2000 Objectives To determine whether a time of flight (TOF) reconstruction algorithm leads to qualitative changes in image appearance or quantitative differences in calculated SUV uptake values as compared to a conventional reconstruction algorithm in a phantom model across a range of acquisition times. Methods In two experiments, a NEMA phantom containing six spheres ranging from 37mm to 10mm was filled with a target background ratio of 4.8: 1 and 10:1 respectively. The phantom was imaged in a single three minute list mode acquisition with the data retrospectively divided into two minute, 1.5 minute, one minute and 30 second subsets. Each set of acquisition data was reconstructed with TOF and non TOF algorithms. For each sphere, a qualitative assessment of lesion visibility was made along with measurements of SUV max and SUV mean. Results With the target to background ratio of 10:1, the spheres were all visible on all reconstructions except for the 10mm sphere on the 30 second non TOF acquisition. However on the 4:1 target to background ratio there were significant qualitative and quantitative differences between the TOF and non TOF acquisitions. On the non TOF acquisition, the 10mm sphere could no longer be visualised on acquisitions of 1.5 minutes or less, whereas on the TOF acquisitions, the 10mm sphere was visible on all but the 30 second acquisition. For all of the experiments, the measured SUV mean and SUV max values were consistently lower in the smaller spheres, and this effect was more pronounced on the non TOF acquisition. Conclusions The TOF reconstruction algorithm improves the visualisation of small lesions at lower target to background levels. This effect becomes significant at lower acquisition times. This implies that the use of TOF reconstruction algorithms may allow preserved lesion visualisation with lower administered doses or shorter scan times

A 73-year-old man with thalassemia intermedia presented acutely with abdominal pain and distension. He had previously undergone a splenectomy. A diagnostic computed tomography (CT) scan through the abdomen and pelvis was performed with oral and intravenous contrast. This showed bilateral paravertebral and retrocrural soft tissue masses. It was believed that this was unlikely to be the cause of the patient's acute presentation. Nevertheless, the possibility of lymphoma or extramedullary hematopoiesis was raised. To avoid an invasive diagnostic biopsy, a Tc-99m sulfur colloid scan was performed. Initially, planar images were obtained; however, no clear corresponding colloid uptake was demonstrated. Therefore, a single-photon computed emission tomography (SPECT)/CT examination was performed. This demonstrated uptake of Tc-99m sulfur colloid in the paravertebral masses, confirming that these are likely to represent extramedullary hematopoiesis rather than lymphoma.

An 80-year-old woman presented with a history of right flank pain and tenderness. Her white cell count and C-reactive protein were elevated at 12.3 × 109/L and 108 mg/L respectively. An ultrasound scan of the abdomen showed moderate right sided hydronephrosis without ureteric dilatation and a collection at the lower pole of the kidney. An isotope renogram was performed using Tc-99m mercaptoacetyltriglycine (MAG3) to assess the presence of renal obstruction and to look for evidence of a urinary leak. Planar images revealed partial obstruction of the right kidney and unusual accumulation of tracer inferior to the kidney. SPECT/CT was performed to further evaluate the location of the abnormal tracer accumulation. Fused images demonstrated a posterior perirenal urinoma due to rupture of the collecting system. The patient underwent retrograde ureteric stenting and made an uneventful recovery.