Modeling the effects of RF penetration in magnetic resonance (MR) imaging requires a knowledge of the local values of conductivity and permittivity. The inverse problem of determining the electlic properties of the materid under investigation using the M R images themselves has not previously been addressed.W e review such an approach for the heterogeneous layer model and examine the parsmeter sensitivity l o geometry and signal-to-noise ratio. For a few-layer system, it is within the realm of present day M a systems to extract the electric properties 10 within 10% or better. Knowledge of the electrical propertis will then allow a better prediction of the R F penetration and power deposition at high fields.

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Magnetoelectric (ME) composite ceramics of NiFe2O4 (NFO) and lead zirconate titanate (PZT) were synthesized by a simple in situ processing based on a sol–gel method followed by a conventional sintering. X-ray diffraction patterns and scanning electron microscopy images revealed that this processing can produce two pure phases simultaneously. The in situ grown magnetic NiFe2O4 grains were well dispersed in the PZT matrix. The results demonstrated an attractive ME response of about 28.5 V cm−1 Oe−1 in the 0.35 NiFe2O4/0.65PZT at a resonance frequency of around 287 kHz.

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Radiation therapy for cervical cancer involves a team of specialists, including diagnostic radiologists (DRs), radiation oncologists (ROs), and medical physicists (MPs), to optimize imaging‐based radiation therapy planning. The purpose of the study was to investigate the interobserver variations in tumor delineation on MR images of cervical cancer within the same and among different specialties. Twenty MRI cervical cancer studies were independently reviewed by two DRs, two ROs, and two MPs. For every study, each specialist contoured the tumor regions of interest (ROIs) on T2‐weighted Turbo Spin Echo sagittal images on all slices containing tumor, and the total tumor volume was computed for statistical analysis. Analysis of variance (ANOVA) was used to compare the differences in tumor volume delineation among the observers. A graph of all tumor‐delineated volumes was generated, and differences between the maximum and minimum volumes over all the readers for each patient dataset were computed. Challenges during the evaluation process for tumor delineation were recorded for each specialist. Interobserver variations of delineated tumor volumes were significant (p<0.01) among all observers based on a repeated measures ANOVA, which produced an F(5,95)=3.55. The median difference between the maximum delineated volume and minimum delineated volume was 33.5 cm3 (which can be approximated by a sphere of 4.0 cm diameter) across all 20 patients. Challenges noted for tumor delineation included the following: (1) partial voluming by parametrial fat at the periphery of the uterus; (2) extension of the tumor into parametrial space; (3) similar signal intensity of structures proximal to the tumor such as ovaries, muscles, bladder wall, bowel loops, and pubic symphysis; (4) postradiation changes such as heterogeneity and necrosis; (5) susceptibility artifacts from bowels and vaginal tampons; (6) presence of other pathologies such as atypical myoma; (7) factors that affect pelvic anatomy, including the degree of bladder distension, bowel interposition, uterine malposition, retroversion, and descensus. Our limited study indicates significant interobserver variation in tumor delineation. Despite rapid progress in technology, which has improved the resolution and precision of image acquisition and the delivery of radiotherapy to the millimeter level, such “human” variations (at the centimeter level) may overshadow the gain from technical advancement and impact treatment planning. Strategies of standardization and training in tumor delineation need to be developed.PACS number(s):

Objective: This study evaluated the relationship between follow-up temporomandibular joint positional change and mandibular stability among patients who had orthognathic and orthodontic treatment for a skeletal Class II malocclusion. Methods:Thirty-seven patients who underwent 2-jaw surgery (Le Fort I osteotomy, bilateral sagittal split ramus osteotomy and genioplasty with rigid internal fixation)were included with an average follow-up length of 8.10 ± 2.06 years. They were categorized into a stable and unstable group according to follow-up mandibular change in the sagittal direction. Temporomandibular joint spaces were measured on serial magnetic resonance images, prior to orthodontic treatment (T0), upon completion of orthodontic treatment following surgery (T1), and at least 5 years post-completion of the treatment (T2).Results: While the maxillary position was stable during the follow-up period, the mandibular positional change was statistically significant (the relapse amount was −0.81 ± 1.52 mm at B point). An increase in the anterior joint space and superior joint space was found to correlate with the follow-up mandibular backward movement. Conclusions:Patients who underwent orthognathic and orthodontic treatment to correct mandibular retrognathism displayed follow-up mandibular relapse in the sagittal direction. The relapse is accompanied by condylar positional change. K E Y W O R D Sangle class II, malocclusion, mandibular advancement, mandibular reconstruction, orthognathic surgery, temporomandibular joint

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