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summary 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.

The Internet and particularly the World-Wide-Web is becoming a useful tool for the nuclear medicine community.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.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.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.

A data base of clinical studies is required for quality assurance of software used for analysis of radionuclide cardiac imaging procedures. Studies used must be rigorously validated in terms of both the clinical condition of the patient undergoing the procedure and the imaging protocol used. Selection protocols for the creation of a software phantom data base of normal studies and three typical patterns of cardiac disease--recent transmural myocardial infarction, isolated myocardial ischaemia and dilated cardiomyopathy--have been developed by the Cardiac Working Group of the European COST B2 project in association with the Cardiac Task Group of the European Association of Nuclear Medicine and the Working Group on Nuclear Cardiology of the European Society of Cardiology. These protocols include criteria for the interpretation of qualitative and quantitative non-radionuclide data. Compliance of the clinical data with the selection criteria will have to pass scrutiny by an international team for each study used as a software phantom. The radionuclide studies encompass stress and rest myocardial perfusion studies (planar and single photon emission tomography) using thallium-201 and technetium-99m methoxyisobutylisonitrile and rest gated blood pool studies. Methods for acquisition of data are defined for each type of study and for each individual study a portfolio of all clinical data is established. A pilot study is required to investigate the problems and logistics of distributing clinical radionuclide studies between a range of computers and institutes, and to ascertain the procedures necessary for analytical comparison of the results obtained.

Bernie Huang is an acknowledged expert in the field of PACS and enjoys a well deserved international reputation. In 1996 he published a book entitled `PACS in Biomedical Imaging' which was intended for the training of medical informatics scientists. The present book is, by the author's admission, directed towards a wider audience beyond engineers and medical physicists. It is, in effect, a revision of his earlier book with a number of additional chapters and expanded material. The author has been able to draw upon the experience of past graduate students, postdoctoral fellows and colleagues who have contributed a number of sections. The text is comprehensive in scope ranging all the way from the fundamentals of digital imaging (including microscopic imaging, as well as MRI and nuclear medicine), through standards, compression algorithms, to telecommunications and system design. It concludes with some observations on applications, pitfalls to avoid and projected future developments of PACS. This reviewer found the material lacking in one significant respect. The only reference to any cost analysis of PACS is found in a short section tucked away at the beginning of chapter 15. Not surprisingly, it alludes to a study that demonstrates the cost effectiveness of PACS at a relatively small workload. Only one study is offered as evidence to support the installation of PACS and no contrary arguments are presented. Given the huge investment that PACS implies for any organization contemplating it, this appears to be a major omission in a text dealing with the implementation of the technology. The book should be capable of reaching the wider audience desired by the author. It is well presented with plenty of figures and illustrations to augment the text. It will certainly make a handy reference text for students in medical imaging. However, for those engaged in implementing PACS, it is disappointing not to see a broader overview of the subject with a more intense interest in the value of the technology and its place in the `business' of radiology. The material in this book is still very much bound to the world of academia, without focus on the wider provision of radiological services.

The recent paper by Maguire and Noz [Med. Phys. 1 6, 818–823 (1989)] provides a valuable review of the present situation regarding the interchange of digital image files. They are to be commended for the efforts they have made to promote a suitable standard for image file interchange both within individual modalities and between modalities.

The left ventricular function of 30 patients with coronary artery disease and 11 control subjects was studied by electrocardiography gated cardiac blood pool scintigraphy as the participants lay on their backs and either rested or exercised on a cycle ergometer at graded levels on intensity. The control subject showed a progressive increase in ejection fraction from rest (51% +/- 7%) to intermediate (56% +/- 10%, P less than 0.05) and maximum levels of exercise (64% +/- 10%, P less than 0.001). All the patients showed a decrease in ejection fraction from rest (42% +/- 16%) to their maximal level of exercise (36% +/- 11%, P less than 0.001). However, the response of some of the patients to intermediate exercise ranged from a decrease or no change to an increase in ejection fraction. Thus, exercise at maximal intensity is necessary to induce the left ventricular dysfunction that is diagnostic of coronary artery disease.

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.

Left ventricular function and volume changes during supine isotonic exercise were assessed in 32 patients with coronary artery disease (CAD) and 12 normal subjects by electrocardiographically gated blood pool cardiac scintigraphy. Ejection fraction (EF) in normal subjects was 49 +/- 10% at rest, 54 +/- 10% during intermediate exercise (P less than 0.05 vs. rest), and 62 +/- 14% during maximal exercise (P less than 0.01 vs. rest). In patients with CAD the resting EF was 42 +/- 14%, 43 +/- 23% at intermediate exercise (P = nonsignificant vs. rest) and 36 +/- 11% at maximal exercise (P less than 0.01 vs. rest). Changes of average and maximal ejection rates from rest to exercise were similar to those of EF but had a lesser degree of statistical significance. End-diastolic volume index (EDVI) in patients with CAD, at intermediate exercise was equal to that at rest, but it increased during maximal exercise (P less than 0.01). In normal subjects EDVI did not change with exercise. Thus, during supine exercise the Frank-Starling mechanism is apparent in patients with CAD but not in normal subjects. Analysis of EF response to exercise is a highly sensitive technique to detect CAD provided that adequate exercise is achieved.

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.

Currently, the practice of nuclear medicine in larger institutions is practically dependent upon the availability of a computer system. Gamma cameras are connected online to mini-computer systems which have the ability to collect image data in a number of different formats. This permits sophisticated analysis techniques to be used so that quantitative data may be extracted from the images. In some instances, as in tomography, data are reconstructed into images to give views of organs that would otherwise be impossible to obtain.

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.

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.