Biomedical subjects
Publications and source records attributed to J W Keyes.
Explore the source record for details and available documents.
The effectiveness of intra-arterial chemotherapy is dependent on a high tumour to normal blood flow ratio (T/NT). This report demonstrates the use of a vasoconstrictor (NE) to improve the relative blood flow to head and neck tumours by causing vasoconstriction and decreased blood flow to normal soft tissue. Five quantitative planar Tc-MAA perfusion studies were performed on three patients with increasing dose rates of norepinephrine (NE) to determine the optimal dose in each patient that would produce the best T/NT. All patients demonstrated a change in perfusion pattern with increasing dose rates (0.1 to 15 micrograms min-1), although there was considerable variation between patients. Quantitative SPECT was performed on two patients. In one, there was a 35% increase in the T/NT and a 16% decrease in arteriovenous (A-V) shunting to the lung.
The utility of single-photon emission computed tomography (SPECT) for hepatic arterial perfusion scintigraphy was evaluated in 86 patients (91 studies). Previous reports have shown planar studies to be valuable for the clinical management of patients receiving intraarterial chemotherapy and more reliable than angiography in determining blood flow distribution. However, overlying areas of intra- and extrahepatic perfusion can sometimes make interpretation of these two-dimensional images difficult. Since SPECT has the potential to depict the three-dimensional distribution of perfusion, separate out overlying activity, and improve contrast resolution, SPECT Tc-MAA perfusion studies were compared to planar studies. Planar and SPECT studies both demonstrated the extent of hepatic and tumor perfusion, although occasionally SPECT added additional information. SPECT was most useful in confirming or excluding extrahepatic perfusion that was suspected but not definite on planar studies. Extrahepatic abdominal perfusion was found to be present in 11 (12%) of 91 studies. All patients with confirmed extrahepatic perfusion who received intraarterial chemotherapy had symptoms of drug toxicity compared to only a 23% incidence in those without evidence of extrahepatic perfusion (p less than 0.001). This report demonstrates that SPECT can improve the qualitative interpretation of hepatic arterial perfusion studies.
Explore the source record for details and available documents.
The therapeutic advantage of intraarterial infusion chemotherapy depends upon delivery of a high drug concentration to the entire tumor bulk with maximum sparing of critical normal tissues. It is clear that successful application of regional therapy must include methodology to assess quantitatively and qualitatively the infused area. 99mTc macroaggregated albumin (Tc-MAA) injected intraarterially is held on first pass in the arteriolar capillary bed, thus providing a map of blood flow distribution. Analog and digital planar images and single photon emission computed tomography (SPECT) after Tc-MAA injections provide static and transaxial tomographic images of head and neck intraarterial infusions. SPECT can be viewed as an endless movie-type display, thus producing a "rotating cimematic display." These radionuclide localization techniques provide a three-dimensional delineation of the tissues infused, including subsurface details not appreciated with dye injection alone. These procedures should be considered an integral part of intraarterial therapy of head and neck cancer.
The clinical utility of a computer-generated dynamic cine display (rotating display) of the unprocessed projection images of the liver and spleen obtained with rotating gamma-camera tomography was prospectively compared with that of the standard multi-view static scintigram display. Two hundred cases were independently and blindly analyzed by three observers. Each study was coded from 1-5, indicating the certainty of normality or abnormality present. When abnormality was noted, the study was assessed for the presence of metastatic disease, inhomogeneous uptake, hepatosplenomegaly, and colloid distribution shift. ROC analysis was then performed on the initial coding for certainty of abnormality, and the causes for discrepancies were evaluated from the assessment of the type of abnormality present. No significant interdisplay differences could be demonstrated. In the small percentage of cases where interdisplay disagreement occurred, this was usually accompanied by marked interobserver variation and was most commonly due to differing assessment of organ size. It is concluded that the static and rotating display formats can be used interchangeably in the evaluation of technetium-99m-labeled sulfur colloid liver studies.
A prospective comparison of conventional scintigrams and single-photon emission computed tomography (SPECT) studies of the liver and spleen was carried out. Care was taken to insure high-quality, artifact-free studies. Two hundred patients were imaged by both methods. A definitive diagnosis of normal was established in 86 cases, abnormal in 107 cases, and seven cases were indeterminate. All studies were read by two observers and graded as to degree and type of abnormality seen. ROC curves were constructed and errors of interpretation studied to identify problems. One observer showed no difference in performance between the two methods. The other showed a small improvement with SPECT. Image artifacts apparently contributed to errors of interpretation in 24 of 54 cases using SPECT. SPECT appears comparable with conventional scintigraphy and may improve specificity. Improvements are needed in SPECT imaging equipment and image display capability to realize fully the potential of SPECT.
Single photon emission computerized tomography coupled with Tc-99m MAA hepatic-arterial perfusion scintigraphy has been used to examine the density of the functional microcirculation of hepatic tumors relative to normal liver in 24 patients. In both colorectal and carcinoid tumors we have demonstrated an average three-fold greater arteriolar-capillary density in areas of tumor proliferation. The depth of the evoked tumor hypervascularity was found to extend about 4 cm. Tumors greater than 8-9 cm in diameter were uniformly found to have a central hypovascular core. These observations are of importance in the design of selective strategies utilizing therapeutic microspheres directed against the hypervascular proliferating regions of human tumors.
SPRINT, a prototype single photon tomograph, has been designed primarily for high-resolution brain imaging in humans with I-123-labeled compounds such as iodoamphetamine, hydroxyiodopropyldiamine (HIPDM), and iodobenzene (IBZ). SPRINT uses a ring of stationary, discrete Nal detectors, and fan-beam sampling is accomplished with a rotating eight-slit aperture ring that acquires a complete projection set in 1/8 revolution. In-plane and cross-plane resolutions are 8mm and 10mm FWHM, respectively, measured on axis. Sensitivity with an 18% energy window is 1000 cprs per microCi/cc for Tc-99m in a 20 cm diameter phantom. A detailed evaluation of system performance has been completed, and preliminary human brain blood flow images have been obtained using HIPDM.
Limited-angular-range tomography leads to an elongating distortion of the object in the direction of the z axis (perpendicular to the camera face). Two-view tomography appends to the usual data set another set of projections taken after the camera is rotated 90 degrees about an axis perpendicular to z. We investigated two-view tomography using a rotating-slant-hole collimator, 12 projections per view and the SMART iterative algorithm. Computer simulations extended previous results to include noise and attenuation. Phantoms imaged were the Au-rings in air and a ventricle phantom angled with respect to the z axis and placed in a water bath. Two-view results were generally superior compared to one-view results, were subject to some artifact in imaging defects, but could detect defects by looking at the differences between two sets of images, and were fairly insensitive to ventricle angulation. Therefore, two-view tomography has promise for thallium-type imaging.
Explore the source record for details and available documents.
The evaluation of jeopardized myocardial mass is important in defining the effect of interventions during myocardial infarction. To quantitate the in vivo mass at risk, 2-dimensional echocardiography (2-D echo) and thallium-201 single-photon emission computed tomography (SPECT) was performed in 10 closed-chest dogs after circumflex coronary artery occlusion. The 2-D images were manually digitized to compute left ventricular (LV) mass using a modified Simpson's rule algorithm. This measure of LV mass correlated well with the actual LV mass (r = 0.97). Perfused myocardial mass was estimated from thallium SPECT images 4 hours after occlusion using a region-growing algorithm. After the dogs were killed, the jeopardized mass was outlined using a dual perfusion staining technique using triphenyltetrazolium chloride and Evans blue dye. The actual perfused mass was well estimated by the thallium images (r = 0.96). The noninvasively determined mass at risk was calculated as: 2-D mass--thallium SPECT mass, and correlated well with the pathologically determined mass at risk (r = 0.91). Thus, the jeopardized mass may be determined noninvasively by using 2-D echo and thallium-201 tomography. This approach may provide further information regarding the effect of intervention therapy on jeopardized myocardium.
A technique is presented for the bedside performance of radionuclide cisternography in the preterm neonate. Using a portable gamma camera, with a low energy, converging collimator, high quality diagnostic images were obtained in 31 infants, following the lumbar subarachnoid injection of 100 micro Ci In-111 DTPA. The technique is safe, and provides valuable information about CSF dynamics unavailable by any other method.
Radionuclide lumbar cisternography using indium 111-diethylenetriamine pentaacetic acid (111In-DTPA) and a mobile gamma-camera with a converging collimator was utilized as a bedside procedure to evaluate CSF dynamics and the patency of the cerebral ventricular system in 30 preterm infants with hydrocephalus. Serial images of the brain were obtained at 0, 1, 2, 6, 24, and 48 hours after instillation of the isotope in the lumbar subarachnoid space. Three distinct patterns were seen. Infants with posthemorrhagic hydrocephalus displayed prompt ventricular filling but markedly delayed emptying with minimal flow over the cerebral convexities. Infants with ventriculomegaly secondary to suspected brain atrophy or periventricular leukomalacia demonstrated a pattern of prompt ventricular filling, delayed emptying, but with flow present over the convexities. An infant with noncommunicating hydrocephalus secondary to an Arnold-Chiari malformation showed a pattern of complete obstruction with no ventricular filling. Radionuclide lumbar cisternography appears to be a safe, well-tolerated procedure which produces images of sufficient resolution to provide valuable information about CSF dynamics, delineating basal cisternae, ventricles, and subarachnoid flow paths.
Two diagnostic schemes for detection of pulmonary embolism by ventilation-perfusion (V-P) scintigraphy were compared for relative accuracy by two groups of observers interpreting 70 V-P scintiscans. Observers in Group B, who used the criteria recently proposed by Biello et al., had a significantly smaller average number of "indeterminate" interpretations (41%) than did the observers in Group A (55%), who used a simpler scheme (p less than 0.05). In addition, Group B showed a slight improvement in positive predictive value without a deterioration in the negative predictive value compared with Group A. Along with this improvement in diagnostic performance, Group B achieved a significant reduction in interobserver variability compared with Group A for patients without pulmonary embolism (p less than 0.05). There was no significant difference in interobserver variability between the two groups for patients with pulmonary embolism. The diagnostic scheme introduced by Biello et al. represents a useful improvement for the diagnosis of pulmonary embolism by V-P imaging.
Explore the source record for details and available documents.
Emission computed tomography with a rotating camera places stringent requirements on camera uniformity and the stability of camera response. In terms of clinical tomographic imaging, we have studied the statistical accuracy required for camera flood correction, the requirements for flood accuracy, the utility and validity of flood and data image smoothing to reduce random noise effects, and the magnitude and effect of camera variations as a function of angular position, energy window, and tuning. Uniformity of the corrected flood response must be held to better than 1% to eliminate image artifacts that are apparent in a million-count image of a liver slice. This requires calibration with an accurate, well-mixed flood source. Both random fluctuations and variations in camera response with rotation must be kept below 1%. To meet the statistical limit, one requires at least 30 million counts for the flood-correction image. Smoothing the flood image alone introduces unacceptable image artifacts. Smoothing both the flood image and data, however, appears to be a good approach toward reducing noise effects. Careful camera tuning and magnetic shield design provide camera stability suitable for present clinical applications.
Explore the source record for details and available documents.