Improved lesion detection from spatially adaptive, minimally complex, Pixon reconstruction of planar scintigraphic images.

Pixon noise reduction was applied to 18 planar images, six each from 99mTc-methylene diphosphonate (99mTc-MDP), 67Ga citrate (67Ga), and (123)I-metaiodobenzylguanidine ((123)I-MIBG) studies. Pixon processing increased patient signal-to-noise ratio, 6.8-11.8 fold. Three specialists preferred processed images 44 of 54 times with good agreement (87%). Most (9/10, p<0.02) of the null and negative preferences were from (123)I-MIBG studies. Inter-rater association was shown for 1-4 scale rated artifact p<0.1, noise p<0.01 and lesion detection p<0.05. Pixon images had superior lesion detection ability, p<0.02, and noise levels, p<0.02 and no statistically significant change in artifacts.

Comparative imaging of differential pulmonary blood flow in patients with congenital heart disease: magnetic resonance imaging versus lung perfusion scintigraphy.

BACKGROUND: Lung perfusion scintigraphy is considered the gold standard to assess differential pulmonary blood flow while magnetic resonance (MR) has been shown to be an accurate alternative in some studies. OBJECTIVE: The purpose of the study was to assess the accuracy of phase contrast magnetic resonance (PC-MR) in measuring pulmonary blood flow ratio compared with lung perfusion scintigraphy in patients with complex pulmonary artery anatomy or pulmonary hypertension and to document reasons for discrepant results. MATERIALS AND METHODS: We identified 25 cases of congenital heart disease between January 2000 and 2003, in whom both techniques of assessing pulmonary blood flow were performed within a 6-month period without an interim surgical or transcatheter intervention. The study group included cases with branch pulmonary artery stenosis, intracardiac shunts, single ventricle circulation, pulmonary venous anomalies and conotruncal defects. The mean age at study was 5.7 years (range 0.33-12) with a mean weight of 20.3 kg (range 6.5-53.6). The two methods were compared using a Bland-Altman analysis, and the Pearson correlation coefficient was calculated using the lung scan as the gold standard. Discrepant results were examined by reviewing the source images to elucidate reasons for error by MR. RESULTS: Bland-Altman analysis comparing right pulmonary artery (RPA) blood flow percentage, as measured by each modality, showed a mean difference of 1.43+/-9.8 (95% limits of agreement: -17.8, 20.6) with a correlation coefficient of r=0.84, P<0.0001. In six (24%) cases a large difference (>10%) was found with a mean difference between techniques of 17.9%. The reasons for discrepant results included MR artifacts, dephasing owing to turbulent flow, site of data acquisition and lobar lung collapse. CONCLUSION: When using PC-MR to assess pulmonary blood flow ratio, important technical errors occur in a significant proportion of patients who have abnormal pulmonary artery anatomy or pulmonary hypertension. If these technical errors are avoided, PC-MR is able to supply both anatomic and quantitative functional information in this patient population.

Initial experience with FSE STIR whole-body MR imaging for staging lymphoma in children.

Our objective was to compare fast spin-echo (FSE) short inversion time inversion recovery (STIR) whole-body MR imaging with standard procedures in staging children with lymphoma. Eight children (age range, 2-16 years) underwent multi-station FSE STIR whole-body MR at initial staging (n=5) or for restaging following completion of therapy (n=5). Whole-body MR and conventional staging procedures, including CT (n=10), gallium-67 scintigraphy (n=9), bone scintigraphy (n=3) and bone marrow biopsy (n=7) were retrospectively compared for detection of sites involved by lymphoma and for the assigned stage. FSE STIR whole-body MR detected more sites of possible lymphomatous involvement at initial staging (87/88) and at restaging (5/5) than did conventional imaging (74/88, 3/5). MR was more sensitive than conventional imaging in detecting bone marrow involvement at initial staging. Following treatment, however, residual and therapy-induced bone marrow signal abnormalities could not be differentiated from lymphomatous involvement. Detection of nodal and visceral involvement correlated well. Our results suggest that FSE STIR whole-body MR imaging is a sensitive technique for evaluating lymphomatous involvement of bone marrow as well as non-marrow sites. Larger prospective trials are needed to determine if FSE STIR whole-body MR can replace standard radiographic procedures for initial staging and contribute in the follow-up of lymphoma in children.

Relative accuracy of renal scan in estimation of renal function during partial ureteral obstruction.

This study is designed to evaluate the relative ability of DMSA and DTPA renal scans to accurately reflect differential renal function (DRF) compared with inulin clearance in the presence of partial unilateral ureteral obstruction. DRF was determined in 29 young rabbits by both renal scans. In the experimental group (n=21), left partial ureteral obstruction was created. Following 8 to 24 weeks, individual renal function in the obstructed animals were assessed by both renal scans and clearance of inulin. Eight animals were used as control. In the control group, DRF measured by DMSA, but not DTPA, correlated well with inulin clearance. Both scans documented a significant change in the DRF of the obstructed group (p<0.001). In the partially obstructed kidneys DRF derived by inulin was significantly lower than that measured by DMSA or DTPA scans (p<0.001 and p<0.0001). DRF measured by DMSA correlates well with inulin clearance in the control group. A similar correlation was not obtained by DMSA in the presence of obstruction. DTPA does not correlate with inulin clearance either in the control or the obstructed group.