In:
Medical Physics, Wiley, Vol. 23, No. 1 ( 1996-01), p. 115-126
Abstract:
Recently, guidelines for the use of MRI in the monitoring of MS have recommended the use of imaging systems with mid‐field (0.5–1.0 T) or high‐field (greater than 1.0 T) strengths. Higher field strengths provide many advantages, including increased signal‐to‐noise ratios (SNR). SNR also may be increased by post‐processing algorithms that reduce noise. In this paper we evaluate the impact on operator variability of (a) lesion quantification in high‐field (1.5 T) versus mid‐field (0.5 T) exams; and (b) an anisotropic diffusion filter algorithm that reduces image noise without blurring or moving object boundaries. Inter‐ and intra‐operator reliability and variability were studied using repeated quantification of lesions in 1.5 and 0.5 T filtered and unfiltered MR exams of a MS patient. Results indicate that inter‐operator variability in 1.5 T unfiltered exams was 0.34 cm 3 and was significantly larger than that in 1.5 T filtered (0.27 cm 3 ), 0.5 T unfiltered (0.26 cm 3 ), and 0.5 T filtered (0.24 cm 3 ) exams. Similarly, intra‐operator variability in 1.5 T unfiltered exams was 0.23 cm 3 and was significantly larger than that in 1.5 T filtered (0.19 cm 3 ), 0.5 T unfiltered (0.19 cm 3 ), and 0.5 T filtered (0.18 cm 3 ) exams. In addition, the minimum significant change between two successive measurements of lesion volume by the same operator, was 0.64 cm 3 in 1.5 T unfiltered exams, but 0.53 cm 3 or less in other exams. For two different operators making successive measurements, the minimum significant change was 0.94 cm 3 in 1.5 T unfiltered exams, but only 0.75 cm 3 or less in other exams. Finally, the number of lesions to be monitored for an average change in volume at a given power and significance level was greater by 30%–60% for quantification in 1.5 T unfiltered exams. These results suggest that inter‐ and intra‐operator variability are reduced by anisotropic filtering, and by quantification in 0.5 T exams. Reduced operator variabilities may result from higher detail signal‐to‐noise ratios (dSNRs) in 0.5 T and filtered exams.
Type of Medium:
Online Resource
ISSN:
0094-2405
,
2473-4209
Language:
English
Publisher:
Wiley
Publication Date:
1996
detail.hit.zdb_id:
1466421-5
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