Cost containment in Oregon: as simple as A x B?
Explore the source record for details and available documents.
Cost Control↗
Biomedical subjects
M L Goris
Publications and source records attributed to M L Goris.
Overview of animal studies comparing radioimmunotherapy with dose equivalent external beam irradiation.
As the field of radioimmunotherapy (RIT) continues to develop and looks increasingly promising, there is growing interest in the radiobiology of RIT. Recently, several investigators have conducted studies in animal models comparing the relative efficacy of RIT with dose equivalent external beam irradiation. Although these studies are the first of many to follow, the results are provocative and several patterns are suggested by the available data. The results of the studies are summarized and compared, and preliminary hypotheses that might explain the reported observations are discussed. In summary, results from studies comparing the efficacy of RIT with external beam irradiation have been variable and may be indicative of different underlying mechanisms. While the particular experimental model, design and methodology used to compare the efficacy of RIT with external beam irradiation are probably important influences upon subsequent observations, it appears that for a given tumor type, the size of the survival curve shoulder or alpha/beta ratio, and tumor doubling time are important determinants of the magnitude of the dose rate effect. When this effect is minimal, it is possible that other factors such as reoxygenation, the arrest of cells in G2, and selective targeting of tumor by radiolabelled antibody may explain, in part, the increased efficacy of RIT compared with external beam irradiation that has been observed in some systems.
Animals↗
The effect of unlabelled monoclonal antibody (mAb) on the biodistribution of 131I-anti-idiotype mAb in murine B cell lymphoma.
The 38C13 murine B cell lymphoma model was used to study the effect of the preinjection of unlabelled anti-idiotype monoclonal antibody (mAb) on the subsequent biodistribution of 131I-anti-idiotype mAb. Mice with established tumors received 0-500 micrograms of unlabelled anti-idiotype mAb 24 h prior to the administration of 131I-anti-idiotype (specific), or both 125I-anti-idiotype and 131I-isotype-matched irrelevant control (nonspecific) mAb. Mice were counted daily in a gamma counter and sacrificed at 2-144 h following injection. Mice were dissected and the weight and activity of the animals and organs were measured. Mice were bled periodically and circulating idiotype levels were measured using an ELISA assay. Five hundred micrograms of unlabelled anti-idiotype mAb increased the retention time of the specific but not the nonspecific mAb in all organs and tumor. Following pretreatment with unlabelled mAb, the cumulative tumor/whole body and tumor/normal organ ratios became similar to those of the nonspecific mAb, with concentration ratios (specific/nonspecific mAb) of approximately 1, which persisted until 96 h post injection when circulating idiotype reappears in antigen excess. In the absence of unlabelled mAb there was less retention in tumor and normal tissue. This is presumed to be due in part to decreased levels of circulating 131I-mAb secondary to rapid plasma clearance of antigen-antibody complexes and tumor cell mediated dehalogenation, which results when the specific mAb specifically binds the targeted antigen. Thus, the addition of unlabelled mAb increased the retention by decreasing the specific behavior of the anti-idiotypic antibody.
Animals↗
Parathyroid imaging. Use of dual isotope scintigraphy for the localization of adenomas before surgery.
Seventy-nine patients with primary hyperparathyroidism, whose average preoperative blood calcium level was 11.6 mg/dl, underwent thallium-technetium dual isotope scintigraphy of the thyroid and parathyroids. For patients who had surgery, the detection and localization rate of parathyroid disease or the sensitivity was low (0.53), but the positive predictive value for the location was high (0.80). Correct localization correlated positively with the weight of the tumor but not significantly with the parathyroid hormone blood level nor with the blood calcium level. Unprocessed data alone were sufficient to predict correctly the location in two thirds of the detected cases. Computer processing increased the sensitivity without decreasing the specificity. Those results, at variance with earlier published data but congruent with another more recent study, require a reevaluation of the role of this scintigraphic technique in the management of hyperparathyroidal patients.
Adenoma↗
Of theoretical derivations and empirical evidence.
Explore the source record for details and available documents.
Heart↗
Long-term scintigraphic appearance of extremities following bone tumor resection and allograft reconstruction.
The authors retrospectively reviewed the Tc-99m medronate scan findings in six patients who had no evidence of metastatic disease following en bloc resection of a primary osteosarcoma and subsequent limb reconstruction using allograft bone. Persistently increased radionuclide uptake was noted at the junction between the host bone and the graft, while the graft cortical bone showed persistently decreased activity. Radionuclide uptake at the periphery of the graft varied. Over time the youngest patient in the series had increasingly normal scan findings.
Adolescent↗
The biodistribution of 111In-anti-bFGF in a variety of tumors. Correlation with cell-binding assays.
Explore the source record for details and available documents.
Animals↗
Parathyroid imaging.
Explore the source record for details and available documents.
Costs and Cost Analysis↗
The quantification of planar scintigraphy using three dimensional modelling of organ shadows.
A method to define biodistribution from planar scintigraphic data is presented. Sampling regions or regions of interest (ROI's) are first defined as the projection contour of organs. From anatomical knowledge the three dimensional volume of the organ whose shadow has been traced is reconstructed. When the relevant organ volumes including the whole body or relevant whole body part have been defined, the count rate density in each pixel is assumed to represent the sum of the product of the projecting organ partial volumes times the tracer concentrations in the underlying organs. The solution (the definition of organ concentrations) is found by a matrix inversion. Validation is obtained in two ways. The first method is illustrative: an image is reconstructed from the defined volumes modulated by the computed concentrations. This image, if the method is correct, should be a crisp equivalent of the original data and closely similar to it following blurring with a convolution kernel equal to the imaging system's point spread function. The second is analytical: from reconstructed S.P.E.C.T. data in which voxel values are directly proportional to organ concentrations, a planar image is reconstructed. Organ average voxel values are computed in the S.P.E.C.T. image with volumetric ROI's and in the reprojected planar image using the method described here. The methods should yield the same concentration data but for a scaling factor. The method has the advantage that it yields volumetric and concentration data which are directly applicable to MIRD type analysis. In effect, the standard man assumptions in MIRD analysis have been incorporated in the calculation of the concentrations.
Humans↗
Determinants of the antitumor effect of radiolabeled monoclonal antibodies.
The murine B-cell lymphoma 38C13 model was used to study the radiobiological effect of 131I-monoclonal antibody (MAB) therapy compared with dose equivalent external beam irradiation. Continuous exponentially decreasing low dose rate (LDR) gamma-irradiation, and multiply fractionated (MF) X-irradiation were compared with dose equivalent 131I-MAB. The relative therapeutic efficacy of radioimmunotherapy, and the relative contribution of (a) low dose rate; (b) whole body irradiation; and (c) microdosimetry to the overall effect were determined. Groups of mice with or without B-cell lymphoma were treated with either (a) 131I-anti-idiotype MAB; (b) 131I-isotype-matched irrelevant control MAB; (c) 5-15 Gy 250 kV X-irradiation given as a single fraction; (d) 2.5-30 Gy 250 kV X-irradiation given in 10 fractions/2 weeks; or by (e) continuous exponentially decreasing gamma-irradiation via a 137Cs source, which simulated the effective t1/2 of the 131I-MAB. In tumor-free mice the LD50/30 was approximately 10 Gy for MF and LDR external irradiation, and 11-12 Gy for 131I-MAB. However, the effect of these modes of irradiation on tumor size differed significantly. The cumulative percentage of tumor reduction averaged over 12 days was 0.635 +/- 0.055%/Gy for MF, and 1.36 +/- 0.061%/Gy for LDR external irradiation (a relative efficacy factor of 1.63 for LDR irradiation; P = 0.01). Assuming homogeneous body distribution, the tumor reduction effect over 12 days for 131I-MAB was 2.064 +/- 0.133%/Gy for specific, and 1.742 +/- 0.1%/Gy for nonspecific isotype-matched irrelevant 131I-MAB (P = 0.02). When 131I-MAB was compared to LDR external irradiation, the relative efficacy factor was 1.99 (P less than 0.001). In summary, there was a dose rate effect on tumor response, which may in part explain the efficacy of radioimmunotherapy. The additional effect of 131I-MAB on tumor response was only partially explained by the cumulative concentration ratio of 131I-MAB tumor/131I-MAB whole body, which was on average 1.7. This relatively low concentration ratio was partly due to tumor-mediated dehalogenation. Thus, the overall tumor response was a function of the total dose, dose rate, and both the specific and nonspecific distribution of 131I-MAB.
Animals↗
Validation of diagnostic procedures on stratified populations: application on the quantification of thallium myocardial perfusion scintigraphy.
In this report we present a method for the quantitative description of the degree of deviation from the norm of 201thallium single photon emission tomographic (SPECT) data. Validation is obtained from the frequency of "positive" outcomes in subgroup of patients in whom the prevalence of coronary artery disease, for the group as a whole, is known, even if individual patient outcomes are not verified. This approach overcomes the bias associated with nonrandomized clinical studies, in which the likelihood that a more invasive but definitive procedure (coronary arteriogram) will be performed is influenced by the result of the outcome of the procedure under study.
Coronary Disease↗
Improved specificity of prone versus supine thallium SPECT imaging.
Explore the source record for details and available documents.
Exercise Test↗
Noninvasive assessment of donor and native heart function after heterotopic heart transplantation.
The contribution of the donor heart to total circulatory performance after heterotopic heart transplantation has been difficult to assess. First-pass nuclear angiocardiography and directional Doppler echocardiography were used to examine separately left and right ventricular function of the donor heart after heterotopic transplantation. A comparison was made between two patients, one with a low initial pulmonary vascular resistance and one with a high, relatively fixed pulmonary vascular resistance. In both cases, currently available noninvasive techniques allowed confirmation of the expectation that the donor left ventricle can function effectively as a left ventricular bypass. In neither case was recovery of the native heart demonstrated. The contribution of the donor right ventricle to total right ventricular output appeared to be dependent on the condition of the donor heart and on the pulmonary vascular resistance. In situations with a high pulmonary vascular resistance and end-stage right ventricular failure, it was concluded that the donor heart may not at first constitute an effective assist for the native right ventricle. Native right ventricular failure may then become a major factor influencing survival after heterotopic heart transplantation.
Adolescent↗
Considerations in the purchase of a nuclear medicine computer system.
Selection of a nuclear medicine computer system is a process that should be approached with care and forethought. The general scheme should be to define your needs and constraints, determine what is available, investigate the leading candidates, make a site visit, and, finally, submit an order. Through a series of discussions between members of the Computer Council of the Society of Nuclear Medicine and representatives from the manufacturers of computer systems, a set of important considerations emerged, which are reported in this paper. This paper is not intended to be a step-by-step guideline to the purchase of a computer system. Rather, it is a set of concepts and considerations with which the prospective purchaser should be familiar before undertaking such a purchase.
Computer Systems↗
Two-dimensional mapping of three-dimensional SPECT data: a preliminary step to the quantitation of thallium myocardial perfusion single photon emission tomography.
A method is presented by which tomographic myocardial perfusion data are prepared for quantitative analysis. The method is characterized by an interrogation of the original data, which results in a size and shape normalization. The method is analogous to the circumferential profile methods used in planar scintigraphy but requires a polar-to-cartesian transformation from three to two dimensions. As was the case in the planar situation, centering and reorientation are explicit. The degree of data reduction is evaluated by reconstructing "idealized" three-dimensional data from the two-dimensional sampling vectors. The method differs from previously described approaches by the absence in the resulting vector of a coordinate reflecting cartesian coordinate in the original data (slice number).
Coronary Circulation↗
Interrogation and display of single photon emission tomography data as inherently volume data.
The purpose of single photon emission computed tomography (SPECT) data is to map the tracer concentration from the three-dimensional object into a three-dimensional image array. The conventional interrogation of the data is through slice interrogation. In this paper we explore display methods in which the data are directly interrogated and processed as three-dimensional data. This includes direct addressing of sagittal, transverse, and frontal slices, around a targeted subvolume, and direct addressing of nonorthogonal slices. The three-dimensional aspect of the data is further accommodated by thresholding and edge definition in space. Finally, morphological information, which is sparse in scintigraphic slices, is recaptured by the generation of planar data derived from data processed in the three-dimensional space.
Data Display↗
Reliability and reproducibility of interpretation of 99mtechnetium pyrophosphate myocardial scintigrams.
The interpretations of 156 99mtechnetium pyrophosphate myocardial scintigrams by four observers were analyzed in order to determine the reliability and reproducibility of the subjective process of reading scintigrams. The scintigrams were scored on an integral scale from 0 to 4, depending upon the degree of myocardial radionuclide accumulation, and the site and nature of uptake were specified. Exact agreement upon score was generally poor but approximate concurrence of interpretation was good (90.4 and 92.5% inter- and intra-observer agreement, respectively). There was somewhat less agreement on scintigrams with the higher scores of 3 and 4 (83.3 and 78.0%, respectively). A high level of concurrence upon the differentiation between diffuse and localized uptake, and upon the site of uptake, was found. We conclude that only approximate rather than exact agreement of individual readers' interpretations can be expected in this subjective technique, that scintigrams with higher degrees of radionuclide accumulation produce slightly greater observer disagreement, and that variability of interpretation could account for some of the diagnostic inaccuracy of 99mtechnetium pyrophosphate myocardial scintigraphy.
Angina Pectoris↗
Cardiac damage produced by direct current countershock applied to the heart.
This study examined the pathophysiology of the myocaridal damage produced by direct current shock over a dose range of 10 to 90 watt-seconds, applied directly to the heart in 26 dosgs. The extent of injury produced was assessed with creatine kinase depletion and light and electron microscopy, and was correlated with in vivo imaging and tissue distributions of the isotopes technetium-99m pyrophosphate and thallium-201. Changes in intramyocardial temperature and regional myocardial blood flow were also measured. Uptake of technetium-99m pyrophosphate occurred exponentially with graded increases in shocks, and this agent was more sensitive than thallium-201 in detecting injury both on imaging and at tissue level. The threshold for significant injury was approximately 30 watt-seconds, and on electron microscopy a characteristic feature was marked dehiscence of the intercalated disks between the damaged myocytes. The use of different-size paddles did not appear to affect the total number of cells damaged. However, with large paddles the injury was more superficial and spread over a wider area. With short time intervals between successive shocks, a greater amount of injury occurred, in part because of a compounding of the thermal component of the damage. Hypothermia can reduce the degree of injury.
Animals↗