Quantification of inflammatory bowel disease activity using technetium-99m HMPAO labelled leucocyte single photon emission computerised tomography (SPECT).

Technetium-99m HMPAO labelled white cell bowel uptake was quantified in 23 patients with suspected colitis by means of the novel technique of single photon emission computerised tomography (SPECT) using a standard gamma-camera. Uptake in colon segments was quantified on transaxial images and expressed as a fraction of marrow uptake (SPECT score). Segmental histological disease activity was assessed at colonoscopy (20) or at surgery (3). Segmental histology score correlated with SPECT score r = 0.79 (p < 0.001). Overall SPECT score for all affected segments correlated with Crohn's disease activity index (CDAI) r = 0.66, p = 0.001 and with laboratory activity indices; erythrocyte sedimentation rate r = 0.44, p = 0.03, C reactive protein r = 0.38, p = 0.05, and albumin r = -0.46, p = 0.03. Small bowel SPECT score in 13 patients correlated with CDAI r = 0.65, p < 0.01 but not with erythrocyte sedimentation rate or C reactive protein. Five patients with positive small bowel white cell uptake had normal C reactive protein and erythrocyte sedimentation rate. Overall SPECT score for disease at all sites correlated with both CDAI and with laboratory indices of inflammation. 99mTc HMPAO SPECT provides non-invasive and accurate quantification of inflammatory bowel disease activity in both large and small bowel and may be useful in the objective evaluation of treatment for inflammatory bowel disease.

Radiation dose assessment in radioiodine therapy. 2. Practical implementation using quantitative scanning and PET, with initial results on thyroid carcinoma.

We have designed special high-resolution, low-sensitivity collimators for a dual-headed whole-body scanner for imaging and quantifying therapy levels of iodine-131. In addition, we have used positron emission tomography (PET) with a low-cost large-area PET camera to achieve improved accuracy in the estimate to tumor mass. The physical performance of these two imaging systems is described. In order to illustrate the practical implementation of these systems for the assessment of radiation dose to normal and tumour tissue during radioiodine therapy, three clinical examples are reported, and a summary of the initial clinical results obtained from 16 patients with carcinoma of the thyroid is presented. The dose to normal thyroid remnants for patients undergoing ablation ranged from 16 to 400 Gy, while the dose to involved neck nodes ranged from 2.5 to 33 Gy for patients undergoing post-ablation radioiodine therapy. In one patient with distant metastasis in the spine, a dose of 100 Gy was achieved. The techniques described in this paper can be used to determine if sufficient activity can be accumulated in tumours to provide a therapeutic effect while minimising irradiation of normal tissues by avoiding administrations which do not provide tumouricidal radiation doses.