Comparison of scatter doses from a multislice and a single slice CT scanner.

During shielding calculations for a new multislice CT (MSCT) scanner it was found that the manufacturer's data indicated significantly higher external scatter doses than would be generated for a single slice CT (SSCT). Even allowing for increased beam width, the manufacturer's data indicated that the scatter dose per scan was higher by a factor of about 3 to 4. The magnitude of the discrepancy was contrary to expectations and also contrary to a statement by the UK ImPACT group, which indicated that when beam width is taken into account, the scatter doses should be similar.

Recommendations for a technical quality control program for diagnostic X-ray equipment.

This position paper was produced by a working party set up by the Radiology Special Interest Group of the ACPSEM in 2001. It is designed to give the consensus view of College members in Australia and New Zealand on the nature and frequency of tests which should be performed on diagnostic x-ray equipment to maintain adequate quality control of imaging performance and radiation safety. Tests on mammographic equipment have been excluded having been covered in a previous ACPSEM position paper (Australas Phys Eng Sci Med, 24(3):107-131, 2001).

A critique of the Montagnier evidence for the HIV/AIDS hypothesis.

In 1983 Luc Montagnier and his colleagues claimed to have discovered a novel retrovirus presently known as human immunodeficiency virus (HIV). By 1984 HIV was almost universally accepted to be the cause of AIDS. However, 20 years later, HIV cannot account for the phenomena for which the retroviral hypothesis was proposed, namely, Kaposi's sarcoma, decrease in T4 lymphocytes and thus the opportunistic infections in AIDS patients which were assumed to be the direct results of this decrease.

A critical analysis of the pharmacology of AZT and its use in AIDS.

The triphosphorylated form of the nucleoside analogue 3'-azido-3'-deoxythymidine (Zidovudine, AZT) is claimed to interrupt the HIV replication cycle by a selective inhibition of viral reverse transcriptase, thereby preventing the formation of new proviral DNA in permissive, uninfected cells. Given that initial HIV infection of an individual instigates abundant HIV replication from inception until death, and that the life of infected T-cells is only several days, the administration of AZT should lead both in vitro and in vivo (i) to decreased formation of proviral DNA; and thus (ii) to decreased frequencies of 'HIV isolation' (detection of p24 or reverse transcription or both) in stimulated cultures/cocultures of T-cells from seropositive individuals; (iii) to decreased synthesis of HIV p24 and RNA ('antigenaemia', 'plasma viraemia', 'viral load') ultimately resulting in low or absent levels of all three parameters; and (iv) to a perfect and direct correlation between all these parameters. A critical analysis of the presently available data shows that no such evidence exists, an outcome not unexpected given the pharmacological data on AZT.

HIV antibodies: further questions and a plea for clarification.

The existence of specific antibody/protein reactions is the crucial assumption underlying proof of HIV isolation, proof of HIV infection and the causative role of HIV in AIDS. However, since 1. antibodies which react with the 'HIV' proteins arise following allogenic stimuli in non-HIV-infected animals and humans, as well as in mice and humans with autoimmune disorders; antibodies to antigens from both mycobacteria and yeasts cross-react with HIV env and gag proteins; 2.

A critical analysis of the HIV-T4-cell-AIDS hypothesis.

The data generally accepted as proving the HIV theory of AIDS, HIV cytopathy, destruction of T4 lymphocytes, and the relationship between T4 cells, HIV and the acquired immune deficiency clinical syndrome are critically evaluated. It is concluded these data do not prove that HIV preferentially destroys T4 cells or has any cytopathic effects, nor do they demonstrate that T4 cells are preferentially destroyed in AIDS patients, or that T4 cell destruction and HIV are either necessary or sufficient prerequisites for the development of the clinical syndrome.

Factor VIII, HIV and AIDS in haemophiliacs: an analysis of their relationship.

In this review, the association between the Acquired Immune Deficiency Syndrome (AIDS) and haemophilia has been carefully examined, especially the data that have been interpreted as indicating transmission of the human immunodeficiency virus (HIV) to the recipients of purportedly contaminated factor VIII preparations. In our view, the published data do not prove the hypothesis that such transmission occurs, and therefore HIV cannot account for AIDS in haemophiliacs.

Regional pulmonary distribution of krypton-81m gas delivered by different breathing systems.

Regional pulmonary distribution of 81mKr gas delivered by three breathing systems was determined. Data from 18 patients were analyzed. Posterior images were obtained using each breathing system in turn.

Regional specific mean expiratory gas flow from 81mKr equilibrium inhalation data.

A new method of analysing the data available from routine 81m Kr equilibrium inhalation investigations has been developed. The data for analysis are acquired from a gamma camera in the form of a sequential series of images from which multiple breath activity-time curves are generated for eight regions in the lung. The method is based on a description of the behaviour of the radioactive gas in the lung using a mathematical model.

Measurements of the rubidium isotopic activities and the elution parameters of 81mKr generators using a standardized 114mIn source.

A method is described for measuring a number of parameters associated with an inorganic ion-exchange krypton generator. These are the activities of rubidium isotopes in inorganic ion-exchange krypton generators, the 81mKr extraction rate, the 81mKr activity delivered to patients during ventilation studies, the elution efficiency, and the radionuclide purity of the eluted gas. The method is based on the calibration of detectors, Ge(Li) and NaI(Tl), with a standardized 114mIn source at matching photon energies.

Quantitation and the elimination of errors in bile reflux tests using a gamma camera.

Entero-gastric reflux may be assessed quantitatively using 99mTc HIDA and a gamma camera. We have devised a computer program which applies corrections for several sources of error. The technique was validated using naso-gastric aspiration and phantom experiments.

A quantitative evaluation of breathing systems used with Kr-81m generators.

A quantitative evaluation of breathing systems currently in use with Rb-81 leads to Kr-81m generators is presented. Four systems were evaluated: a reservoir unit, a disposable oxygen face mask unit, and two types of nasal oxygen cannula units. These systems were used on 30 patients.