Comparison of I-123 and I-131 for whole-body imaging after stimulation by recombinant human thyrotropin: a preliminary report

PURPOSE: Many studies have established I-123 whole-body scanning (WBS) as an alternative to I-131 WBS in the evaluation of differentiated thyroid cancer. Similarly, recombinant human thyroid-stimulating hormone (rhTSH) has been shown to be an effective alternative to thyroid hormone withdrawal in the stimulation of TSH levels for WBS. The purpose of the current investigation was to compare the ability of rhTSH-stimulated I-123 WBS to that of rhTSH-stimulated I-131 WBS in the evaluation of thyroid cancer. METHODS: The reports of 101 consecutive I-123 WBS and 101 consecutive I-131 WBS were analyzed. All patients had undergone near-total thyroidectomy, were considered to have a low risk for recurrence, and had rhTSH-stimulated serum thyroglobulin levels measured at the time of imaging. Findings of an examination were considered positive if either residual thyroid tissue was detected on imaging or the serum thyroglobulin level was greater than 2 ng/dl. RESULTS: The results of rhTSH-stimulated I-123 scans and thyroglobulin levels were concordant in 91 (90%) cases, whereas the results of rhTSH-stimulated I-131 scans and thyroglobulin levels were concordant in 85 (84%) cases. I-123 WBS detected 9 foci of disease in 6 patients, whereas I-131 WBS detected 10 foci of disease in 9 patients. CONCLUSION: The results of this preliminary investigation are promising regarding the utility of rhTSH-stimulated I-123 WBS as an alternate approach to rhTSH-stimulated I-131 WBS in patients at low risk for recurrence.     

Brain metabolism in the cerebellum and visual cortex correlates with neuropsychological testing in patients with Alzheimer's disease

This study was designed to measure glucose metabolic deficits in areas not typically recognized as abnormal on 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) scans in patients with Alzheimer's disease (AD), and to correlate such findings with subtle neuropsychological impairment. FDG-PET scans on 38 AD patients with no clinical evidence of visual, spatial or motor deficits were acquired on the PET HEAD scanner 40 min following the intravenous administration of 115 microCi.kg-1 of FDG. All FDG-PET scans were analysed blindly using a region of interest (ROI) template with regions for the primary visual cortex (PVC), secondary visual cortex (SVC) and cerebellum. Counts from the ROIs of these regions were normalized to whole brain activity and the results were compared with psychometric and neuropsychological measures. A number of significant correlations were found between these structures and various neuropsychological measures (P<0.05). Specifically, there were significant correlations between clock drawing and the cerebellum activity; memory and activity in the PVC, SVC and cerebellum; social score and activity in the PVC and left cerebellum; judgement and activity in the right SVC and right PVC; and the overall Mini-Mental State Examination and activity in the PVC, SVC and cerebellum. The results of this study suggest that metabolism in areas not typically recognized as abnormal on FDG-PET scans in AD, such as the PVC, SVC and cerebellum, is correlated with deficits in neuropsychological function. This may have important clinical and pathophysiological implications in the study of AD and other illnesses of dementia.     

Applications of fluorodeoxyglucose positron emission tomography in the diagnosis of infection

The purpose of this study was to assess the accuracy of fluorodeoxyglucose positron emission tomography (FDG PET) in diagnosing infection in a large population of patients and in a variety of clinical circumstances where the performance of conventional imaging modalities has been questioned. We retrospectively analysed 167 FDG PET scans obtained to evaluate 175 anatomical sites for the presence of infection. The major indications for the scans were (1) complicated orthopaedic hardware (n=97), (2) chronic osteomyelitis (n=56), and (3) other (n=14: six fever of unknown origin, three vascular grafts, and five soft tissue). We assessed the overall diagnostic accuracy of FDG PET for each of these indications. In addition, we further analysed this modality's effectiveness by grouping the scans into specific clinical situations. A final diagnosis was made on the basis of surgical pathology and clinical follow-up for a minimum of 6 months. The overall accuracy of FDG PET in evaluating orthopaedic hardware was 96.2% for hip prosthesis, 81% for knee prosthesis, and 100% in 15 patients with other orthopaedic devices. Among the patients in our sample suspected of having chronic osteomyelitis, the accuracy was 91.2%. FDG PET was inaccurate in three cases of fever of unknown origin and accurate in all vascular graft and soft tissue infections. In 49 patients with a clinically apparent soft-tissue infection, FDG PET was able to detect or exclude underlying osteomyelitis with an accuracy of 92.3%. Among the 23 patients who had recent orthopaedic procedures, FDG PET imaging was accurate in 87% of cases. It is concluded that FDG PET is a highly effective imaging modality in the assessment of patients with suspected infection.     

Normal patterns and variants in single-photon emission computed tomography and positron emission tomography brain imaging

One of the most important issues in evaluating functional brain scans for research or clinical purposes is to be able to identify normal variants. Determining the baseline "normal" state of the brain is not easy to characterize since many normal brain functions and mental processes affect brain activity. This article reviews issues pertaining to the technical and neurophysiological aspects of functional brain imaging that might alter "normal" activity and will also consider how normal brain activity changes throughout the lifespan.     

Neuroimaging in patients with head injury

Head trauma affects thousands of people every year. Neuroimaging techniques provide some of the most important diagnostic, prognostic, and pathophysiological information in the management of brain injury. Anatomical imaging modalities can help assess intracranial hemorrhage, fractures, and other structural lesions. Functional imaging has been shown to be helpful in assessing the areas of the brain affected by the trauma as well as determining long term prognosis and rehabilitation potential. This article will review the current uses of neuroimaging techniques in head trauma and delineate future applications.