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Normalized glandular dose (DgN) coefficients obtained using homogeneous breast phantoms are commonly used in breast dosimetry for mammography. However, glandular tissue is heterogeneously distributed in the breast. This study aimed to construct three-layer heterogeneous mammographic phantoms (THEPs) to examine the effect of glandular distribution on DgN coefficient. Each layer of THEPs was set to 25%, 50%, or 75% glandular fraction to emulate heterogeneous glandular distribution. Monte Carlo simulation was performed to attain mean glandular dose (MGD) and air kerma at 22–36 kVp and W/Al, W/Rh, and W/Ag target–filter combinations. The heterogeneous DgN coefficient was calculated as functions of the mean glandular fraction (MGF), breast thickness, tube voltage, and half-value layer. At 50% MGF, the heterogeneous DgN coefficients for W/Al, W/Rh, and W/Ag differed by 40.3%, 36.7%, and 31.2%. At 9-cm breast thickness, the DgN values of superior and inferior glandular distributions were 25.4% higher and 29.2% lower than those of uniform distribution. The proposed THEPs can be integrated with conventional breast dosimetry to consider the heterogeneous glandular distribution in clinical practice.

On-board cone-beam computed tomography (CBCT) was used to scan the N-isopropylacrylamide (NIPAM) gel dosimeter. A dose-response curve from 1 to 12 Gy was created. The dose profile and depth dose curve were measured, and the dose distribution acquired from CBCT was then compared with that obtained from a treatment planning system (TPS). The linearity of the dose-response curve obtained by CBCT scanning of the NIPAM gel was 0.985. The mean percent standard deviation of various doses was 12.8%. A 12- to 24-h post-irradiation time was required to achieve stable CBCT readouts. Both dose profile and depth dose were in agreement with the results of TPS. The dose difference at the isocenter between CBCT and TPS was 3.8%. The gamma evaluation under the conditions of 5% dose difference and 5 mm distance-to-agreement was performed with the pass rate of 92.6%. These results indicate that an on-board CBCT can be used for scanning gel dosimeters in clinical radiotherapy.

Purpose Polymer gel dosimeters provide three-dimensional absorbed dose information and have gradually become a popular tool for quality assurance in radiotherapy. This study aims to incorporate iodine into the MAGAT-based gel as radiation sensitizer and investigate whether it can be used to measure the radiation dose and slice thickness for CT scans. Methods The nMAGAT(I) gel was doped with 0.03, 0.05, and 0.07-M iodine. The absorbed dose was delivered using a CT scanner (Alexion 16, Toshiba Medical Systems, Japan) with tube voltages of 80, 100, 120, and 135 kVp. The irradiated nMAGAT(I) gel was read using a cone beam optical CT scanner to produce dose-response curves. The nMAGAT(I) gel was used to obtain the slice sensitivity profile (SSP) and the CT dose index (CTDI) for quality assurance of CT scans. Results The 0.07-M iodine-doped nMAGAT(I) gel exhibited maximum sensitivity with the dose enhancement ratio of 2.12. The gel was chemically stable 24 h after its preparation, and the polymerization process was completed 24–48 h after the irradiation. For CT quality assurance, the full width at half maximum measured by the nMAGAT(I) gel matched the nominal slice thickness of CT. The CTDI at center, CTDI at peripheral, and weighted CTDI obtained by the nMAGAT(I) gel differed from those obtained by the ionization chamber by −4.2%, 3.1%, and 0.7%, respectively. Conclusions The nMAGAT(I) gel can be used to assess radiation doses and slice thickness in CT scans, thus rendering it a potential quality assurance tool for CT and other radiological diagnostic applications.

Hydrogen evolution reaction (HER) from water electrolysis is a promising route for hydrogen fuel production. However, an effective conversion technology from distributed energy resources, such as solar energy and thermal energy, to hydrogen energy is still a challenging research. Here, earth-abundant and multifunctional Ni nanosheets array as electrocatalysts and light absorption layer integrated thermoelectric (TE) device for overall water splitting was proposed. Instead of the traditional power source, the output voltage from thermoelectric (TE) device was directly used for water splitting. More importantly, the structural, photothermal transformation and electrocatalytic characterizations confirmed that the earth-abundant and multifunctional Ni nanosheets array grown on the hot side of TE device was not only as an efficient photothermal conversion layer for providing temperature difference (ΔT) of TE, but also as an active electrocatalysts for HER. The Electrolyzer-TE hybrid devices were designed for overall water splitting in a two-electrode configuration, which possessed high hydrogen production rate of 1.818 mmol/h and oxygen production rate of 0.912 mmol/h. The proposed integrative TE device herein offered great advantages in terms of designing the overall water splitting system, which are helpful for its practical applications for utilization of solar thermal and waste heat.

Engineering transport properties of thermoelectric (TE) materials leads to incessantly breakthroughs in the zT values. Nevertheless, modular design holds a key factor to advance the TE technology. Herein, we discuss the structures of TE module and illustrate the inter-diffusions across the interface of constituent layers. For Bi2Te3-based module, soldering is the primary bonding method, giving rise to the investigations on the selections of solder, diffusion barrier layer and electrode. For mid-temperature PbTe-based TE module, hot-pressing or spark plasma sintering are alternative bonding approaches; the inter-diffusions between the diffusion barrier layer, electrode and TE substrate are addressed as well.

Adequate compression during mammography lowers the absorbed dose in the breast and improves the image quality. The compressed breast thickness (CBT) is affected by various factors, such as breast volume, glandularity, and compression force. In this study, we used the finite element analysis to simulate breast compression and deformation and validated the simulated CBT with clinical mammography results. Image data from ten subjects who had undergone mammography screening and breast magnetic resonance imaging (MRI) were collected, and their breast models were created according to the MR images. The non-linear tissue deformation under 10−16 daN in the cranial-caudal direction was simulated. When the clinical compression force was used, the simulated CBT ranged from 2.34 to 5.90 cm. The absolute difference between the simulated CBT and the clinically measured CBT ranged from 0.5 to 7.1 mm. The simulated CBT had a strong positive linear relationship to breast volume and a weak negative correlation to glandularity. The average simulated CBT under 10, 12, 14, and 16 daN was 5.68, 5.12, 4.67, and 4.25 cm, respectively. Through this study, the relationships between CBT, breast volume, glandularity, and compression force are provided for use in clinical mammography.

Metal implants often produce severe artifacts in the reconstructed computed tomography (CT) images, causing information and image detail loss and making the CT images diagnostically unusable. In order to eliminate the metal artifacts and enhance the diagnostic value of the reconstructed CT images, a post-processing metal artifact reduction algorithm, based on a tissue-class model segmented by thresholding and k-means clustering with spatial information, is proposed. The image inpainting technique is incorporated into the algorithm to improve the segmentation accuracy for CT images severely corrupted by metal artifacts. A study of a water phantom and of two sets of clinical CT images was performed to test the algorithm performance. The proposed method effectively eliminates typical metal artifacts, restores the average CT numbers of different tissues to the proper levels, and preserves the edge and contrast information, thus allowing the accurate reconstruction of the tissue attenuation map. The quality of the artifact-corrected CT images allows them to be subsequently used in other clinical applications, such as three-dimensional rendering, dose estimation for radiotherapy, attenuation correction for PET and SPECT, etc. The algorithm does not rely on the use of the raw sinogram and so is not limited by the proprietary format restrictions.

Breast nuclear medicine imaging has gradually become a supplemental method for detection of mammographically occult cancer in dense breasts. However, mammary glands and ducts are highly sensitive to radiation; the absorbed dose to glandular tissue may increase the risk of secondary breast cancer. Therefore, accurate suborgan breast dosimetry for breast nuclear medicine imaging represents an important issue. In this study, a series of anthropomorphic software breast phantoms (ASBPs) with various volumes and glandularities were built. The realism of the ASBPs was assessed by using the two-dimensional projection and fractal dimension (FD) analysis. Breast self S values and suborgan S values for 18F and 99mTc were simulated using the Monte Carlo technique. The projected images of the ASBPs were similar to clinical mammograms in tissue distribution and image contrast. The mean FD value for the ASBPs was 2.23. The maximum differences between the breast self S values of ASBPs and OLINDA/EXM for 18F and 99mTc were −14.4% and −16.7%, respectively. For the breast suborgan S values, the maximum ratios between the S value from gland to gland S(g←g) and the S value from breast to breast S(b←b) were 4.84 for 18F and 3.60 for 99mTc. The mean ratios between the S value from gland to duct S(d←g) and that from gland to gland S(g←g) were 0.296 for 18F and 0.356 for 99mTc. The suborgan breast dosimetry based on the ASBPs can be used for internal dose evaluation and carcinogenic risk assessment of mammary glands and ducts in breast nuclear medicine imaging.

Objectives. Dual-energy X-ray absorptiometry (DXA) is frequently used to measure the areal bone mineral density (aBMD) in clinical practice. However, DXA measurements are affected by the bone thickness and the body size and are unable to indicate nonosseous areas within the trabecular bone. This study aims to quantify the volumetric bone mineral density (vBMD) using computed tomography (CT) images and the two-compartment model (TCM) methods. Methods. The TCM method was proposed and validated by dipotassium phosphate (K2HPO4) phantoms and a standard forearm phantom. 28 cases with DXA scans and pelvic CT scans acquired within six months were retrospectively collected. The vBMD calculated by TCM was compared with the aBMD obtained from DXA. Results. For the K2HPO4 phantoms with vBMD ranging from 0.135 to 0.467 g/cm3, the average difference between the real and calculated vBMD was 0.009 g/cm3 and the maximum difference was 0.019 g/cm3. For the standard forearm phantom with vBMD of 0.194, 0.103, and 0.054 g/cm3, the average differences between the real and calculated vBMD were 0.017, 0.014, and 0.011 g/cm3. In the clinical CT image validation, a good linear relationship between vBMD and aBMD was observed with the Pearson correlation coefficient of 0.920 (p<0.01). Conclusions. The proposed TCM method in combination with the homemade cortical bone equivalent phantom provides accurate quantification and spatial distribution of bone mineral content.

Background/PurposeCone-beam computed tomography (CBCT) can provide valuable data for root canal systems of human teeth in vivo. This study used CBCT to evaluate the number of roots and canals of 300 mandibular first premolars in 150 northern Taiwanese patients.MethodsThe root canal systems of 300 mandibular first premolars in 150 northern Taiwanese patients with bilateral premolars were analyzed by CBCT.ResultsOf the 300 mandibular first premolars, 197 (65.7%) had one root with one canal (1R1C), 49 (16.3%) had one root with two canals (1R2C), 51 (17.0%) had two roots with one canal in each root (2R2C), and three (1.0%) had three roots with one canal in each root (3R3C). Statistical analyses showed that women had a significantly higher incidence of 1R1C mandibular first premolars (71.4%) than men (58.8%, p = 0.031), and men had a significantly higher incidence of 2R2C mandibular first premolars (27.2%) than women (8.5%, p

One of the problems in obtaining quality results is image registration when a gel dosimeter is used in conjunction with optical computed tomography (CT). This study proposes a passive alignment mechanism to obtain a precisely measured dose map. A holder plate with two pin–hole pairs is placed on the gel container cap. These two pin–hole pairs attach the gel container to the vertical shaft and can be precisely aligned with the rotation center of the vertical shaft at any time. Accordingly, a better reconstructed image quality is obtained. After obtaining a precisely measured dose map, the scale invariant feature transform (SIFT)-flow algorithm is utilized as an image registration method to align the treatment plan software (TPS) image with the measured dose map image. The results show that the gamma pass rate for the single-field irradiation increases from 83.39% to 94.03% when the algorithm is applied. And the gamma pass rate for the five-field irradiation treatment plan increases from 87.36% to 94.34%. The translation, scaling, and rotation occurring in the dose map image constructed using an optical CT scanner are also aligned with those in the TPS image using the SIFT-flow algorithm. Accordingly, improved gamma comparison results and a higher gamma pass rate are obtained.

Reference man has been widely used for external and internal dose evaluation of radiation protection. The parameters of the mathematical model of organs suggested by the International Commission of Radiological Protection (ICRP) are adopted from the average data of Caucasians. However, the organ masses of Asians are significantly different from the data of Caucasians, leading to potentially dosimetric errors. In this study, a total of 40 volunteers whose heights and weights corresponded to the statistical average of Taiwanese adults were recruited. Magnetic resonance imaging was performed, and T2-weighted images were acquired. The Taiwanese reference man and woman were constructed according to the measured organ masses. The dose conversion coefficients (DCFs) for anterior-posterior (AP), posterior-anterior (PA), right lateral (RLAT) and left lateral (LLAT) irradiation geometries were simulated. For the Taiwanese reference man, the average differences of the DCFs compared with the results of ICRP-74 were 7.6, 5.1 and 11.1 % for 0.1, 1 and 10 MeV photons irradiated in the AP direction. The maximum difference reached 51.7 % for the testes irradiated by 10 MeV photons. The size of the trunk, the volume and the geometric position of organs can cause a significant impact on the DCFs for external exposure of radiation. The constructed Taiwanese reference man and woman can be used in radiation protection to increase the accuracy of dose evaluation for the Taiwanese population.

Computed tomography (CT) has been widely used in clinical diagnosis. It is important to estimate radiation dose and perform image quality assurance procedures for CT scans. In this study, nMAG gel dosimeters were used to simultaneously measure the 300-mm weighted CT dose index (CTDI) and slice sensitivity profile (SSP) for multiple detector CT (MDCT). Magnetic resonance imaging (MRI) was performed on the irradiated gel to create R2‒dose response curves for the tube voltages of 120 and 140 kVp. The gel dosimeters were loaded in three home-made cylindrical phantoms to obtain CTDI100 and CTDI300. The full width at half maximum (FWHM) for 2, 5, 10, 14.4, and 38.4-mm slice thicknesses was measured and compared with the result obtained by radiochromic films. The difference in weighted CTDI100 obtained by the gel dosimeter and ionization chamber was less than 1%. The CTDI efficiency at 120 and 140 kVp was in the range of 80.1%–82.5%. The FWHM of SSP measured by the gel dosimeter matched very well with the nominal slice thickness. The use of nMAG gel dosimeters combined with the home-made cylindrical phantoms can provide 300-mm weighted CTDI and slice thickness information, showing potential for quality assurance and clinical applications in MDCT.

The RC delay, electro migration (EM) and TDDB performance become more challenges to meet device requirement as continuous geometry shrink on BEOL dual damascene interconnects. To overcome these challenges from interconnect patterning point of view, we proposed Cu subtractive RIE as a potential solution for next generation Cu/Low-k interconnects.

Background Intermittent parathyroid hormone (PTH) can be used to treat osteoporosis of the spine and hip. However, whether it can be used to treat osteoporosis of the mandible is unclear. The purpose of this study was to explore the influence of applying intermittent PTH to ovariectomized rats on the trabecular bone microarchitecture of the mandible and femoral head. Methods Eighteen female rats were divided into three groups: the healthy group, ovariectomized (OVX) group, and OVX + PTH group. The OVX group and OVX + PTH group had an OVX at 8 weeks of age. The OVX + PTH group received intermittent PTH therapy for 12 weeks. The mandibles and femurs of all rats were removed at 20 weeks and were then scanned using microcomputed tomography (micro-CT). Results From the micro-CT analysis, the trabecular bone microarchitecture of the mandible and femoral head are offered as follows: (1) The bone volume fraction and trabecular thickness in the OVX group were lower than those in the healthy group. (2) The bone volume fraction and trabecular thickness in the OVX + PTH group approximated those in the healthy group. Conclusion The conclusions of this study regarding the trabecular bone microarchitecture of the mandible and femoral head are offered as follows: (1) The BV/TV and TbTh in the OVX group were lower than those in the healthy group. (2) The BV/TV and TbTh in the OVX + PTH group approximated those in the healthy group, therefore, intermittent PTH displayed high efficacy for treating femoral or mandibular deterioration of bone microstructure resulting from loss of ovarian function. Osteoporosis of the femur or mandible in the rats was ameliorated by intermittent PTH therapy.

Reference phantoms are widely applied to evaluate the radiation dose for external exposure. However, the frequently used reference phantoms are based on Caucasians. Dose estimation for Asians using a Caucasian phantom can result in significant errors. This study recruited 40 volunteers whose body sizes are close to the average Taiwanese population. Magnetic resonance imaging was performed to obtain the organ volume for construction of the Taiwanese reference man (TRM) and Taiwanese reference woman (TRW). The dose conversion coefficients (DCC) resulting from photo beams in anterior-posterior, posterior-anterior, right-lateral, left-lateral, and isotropic irradiation geometries were estimated. In the anterior-posterior geometry, the mean DCC differences among organs between the TRM and ORNL phantom at 0.1, 1, and 10 MeV were 7.3%, 5.8%, and 5.2%, respectively. For the TRW, the mean differences from the ORNL phantom at the three energies were 10.6%, 7.4%, and 8.3%. The DCCs of the Taiwanese reference phantoms and the ORNL phantom presented similar trends in other geometries. The torso size of the phantom and the mass and geometric location of the organ have a significant influence on the DCC. The Taiwanese reference phantoms can be used to establish dose guidelines and regulations for radiation protection from external exposure.

Osteoporosis is a disease characterized by a degradation of bone structures. Various methods have been developed to diagnose osteoporosis by measuring bone mineral density (BMD) of patients. However, BMDs from these methods were not equivalent and were incomparable. In addition, partial volume effect introduces errors in estimating bone volume from computed tomography (CT) images using image segmentation. In this study, a two-compartment model (TCM) was proposed to calculate bone volume fraction (BV/TV) and BMD from CT images. The TCM considers bones to be composed of two sub-materials. Various equivalent BV/TV and BMD can be calculated by applying corresponding sub-material pairs in the TCM. In contrast to image segmentation, the TCM prevented the influence of the partial volume effect by calculating the volume percentage of sub-material in each image voxel. Validations of the TCM were performed using bone-equivalent uniform phantoms, a 3D-printed trabecular-structural phantom, a temporal bone flap, and abdominal CT images. By using the TCM, the calculated BV/TVs of the uniform phantoms were within percent errors of ±2%; the percent errors of the structural volumes with various CT slice thickness were below 9%; the volume of the temporal bone flap was close to that from micro-CT images with a percent error of 4.1%. No significant difference (p >0.01) was found between the areal BMD of lumbar vertebrae calculated using the TCM and measured using dual-energy X-ray absorptiometry. In conclusion, the proposed TCM could be applied to diagnose osteoporosis, while providing a basis for comparing various measurement methods.

PET imaging has been widely used in the detection and staging of malignancies and the evaluation of patient-specific dosimetry for PET scans is important in nuclear medicine. However, patient-specific dosimetry can be estimated only by Monte Carlo methods which are usually time-consuming. The purpose of this study is to develop a fast dose evaluation system namely SimDOSE. SimDOSE is a Monte Carlo code embedded in SimSET with a dose scoring routine to record the deposited energy of the photons and electrons. Fluorine-18 is one of the most commonly used radionuclides that decay predominantly by positron emission. Only a 635 keV (Emax) positron and two annihilation photons should be concerned in F-18 radiation dosimetry, hence simulation is relatively simple. To evaluate the effects of resolution, an F-18 point source placed in a 20 cm diameter sphere filled with water was simulated by SimDOSE and GATE v6.1. Grid sizes of 1 mm, 3 mm, and 5 mm were tested and each was simulated with a total of 10 7 decays. The resultant dose distribution functions were compared. Dose evaluation on ORNL phantom was also performed to validate the accuracy of SimDOSE. The grid size of phantom was set as 3 mm and the number of decays was 10 7 . The S -values of liver computed by SimDOSE were compared with GATE and OLINDA (Organ Level INternal Dose Assessment) for 11 C, 15 O, and 18 F.Finally, the CPU time of simulations was compared between SimDOSE and GATE. The dose profiles show the absorption doses located 3 mm outside the center are similar between SimDOSE and GATE. However, 71% (19%) difference of the center dose between SimDOSE and GATE are observed for 1 mm (3 mm) grid. The differences of the profile lie in the assumption in SimDOSE that all kinetic energies of electrons are locally absorbed. The ratios of S values of (SimDOSE/OLINDA) range from 0.95 to 1.11 with a mean value of 1.02±0.043. To compare simulation time from SimDOSE to GATE for calculation of 1 mm, 3 mm, 5 mm gird point source and S values of ORNL phantom are 1.3%, 1.2%, 1.2% and 1.2%, respectively. In conclusion, SimDOSE is an efficient and accurate toolkit to generate patient-specific dose distribution in clinical PET application.

Dental cone beam computed tomography (CBCT) provides high-resolution tomographic images and has been gradually used in clinical practice. Thus, it is important to examine the amount of radiation dose resulting from dental CBCT examinations. In this study, we developed an in-house anthropomorphic adult head phantom to evaluate the level of effective dose. The anthropomorphic phantom was made of acrylic and filled with plaster to replace the bony tissue. The contour of the head was extracted from a set of adult computed tomography (CT) images. Different combinations of the scanning parameters of CBCT were applied. Thermoluminescent dosimeters (TLDs) were used to measure the absorbed doses at 19 locations in the head and neck regions. The effective doses measured using the proposed phantom at 65, 75, and 85 kVp in the D-mode were 72.23, 100.31, and 134.29 µSv, respectively. In the I-mode, the effective doses were 108.24, 190.99, and 246.48 µSv, respectively. The maximum percent error between the doses measured by the proposed phantom and the Rando phantom was l4.90%. Therefore, the proposed anthropomorphic adult head phantom is applicable for assessing the radiation dose resulting from clinical dental CBCT.

Aim The frequency of employing radiography is increasing. Long-term risks of performing X-ray procedures on children and adolescents for medical diagnosis have raised significant concerns. Methods In this study, we adopt the case-control methodology to evaluate the relationship between the incidence rate of acute leukaemia and exposure to radiation during diagnostic X-ray examinations for children. Based on 1998–2010 data obtained from the Taiwan Bureau of National Health Insurance database, we selected 58 children with leukaemia and randomly selected an additional 232 children as the control group. Results The mean age of children with leukaemia is 8.92 ± 5.24 years. The risk of leukaemia in children who underwent X-ray examinations increased 2.14-fold (95% CI, 1.18–3.87). In this study, we identified that, when undergoing X-ray examinations, the risk of leukaemia in children increased for both sex and age groups. Specifically, the relationship between leukaemia and X-ray in boys (OR = 3.28, 95%CI, 1.33–8.07) and in ages of 6 to 11 years (OR = 2.58, 95%CI, 1.09–6.10) was significant. Overall, the risk of leukaemia in children who underwent X-ray examinations progressively increased from a ratio of 1.65 to 3.14. Moreover, an identical trend was observed for boys (1.85 to 6.42). Conclusion Exposure to X-ray increased the risk of leukaemia in children.

TPS3146 Background: Tropomysin receptor kinase A (TrkA) is a protein encoded by the NTRK1 gene. NTRK fusions involving the kinase domain are oncogenic for multiple tumor types and larotrectinib was recently approved for advanced solid tumors harboring NTRK gene fusions. Larotrectinib, an ATP-competitive, reversible pan-TrkA/B/C inhibitor, has shown impressive response rates in patients harboring these fusions; however, resistance can develop due to acquired ATP-site mutations. This has been previously identified in other oncogenic driver kinases such as ALK and EGFR treated with ATP-competitive kinase inhibitors. A newly approved allosteric ALK/EGFR inhibitor brigatinib was able to clinically overcome acquired resistance of many ATP-competitive ALK/EGFR inhibitors (1). Also, irreversible EGFR inhibitors such as afatinib (ATP-competitive) were active against tumors resistant to first-generation inhibitors (2), although their efficacy can be compromised by acquired ATP-site mutations (3). VMD-928 is the first oral small-molecule TrkA (NTRK1) selective inhibitor with dual allosteric and irreversible mechanisms of action. It inhibits TrkA non-competitively at an allosteric (non-ATP) site and has no resistance in vitro to acquired ATP-site mutations such as G667C. VMD-928 in vitro has little or no activity against 348 other kinases including TrkB (NTRK2) and TrkC (NTRK3). We are conducting the first time in human phase 1 trial of oral VMD-928, a novel allosteric and irreversible TrkA selective inhibitor. Methods: This is an open label, Phase 1 study investigating the safety, pharmacokinetics (PK) and pharmacodynamics (PD) of oral VMD-928 in adults with advanced solid tumors or lymphoma (NCT03556228). In part 1 of the study, an accelerated titration scheme will be utilized to determine the recommended phase 2 dose and evaluate PK / PD of VMD-928. In part 2, expansion cohorts including patients with thymic, pancreatic, triple-negative breast carcinoma, or solid tumors with TrkA alterations will be accrued to further evaluate safety and efficacy. Part 3 of the study will characterize the biologically active dose. The study is open and accruing patients at City of Hope. Clinical trial information: NCT03556228.

This study compared the capabilities of micro-computed tomography (micro-CT) and dental cone-beam computed tomography (CBCT) in assessing trabecular bone parameters and cortical bone strength. Micro-CT and CBCT scans were applied to 28 femurs from 14 rats to obtain independent measurements of the volumetric cancellous bone mineral density (vCanBMD) in the femoral head, volumetric cortical bone mineral density (vCtBMD) in the femoral diaphysis, cross-sectional moment of inertia (CSMI), and bone strength index (BSI) (=CSMI×vCtBMD). Five structural parameters of the trabecular bone of the femoral head were calculated from micro-CT images. A three-point bending test was then conducted to measure the fracture load of each femur. Bivariate linear Pearson analysis was conducted to calculate the correlation coefficients (r values) of the micro-CT, dental CBCT, and three-point bending measurements. The statistical analyses showed a strong correlation between vCanBMD values obtained using micro-CT and dental CBCT (r=0.830). There were strong or moderate correlation between vCanBMD measured using dental CBCT and five parameters of trabecular structure measured using micro-CT. Additionally, the results were satisfactory regardless of whether micro-CT or dental CBCT was used to measure the femoral diaphysis vCtBMD (r=0.733 and 0.680, respectively), CSMI (r=0.756 and 0.726, respectively), or BSI (r=0.846 and 0.847, respectively) to predict fracture loads. This study has yielded a new method for using dental CBCT to evaluate bone parameters and bone strength; however, further studies are necessary to validate the use of dental CBCT on humans.

Polymer gel dosimeters have been proved as a useful tool in the verification of treatment planning for three-dimensional radiation therapy. The degree of radiation-induced polymerization (DP) is a function of absorbed dose, and it can be determined in macro-scale by several imaging modalities, such as magnetic resonance imaging (MRI), optical computed tomography, and computed tomography (CT). In this study, we determined the DP for the polymer gel dosimeter in micro-scale by texture analysis on scanning electron microscope (SEM) images. The irradiated n-NIPAM gels with absorbed doses of 5 to 20 Gy delivered by the linear accelerator were freeze-dried and sliced. The SEM images were acquired at magnification of 50t, 500ntn and 3500t , respectively. Four image texture indices, including the entropy, contrast, energy and homogeneity, were estimated from the grey level co-occurrence matrix of each SEM image. The relationships between the radiation dose and texture indices were determined. The SEM images with 500t and 3500t magnification showed significant changes in morphological features of the irradiated gel. The r2 of the linear fitting from 3500t SEM images was 0.8194 (entropy), 0.6024 (contrast), 0.7681 (energy), and 0.9978 (homogeneity), respectively. We conclude that the texture analysis on SEM images is a feasible method to estimate the dose response of the polymer gel dosimeter.

Few studies involving human participants have been conducted to investigate the effect of orthodontic treatment on alveolar bone density around the teeth. Our previous study revealed that patients who received 6 months of active orthodontic treatment exhibited an ∼24% decrease in alveolar bone density around the teeth. However, after an extensive retention period following orthodontic treatment, whether the bone density around the teeth can recover to its original state from before the treatment remains unclear, thus warranting further investigation. The purpose of this study was to assess the bone density changes around the teeth before, during, and after orthodontic treatment. Dental cone-beam computed tomography (CBCT) was used to measure the changes in bone density around 6 teeth in the anterior maxilla (maxilla central incisors, lateral incisors, and canines) of 8 patients before and after orthodontic treatment. Each patient underwent 3 dental CBCT scans: before treatment (T0); at the end of 7 months of active orthodontic treatment (T1); after several months (20–22 months) of retention (T2). The Friedman test was applied to evaluate the changes in the alveolar bone density around the teeth according to the 3 dental CBCT scans. From T0 to T1, a significant reduction in bone density was observed around the teeth (23.36 ± 10.33%); by contrast, a significant increase was observed from T1 to T2 (31.81 ± 23.80%). From the perspective of the overall orthodontic treatment, comparing the T0 and T2 scans revealed that the bone density around the teeth was relatively constant (a reduction of only 0.75 ± 19.85%). The results of the statistical test also confirmed that the difference in bone density between T0 and T2 was nonsignificant. During orthodontic tooth movement, the alveolar bone density around the teeth was reduced. However, after a period of bone recovery, the reduced bone density recovered to its previous state from before the orthodontic treatment. However, the bone density around ∼10% of the teeth in this region could not recover to 80% of its state from before the orthodontic treatment.

Transparent indium tin oxide (ITO) and cosputtered ITO-zinc oxide (ZnO) films’ contacts to an n-GaN epilayer were investigated. Both of these electrodes’ contact to the n-GaN epilayer showed Schottky behavior, although the contact resistance of the ITO-ZnO/n-GaN system was lower than that of the ITO/n-GaN system. By placing a thin Ti interlayer between the ITO-ZnO/n-GaN interface, nonalloyed ohmic contact was achieved. The inset Ti interlayer was both beneficial both for enhancing the outdiffusion of the nitrogen atoms at the surface of the n-GaN and suppressing the indiffusion of oxygen atoms from the surface of the ITO-ZnO to n-GaN. The figure-of-merit (FOM), evaluated from the specific contact resistance and optical property of the Ti/ITO-ZnO system’s contact to the n-GaN epilayer, was optimized further at an adequate thickness of the Ti interlayer.

Monte Carlo (MC) simulation has been commonly used in the dose evaluation of radiation accidents and for medical purposes. The accuracy of simulated results is affected by the particle-tracking algorithm, cross-sectional database, random number generator and statistical error. The differences among MC simulation software packages must be validated. This study simulated the dose point kernel (DPK) and the cellular S-values of monoenergetic electrons ranging from 0.01 to 2 MeV and the radionuclides of (90)Y, (177)Lu and (103 m)Rh, using Fluktuierende Kaskade (FLUKA) and MC N-Particle Transport Code Version 5 (MCNP5). A 6-μm-radius cell model consisting of the cell surface, cytoplasm and cell nucleus was constructed for cellular S-value calculation. The mean absolute percentage errors (MAPEs) of the scaled DPKs, simulated using FLUKA and MCNP5, were 7.92, 9.64, 4.62, 3.71 and 3.84 % for 0.01, 0.1, 0.5, 1 and 2 MeV, respectively. For the three radionuclides, the MAPEs of the scaled DPKs were within 5 %. The maximum deviations of S(N←N), S(N←Cy) and S(N←CS) for the electron energy larger than 10 keV were 6.63, 6.77 and 5.24 %, respectively. The deviations for the self-absorbed S-values and cross-dose S-values of the three radionuclides were within 4 %. On the basis of the results of this study, it was concluded that the simulation results are consistent between FLUKA and MCNP5. However, there is a minor inconsistency for low energy range. The DPK and the cellular S-value should be used as the quality assurance tools before the MC simulation results are adopted as the gold standard.

Unique tooth-like (milky white) color β-Ti dental arch wires are prepared by anodization in a 1M H2SO4 electrolyte at 30 o C and 30 V for 88 min and 40 s. Aggregates are formed on these surfaces of the anodized wires with tooth-like colors, and the results are different from those of the anodized wires with monochromatic colors which have smooth oxide surfaces. Similar to the monochromatic wires, the composition of the oxide layer is TiO2-x and the x approaches zero at the outer layer. But different from the amorphous structure observed in monochromatic wires, the oxide layers are partially crystallized with an anatase structure. The milky white colors result from the rough and crystalized oxide layers, not by the interference effect as observed in monochromatic wires.

OBJECTIVE: The purpose of this study was to improve detectability of microcalcifications using a dual-energy digital mammographic (DEDM) technique. METHODS: Slabs of uniform breast-equivalent plastic and an additional plate were used to mimic various breast thicknesses, from 3 to 7 cm, and to simulate microcalcification with diameters from 0.16 to 0.39 mm. Free-response receiver operating characteristics and area under the curves (Az) were used to evaluate the sensitivity of detecting microcalcifications using the DEDM compared with using the conventional single-energy digital mammography (SEDM). RESULTS: The mean number of false-positives per image was 0.0198 (Az = 0.956 ± 0.027) using DEDM compared with 0.292 (Az = 0.681 ± 0.235) using SEDM. A lower radiation dose could be possibly obtained for the DEDM technique with a thickness of less than 5 cm compared with the SEDM with a thickness larger than 5 cm. CONCLUSIONS: Microcalcifications could be more accurately and efficiently detected using the DEDM, which might bring reliable and promising applications on early computer-aided diagnosis of breast cancer.

Background The aim of this study was to investigate patient doses in prospective electrocardiogram (ECG)-triggered CT coronary angiography (CTCA) combined with multi-segment reconstruction on a 320-detector-row CT. Methods CTCA data acquired with prospective ECG (pECG) triggering at 0–100% (pECG100%), 30–80% (pECG50%), 70–80% (pECG10%) of the R–R interval and reconstructed using mono-, two- and three-segment reconstruction were investigated. Effective doses were estimated by using LiF-TLDs placed at several organ sites in an Alderson-Rando phantom. Results With pECG100%, the estimation of effective dose of data reconstructed using mono-segment (pECG100%_1S) reconstruction was 10.01 ± 0.56 mSv. For data acquired using pECG50%, the effective doses were 6.16 ± 0.12, 9.92 ± 0.37 and 13.51 ± 0.17 mSv in mono-segment (pECG50%_1S), two-segment (pECG50%_2S) and three-segment (pECG50%_3S) reconstruction, respectively. The effective dose of data acquired with pECG10% and reconstructed using mono-segment (pECG10%_1S) reconstruction was 3.61 ± 0.07 mSv. We observed a difference of around 7.46% between effective doses estimated using TLD-phantom measurement and CT dose index (CTDI) obtained from the scanner. Conclusion For patients with low and intermediate heart rate, radiation exposure could be reduced by 38.6% or more by narrowing pulsing window width. Although slightly higher radiation dose was observed in multi-segment reconstruction, this method can be used in high heart rate patients to provide data of high temporal resolution without increasing radiation exposure when it is combined with prospective ECG triggering.

Background Our aim was to investigate CT dose reduction strategies on a hybrid PET/CT scanner for cardiac applications. Materials Image quality and dose estimation of different CT scanning protocols for CT coronary angiography (CTCA), and CT-based attenuation correction for PET imaging were investigated. Fifteen patients underwent CTCA, perfusion PET imaging at rest and under stress, and FDG PET for myocardial viability. These patients were divided into three groups based on the CTCA technique performed: retrospectively gated helical (RGH), ECG tube current modulation (ETCM), and prospective gated axial (PGA) acquisitions. All emission images were corrected for photon attenuation using CT images obtained by default setting and an ultra-low dose CT (ULDCT) scan. Results Radiation dose in RGH technique was 22.2±4.0 mSv. It was reduced to 10.95±0.82 and 4.13±0.31 mSv using ETCM and PGA techniques, respectively. Radiation dose in CT transmission scan was reduced by 96.5% (from 4.53±0.5 to 0.16±0.01 mSv) when applying ULDCT as compared to the default CT. No significant difference in terms of image quality was found among various protocols. Conclusion The proposed CT scanning strategies, i.e. ETCM or PGA for CTCA and ULDCT for PET attenuation correction, could reduce radiation dose up to 47% without degrading imaging quality in an integrated cardiac PET/CT coronary artery examination.

The quantitative ability of PET/CT allows the widespread use in clinical research and cancer staging. However, metal artifacts induced by high-density metal objects degrade the quality of CT images. These artifacts also propagate to the corresponding PET image and cause a false increase of 18F-FDG uptake near the metal implants when the CT-based attenuation correction (AC) is performed. In this study, we applied a model-based metal artifact reduction (MAR) algorithm to reduce the dark and bright streaks in the CT image and compared the differences between PET images with the general CT-based AC (G-AC) and the MAR-corrected-CT AC (MAR-AC). Results showed that the MAR algorithm effectively reduced the metal artifacts in the CT images of the ACR flangeless phantom and two clinical cases. The MAR-AC also removed the false-positive hot spot near the metal implants of the PET images. We conclude that the MAR-AC could be applied in clinical practice to improve the quantitative accuracy of PET images. Additionally, further use of PET/CT fusion images with metal artifact correction could be more valuable for diagnosis.

We present an alternative effective method for verifying the multileaf collimator (MLC) leaves speed using a digital-video imaging system in daily dynamic conformal radiation therapy (DCRT) and intensity-modulation radiation therapy (IMRT) in achieving increased convenience and shorter treatment times. The horizontal leaves speed measured was within 1.76–2.08 cm/s. The mean full range of traveling time was 20 s. The initial speed-up time was within 1.5–2.0 s, and the slowing-down time was within 2.0–2.5 s. Due to gravity the maximum speed-up effect in the X1 bank was +0.10 cm/s, but the lagging effect in the X2 bank was −0.20 cm/s. This technique offered an alternative method with electronic portal imaging device (EPID), charged coupled device (CCD) or a light field for the measurement of MLC leaves speed. When time taken on the linac was kept to a minimum, the image could be processed off-line.

This study is to evaluate the influence of using different matrix size of smoothing filter for image post-processing and various slice thickness during MR imaging on dose estimation in Ir-192 HDR brachytherapy via normoxic polymer gel dosimeter. Our results show its sensitive nature in gel dosimeter while changing these parameters, among which the combination of 2 mm slice thickness of MR images and [5×5] smoothing filter are considered the optimal parameters to provide accurate dose estimations and isodose curves.

In this paper we develop a new impulse-radio-based RF front-end module for ultrawideband communications. The proposed transceiving module is designed based a novel compact microwave sampler. The microwave sampler consists of a multilayered magic-T and a balanced sampling bridge. By utilizing a wideband microstrip- to-slotline Marchand balun, the newly proposed magic-T features an improved bandwidth of 94.2%. The design concept, circuit topology, and experimental results of the magic-T and microwave sampler are investigated in the first half of this paper. By utilizing the equivalent time sampling theory, in the second half of this paper we investigate an impulse-radio-based ultrawideband transceiving front-end module. Two transmission data rates, 90 and 270 Kbps, are demonstrated with various bit patterns. The experimental results reveal that the transceiving module has a coverage range up to 4.5 m. The circuit configuration, modulation scheme, and system performance of the front-end module are discussed thoroughly. The tradeoff for increasing the data rate is discussed at the end of this paper as well.

Parkinson’s disease (PD) is a neurodegenerative disease characterized by progressive loss of dopaminergic neurons in the basal ganglia. Single photon emission computed tomography (SPECT) scans using [99mTc]TRODAT-1 can image dopamine transporters and provide valuable diagnostic information of PD. In this study, we optimized the scanning parameters for [99mTc]TRODAT-1/SPECT using the Taguchi analysis to improve image quality. SPECT scans were performed on forty-five healthy volunteers according to an L 9 orthogonal array. Three parameters were considered, including the injection activity, uptake duration, and acquisition time per projection. The signal-to-noise ratio (SNR) was calculated from the striatum/occipital activity ratio as an image quality index. Ten healthy subjects and fifteen PD patients were used to verify the optimal parameters. The estimated optimal parameters were 962 MBq for [99mTc]TRODAT-1 injection, 260 min for uptake duration, and 60 s/projection for data acquisition. The uptake duration and time per projection were the two dominant factors which had an F-value of 18.638 (38%) and 25.933 (53%), respectively. Strong cross interactions existed between the injection activity/uptake duration and injection activity/time per projection. Therefore, under the consideration of as low as reasonably achievable (ALARA) for radiation protection, we can decrease the injection activity to 740 MBq. The image quality remains almost the same for clinical applications.

Organ motion caused by respiration is a major challenge in positron emission tomography (PET) imaging. This work proposes a technique to reduce smearing in PET imaging caused by respiratory motion. Dynamic scanning at 1 frame/s is used. A point source, used as a marker, is attached to the object's abdomen during the scan. The source position in the projection view moves with respiratory motion and can be used to represent the respiratory phase within the time interval in which each frame data are acquired. One hundred and twenty frames are obtained for each study. The range of the positions of the marker is divided into four groups, representing different respiratory phases. The frames in which the organ positions (phases) are the same summed to produce a static sub-sinogram. Each sub-sinogram then undergoes regular image reconstruction to yield a motion-free image. The technique is applied to one volunteer under both free and coached breathing conditions. A parameter called the volume reduction factor is adopted to evaluate the effectiveness of this motion-reduction technique. The preliminary results indicate that the proposed technique effectively reduces motion artifacts in the image. Coached breathing yields better results than free breathing condition. The advantages of this method are that (1) the scanning time remains the same; (2) free breathing is allowed during the acquisition of the image; and (3) no user intervention is required.

To improve the counting efficiency, modern positron emission tomography scanners generally perform 3D data acquisition with the septa retracted. As a consequence, the scatter fraction can surge to as high as 40%. Our previous method proposed the use of a beam stoppers (BS) device to directly measure the scatter and to remove it from the sinogram. The BS partially attenuate the primary radiation of certain lines of response (LOR) without affecting the scattering events. To measure the scatter, dual scans are performed with and without the device in place. This study proposes an improved method. The dual scans are performed with the device placed at two different locations. The proposed method reduces the effective sampling distance without the need to actually increase the stopper's number. The scatter component at the LOR blocked by each stopper can be estimated. Assuming that the scattered radiation has a spatially slow-varying distribution, the whole scattered sinogram can be recovered using interpolation from these local measurements. Once the scatter component is estimated, the sinogram of the primary radiation can be obtained by subtracting the scatter component from the original data. The scatter free image is then reconstructed from the primary sinogram. This method was applied to scanned data of two digital phantoms using the Simulation System for Emission Tomography simulation package to demonstrate its effectiveness. Preliminary results showed that this method has slightly better performance than the previous BS method and the conventional single scatter simulation technique with smaller mean squared error and less noise in the corrected image.

Introduction [ 123 I]-2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine ([ 123 I]ADAM), a novel radiotracer, has promising application in the imaging of the serotonin transporter (SERT) in the human brain. In this study, the optimal scanning time for acquiring brain single photon emission computed tomography (SPECT) images was determined by performing dynamic SPECT studies at intervals from 0 to 6 h postinjection of [ 123 I]ADAM. Additionally, radiation-absorbed doses were determined for three healthy human subjects using attenuation-corrected images. Methods Twelve subjects were randomized into one of three study groups as follows: whole-body distribution imaging ( n =3), dynamic SPECT imaging ( n =3) and brain SPECT imaging ( n =6). The radiation-absorbed dose was calculated using MIRDOSE 3.0 software with attenuation-corrected data. The specific binding (SB) ratio of the brain stem was measured from dynamic SPECT images to determine the optimal scanning time. Results Dynamic SPECT images showed that the SB of the brain stem gradually increased to a maximum 4 h postinjection. Single photon emission computed tomography images at 4 h postinjection showed a high uptake of the radiotracer (SB) in the hypothalamus (1.40±0.12), brain stem (1.44±0.16), pons (1.13±0.14) and medial temporal lobe (0.59±0.10). The mean adult male value of effective dose was 3.37×10 −2 mSv/MBq with a 4.8-h urine-voiding interval. Initial high uptake in SERT-rich sites was demonstrated in the lung and brain. A prominent washout of the radiotracer from the lung further increased brain radioactivity that reached a peak value of 5.03% of injected dose 40 min postinjection. Conclusions [ 123 I]ADAM is a promising radiotracer for SPECT imaging of SERT in humans with acceptable dosimetry and high uptake in SERT-rich regions. Brain SPECT images taken within 4 h following injection show optimal levels of radiotracer uptake in known SERT sites. However, dynamic changes in lung SERT distribution must be carefully evaluated.

An ultrawideband (UWB) monocycle pulse generator with dual resistive loaded shunt stubs is present in this article. The proposed pulse generator consists of a step recovery diode (SRD), a Schottky diode, a pair of resistive loaded stubs, and a pair of short-circuited stubs. By introducing an additional resistive loaded stub between the SRD and the Schottky diode, the ringing tail of the impulse waveform can be substantially suppressed and the resultant monocycle pulse is well-behaved with very low ringing level. The measurement result demonstrates a monocycle pulse with peak-to-peak amplitude of 550 mV, pulsewidth of 320 ps, ringing level of as low as −22 dB, and good pulse symmetry. This pulse generator is suitable for various UWB applications. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 459–462, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22145

The objective of this study was to evaluate the effect of clenching tasks on the stress and stability of a temporomandibular joint (TMJ) condylar prosthesis, as well as on the stress and strain in the whole mandible and bone surrounding three screws. Three-dimensional finite element models of the mandible and a TMJ condylar prosthesis using three screws were established. Six static clenching tasks were simulated in this study: incisal clench (INC), intercuspal position (ICP), right unilateral molar clench (RMOL), left unilateral molar clench (LMOL), right group function (RGF), and left group function (LGF). Based on the simulation of the six clenching tasks, none of the inserted screws or the TMJ condylar prosthesis were broken. In addition, the stability of the TMJ condylar prosthesis was sufficiently high for bone ongrowth. For the whole mandibular bone, the maximum von Mises stress and von Mises strain observed in the cortical bone and cancellous bone were yielded by the ICP and RMOL, respectively. For the bone surrounding the inserted screws, the maximum von Mises stress and von Mises strain in both the cortical bone and cancellous bone were yielded by the LMOL. Clenching tasks had significant effects on the stress distribution of the TMJ condylar prosthesis, as well as on the stress and strain distribution of the whole mandible and the bone surrounding the inserted screws.

Modern positron emission tomography scanners generally perform three-dimensional data collection without septa, which increases not only true coincidences but also scattered coincidences. In this study, a beam stopper (BS) device which is made of lead was used to estimate the scatter component in the PET sinogram. Scattered events were then directly measured from those lines of response blocked by stoppers. By assuming that the scatter distribution is a spatially slow-varying function, the scatter component can be recovered using the cubic-spline interpolation from the local measurements. Monte Carlo simulations of an abdomen phantom and the Zubal phantom were performed. Preliminary results demonstrated that the proposed BS method can improve image contrast and quantitative accuracy. Among different configurations, the BS device consisting of twelve lead stoppers with 3 mm radius yielded the optimal result compared to the other BS configurations. This BS method also outperformed the dual-energy window method up to 40% based on the mean squared error. The results indicated that the proposed BS method permits a direct, fast, and accurate scatter correction.

An ectopically located gallbladder is rare and unusual. In this study, we described a case of a 52-year-old woman who underwent SPECT-myocardial perfusion imaging because of exertional dyspnea and chest tightness. The rest sinograms reveal 2 substantially increased tracer uptakes in the right chest. Subsequently, a SPECT/CT scan was performed to clarify the indeterminate findings on the SPECT-myocardial perfusion imaging. The coregistered SPECT/CT images depict intense focal activity in the right chest, which corresponds to the gallbladder on the CT scan, thus explaining the peculiar ectopic gallbladder finding.

The objective of this study was to develop a method for measuring quality degradation in lossy wavelet image compression. Quality degradation is due to denoising and edge blurring effects that cause smoothness in the compressed image. The peak Moran z histogram ratio between the reconstructed and original images is used as an index for degradation after image compression. The Moran test is applied to images randomly selected from each medical modality, computerized tomography, magnetic resonance imaging, and computed radiography and compressed using the wavelet compression at various levels. The relationship between the quality degradation and compression ratio for each image modality agrees with previous reports that showed a preference for mildly compressed images. Preliminary results show that the peak Moran z histogram ratio can be used to quantify the quality degradation in lossy image compression. The potential for this method is applications for determining the optimal compression ratio (the maximized compression without seriously degrading image quality) of an image for teleradiology.

GEANT4 Application for Tomographic Emission (GATE) is a powerful Monte Carlo simulator that combines the advantages of the general-purpose GEANT4 simulation code and the specific software tool implementations dedicated to emission tomography. However, the detailed physical modelling of GEANT4 is highly computationally demanding, especially when tracking particles through voxelized phantoms. To circumvent the relatively slow simulation of voxelized phantoms in GATE, another efficient Monte Carlo code can be used to simulate photon interactions and transport inside a voxelized phantom. The simulation system for emission tomography (SimSET), a dedicated Monte Carlo code for PET/SPECT systems, is well-known for its efficiency in simulation of voxel-based objects. An efficient Monte Carlo workflow integrating GATE and SimSET for simulating pinhole SPECT has been proposed to improve voxelized phantom simulation. Although the workflow achieves a desirable increase in speed, it sacrifices the ability to simulate decaying radioactive sources such as non-pure positron emitters or multiple emission isotopes with complex decay schemes and lacks the modelling of time-dependent processes due to the inherent limitations of the SimSET photon history generator (PHG). Moreover, a large volume of disk storage is needed to store the huge temporal photon history file produced by SimSET that must be transported to GATE. In this work, we developed a multiple photon emission history generator (MPHG) based on SimSET/PHG to support a majority of the medically important positron emitters. We incorporated the new generator codes inside GATE to improve the simulation efficiency of voxelized phantoms in GATE, while eliminating the need for the temporal photon history file. The validation of this new code based on a MicroPET R4 system was conducted for (124)I and (18)F with mouse-like and rat-like phantoms. Comparison of GATE/MPHG with GATE/GEANT4 indicated there is a slight difference in energy spectra for energy below 50 keV due to the lack of x-ray simulation from (124)I decay in the new code. The spatial resolution, scatter fraction and count rate performance are in good agreement between the two codes. For the case studies of (18)F-NaF ((124)I-IAZG) using MOBY phantom with 1 × 1 × 1 mm(3) voxel sizes, the results show that GATE/MPHG can achieve acceleration factors of approximately 3.1 × (4.5 ×), 6.5 × (10.7 ×) and 9.5 × (31.0 ×) compared with GATE using the regular navigation method, the compressed voxel method and the parameterized tracking technique, respectively. In conclusion, the implementation of MPHG in GATE allows for improved efficiency of voxelized phantom simulations and is suitable for studying clinical and preclinical imaging.

Objective The objective of this study was to evaluate the relationship between the trabecular bone microarchitecture and cortical bone morphology by using micro-computed tomography (micro-CT) and dental cone-beam computed tomography (dental CT). Materials and Methods Sixteen femurs and eight fifth lumbar vertebrae were collected from eight male Sprague Dawley rats. Four trabecular bone microarchitecture parameters related to the fifth lumbar vertebral body (percent bone volume [BV/TV], trabecular thickness [TbTh], trabecular separation [TbSp], and trabecular number [TbN]) were calculated using micro-CT. In addition, the volumetric cancellous bone grayscale value (vCanGrayscale) of the fifth lumbar vertebral body was measured using dental CT. Furthermore, four cortical bone morphology parameters of the femoral diaphysis (total cross-sectional area [TtAr], cortical area [CtAr], cortical bone area fraction [CtAr/TtAr], and cortical thickness [CtTh]) were calculated using both micro-CT and dental CT. Pearson analysis was conducted to calculate the correlation coefficients (r) of the micro-CT and dental CT measurements. Paired-sample t tests were used to compare the differences between the measurements of the four cortical bone morphology parameters obtained using micro-CT and dental CT. Results High correlations between the vCanGrayscale measured using dental CT and the trabecular bone microarchitecture parameters (BV/TV [r = 0.84] and TbTh [r = 0.84]) measured using micro-CT were observed. The absolute value of the four cortical bone morphology parameters may be different between the dental CT and micro-CT approaches. However, high correlations (r ranged from 0.71 to 0.90) among these four cortical bone morphology parameters measured using the two approaches were obtained. Conclusion We observed high correlations between the vCanGrayscale measured using dental CT and the trabecular bone microarchitecture parameters (BV/TV and TbTh) measured using micro-CT, in addition to high correlations between the cortical bone morphology measured using micro-CT and dental CT. Further experiments are necessary to validate the use of dental CT on human bone.

The rapid development of picture archiving and communication systems (PACSs) thoroughly changes the way of medical informatics communication and management. However, as the scale of a hospital’s operations increases, the large amount of digital images transferred in the network inevitably decreases system efficiency. In this study, a server cluster consisting of two server nodes was constructed. Network load balancing (NLB), distributed file system (DFS), and structured query language (SQL) duplication services were installed. A total of 1 to 16 workstations were used to transfer computed radiography (CR), computed tomography (CT), and magnetic resonance (MR) images simultaneously to simulate the clinical situation. The average transmission rate (ATR) was analyzed between the cluster and noncluster servers. In the download scenario, the ATRs of CR, CT, and MR images increased by 44.3%, 56.6%, and 100.9%, respectively, when using the server cluster, whereas the ATRs increased by 23.0%, 39.2%, and 24.9% in the upload scenario. In the mix scenario, the transmission performance increased by 45.2% when using eight computer units. The fault tolerance mechanisms of the server cluster maintained the system availability and image integrity. The server cluster can improve the transmission efficiency while maintaining high reliability and continuous availability in a healthcare environment.

The objective of this study was to evaluate the location of the mandibular canal and the thickness of the occlusal cortical bone at dental implant sites in the lower second premolar and lower first molar by using dental cone-beam computed tomography (CBCT). Seventy-nine sites (47 second premolar and 32 first molar sites) were identified in the dental CBCT examinations of 47 patients. In this study, 4 parameters were measured: (1) MC—the distance from the mandibular canal to the upper border of the mandible; (2) CD—the distance from the mandibular canal to the buccal border of the mandible; (3) MD—the distance from the mandibular canal to the lingual border of the mandible; (4) TC—the thickness of the cortical bone at the occlusal side. A statistical analysis was employed to compare the size and differences between these 4 parameters at the lower second premolar and lower first molar. Regarding the MC and MD, the experimental results showed no statistical difference between the first molar and second premolar. However, the TC for the second premolar was greater than that of the first molar. Thus, careful consideration is necessary in choosing the size of and operation type for dental implants.

The Monte Carlo (MC) technique has been widely used as the gold standard for interaction of radiation with matter in the fields of medical physics, radiation therapy, and nuclear medicine. However, MC simulation is time consuming and requires a lot of computational resources. Generally, a dedicated high performance computing cluster is use to improve efficiency, but it is costly and lacks of the ability to run routine errands in healthcare facilities. In this study, we proposed a method for rapid deployment of computing platform for MC simulation in the PACS environment using review workstations as computing nodes. The workstations were booted from the network and initialed a RAM disk as the boot sector. The simplified Linux operating system and the Monte Carlo N-Particle Transport Code Version 5 (MCNP5) were transferred from the DRBL (Diskless Remote Boot in Linux) server to each node automatically. The cluster computing environment can be established within four minutes. We compared a commercially available dedicated cluster with the DRBL cluster. The results showed that the commercial cluster had a slightly higher acceleration factor than the DRBL cluster. The simulation time of the commercial and the DRBL clusters for 2×10 8 particle histories was 37,151 and 40,021 sec, respectively. When the number of rendezvous increased to 20, the maximum time differences between both clusters were 95 and 85 sec for the megabit and the gigabit switches. We conclude that the DRBL cluster can be quickly deployed to the non-workloaded review workstations in the PACS. Thus, the MC technique could be broadly used to enhance the research capability of radiological sciences in healthcare facilities.

Under high pressure of flight mission and dynamic aircraft maneuvers in the tactic missions, pilot faces additional difficulties and increased mental workload. Workload could increase the error of flight operation, decrease efficiency of pilot's decision-making. Experts had significantly shorter dwells, more total fixations, more aim point and airspeed fixations and fewer altimeter fixations than novices, experts were also found to have better defined eye-scanning patterns. This research applies the eye-tracking technology for analyzing visual attention, emWave-2 for measuring physiological coherence, and NSAS-TLX for investigating subjective cognitive efforts. The participants of this research consisted of 41 fighter pilots. The present study is applying new technology to understand the pilots' workload and visual attention in the cockpit for conducting a simulated air-to-air tactic operation. There is a raising need for further research regarding mental workload and stress management program for real-time flight operations.