SeHCAT retention values as measured with a collimated and an uncollimated gamma camera: a method comparison study.

TauroH-23-(Se) selena-25-homocholic acid retention values are used in the diagnosis of bile acid malabsorption. The standard method for measuring values is with an uncollimated gamma camera, which can create some logistic difficulties, with other background sources of activity, which are irrelevant when a collimator is used, becoming significant. In this study we compare the retention values obtained with a collimated and an uncollimated gamma camera in phantoms and in 23 patients. Bland-Altman plots were created using the data, which showed a mean bias in retention of 0.10% in the phantom study and 0.55% in the patient study between methods. A Wilcoxon signed-rank test with the null hypothesis of zero median difference between uncollimated and collimated methods was not statistically significant to P values less than 0.05 in the patient and phantom studies. In the patient study, on using a fixed boundary of retention (10%) between positive and negative status, the status of one patient was changed from negative (12%) to positive (9%). We conclude that measurement of retention with a collimated gamma camera is similar but not identical to that of uncollimated values. The clinical significance of this shift is unclear, as the threshold of significance and the method of integrating this measure with other clinical factors into management remain unclear.

Improvement in DMSA imaging using adaptive noise reduction: an ROC analysis.

Dimercaptosuccinic acid imaging is the 'gold standard' for the detection of cortical defects and diagnosis of scarring of the kidneys. The Siemens planar processing package, which implements adaptive noise reduction using the Pixon algorithm, is designed to allow a reduction in image noise, enabling improved image quality and reduced acquisition time/injected activity. This study aimed to establish the level of improvement in image quality achievable using this algorithm. Images were acquired of a phantom simulating a single kidney with a range of defects of varying sizes, positions and contrasts. These images were processed using the Pixon processing software and shown to 12 observers (six experienced and six novices) who were asked to rate the images on a six-point scale depending on their confidence that a defect was present. The data were analysed using a receiver operating characteristic approach. Results showed that processed images significantly improved the performance of the experienced observers in terms of their sensitivity and specificity. Although novice observers showed significant increase in sensitivity when using the software, a significant decrease in specificity was also seen. This study concludes that the Pixon software can be used to improve the assessment of cortical defects in dimercaptosuccinic acid imaging by suitably trained observers.

Shape analysis of 123I-N-omega-fluoropropyl-2-beta-carbomethoxy-3beta-(4-iodophenyl) nortropane single-photon emission computed tomography images in the assessment of patients with parkinsonian syndromes.

PURPOSE: The purpose of this study was to show the viability and performance of a shape-based pattern recognition technique applied to I-N-omega-fluoropropyl-2-beta-carbomethoxy-3beta-(4-iodophenyl) nortropane single-photon emission computed tomography (FP-CIT SPECT) in patients with parkinsonism. METHODS: A fully automated pattern recognition tool, based on the shape of FP-CIT SPECT images, was written using Java. Its performance was evaluated and compared with QuantiSPECT, a region-of-interest-based quantitation tool, and observer performance using receiver operating characteristic analysis and kappa statistics. The techniques were compared using a sample of patients and controls recruited from a prospective community-based study of first presentation of parkinsonian symptoms with longitudinal follow up (median 3 years). RESULTS: The shape-based technique as well as the conventional semiquantitative approach was performed by experienced observers. The technique had a high level of automation, thereby avoiding observer/operator variability. CONCLUSION: A pattern recognition approach is a viable alternative to traditional methods of analysis in FP-CIT SPECT and has additional advantages.

A survey of nuclear medicine services in Scotland 2004-2005.

OBJECTIVE: Audit Scotland has recommended that NHS boards should ensure that medical equipment performance information is used to assess whether the local area is making the best use of its medical equipment. A survey of nuclear medicine departments in Scotland was carried out to provide a benchmark. METHOD: A questionnaire was sent to every nuclear medicine department in Scotland. Information requested included the amount, type and age of equipment and its service support. It also requested information to assess cost-effectiveness and quality measures such as waiting times. RESULTS: The response rate to the survey from the 21 nuclear medicine departments in Scotland was 100%. During 2004/2005, there were 71 426 nuclear medicine procedures carried out in Scotland, just over 14 per 1000 of population. A mean of 1619 procedures per imager was found. The mean number of procedures per whole time equivalent member of staff was found to be 499 and the mean cost per procedure, excluding radiopharmaceutical costs, was pound82. Relatively, long waiting times were found for bone scans, myocardial perfusion imaging and brain single-photon emission computed tomography. CONCLUSION: The survey shows that nuclear medicine activity in Scotland is higher than in the United Kingdom as a whole. The move from single-to dual-headed gamma cameras in recent years is demonstrated. The total number of staff employed in nuclear medicine departments in Scotland is only 143 whole time equivalent divided amongst several staff groups. Performance indicators have been identified and a report has been issued to participating departments enabling them to benchmark themselves as recommended by Audit Scotland.

The suitability of gamma camera coincidence systems for nitrogen 13-labeled ammonia myocardial perfusion imaging: a quantitative comparison with full-ring PET.

BACKGROUND: The aim of this study was to examine the quality of nitrogen 13-labeled ammonia (NH(3)) perfusion data from coincidence-capable gamma camera positron emission tomography (GC-PET) systems compared with that from full-ring positron emission tomography (FR-PET). METHODS AND RESULTS: The performance parameters of the GC-PET system were examined and found adequate for imaging at the activity levels used clinically. We studied 15 patients who underwent stress and rest N-13-labeled NH(3) perfusion imaging on FR-PET and GC-PET systems. Quantitative analysis of perfusion values showed that GC-PET uptake was significantly lower than FR-PET uptake in 67.6% of segments. Bland-Altman analysis showed that the mean difference between FR-PET and GC-PET values was from 5.3% to 5.9%. Stress FR-PET identified 49 segments as having impaired perfusion, 46 (93.9%) of which were also identified by GC-PET. Fifty-six additional segments were identified as abnormal by GC-PET. These findings indicated a general overestimation of defect size on GC-PET. Analysis of the degree of perfusion reduction also found that GC-PET tended to overestimate defect contrast. These findings are similar to those previously found by workers examining fluorine 18-fluorodeoxyglucose uptake by both techniques. CONCLUSIONS: Good concordance was shown between GC-PET and FR-PET systems for N-13-labeled NH(3) perfusion imaging, although further work is required to optimize the technique.

Cerebral blood flow and cognitive responses to rivastigmine treatment in Alzheimer's disease.

Twenty seven patients with mild AD were enrolled in a prospective open label controlled study of rivastigmine. Assessments included a range of neuropsychiatric and behavioural measures and rCBF using HMPAO SPECTat baseline, three and six months. Significant enhancement of frontal, parietal and temporal brain blood flow with related psychometric improvement was observed in twelve of the treated patients. A pattern of reduced rCBF and cognitive performance was observed in four unresponsive and eleven untreated patients. The results suggest that alterations in the clinical and cognitive status of patients receiving a cholinesterase inhibitor are paralleled by changes in rCBF. Longitudinal assessment with repeated imaging offers a method of better understanding the effects of cholinesterase inhibition on the AD brain.