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Aim: The aim of this study was to use statistical parametric mapping (SPM) to investigate differences in the regional cerebral blood flow (rCBF) of decompression illness (DCI) and non-diving control subjects., Methods: Twenty DCI subjects were imaged using 99Tcm hexamethylproplylene amine oxime (HMPAO) single photon emission tomography (SPET) within days of their incident of DCI, and on a second occasion between 2 and 27 months after their DCI event. SPM was used to make a comparison between decompression illness studies and a second group of non-diving control studies for both early and late imaging of DCI. A paired comparison of early and late imaging was also performed testing for correlation between time of imaging and changes in the rCBF pattern., Results: The comparison between control subjects and early imaging of decompression illness showed a large, significant (P = 0.002), irregularly shaped, multi-focal area of reduced uptake in the left occipito-parieto-temporal region of the brain. Comparisons between control and repeat decompression illness imaging studies showed two areas of reduced uptake. The first was similar to that found in the initial comparison although it was less significant (P = 0.035). The second region was similar but contra-lateral to the first region with significance P < 0.001. An attempt to correlate any changes in rCBF with the time that elapsed between each set of imaging found no areas of significant correlation., Conclusion: 99Tcm HMPAO SPET images of decompression illness display areas of reduced perfusion, which persist in the majority of cases.

Objectives: To explore the use of 99technetiumm-hexamethyl propylene amine oxime single photon computed tomography (HMPAO-SPECT) of the brain as a means of detecting nervous tissue damage in divers and to determine if there is any correlation between brain image and a diver's history of diving or decompression illness (DCI)., Methods: 28 commercial divers with a history of DCI, 26 divers with no history of DCI, and 19 non-diving controls were examined with brain HMPAO-SPECT. Results were classified by observer assessment as normal (I) or as a pattern variants (II-V). The brain images of a subgroup of these divers (n = 44) and the controls (n = 17) were further analysed with a first order texture analysis technique based on a grey level histogram., Results: 15 of 54 commercial divers (28%) were visually assessed as having HMPAO-SPECT images outside normal limits compared with 15.8% in appropriately identified non-diver control subjects. 18% of divers with a history of DCI were classified as having a pattern different from the normal image compared with 38% with no history of DCI. No association was established between the presence of a pattern variant from the normal image and history of DCI, diving, or other previous possible neurological insult. On texture analysis of the brain images, divers had a significantly lower mean grey level (MGL) than non-divers. Divers with a history of DCI (n = 22) had a significantly lower MGL when compared with divers with no history of DCI (n = 22). Divers with > 14 years professional diving or > 100 decompression days a year had a significantly lower MGL value., Conclusions: Observer assessment of HMPAO-SPECT brain images can lead to disparity in results. Texture analysis of the brain images supplies both an objective and consistent method of measurement. A significant correlation was found between a low measure of MGL and a history of DCI. There was also an indication that diving itself had an effect on texture measurement, implying that it had caused subclinical nervous tissue damage.

Unlabelled: Diving for sport and recreation has increased in recent years, resulting in more incidences of diving illness. Therefore, we studied potential use of regional cerebral blood flow SPECT imaging with 99mTc-HMPAO in the management of divers who have experienced decompression illness (DCI)., Methods: A group of ten sports divers who had no experience of DCI were compared with ten sports divers who had experienced at least one episode of DCI. Transaxial SPECT images were first compared objectively using a first-order texture measure and then subjectively using a receiver operator characteristic (ROC) experiment. Experienced observers were asked to rate images subjectively in terms of the images' textural appearance., Results: Both these techniques showed that there is a statistically significant difference between the two groups and the images produced by the DCI divers were generally more coarsely patchy when compared to the non DCI divers. The quantitative texture technique proved significantly better in identifying divers with DCI than the visual analysis by observers using ROC curves., Conclusion: Differences between the cerebral blood flow patterns of sports divers who have experienced DCI and sports divers who have no experience of DCI can be detected using 99mTc-HMPAO SPECT and a texture analysis technique.

The potential use of regional cerebral blood flow (rCBF) single photon emission tomography (SPET) imaging with 99Tcm-hexamethylpropyleneamine oxime (HMPAO) in the management of divers who have undergone a form of decompression sickness (DCS) was investigated using texture analysis. We imaged 50 divers, 10 of whom had only experienced DCS which had been categorized as Type 1, 20 of whom had a history of DCS classified as Type 2 and 20 of whom had not suffered an episode of DCS. A number of divers who had experienced Type 2 DCS had also had incidents of Type 1. The reconstructed SPET images were pre-processed and analysed using a first-order texture analysis technique based on a grey level histogram. The results showed that there was a significant textural difference between the divers who had only suffered episodes of DCS Type 1 and the diving controls and a difference between the divers with a history of Type 2 and the diving controls. No differences were found between the two groups of divers who had a history of DCS. This result suggests that DCS produces a detectable change in 99Tcm-HMPAO SPET brain images. However, the segmentation between the groups investigated was not complete and so the usefulness of this approach appears limited in individual cases but may provide useful information about the effects of different diving practices.