Horace H. Hines

New approach to interpretation of technetium-99m pyrophosphate scintigraphy in detection of acute myocardial infarction: Clinical assessment of diagnostic accuracy

A modified classification for interpreting technetium-99m pyrophosphate scintigrams defines the 2+ diffuse pattern of tracer uptake as equlvocal rather than positive for acute myocardial infarction. Results of scintigraphy using this classification were compared with results of standard diagnostic tests for myocardial infarction in 235 patients admitted to a coronary care unit with acute chest pain. Of 81 patients with acute transmural infarction by standard clinical, electrocardiographic and serum enzyme criteria, 76 had a positive, 5 an equivocal and none a negative scintigram. Of 18 with acute nontransmural infarction by standard criteria, 7 had a positive, 9 an equivocal and 2 a negative scintigram. This it was uncommon for a patient with acute myocardial infarction, transmural or nontransmural, to have a definitely negative technetium-99m pyrophosphate study. Ten patients had equivocal evidence of infarction by standard criteria. Of the remaining 126 patients with no evidence of acute myocardial infarction by standard criteria, 87 had a negative, 35 an equivocal and 4 a definitely positive scintigram. Thus the definitely positive scintigraphic pattern was relatively highly specific for acute myocardial infarction. If the 2+ pattern had been considered positive, the specificity of the technique would have been greatly decreased. Computer processing strengthened observer certainty of the visual impression but changed the scintigraphic evaluation in only eight cases. Thus, use of an equivocal pattern renders technetium-99m pyrophosphate imaging both an extremely sensitive and specific method for detecting acute myocardial infarction.

Requirements for a treatment planning system for radioimmunotherapy

Cancer-seeking antibodies carrying radionuclides can, in theory, be very powerful agents for the radiotherapy of cancer. However, as with all radiotherapy, the undesired dose to critical normal organs is the limiting factor that determines success or failure. The distribution of radiation dose in cancer and noncancer tissue is highly dependent on choices the therapist can make: choices of the antigens to be targeted, choices of the antibodies or antibody fragments to be used, choices of radionuclides, of amounts, of timing, and other electives. New technologies, especially of monoclonal antibody production, make the options myriad. Optimization of this therapy depends on a foreknowledge of the radiation dose distributions to be expected. The necessary data can be acquired by established tracer techniques, in individual patients, for particular treatment selections. These tracer techniques can now be implemented by advanced equipment for quantitative, tomographic radionuclide imaging and strengthened by dynamic modeling of the physiological parameters which govern radionuclide distribution, and hence radiation dose distribution.

Recommendations for implementing SPECT instrumentation quality control

This document describes a general approach to routine quality control (QC) of single-photon emission tomography (SPECT) instrumentation. Its intent is to provide recommendations, based upon good clinical practice, that both the manufacturers and the user community can support. It represents a broad spectrum of views of manufacturers, medical physicists and nuclear medicine technologists. The document’s further intent is to provide insights into the need for SPECT QC, to describe some of the critical performance parameters of a scintillation camerabased SPECT system that are likely to vary with time, and to describe in general terms the set of tests deemed most helpful for a routine QC program. Three important points must be made at the outset: 1. The purpose of routine QC is to detect changes in per formance from a baseline condition. Typically, base line characterization is performed by acceptance testing (for example, following the NEMA protocols described in NU 1, “NU 1-1994, Performance Measurement of Scintillation Cameras.”). Thus, routine QC measurements focus on the detection of a change from baseline, rather than on absolute characterization per se. 2. Performance requirements for a scintillation camerabased SPECT system are more stringent than the requirements for planar imaging with the same camera. Therefore, performing the measurements described in this document will satisfy planar imaging QC in addition to SPECT QC. 3. A routine QC program must include a sufficiently comprehensive suite of individual measurements to ensure adequate sensitivity to detection of detrimental changes in performance. At the same time, the criteria used to judge the outcome of routine QC must not be so strict as to misleadingly identify insignificant changes as important. In this regard, a routine SPECT QC program should give technologists and clinicians the data with which to decide whether: – to image patients normally, or – to image patients while putting in a call to have the system serviced, or – to put off imaging patients until the system has been serviced and fixed. In generating the recommendations described herein, several characteristics of an acceptable SPECT QC program were deemed critical: • It should not be burdensome. • It should realistically reflect the clinical use of the system. • It should emphasize measures of the stability of the system. • It should accurately reflect the adequacy of the state of the system for clinical use. Since SPECT systems vary significantly in design, it was not possible to describe in detail all measurements to be performed (for example, specific acquisition and reconstruction parameters); for this, the user is referred to the specific recommendations of the system’s manufacturer. In this regard, when specific aspects of the recommendations given herein contradict manufacturer’s specific recommendations, the manufacturer’s recommendations take precedence. One final word of caution: The fundamental design of scintillation camera-based SPECT systems results in multiple performance parameters being coupled or linked. Thus, it is likely that an electrical or mechanical change in the system will result in changes in several measured parameters. In such a situation, it is tempting to rely on the measurement of only one or two parameters (e.g., uniformity)

Problem of diffuse cardiac uptake of technetium-99m pyrophosphate in the diagnosis of acute myocardial infarction: Enhanced scintigraphic accuracy by computerized selective blood pool subtraction

Abstract Because considerable controversy attends the interpretation of the diffuse uptake pattern of technetium-99m pyrophosphate scintigraphy, a practical computerized method for selective subtraction of the cardiac blood pool from these equivocal technetium-99m pyrophosphate scintigrams is described. The technique employs injection of a readily available radiopharmaceutical (technetium-99m pertechnetate) and standard computer software. The subtraction process allows subclassification of the equivocal scintigrams into two groups: one with definite myocardial localization of radioactivity, and the other without evidence of myocardial labeling. The clinical utility of this selective subtraction technique was assessed in 35 patients with equivocal pyrophosphate scintigrams and in an additional 13 patients with probably abnormal scintigrams by comparing the results of the subtraction scintigraphy with the final clinical diagnosis based on history, serial electrocardiograms and serial cardiospecific serum enzyme determinations. The results demonstrated that the subclassification based on computerized selective blood pool subtraction is clinically useful: If definite myocardial localization is demonstrated after subtraction, acute infarction is likely, whereas, if no myocardial localization is evident after subtraction, acute infarction is highly unlikely. Therefore, the addition of this simple selective blood pool subtraction technique to standard pyrophosphate imaging has been found to improve the overall effectiveness of pyrophosphate scintigraphy in the detection of acute myocardial infarction.

Video Requirements For Digital Subtraction Angiography

The television camera comprises an important link in the imaging chain of digital subtraction angiography equipment. Various factors including spatial resolution, signal to noise ratio (SNR), progressive and interlaced read out, exposure utilization and camera lag are investigated. Requirements for the video camera for optimized DSA studies include sufficient bandpass to satisfy digitization matrix sizes, an 800:1 camera SNR, progressive read out of the camera target, and bias light to minimize build-up lag response.

Information Detection In Diagnostic Radiology

We use Digital Subtraction Radiography (DSR) as a vehicle to clarify, simplify and correct some contemporary notions of the physics and psychophysics of radiological image detection.