Millimeter-Wave Band Electro-Optical Imaging System Using Polarization CMOS Image Sensor and Amplified Optical Local Oscillator Source.

In this study, we developed and demonstrated a millimeter-wave electric field imaging system using an electro-optic crystal and a highly sensitive polarization measurement technique using a polarization image sensor, which was fabricated using a 0.35-µm standard CMOS process. The polarization image sensor was equipped with differential amplifiers that amplified the difference between the 0° and 90° pixels. With the amplifier, the signal-to-noise ratio at low incident light levels was improved. Also, an optical modulator and a semiconductor optical amplifier were used to generate an optical local oscillator (LO) signal with a high modulation accuracy and sufficient optical intensity. By combining the amplified LO signal and a highly sensitive polarization imaging system, we successfully performed millimeter-wave electric field imaging with a spatial resolution of 30×60 µm at a rate of 1 FPS, corresponding to 2400 pixels/s.

Estimation of the whole-body averaged SAR of grounded human models for plane wave exposure at respective resonance frequencies.

According to the international guidelines, the whole-body averaged specific absorption rate (WBA-SAR) is used as a metric of basic restriction for radio-frequency whole-body exposure. It is well known that the WBA-SAR largely depends on the frequency of the incident wave for a given incident power density. The frequency at which the WBA-SAR becomes maximal is called the 'resonance frequency'. Our previous study proposed a scheme for estimating the WBA-SAR at this resonance frequency based on an analogy between the power absorption characteristic of human models in free space and that of a dipole antenna. However, a scheme for estimating the WBA-SAR in a grounded human has not been discussed sufficiently, even though the WBA-SAR in a grounded human is larger than that in an ungrounded human. In this study, with the use of the finite-difference time-domain method, the grounded condition is confirmed to be the worst-case exposure for human body models in a standing posture. Then, WBA-SARs in grounded human models are calculated at their respective resonant frequencies. A formula for estimating the WBA-SAR of a human standing on the ground is proposed based on an analogy with a quarter-wavelength monopole antenna. First, homogenized human body models are shown to provide the conservative WBA-SAR as compared with anatomically based models. Based on the formula proposed here, the WBA-SARs in grounded human models are approximately 10% larger than those in free space. The variability of the WBA-SAR was shown to be ±30% even for humans of the same age, which is caused by the body shape.

Periventricular nodular heterotopia is related to severity of the hindbrain deformity in Chiari II malformation.

BACKGROUND: Knowledge of the occurrence of malformations of cortical development (MCDs) and its relationship to hindbrain deformity in Chiari II malformation (CIIM) is limited. OBJECTIVE: To assess malformations of cortical development and its relationship to hindbrain deformity regarding Chiari II malformation. MATERIALS AND METHODS: Brain and cervical spinal MRI from 66 children (age range, 1-256 days; mean age, 22.3 days) with Chiari II malformation were retrospectively reviewed. If present, the type, number and location of malformations of cortical development were recorded. Hindbrain deformity was assessed for the level of the medullary kink, the descent of the pons and the shape of the fourth ventricle; these parameters were compared in children with and without malformations of cortical development. RESULTS: Twenty children with malformations of cortical development were identified. Only periventricular nodular heterotopia was noted. The median level of the medullary kink was significantly lower in children with malformations of cortical development compared with children without it (P = 0.037). A low pontomesencephalic junction was identified more frequently in children with malformations of cortical development (65.0%), relative to children without malformations of cortical development (34.8%) (P = 0.045). The fourth ventricular shape was not significantly different in children with or without malformations of cortical development (P = 0.684). CONCLUSION: Periventricular nodular heterotopia was seen in a relatively high proportion of children with Chiari II malformation, suggesting that it may be associated with severe hindbrain deformity.

Neoadjuvant chemotherapy in breast cancer: prediction of pathologic response with PET/CT and dynamic contrast-enhanced MR imaging--prospective assessment.

PURPOSE: To clarify whether fluorine 18 ((18)F) fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) and dynamic contrast-enhanced (DCE) magnetic resonance (MR) imaging performed after two cycles of neoadjuvant chemotherapy (NAC) can be used to predict pathologic response in breast cancer. MATERIALS AND METHODS: Institutional human research committee approval and written informed consent were obtained. Accuracy after two cycles of NAC for predicting pathologic complete response (pCR) was examined in 142 women (mean age, 57 years: range, 43-72 years) with histologically proved breast cancer between December 2005 and February 2009. Quantitative PET/CT and DCE MR imaging were performed at baseline and after two cycles of NAC. Parameters of PET/CT and of blood flow and microvascular permeability at DCE MR were compared with pathologic response. Patients were also evaluated after NAC by using Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 based on DCE MR measurements and European Organization for Research and Treatment of Cancer (EORTC) criteria and PET Response Criteria in Solid Tumors (PERCIST) 1.0 based on PET/CT measurements. Multiple logistic regression analyses were performed to examine continuous variables at PET/CT and DCE MR to predict pCR, and diagnostic accuracies were compared with the McNemar test. RESULTS: Significant decrease from baseline of all parameters at PET/CT and DCE MR was observed after NAC. Therapeutic response was obtained in 24 patients (17%) with pCR and 118 (83%) without pCR. Sensitivity, specificity, and accuracy to predict pCR were 45.5%, 85.5%, and 82.4%, respectively, with RECIST and 70.4%, 95.7%, and 90.8%, respectively, with EORTC and PERCIST. Multiple logistic regression revealed three significant independent predictors of pCR: percentage maximum standardized uptake value (%SUV(max)) (odds ratio [OR], 1.22; 95% confidence interval [CI]: 1.11, 1.34; P < .0001), percentage rate constant (%k(ep)) (OR, 1.07; CI: 1.03, 1.12; P = .002), and percentage area under the time-intensity curve over 90 seconds (%AUC(90)) (OR, 1.04; CI: 1.01, 1.07; P = .048). When diagnostic accuracies are compared, PET/CT is superior to DCE MR for the prediction of pCR (%SUV(max) [90.1%] vs %κ(ep) [83.8%] or %AUC(90) [76.8%]; P < .05). CONCLUSION: The sensitivities of %SUV(max) (66.7%), %k(ep) (51.7%), and %AUC(90) (50.0%) at (18)F-FDG PET/CT and DCE MR after two cycles of NAC are not acceptable, but the specificities (96.4%, 92.0%, and 95.2%, respectively) are high for stratification of pCR cases in breast cancer.

Effective performance of T(1)-weighted FLAIR Imaging with BLADE in pediatric brains.

PURPOSE: In magnetic resonance imaging of the brain, BLADE is used to compensate for head motion. The technique focuses mainly on acquisition of T(2)-weighted or contrast-enhanced T(1)-weighted images in adults; its utility for nonenhanced T(1)-weighted imaging in children is not well established. We compared the quality of T(1)-weighted fluid-attenuated inversion recovery brain imaging with BLADE (T(1)-FLAIR-BLADE) to that of conventional spin-echo T(1)-weighted imaging (T(1)-SE) in pediatric patients who cannot stay still during MR imaging. MATERIALS AND METHODS: Our investigation included a volunteer study and a retrospective clinical study. Six healthy adult volunteers underwent scanning to compare the contrast of T(1)-SE, T(1)-weighted fluid-attenuated inversion recovery imaging (T(1)-FLAIR), and T(1)-FLAIR-BLADE at both 1.5 and 3 tesla. Comparison was based on scores assigned independently by 2 blinded observers and by calculated contrast-to-noise ratio. The clinical study included 20 children who underwent both T(1)-SE and T(1)-FLAIR-BLADE at either 1.5 (n = 9) or 3 T (n = 11). On each sequence, 2 blinded observers independently scored visualization of the cerebral gyri and contrast between gray and white matter. We compared scores between sequences separately for 1.5 and 3T using Wilcoxon signed-rank tests. RESULTS: At both 1.5 and 3T, contrast was better using T(1)-FLAIR and T(1)-FLAIR-BLADE than T(1)-SE in volunteers, and overall scores were significantly higher with T(1)-FLAIR-BLADE (P < 0.05) than T(1)-SE in the clinical study. CONCLUSION: T(1)-FLAIR-BLADE may be superior to T(1)-SE in demonstrating brain structures in children who cannot stay still and may be used to supplement or replace T(1)-SE when T(1)-SE is insufficient for patient motion.

Accelerating three-dimensional FDTD calculations on GPU clusters for electromagnetic field simulation.

Electromagnetic simulation with anatomically realistic computational human model using the finite-difference time domain (FDTD) method has recently been performed in a number of fields in biomedical engineering. To improve the method's calculation speed and realize large-scale computing with the computational human model, we adapt three-dimensional FDTD code to a multi-GPU cluster environment with Compute Unified Device Architecture and Message Passing Interface. Our multi-GPU cluster system consists of three nodes. The seven GPU boards (NVIDIA Tesla C2070) are mounted on each node. We examined the performance of the FDTD calculation on multi-GPU cluster environment. We confirmed that the FDTD calculation on the multi-GPU clusters is faster than that on a multi-GPU (a single workstation), and we also found that the GPU cluster system calculate faster than a vector supercomputer. In addition, our GPU cluster system allowed us to perform the large-scale FDTD calculation because were able to use GPU memory of over 100 GB.

Multi-GPU accelerated three-dimensional FDTD method for electromagnetic simulation.

Numerical simulation with a numerical human model using the finite-difference time domain (FDTD) method has recently been performed in a number of fields in biomedical engineering. To improve the method's calculation speed and realize large-scale computing with the numerical human model, we adapt three-dimensional FDTD code to a multi-GPU environment using Compute Unified Device Architecture (CUDA). In this study, we used NVIDIA Tesla C2070 as GPGPU boards. The performance of multi-GPU is evaluated in comparison with that of a single GPU and vector supercomputer. The calculation speed with four GPUs was approximately 3.5 times faster than with a single GPU, and was slightly (approx. 1.3 times) slower than with the supercomputer. Calculation speed of the three-dimensional FDTD method using GPUs can significantly improve with an expanding number of GPUs.

A GPU-based calculation using the three-dimensional FDTD method for electromagnetic field analysis.

Numerical simulations with the numerical human model using the finite-difference time domain (FDTD) method have recently been performed frequently in a number of fields in biomedical engineering. However, the FDTD calculation runs too slowly. We focus, therefore, on general purpose programming on the graphics processing unit (GPGPU). The three-dimensional FDTD method was implemented on the GPU using Compute Unified Device Architecture (CUDA). In this study, we used the NVIDIA Tesla C1060 as a GPGPU board. The performance of the GPU is evaluated in comparison with the performance of a conventional CPU and a vector supercomputer. The results indicate that three-dimensional FDTD calculations using a GPU can significantly reduce run time in comparison with that using a conventional CPU, even a native GPU implementation of the three-dimensional FDTD method, while the GPU/CPU speed ratio varies with the calculation domain and thread block size.

Comparison of SAR in realistic fetus models of two fetal positions exposed to electromagnetic wave from business portable radio close to maternal abdomen.

Since the diversification of the electromagnetic (EM) environment is spreading, it is essential to estimate the EM energy absorption rate [specific absorption rate (SAR)] of a pregnant woman's body and her fetus under various exposure situations. For example, if pregnant women work in jobs where they might wear business portable radios around their abdomens, they should also be concerned about this issue, because the fetuses are in their abdomens. In this paper, in order to evaluate the SAR in the pregnant woman and her fetus when wearing the wireless radio terminal on her abdomen, the SAR distribution in the fetus is calculated using the numerical model of the pregnant woman by exposed to near-field of a normal mode helical antenna (NHA) with a metallic case at 150 MHz. In addition, the SAR in the fetus will be evaluated under two fetal positions. It was found that the fetal SARs are greatly affected by the distance and penetration path from the antenna to the fetal surface. In addition, the fetal SARs are lower than the RF safety guidelines for occupational exposure.

Computational dosimetry in embryos exposed to electromagnetic plane waves over the frequency range of 10 MHz-1.5 GHz.

This paper presents calculated specific absorption rate (SAR) dosimetry in 4 and 8 week Japanese pregnant-woman models exposed to plane waves over the frequency range of 10 MHz-1.5 GHz. Two types of 2 mm spatial-resolution pregnant-woman models comprised a woman model, which is similar to the average-sized Japanese adult female in height and weight, with a cubic (4 week) embryo or spheroidal (8 week) one. The averaged SAR in the embryos exposed to vertically and horizontally polarized plane waves at four kinds of propagation directions are calculated from 10 MHz to 1.5 GHz. The results indicate that the maximum average SAR in the embryos exposed to plane waves is lower than 0.08 W kg(-1) when the incident power density is at the reference level of ICNIRP guideline for general public environment.

Extrapulmonary soft-tissue fibrosis resulting from hypofractionated stereotactic body radiotherapy for pulmonary nodular lesions.

PURPOSE: To clarify the incidence, symptoms, and timing of extrapulmonary fibrosis developing after hypofractionated stereotactic body radiotherapy. PATIENTS AND METHODS: We analyzed 379 consecutive patients who underwent stereotactic body radiotherapy for lung tumors at four institutions between February 2001 and March 2007. The median follow-up time was 29 months (range, 1-72). We investigated the subjective and objective characteristics of the extrapulmonary masses, redelineated the origin tissue of each on the treatment planning computed tomography scan, and generated dose-volume histograms. RESULTS: In 9 patients (2.4%), extrapulmonary masses were found 3-36 months (median, 14) after irradiation. Coexisting swelling occurred in 3 patients, chest pain in 2, thumb numbness in 1, and arm edema in 1 patient. Extrapulmonary masses occurred in 5 (5.4%) of 92 and 4 (1.4%) of 287 patients irradiated with a 62.5-Gy and 48.0-Gy isocenter dose, respectively. The mean and maximal dose to the origin tissue was 25.8-53.9 Gy (median, 43.7) and 47.5-62.5 Gy (median, 50.2), respectively. In 5 of 9 patients, the standardized uptake values on 18F-fluorodeoxyglucose-positron emission tomography was 1.8-2.8 (median, 2.2). Percutaneous needle biopsy was performed in 3 patients, and all the specimens showed benign fibrotic changes without malignant cells. CONCLUSION: All patients should be carefully followed after stereotactic body radiotherapy. The findings of any new lesion should prompt an assessment for radiation-induced extrapulmonary fibrosis before an immediate diagnosis of recurrence is made. Careful beam-shape modification and dose prescription near the thoracic outlet are required to prevent forearm neuropathy and lymphedema.

A comparison of foetal SAR in three sets of pregnant female models.

This paper compares the foetal SAR in the HPA hybrid mathematical phantoms with the 26-week foetal model developed at the National Institute of Information and Communications Technology, Tokyo, and the set of 13-, 26- and 38-week boundary representation models produced at Rensselaer Polytechnic Institute. FDTD calculations are performed at a resolution of 2 mm for a plane wave with a vertically aligned electric field incident upon the body from the front, back and two sides from 20 MHz to 3 GHz under isolated conditions. The external electric field values required to produce the ICNIRP public exposure localized restriction of 2 W kg(-1) when averaged over 10 g of the foetus are compared with the ICNIRP reference levels.

[Discrepancy between the intended isocenter and that from orthogonal linacgrams in the treatment of CT-guided stereotactic body radiotherapy(SBRT)].

PURPOSE: In our institution a CT scanner was installed in the same room as the linear accelerator. In stereotactic body radiotherapy (SBRT) we confirmed the isocenter position by serial thin-slice and long-scan-time CT images before every treatment as well as in planning. In planning we constructed digitally reconstructed radiography (DRR) of both the anterior and lateral views. At the first treatment we also checked the isocenter with linacgraphy. Then we compared the isocenter positions obtained from the DRR and linacgraphy. MATERIALS AND METHODS: Between Feb. 2005 and Oct. 2006, we treated 75 lung and liver tumors with SBRT in this way. Based on bony structures, we measured the differences between in-isocenter positions for SI, LR, and AP directions between DRR and linacgraphy. RESULTS: The median (min-max) of the differences in-isocenter positions for SI, LR, and AP directions between DRR and linacgraphy were 0.0 mm (0-6.0), 0.0 mm (0-10.0), and 0.0 mm (0-10.0), respectively, as well as 3.2 mm (0-12.3) for 3-dimensional distance. In 28 tumors (37%) the differences exceeded 5 mm in three-dimensional distance. The frequency of differences exceeding 5 mm in upper lung lesions tended to be more than that in liver lesions, and that in left pulmonary lesions was significantly more than that in right ones. CONCLUSION: This result suggests that the relative position of the target volume to the bony structure differ in planning and in every treatment. It was recommended to verify isocenter accuracy in institutions where isocenter position is checked only by orthogonal linacgraphy in SBRT.

Conservative estimation of whole-body-averaged SARs in infants with a homogeneous and simple-shaped phantom in the GHz region.

We calculated the whole-body-averaged specific absorption rates (WBSARs) in a Japanese 9-month-old infant model and its corresponding homogeneous spheroidal and ellipsoidal models with 2/3 muscle tissue for 1-6 GHz far-field exposure. As a result, we found that in comparison with the WBSAR in the infant model, the ellipsoidal model with the same frontally projected area as that of the infant model provides an underestimate, whereas the ellipsoidal model with the same surface area yields an overestimate. In addition, the WBSARs in the homogenous infant models were found to be strongly affected by the electrical constant of tissue, and to be larger in the order of 2/3 muscle, skin and muscle tissues, regardless of the model shapes or polarization of incident waves. These findings suggest that the ellipsoidal model having the same surface area as that of the infant model and electrical constants of muscle tissue provides a conservative WBSAR over wide frequency bands. To confirm this idea, based on the Kaup index for Japanese 9-month-old infants, which is often used to represent the obesity of infants, we developed linearly reduced 9-month-old infant models and the corresponding muscle ellipsoidals and re-calculated their whole-body-averaged SARs with respect to body shapes. Our results reveal that the ellipsoidal model with the same surface area as that of a 9-month-old infant model gives a conservative WBSAR for different infant models, whose variability due to the model shape reaches 15%.

Postured voxel-based human models for electromagnetic dosimetry.

High-resolution anatomically realistic whole-body voxel models have recently been developed for electromagnetic dosimetry. However, the posture of most models is similar to the standing one, which strongly limits electromagnetic dosimetry when simulating a realistic exposure scenario. In this paper, we present the development of postured models based on anatomically realistic voxel models with standing posture. Voxel models of the Japanese adult male and female were used as the original upright standing models. The Japanese models were composed of 2 mm cubic voxels, each of which was segmented into 51 different tissue types. We developed several different types of posture models using a novel posture transformation method. These posture models were smoothly transformed, while the continuity of the internal tissues and organs was maintained. In this paper, we also present our calculations of the whole-body averaged specific absorption rates (SARs) of sitting male and female models exposed to electromagnetic plane waves at very high (VHF) and ultra high frequency (UHF) bands.

Proportion-corrected scaled voxel models for Japanese children and their application to the numerical dosimetry of specific absorption rate for frequencies from 30 MHz to 3 GHz.

The development of high-resolution anatomical voxel models of children is difficult given, inter alia, the ethical limitations on subjecting children to medical imaging. We instead used an existing voxel model of a Japanese adult and three-dimensional deformation to develop three voxel models that match the average body proportions of Japanese children at 3, 5 and 7 years old. The adult model was deformed to match the proportions of a child by using the measured dimensions of various body parts of children at 3, 5 and 7 years old and a free-form deformation technique. The three developed models represent average-size Japanese children of the respective ages. They consist of cubic voxels (2 mm on each side) and are segmented into 51 tissues and organs. We calculated the whole-body-averaged specific absorption rates (WBA-SARs) and tissue-averaged SARs for the child models for exposures to plane waves from 30 MHz to 3 GHz; these results were then compared with those for scaled down adult models. We also determined the incident electric-field strength required to produce the exposure equivalent to the ICNIRP basic restriction for general public exposure, i.e., a WBA-SAR of 0.08 W kg(-1).

Intercomparison of whole-body averaged SAR in European and Japanese voxel phantoms.

This paper provides an intercomparison of the HPA male and female models, NORMAN and NAOMI with the National Institute of Information and Communications Technology (NICT) male and female models, TARO and HANAKO. The calculations of the whole-body SAR in these four phantoms were performed at the HPA, at NICT and at the Nagoya Institute of Technology (NIT). These were for a plane wave with a vertically aligned electric field incident upon the front of the body from 30 MHz to 3 GHz for isolated conditions. As well as investigating the general differences through this frequency range, particular emphasis was placed on the assumptions of how dielectric properties are assigned to tissues (particularly skin and fat) and the consequence of using different algorithms for calculating SAR at the higher frequencies.

Patterns of local recurrence after intraoperative radiotherapy for advanced neuroblastoma.

OBJECTIVE: The purpose of this study was to retrospectively evaluate local recurrence patterns after intraoperative radiation therapy (IORT) combined with total or subtotal resection and intensive chemotherapy for advanced neuroblastoma. METHODS: The outcomes of 27 patients (14 boys and 13 girls) with advanced-stage neuroblastoma who received IORT as part of multimodality therapy between November 1988 and December 2006 were reviewed in order to evaluate the impact of IORT. Of particular interest was the local recurrence patterns observed. RESULTS: Six patients relapsed in the abdominal area: three out of six relapsed adjacent to the radiation fields. Other three relapsed in the field of electron ports. Among them, one relapsed in paraspinal lymph nodes, which are behind the irradiated volume but out of the reach of the electron beam, while another relapsed in the lymph nodes of the mesocolon, which had been displaced outside the irradiation field at the time of IORT. The last case relapsed beside the vertebral column near the left ureter, which had been shielded by a lead plate. These three 'in-field' recurrences would have been irradiated if external opposite two-beam radiations had been performed, instead of electron beams. CONCLUSIONS: In spite of a complete tumor control in the treated volume, some 'marginal' recurrences were observed. Further investigation--for example, a combination of IORT and external-beam radiotherapy--should be considered to achieve higher local control and decrease complication rates.

An anatomically realistic whole-body pregnant-woman model and specific absorption rates for pregnant-woman exposure to electromagnetic plane waves from 10 MHz to 2 GHz.

The numerical dosimetry of pregnant women is an important issue in electromagnetic-field safety. However, an anatomically realistic whole-body pregnant-woman model for electromagnetic dosimetry has not been developed. Therefore, we have developed a high-resolution whole-body model of pregnant women. A new fetus model including inherent tissues of pregnant women was constructed on the basis of abdominal magnetic resonance imaging data of a 26-week-pregnant woman. The whole-body pregnant-woman model was developed by combining the fetus model and a nonpregnant-woman model that was developed previously. The developed model consists of about 7 million cubical voxels of 2 mm size and is segmented into 56 tissues and organs. This pregnant-woman model is the first completely anatomically realistic voxel model that includes a realistic fetus model and enables a numerical simulation of electromagnetic dosimetry up to the gigahertz band. In this paper, we also present the basic specific absorption rate characteristics of the pregnant-woman model exposed to vertically and horizontally polarized electromagnetic waves from 10 MHz to 2 GHz.

Differences in the definition of internal target volumes using slow CT alone or in combination with thin-slice CT under breath-holding conditions during the planning of stereotactic radiotherapy for lung cancer.

PURPOSE: To investigate how the delineations of the internal target volume (ITV) made from 'slow' CT alter with reference to 'thin-slice' CT. MATERIALS AND METHODS: Thin-slice CT images taken under breath-holding conditions and slow CT images taken under shallow-breathing conditions (8s/image) of 11 lung cancers were used for this study. Five radiation oncologists delineated ITV of the 11 lesions using slow CT images (ITV1), and then redefined them with reference to thin-slice CT images (ITV2). SD-images (standard deviation image) were created for all patients from ITV images in order to visualize the regional variation of the ITVs. RESULTS: The mean value of ITV2 was smaller than that initially defined by ITV1. There was no significant change in ITV1 and ITV2 between operators with regard to standard deviation in volume. There was a significant difference in the distribution of the ratio of ITV1 to ITV2 obtained on thin-slice CTs between cases with and without ground glass opacity. In cases without ground glass opacity there was a tendency for ITV2 to have a smaller volume than ITV1. CONCLUSIONS: Combined use of slow CT and thin-slice CT in delineation of ITV contours appeared to be useful in making adjustments for obscured tumor images caused by respiratory movement.