An interface between several cameras and two computers, using differential analog transmission.

A system has been built to allow up to four scintillation cameras to be connected in parallel with two computers, yet provide for selection of individual pairs of camera/computer combinations with the exclusion of unwanted connections. Since the distances involved were relatively long, signal drivers were used to transmit the analog signals in a differential mode over multiple twin-paired lines rather than coaxial cable. By transmitting the signals differentially, any noise induced on the signal was subtracted at the receiver. The principal features of this system, which has been installed in two institutions, are described. A problem that occurred in connection with one camera is presented (also its solution), with a suggestion concerning parameters to be assessed at the time of system acceptance.

Automated alignment and sizing of myocardial stress and rest scans to three-dimensional normal templates using an image registration algorithm.

UNLABELLED: To optimize the interpretation of myocardial SPECT, we developed an automated method for alignment, sizing and quantification of images using three-dimensional reference templates. METHODS: Stress and rest reference templates were built using a hybrid three-dimensional image registration scheme based on principal-axes and simplex-minimization techniques. Normal patient studies were correlated to a common orientation, position and size. Aligned volumes were added to each other to create amalgamated templates. Separate templates were built for normal stress and rest SPECT 99mTc-sestamibi scans of 23 men and 15 women. The same algorithm was used to correlate abnormal test-patient studies with respective normal templates. The robustness of the fitting algorithm was evaluated by registering data with simulated defects and by repeated registrations after arbitrary misalignment of images. To quantify regional count distribution, 18 three-dimensional segments were outlined on the templates, and counts in the segment were evaluated for all test patients. RESULTS: Our technique provided accurate and reproducible alignment of the images and compensated for varying dimensions of the myocardium by adjusting scaling parameters. The algorithm successfully registered both normal and abnormal studies. The mean registration errors caused by simulated defects were 1.5 mm for position, 1.3 degrees for tilt and 5.3% for sizing (stress images), and 1.4 mm, 2.0 degrees and 3.7% (rest images); these errors were below the limits of visual assessment. CONCLUSION: Automated three-dimensional image fitting to normal templates can be used for reproducible quantification of myocardial SPECT, eliminating operator-dependence of the results.

Effect of scintillation camera nonuniformity on ejection fraction measurements.

A rotating cardiac phantom with three possible ejection fraction (EF) values was used in conjunction with a scintillation camera employing energy correction and count skim arithmetic for uniformity correction. Studies were collected with and without any correction, with the energy window of the analyzer set properly, and with the camera properly tuned. The uniformity was then degraded in one experiment by off-setting the analyzer window both high and low with respect to the primary photopeak and in another experiment by de-tuning a selected photomultiplier tube. In both experiments studies were taken with no correction enabled, and then with each of the correction options enabled. The results of both experiments show that ejection fraction values could be in error when the differential uniformity using National Electrical Manufacturers Association (NEMA) protocols exceeds 10%. If either energy correction alone, or energy correction combined with count skim correction is used, the ejection fraction values return to more acceptable values. Asymmetric windows, improper setting of the energy window or a badly tuned photomultiplier will likely result in poor analog images before the effect on ejection fraction measurements becomes evident. Uniformity correction devices do not adversely affect the numerical results obtained from these phantom studies, but should, nevertheless, be used with caution.

In vivo red blood cell compatibility testing using indium-113m tropolone-labeled red blood cells.

In vivo radionuclide crossmatch is a method for identifying compatible blood for transfusion when allo- or autoantibodies preclude the use of conventional crossmatching techniques. A technique for labeling small volumes of donor red blood cells with [113mIn]tropolone is reported. The use of 113mIn minimizes the accumulation of background radioactivity and the radiation dose especially so when multiple crossmatches are performed. Labeling red cells with [113mIn]tropolone is faster and easier to perform than with other radionuclides. Consistently high labeling efficiencies are obtained and minimal 113mIn activity elutes from the labeled red blood cells. A case study involving 22 crossmatches is presented to demonstrate the technique. The radiation dose equivalent from 113mIn is significantly less than with other radionuclides that may be used to label red cells.

Collaboration using Internet for the development of case-based teaching files: report of the Computer and Instrumentation Council Internet Focus Group.

UNLABELLED: The Internet and particularly the World-Wide-Web is becoming a useful tool for the nuclear medicine community. METHODS: The Computer and Instrumentation Council of the Society of Nuclear Medicine convened an Internet Focus group to discuss collaboration using the Internet. The prototype application considered was development of case-based teaching files using the World-Wide-Web. Teaching file cases (clinical history, images, description of findings and discussion) on World-Wide-Web servers at different institutions are integrated using the Internet. The user can navigate from case to case using point-and-click hypertext linking. RESULTS: The initial experience with collaboration has been encouraging. An etiquette to help foster collaboration has been proposed. Development of quality control mechanisms and introduction of peer review were identified as issues needing further work. CONCLUSION: The World-Wide-Web offers great potential for new forms of collaboration. There is, however, a need to learn how to make best use of this new resource.

Detection of acute myocardial infarction by technetium-99m polyphosphate.

Experimental work has shown that technetium-99m (99mTc) pyrophosphate accumulates in recently infarcted myocardium and can be detected by external imaging techniques. Twenty-two 99mTc polyphosphate myocardial studies were performed in 17 patients (in 3 after cardiac surgery) 3 to 20 days after myocardial infarction. Seventeen myocardial studies were performed in 17 control patients (in 6 after cardiac surgery). Twenty millicuries of 99mTc polyphosphate was injected intravenously 60 to 120 minutes prior to gamma camera imaging in several views. Myocardial images were processed by the Gamma-11 computer system using standardized background subtraction and contrast enhancement. Results of 16 myocardial studies performed 4 to 20 days after transmural myocardial infarction in 12 patients were positive in 13 instances and questionable in 1. The location of the myocardial infarction by imaging corresponded to location by standard electrocardiograhic criteria in 8 of the 10 patients with positive findings. In five patients with nontransmural myocardial infarction, results of myocardial imaging were positive in two, questionable in one and normal in one. In one patient with questionable findings results were normal when imaging was repeated 16 days after nontransmural myocardial infarction. Results of 17 control myocardial imaging studies were normal in 16 and questionable in 1. Therefore, 99mTc polyphosphate myocardial imaging appears promising in the detection and location of transmural myocardial infarction. Its accuracy in detecting nontransmural myocardial infarction may be increased with greater experience and development of sophisticated digital analysis techniques. The method may prove useful in clinical situations such as cardiac surgery in which standard diagnostic aids are difficult to interpret.

Camera-computer systems for rapid dynamic imaging studies.

The extraction of valuable diagnostic information from rapid, dynamic studies performed on a gamma camera requires that the data be recorded for latter analysis. If these data are to be available rapidly and if quantitative analysis is to be performed, it is imperative that a computer be used in conjuction with the gamma camera. This review describes the more important features of a nuclear medicine computer system both from the point of view of hardware and software. The various aspects that cause some limitations to be imposed on the capability of the system in order to carry out fast, dynamic studies are described and some possible solutions are suggested.

Dependence of ejection fraction results on choice of algorithms for a cardiac phantom.

Ejection fraction results obtained from the Vanderbilt rotating cardiac phantom exhibit a strong dependence on the algorithms used to derive the time--activity curves and calculate the ejection fraction from those curves. This problem is caused because the background chamber is located behind the rotating attenuator which is used to produce the pseudo ejection fraction. As a result, the counts due to background in both the regions on the 'left ventricle' and the area assigned for background correction do not remain constant during the 'cardiac cycle'. This leads to a breakdown in the ejection fraction algorithms. Given the same data, but changing the methods by which the time--activity curves and ejection fractions are derived, ejection fraction results varying from a minimum of 45% to a maximum of 69% have been demonstrated for the 50% attenuator. Although the Vanderbilt cardiac phantom is simple to operate it must be used with caution if it is used with the intention of calibrating a particular system or comparing different protocols.

A file format for the exchange of nuclear medicine image data: a specification of Interfile version 3.3.

Working Group 1 of the European project COST-B2 on quality assurance of nuclear medicine software has been concerned with the development of an appropriate mechanism for the transfer of nuclear medicine image data files between computer systems from different vendors. To this end a protocol based upon Report No. 10 of the American Association of Physicists in Medicine (AAPM) [1] was adopted. A previous publication [2] gave a specification (V3.2) for an intermediate file format with a list of key-value pairs for the header data associated with nuclear medicine image data files. This paper presents a revised specification for the intermediate file format and associated keys, now called V3.3, which has evolved from the experience in using the earlier version. It is hoped that the modifications proposed will improve the definition and usability of the file format as given in the earlier version.

A standard protocol for the exchange of nuclear medicine image files.

In order to meet an increasing demand for a standard file format which would facilitate the exchange of image files from one computer to another, the protocol initiated by Report #10 of the American Association of Physicists in Medicine has been adopted. This protocol uses the concept of an ASCII file in which key-value pairs are used to describe the various parameters of the image file. Keys specific to nuclear medicine image files have been established and are published here. In addition, the latest version of the keys has been placed on a list server which is accessible by electronic mail. This will facilitate the development of conversion programs which will also be placed on the same list server as they become available.

Sustainability--the Holy Grail of telehealth?

The sustainability of a telehealth programme is one measure of its success. However, the term 'sustainable telehealth' has almost become an oxymoron. Many telehealth programmes are initiated in good faith and are based upon well founded principles. Unfortunately, the initial funding cycle is rarely long enough to enable the programme to reach maturity and become integrated into the health-care system. Telehealth does not critically depend on technology; change management is much more important and it takes time for personnel to adopt new modes of practice. In addition, a telehealth programme needs a threshold number of installations before it can be deemed fully operational. In many cases an evaluation carried out at the conclusion of the pilot phase will fail to recognize the initial goals. As a consequence, the criteria used to justify further financial support are often at odds with the original goals and aspirations of the project initiators, and this leads to dissatisfaction by all parties concerned.