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Biomedical subjects

P D Esser

Publications and source records attributed to P D Esser.

36 records · Page 2Linked to original sources
PubMed1987

Measurement of infarct size and percentage myocardium infarcted in a dog preparation with single photon-emission computed tomography, thallium-201, and indium 111-monoclonal antimyosin Fab.

Single photon-emission tomography (SPECT) and indium 111-labeled monoclonal antimyosin Fab fragments were used to measure myocardial infarct size in 12 dogs, six subjected to balloon catheter-induced coronary artery occlusion for 6 hr (late reperfusion) and six subjected to occlusion with reperfusion at 2 hr (early reperfusion). Tomographic imaging was performed 24 hr after the intravenous injection of labeled Fab fragments with the use of a dual-head SPECT camera with medium-energy collimators. Immediately after the first tomographic scan, thallium-201 was injected into nine of 12 dogs and imaging was repeated. Estimated infarct size in grams was calculated from transaxially reconstructed, normalized, and background-corrected indium SPECT images with the use of a threshold technique for edge detection. Estimated noninfarcted myocardium in grams was calculated from obliquely reconstructed thallium SPECT images by a similar method. The animals were killed and infarct size in grams and true infarct size as a percentage of total left ventricular myocardial volume were measured by triphenyl tetrazolium chloride staining. Estimated infarct size from indium SPECT images showed an excellent correlation with true infarct size (r = .95, SEE = 4.1 g). Estimated percentage myocardium infarcted was calculated by dividing estimated infarct size from indium images by the sum of estimated infarct size plus estimated noninfarcted myocardium obtained from thallium images. Correlation between the estimated percentage of myocardium infarcted and true percentage of myocardium infarcted was excellent (r = .93, SEE = 4.4%). We conclude that dual-isotope SPECT with indium 111-monoclonal antimyosin antibodies and thallium-201 can accurately estimate infarct size and percentage myocardium infarcted.

Animals↗
PubMed1986

Radionuclide administration to nursing mothers: mathematically derived guidelines.

We determined a formula to establish objective guidelines for the administration of radionuclides to nursing mothers. The formula is based on the maximum permissible dose to the infant's critical organ, serial measurements of breast milk activity, milk volume, and dose to the critical organ per microcurie in milk. Using worst-case assumptions, we believe that cessation of nursing for 24 hours after administration of technetium labeled radiopharmaceuticals is sufficient for safety. Longer-lived agents require greater delays. Iodine-123 radiopharmaceuticals are preferable to iodine-131 agents and should always be used when studying the unblocked thyroid.

Animals↗
PubMed1986

Effect of coronary stenotic lesions on regional myocardial blood flow at rest.

To determine the effect of atherosclerotic coronary lesions on myocardial blood flow in patients at rest, regional myocardial blood flow was measured distal to stenotic lesions in 29 patients with isolated proximal lesions of the left anterior descending artery. Severity of coronary stenosis was measured by computer-assisted cinevideodensitometric analysis of digitized coronary arteriograms. Regional myocardial blood flow was measured from the clearance rate of intracoronary 133Xe injected into the left main coronary artery and recorded with a multicrystal scintillation camera. In 21 patients with stenotic lesions ranging from 19% to 84% area reduction, distal regional myocardial blood flow was normal. In all eight patients with reduced regional myocardial blood flow distal to left anterior descending lesions, the minimum area of each stenotic lesion was less 0.80 mm2 (mean 0.34 +/- 0.2 mm2), minimum calculated diameter was less than 1 mm (mean 0.59 +/- 0.3 mm), and percent stenosis, based on the reduction in cross-sectional area, was greater than 85% (mean 94 +/- 4%). For all patients, distal flow, expressed as a fraction of normal flow, correlated with the lesion cross-sectional area (r = .84), minimum luminal diameter (r = .84), and percent area stenosis (r = -.70). Thus, resting myocardial blood flow distal to stenotic lesions of the proximal coronary arteries remains normal until the degree of narrowing is severe. The dimensions observed for critical coronary stenotic lesions correlate well with theoretical predictions based on fluid mechanics and with experimental preparations in laboratory animals.

Cineangiography↗
PubMed1985

Improvements in SPECT technology for cerebral imaging.

Advancement in three major areas of SPECT (single photon emission computed tomography) technology have resulted in improved image quality for cerebral studies. In the first area, single-crystal camera electronics, extensive use of microprocessors, custom digital circuitry, an data bus architecture have allowed precise external control of all gantry motions and improved signal processing. The new digital circuitry permits energy, uniformity, and linearity corrections to be an integral part of the processing electronics. Calibration of these correlations is controlled by algorithms stored in the camera's memory. In addition, digital signals can be routed directly to interface circuitry of auxiliary computer systems without analog-to-digital conversion. Look-up tables, downloaded to the interface from the central processing unit (CPU), permit computer-controlled real-time processing of coordinate signals, including truncation, magnification, and spatial calibration. The second area of improved SPECT technology is camera collimation and related imaging techniques. In this area, system resolution has been improved without loss of sensitivity by decreasing the air gap between patient and collimator surface. Rotating the detector in close apposition to the head has required various stratagems to avoid detector-shoulder contact: the selective reduction of camera shielding, the use of long bore collimators, and the 30 degrees angulation of the camera head for slant hole collimation. Since cerebral studies characteristically image high-contrast regions less than 1 cm in size, image quality has been improved by increasing collimator resolution even at the expense of sensitivity. Increased resolution also improved image contrast for studies using 123I-labeled pharmaceuticals with 3% to 4% 124I contamination. Such studied acquired with low energy or medium energy collimation and a window centered on the 159 keV 123I photopeak contain appreciable septal breakthrough signals originating from Compton scatter of high energy photons primarily from 124I. The third area of advancements in technology, multidetector instrumentation, offers the promise of increased sensitivity and resolution. For the dynamic computer-assisted tomograph (DCAT) system, which was especially designed for regional blood flow studies with 133Xe or 127Xe, a count rate of 170,000 counts per microCi/cc for three slices has been achieved. This system consists of four detector banks each with 16 rectangular NaI crystals. An alternative system at Harvard uses an array of 12 moving detectors with focused collimators to acquire a single slice.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Assessment of bone grafts used for acetabular augmentation in total hip arthroplasty. A study using roentgenograms and bone scintigraphy.

Total hip arthroplasty was performed in 13 hips with acetabular bone grafts for secure component fixation. The incorporation and healing of acetabular bone grafts were investigated with the aid of roentgenograms, planar bone scans, and a newer scintigraphic technique, three-dimensional single photon emission computed tomography (SPECT). Conventional roentgenograms proved unreliable in evaluating bone graft reconstitution because of overlapping trabecular bone patterns of the graft and iliac wing. There was no evidence of graft failure or acetabular loosening. Bone grafts in the late follow-up group (four to seven years postoperation) exhibited normal radionuclide activity, whereas grafts less than one year postsurgery demonstrated patterns of increased activity. SPECT was helpful in producing an anatomic reconstruction of the acetabulum. The observation that bone grafts exhibited normal biological viability is crucial for ensuring secure acetabular component fixation on a long-term basis.

Acetabulum↗
PubMed1984

The effect of DMSO treatment on the performance of [99mTc]HEDP.

The effect of treating a commercial skeletal imaging kit containing hydroxyethylidene diphosphonate (HEDP) with dimethyl sulfoxide (DMSO) prior to labeling with sodium pertechnetate, 99mTc[TcO4-], was investigated. Statistically, significant differences (P less than 0.05) in soft tissue retention (blood and muscle) were seen in rats after injection with the DMSO-treated HEDP compared to the nontreated HEDP. Based on i.r. and HPLC data, it appears that DMSO acts as an extractant for certain Sn2+-HEDP complexes which contribute to greater soft-tissue retention.

Animals↗
PubMed1984

Left ventricular volume: physical basis for attenuation corrections in radionuclide determinations.

Absolute left ventricular volume has been calculated from gated blood pool studies by estimating an attenuation correction for left ventricular counts. We studied the physical basis of these corrections by evaluating x-ray photon attenuation from CT scans of the thorax (10 second scans, no gating). CT numbers were converted to linear attenuation coefficients (LACs) at 140 keV, and LACs from the center of the left ventricle or esophagus to the chest wall (40 degrees left anterior oblique position) were determined in 12 patients of various body habitus. The mean LACs were virtually identical (0.13 cm-1 +/- 0.02 cm-1 SD), but were less than the LAC of water (0.15 cm-1). However, the esophagus was 66% further from the chest wall than the center of the left ventricle. These results suggest that conventional methods overestimate attenuation and show that LAC variability between individuals can be large. Better methods of attenuation correction may improve count-based estimates of left ventricular volume.

Adult↗
PubMed1984

Quantification of relative coronary arterial stenosis by cinevideodensitometric analysis of coronary arteriograms.

A computerized method for measuring relative coronary arterial stenosis by cinevideodensitometric analysis of 35 mm coronary arteriograms was developed and validated. Video images of projected coronary arteriographic frames were digitized into a 512 X 512 matrix (256 gray levels) by computer analysis that compared integrated contrast density measured over stenotic and normal arterial segments after background subtraction. Pixel density was 70 to 80 pixels/mm2 actual area. In phantom studies performed on plexiglass cylinders, cinevideodensitometric measurements correlated linearly with concentration of contrast medium (r = .99), with cross-sectional areas (r = .99) of contrast-filled cylinders 1 to 4 mm in diameter over a wide range of contrast concentrations (25% to 100%), and with relative stenosis of eccentric lesions in the cylinders (r = .99, SEE = 3.9%). In postmortem studies of patients who died after undergoing coronary arteriography, videodensitometric measurements of relative stenosis correlated highly (r = .97, SEE = 7.0%) with percentage stenosis based on actual area measurements obtained histologically with computer-assisted microscopic planimetry. Cinevideodensitometric analysis of coronary arteriograms was reproducible (r = .92, SEE = 7.7%), and interobserver variability was low (r = .99, SEE = 4.3%). In addition, videodensitometry provided comparable values for eccentric coronary lesions filmed in right anterior oblique and left anterior oblique projections (r = .99, SEE = 1.9%). Cinevideodensitometric analysis is an accurate, rapid method for quantifying the relative stenosis of eccentric coronary lesions without manual tracing of arterial borders.

Absorptiometry, Photon↗
PubMed1984

Angled-collimator SPECT (A-SPECT): an improved approach to cranial single photon emission tomography.

A special 30 degree slant-hole collimator has been developed for rotating camera single photon emission computerized tomography (SPECT) that allows the camera to remain close to the patient's head throughout a standard 360 degrees circular rotation. Compared with SPECT using parallel-hole collimation, angled-collimator SPECT (A-SPECT) yielded approximately a 30% increase in resolution without significant losses in sensitivity. The full width at half maximum in reconstructed transaxial images of Tc-99m line sources was 1.2 cm for the A-SPECT system compared with 1.6 cm for conventional SPECT, and A-SPECT yielded substantial improvements in modulation transfer function for the line source. A-SPECT images of phantoms and of patients with paranasal sinus disease were consistently superior in resolution to those of conventional SPECT. The findings suggest that A-SPECT will improve the quality of cranial images obtained with rotating camera SPECT systems.

Brain↗
PubMed1983

Left ventricular volume determined from scintigraphy and digital angiography by a semi-automated geometric method.

The utility of a semi-automatic method of measuring left ventricular (LV) volume geometrically from gated blood-pool studies and digital subtraction angiography (DSA) was investigated using computerized edge detection and spatial calibration algorithms. LAO LV volumes determined from gated blood-pool studies were compared to volumes obtained from contrast left ventriculograms in 21 patients and the applicability of this method to DSA was evaluated in 25 additional patients who also had conventional left ventriculography. There was excellent correlation between the two, both for radionuclide studies and for DSA. Computer-based geometric determinations of LV volume appear to be rapid, accurate, and less dependent on subjective operator decisions than previously reported geometric approaches.

Adult↗
PubMed1982

Spatial calibration of digital scintigraphic images: work in progress.

Accurate scintigraphic determination of organ dimensions is often difficult because of the wide variety of camera-collimator combinations and display formats used for imaging. An algorithm (SPACE-CAL) was developed for digital spatial calibration of up to six large- or small-field gamma cameras using various collimators and magnification factors. The algorithm employs a master calibration file that can be used at multiple terminals. An interactive subroutine permits the operator to measure distances and areas directly from the images. Evaluation of three operators' measurements of a pine-tree phantom acquired at various magnifications showed that distances could be measured with a high degree of accuracy. Calculation of ejection fraction from end-diastolic and end-systolic areas determined by SPACE-CAL showed a high correlation with automatic count determinations (r = 0.96) and angiographic calculations (r = 0.93) of ejection fraction in 12 patients. SPACE-CAL provides an easily implemented, reproducible, and rapid method for accurate analysis of organ dimensions in digital images.

Computers↗
PubMed1981

Fluorescent thyroid imaging. Physical evaluation of an alternative instrument.

The authors describe a rectilinear scanner-head assembly containing an x-ray tube and a Si(Li) detector developed to stimulate and detect fluorescence from intrinsic iodine in the thyroid. Various operational parameters were evaluated. Because of the abundant supply of photons, a scanning distance of 3 inches (7.62 cm) could be used. The full width at half maximum at this distance was 0.52 cm. Optimal exposure was obtained at 80 kVp, 0.5 mA with a copper-aluminum filter combination. The scanner with an x-ray generator appears to be a workable alternative to imaging devices using long-lived radionuclide sources.

Fluorescence↗
PubMed1979

Fluorescent thyroid imaging: clinical evaluation of an alternative instrument.

Fluorescent imaging of the thyroid was performed successfully in 43 patients with incident low-energy photons generated by an x-ray tube. The images were comparable in quality and information content to those obtained with 123l or 99mTc pertechnetate. The estimated absorbed radiation dose to the gland is approximately 40 mrads. Fluorescent imaging is a clinically useful means of evaluating the thyroid.

Evaluation Studies as Topic↗
PubMed1978

Altered body distribution of [99mTc] pertechnetate in iatrogenic hyperaluminemia.

Failure of intravenously administered [99mTc] pertechnetate to leave the vascular space was observed in a patient with hyperaluminemia due to treatment with an antacid drug containing aluminum hydroxide. A repeat study 3 mo after discontinuing medication, when the plasma aluminum level had fallen, revealed normal in vivo distribution of pertechnetate. It was found that instant thin-layer chromatography, using pertechnetate and an 85% methanol system, can detect plasma aluminum levels as low as 50 microgram/l.

Adult↗
PubMedDate not supplied

Quantitative analysis of coronary arteriograms by microprocessor cinevideodensitometry.

A rapid microprocessor technique for measuring the cross-sectional area, diameter, and relative percentage stenosis of coronary atherosclerotic lesions by cinevideodensitometric analysis was developed and validated. Video images of projected 35-mm coronary arteriographic cine frames were analyzed from cinevideodensitometric profile curves recorded for the catheter shaft, normal artery, and stenotic segment. In radiographic phantom studies of calibrated, contrast-filled, plexiglass cylinders, cinevideodensitometric measurements correlated linearly with percentage relative stenosis (r = 0.98; SEE = 4.1%), diameter (r = 0.99; SEE = 0.12 mm), and cross-sectional area (r = 0.99; SEE = 0.32 mm2). In postmortem studies of two patients dying after coronary arteriography, cross-sectional areas of arterial segments measured by cinevideodensitometry correlated well (r = 0.99; SEE = 0.71 mm) with areas of acrylic resin casts of the coronary arteries. Intraobserver variability (r = 0.99; SEE = 2.6%) and interobserver variability (r = 0.96; SEE = 5.3%) of cinevideodensitometric measurements of coronary arteriograms were low. Additionally, percentage relative stenosis measured in the right anterior oblique projection correlated well with measurements in the left anterior oblique projection (r = 0.98; SEE = 0.11 mm2) of patients with eccentric stenotic lesions. Lastly, cinevideodensitometric measurements were significantly (p less than 0.05) more reproducible than caliper measurements. This inexpensive dedicated microprocessor system provides rapid cinevideodensitometric measurements of coronary arterial dimensions, without requiring manual tracing of arterial segments or the major expense of a main-frame computer system.

Absorptiometry, Photon↗
PubMedDate not supplied

The peanut orbit: a modified elliptical orbit for single-photon emission computed tomography imaging.

The front collimator surface of a conventional single-photon emission computed tomography (SPECT) detector system transcribing an elliptical orbit to approximate body contour could, under certain circumstances, penetrate the ellipse and make patient contact. The problem is associated both with the large front surface dimensions of tomographic cameras and the need to maintain the camera perpendicular to a radius through the axis of rotation. To aid in the development of an improved body contour orbit, software has been developed to simulate SPECT imaging systems. A major feature of the algorithms is a spatially calibrated graphic representation of the pallet, patient and orbit of the camera head. Based on computer simulations performed with this software, a modified elliptical orbit has been proposed for patient contour SPECT scanning on two different types of tomographic acquisition systems: a dual camera, rotating ring system and a single camera, multimotion stand system. This peanut orbit has the advantage of minimizing collimator patient distance, as does the elliptical orbit, but also compensates for camera motion that could potentially produce patient contact. Versions of the peanut orbit algorithms have been installed and are operational on clinical systems similar to those that were simulated. The ring-based gantry system (with cameras mounted on cantilevered arms) requires additional software to correct for translational shift in the field of view as a function of radial distance from the center of the system. This is done during uniformity correction. Standard unmodified backprojection software is used for reconstruction. The peanut orbit may represent an improved approach to body contour imaging in rotational SPECT.

Algorithms↗