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The identification of cerebral volume changes in treated growth hormone-deficient adults using serial 3D MR image
E R Denton1, M Holden, E Christ
1Department of Radiology, Guy's Hospital and Guy's, King's and St. Thomas' School of Medicine, London, England.
Purpose:
A pilot study to detect volume changes of cerebral structures in growth hormone (GH)-deficient adults treated with GH using serial 3D MR image processing and to assess need for segmentation prior to registration was conducted.
Method:
Volume MR scans of the brain were obtained in five patients and six control subjects. Patients were scanned before and after 3 and 6 months of therapy. Control subjects were scanned at the same intervals. A phantom was used to quantify scaling errors. Second and third volumes were aligned with the baseline by maximizing normalized mutual information and transformed using sinc interpolation. Registration was performed with and without brain segmentation and correction of scaling errors. Each registered, transformed image had the original subtracted, generating a difference image. Structural change and effects of segmentation and scaling error correction were assessed on original and difference images. The radiologists' ability to detect volume change was also assessed.
Results:
Compared with control subjects, GH-treated subjects had an increase in cerebral volume and reduction in ventricular volume (p = 0.91 x 10(-3)). Scale correction and segmentation made no difference (p = 1 and p = 0.873). Structural changes were identified in the difference images but not in the original (p = 0.136). The radiologists detected changes >200 microm.
Conclusion:
GH treatment in deficient patients results in cerebral volume changes detectable by registration and subtraction of serial MR studies but not by standard assessment of images. This registration method did not require prior segmentation.