood flow ratio (Qp/Qs) is critical in the appraisal of the need for surgery in patients with left-to-right shunts. Because of the drawbacks present with conventional Fick, indicator dilution, and radionuclide techniques of Qp/Qs measurement, we sought to determine whether an extension of thermodilution technology could accurately predict Qp/Qs. We studied 30 children with clinically suspected or postoperative atrial or ventricular septal defects. The thermodilution temperature curves from the pulmonary artery were printed on a strip chart recorder after right atrial injection of iced solution. Gamma variate curve fitting and area analysis were used to determine Qp/Qs. The correlation between Fick and thermodilution Qp/Qs values was excellent (r = 0.95). The thermodilution technique was rapid, and did not require either arterial entry, radiation after venous catheter placement, or multiple sampling.

The value, limitations, and applications of nuclear dacryocystography.

Nuclear dacryocystography is simple, relatively harmless method of evaluating patients suspected of having abnormalities of the nasolacrimal drainage system. A group of normal saline containing approximately 100 muCi of 99mTc-pertechnetate is placed on the conjunctiva near the lateral canthus, and serial scintigrams are obtained as the pertechnetate flows along the tear strips, through the nasolacrimal drainage system, into the nasal fossa. By using a pinhole collimator with a very small aperture (1mm), the canaliculi, the nasolacrimal sac, and the nasolacrimal duct are readily visualized. When flow is impaired, the site of obstruction can often be identified. Contrast dacryocystography provides similar information but requires the injection of contrast material directly into a canaliculus. Nuclear dacryocystography provides good functional assessment of nasolacrimal drainage but has serious shortcomings in defining pathologic anatomy. Contrast dacryocystography outlines the anatomy well but often misses minor obstructions. The two studies are complementary and together provide an effective means of evaluating the nasolacrimal drainage system.

Adjustable lead glass shielding device for use with an over-the-table x-ray tube.

Sources of scattered radiation exposure to personnel from a ceiling-mounted x-ray tube were examined at the side of cardiac catheterization patients. A fully adjustable mounting for a lead glass shield was designed to afford maximum radiation protection to the attending physician's head and neck area, while minimizing interference with the procedure.