CORRELATION BETWEEN TC-99(M)-HMPAO-SPECT BRAIN IMAGE AND A HISTORY OFDECOMPRESSION ILLNESS OR EXTENT OF DIVING EXPERIENCE IN COMMERCIAL DIVERS

Objectives-To explore the use of (99)technetium(m)-hexamethyl propylen e amine oxime single photon computed tomography (HMPAO-SPECT) of the b rain as a means of detecting nervous tissue damage in divers and to de termine if there is any correlation between brain image and a diver's history of diving or decompression illness (DCI). Methods-28 commercia l 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 w ere classified by observer assessment as normal (1) or as a pattern va riants (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 te xture analysis technique based on a grey level histogram. Results-15 o f 54 commercial divers (28%) were visually assessed as having HMPAO-SP ECT 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 ima ge compared with 38% with no history of DCI. No association was establ ished between the presence of a pattern variant from the normal image and history of DCI, diving, or other previous possible neurological in sult. On texture analysis of the brain images, divers had a significan tly lower mean grey level (MGL) than non-divers. Divers with a history of DCI (n = 22) had a significantly lower MGL when compared with dive rs with no history of DCI (n = 22). Divers with > 14 years professiona l 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 image s supplies both an objective and consistent method of measurement. A s ignificant correlation was found between a low measure of MGL and a hi story of DCI. There was also an indication that diving itself had an e ffect on texture measurement, implying that it had caused subclinical nervous tissue damage.