Comparing nonrigid registration techniques for motion corrected MR prostate diffusion imaging.

PURPOSE: T2-weighted magnetic resonance imaging (MRI) is commonly used for anatomical visualization in the pelvis area, such as the prostate, with high soft-tissue contrast. MRI can also provide functional information such as diffusion-weighted imaging (DWI) which depicts the molecular diffusion processes in biological tissues. The combination of anatomical and functional imaging techniques is widely used in oncology, e.g., for prostate cancer diagnosis and staging. However, acquisition-specific distortions as well as physiological motion lead to misalignments between T2 and DWI and consequently to a reduced diagnostic value. Image registration algorithms are commonly employed to correct for such misalignment. METHODS: The authors compare the performance of five state-of-the-art nonrigid image registration techniques for accurate image fusion of DWI with T2. RESULTS: Image data of 20 prostate patients with cancerous lesions or cysts were acquired. All registration algorithms were validated using intensity-based as well as landmark-based techniques. CONCLUSIONS: The authors' results show that the "fast elastic image registration" provides most accurate results with a target registration error of 1.07 ± 0.41 mm at minimum execution times of 11 ± 1 s.

SU-D-BRB-01: 4D-CT Lung Ventilation Images Vary with 4D-CT Sorting Techniques.

PURPOSE: 4D-CT ventilation imaging is a novel promising technique for lung functional imaging and has potential as a biomarker for radiation pneumonitis, but has not been validated in human subjects. The current 4D- CT technique with phase-based sorting results in artifacts at an alarmingly high frequency (90%), which may introduce variations into ventilation calculations. The purpose of this study was to quantify the variability of 4D- CT ventilation imaging to 4D-CT sorting techniques. METHODS: Two 4D-CT images were generated from the same data set by: (1) phase-based; (2) anatomic similarity- and abdominal displacement-based sorting for five patients. Two ventilation image sets (V_phase and V_anat) were then calculated by deformable image registration of peak-exhale and peak-inhale4D-CT images and quantification of regional volume change based on Hounsfield unit change. The variability of 4D-CT ventilation imaging wasquantified using the voxel-based Spearman rank correlation coefficients and Dice similarity coefficients (DSC) for the spatial overlap of segmented low- functional lung regions. The relationship between the abdominal motionrange variation and ventilation variation was also assessed using linearregression. Furthermore, the correlations between V_phase or V_anat and SPECT ventilation images (assumed ground-truth) were compared. RESULTS: In general, displacement- and anatomic similarity-based sorting reduced 4D- CT artifacts compared to phase-based sorting. The voxel-based correlationsbetween V_phase and V_anat were only moderate (range, 0.57-0.77). The DSCs for the low-functional lung regions were moderate to substantial (0.58-0.70). The relationship between the motion range variation and ventilation variation was strong on average (R2=0.79±0.25), suggesting that ventilation variations are related to 4D-CT artifacts. Vanat was found to improve correlations with SPECT ventilation images compared to V_phase. CONCLUSIONS: 4D-CT ventilation images vary markedly with 4D-CT sorting techniques. 4D-CT artifacts should be considered as a significant source of variation in 4D-CT ventilation imaging during its validation. This study wassupported in part by NIH/NCI R01 93626. SK and CL are employees ofPhilips Research.

Indications, risks, and acceptance of total thyroidectomy for multinodular benign goiter.

Selective morphology- and function-adapted resection is generally regarded as the surgical treatment of choice for benign goiter causing iodine deficiency. This procedure aims to reduce the need for patients to undergo reoperations for recurrence by completely removing all nodules. However, to achieve this sometimes requires a total thyroidectomy, the option of which is often rejected because of a presumed higher rate of complications. In this study, 324 patients who underwent total thyroidectomy were evaluated retrospectively. The patients were interviewed about their postoperative course and their acceptance of the procedure performed. The complications were compared with those associated with subtotal resection or hemithyroidectomies performed in our collective experience. The rate of complications associated with total thyroidectomy, namely, recurrent nerve palsy in 0.9%, hypocalcemia in 0.9%, wound infection in 0.9%, and secondary hemorrhage in 0.6%, did not differ significantly from that associated with subtotal resections/ hemithyroidectomies. Moreover, 88.3% of the patients who underwent total thyroidectomy were satisfied with the results of surgery. These findings indicate that total thyroidectomy is an acceptable surgical alternative for benign multinodular goiters.