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Multiple small beamlets in the delivery of highly modulated single-isocenter HyperArc VMAT plan can lead to dose delivery errors associated with small-field dosimetry, which can be a major concern for stereotactic radiosurgery for multiple brain lesions. Herein, we describe and compare a clinically valuable dynamic conformal arc (DCA)-based VMAT (DCA-VMAT) approach for stereotactic radiosurgery of multiple brain lesions using flattening filter free beams to minimize this effect. Original single-isocenter HyperArc style VMAT and DCA-VMAT plans were created on 7 patients with 2 to 8 brain lesions (total 35 lesions) for 10 MV- flattening filter free beam. 20 Gy was prescribed to each lesion. For identical planning criteria, DCA-VMAT utilizes user-controlled field aperture shaper before VMAT optimization. Plans were evaluated for conformity and target coverage, low- and intermediate dose spillages to brain volume that received more than 30% (V30%) and 50% (V50%) of prescription dose. Additionally, mean brain dose, V8, V12 and maximal dose to adjacent organs-at-risk (OAR) including hippocampi were reported. Total monitor units, beam modulation factor, treatment delivery efficiency, and accuracy were recorded. Comparing with original VMAT, DCA-VMAT plans provided similar tumor dose, target coverage and conformity, yet tighter radio-surgical dose distribution with lower dose to normal brain V30% (p = 0.009), V50% (p = 0.05) and other OAR including lower dose to hippocampi. Lower total number of monitor units and smaller beam modulation factor reduced beam on time by 2.82 min (p0.001), on average (maximum up to 3.8 min). Beam delivery accuracy was improved by 8%, on average (p0.001) and maximum up to 13% in some cases for DCA-VMAT plans. This novel DCA-VMAT approach provided excellent plan quality, reduced dose to normal brain, and other OAR while significantly reducing beam-on time for radiosurgery of multiple brain lesions-improving patient compliance and clinic workflow. It also provided less MLC modulation through the targets-potentially minimizing small field dosimetry errors as demonstrated by quality assurance results. Incorporating DCA-based VMAT optimization in HyperArc module for radiosurgery of multiple brain lesions merits future investigation.

When Delivery Quality Assurance (DQA) results do not coincide with specific criteria, re-measurement and re-treatment planning are required because incorrect beam delivery to the patient may occur. Therefore, an analysis of the plan parameters to find reasons for failure is essential. In this paper, we examine the effect of plan parameters on the DQA passing rate and clarify the plan parameters that should be adjusted mainly for each Tomotherapy when DQA fails and re-planning is required. Two versions of Tomotherapy treatment machines, Tomotherapy Hi-art and Radixact X9, were used. An independent t-test was performed to confirm the significant difference between the DQA passing rates of Tomotherapy Hi-art and Radixact X9. Also, a regression analysis was performed to analyze the correlation between plan parameters and passing rates. The average passing rate for Radixact X9 was 99.82 (standard deviation [SD] = 0.32) and that for Tomotherapy Hi-art was 98.46 (SD = 1.76). The passing rate of Radixact X9 was significantly higher than that of Tomotherapy Hi-art (P = 0.000). Statistically significant independent variables adopted from Tomotherapy Hi-art were IEC Yf (p = 0.025), the modulation factor (p = 0.003), and the number of control points (p = 0.006). The statistically significant parameter for Radixact X9 was IEC Xf (p = 0.000). According to the results, the new version of Tomotherapy(Radixact X9) has a relatively higher DQA pass rate than the old version (Tomotherapy Hi-art), and if the DQA fails and re-planning is required, each of the plan parameters can be adjusted to achieve a higher pass rate.

Objectives: Hippocampus-sparing whole-brain radiotherapy (HS-WBRT) using tomotherapy is known to provide a better dose distribution than volumetric-modulated arc therapy but requires an extended irradiation time. The present study aimed to investigate whether irradiation time can be shortened by reducing the modulation factor (MF) without losing the target dose distribution. Methods: Using six tilted computed tomography images in the head area, the planning target volume (PTV) and hippocampal doses, and the irradiation time was investigated with a jaw width of 1 cm, a pitch of 0.200, and the MF changed from 3.0 to 2.6, 2.2, 1.8, and 1.4. Results: No significant changes in the PTV or hippocampus were found with MF in the range from 3.0 to 1.8, but marked deterioration was found with that of 1.4. The irradiation time showed a linear relationship with the MF within the range from 3.0 to 1.8, with 1334, 1158, 986, and 817 s at modulation factors of 3.0, 2.6, 2.2, and 1.8, respectively. However, when the MF was 1.4, the irradiation time was 808 s. Conclusions: When HS-WBRT is performed with a tilted body position and a jaw width of 1 cm, with a MF of 1.8, a favorable balance between dose parameters and irradiation time is achieved, whereas with a MF of 1.4, the quality of the radiotherapy plan deteriorates, and the irradiation time is approximately the same as that with a MF of 1.8.

Background and Purpose: The topotherapy technique was recently suggested as a robust alternative to helical radiation delivery for total body irradiation (TBI). It allows to deliver a discrete number of beams with fixed gantry. A Topotherapy-based low-dose TBI technique was optimized and clinically implemented. Materials and methods: TBI delivery was split in two parts: the first treating from the head to half thigh and the second the remaining legs. An in-silico investigation aimed to optimize plan parameters was first carried out on four patients. For the upper plan, field width and pitch were fixed to 5 cm and 0.5: the combined impact of five modulation factor (MF) values and different field configurations (6/8/12 fields) was investigated. For the lower plan, two anterior/posterior beams (field width: 5 cm; pitch: 0.5; MF:1.5) were used. After assessing the optimal technique, set-up/quality assurance/image-guidance procedures were defined and the technique clinically implemented: 23 patients were treated up to now. Results: The best compromise between treatment time and planning target volume (PTV) coverage/homogeneity was found for MF = 1.5 and 8 fields. All clinical plans were automatically optimized using an “ad-hoc” plan template: excellent PTV coverage (PTV95%>98.5%) and homogeneity (median SD:4%) were found with a median beam-on time of 17/9 min for the upper/lower plan. All patients were successfully treated and transplanted. Conclusions: TBI delivered with the topotherapy approach robustly guarantees adequate coverage and dose homogeneity. Semi-automatic clinical plans can be quickly generated and efficiently delivered. Keywords: TBI, TomoDirect, Tomotherapy, Automatic planning

TomoTherapy® is a modern radiation treatment technique in which intensity-modulated radiation therapy (IMRT) is delivered in helical fashion. A two-dimensional (2D) array which has been existing for IMRT patient-specific quality assurance (PSQA) verifications for many years is I'MatriXX. Our objectives were to validate this I'MatriXX and to evaluate it for different patient sites and fractionation schedules of TomoTherapy treatment. Twenty-five plans were created with virtual target for different possible pitch values and field widths for validation. Gamma index criteria of 3%/2% dose differences and 3/2 mm distance to agreement were used. QA plans of 26 different treatment sites and different fractionation schedules were used. Results indicated that the matrix response is independent of field width, pitch, and modulation factor of TomoTherapy with 3%, 3 mm criteria. High passing rate ranging from 99.7% to 90.7% was observed for selected patient plans. We found that I'MatriXX 2D array can be utilized for easy and quick TomoTherapy PSQA.

There is no ideal detector-phantom combination to perform patient specific quality assurance (PSQA) for Total Marrow (TMI) and Lymphoid (TMLI) Irradiation plan. In this study, 3D dose reconstruction using mega voltage computed tomography detectors measured Leaf Open Time Sinogram (LOTS) was investigated for PSQA of TMI/TMLI patients in helical tomotherapy. The feasibility of this method was first validated for ten non-TMI/TMLI patients, by comparing reconstructed dose with (a) ion-chamber (IC) and helical detector array (ArcCheck) measurement and (b) planned dose distribution using 3Dγ analysis for 3%@3mm and dose to 98% (D98%) and 2% (D2%) of PTVs. Same comparison was extended for ten treatment plans from five TMI/TMLI patients. In all non-TMI/TMLI patients, reconstructed absolute dose was within ± 1.80% of planned and IC measurement. The planned dose distribution agreed with reconstructed and ArcCheck measured dose with mean (SD) 3Dγ of 98.70% (1.57%) and 2Dγ of 99.48% (0.81%). The deviation in D98% and D2% were within 1.71% and 4.10% respectively. In all 25 measurement locations from TMI/TMLI patients, planned and IC measured absolute dose agreed within ± 1.20%. Although sectorial fluence verification using ArcCHECK measurement for PTVs chest from the five upper body TMI/TMLI plans showed mean ± SD 2Dγ of 97.82% ± 1.27%, the reconstruction method resulted poor mean (SD) 3Dγ of 92.00% (± 5.83%), 64.80% (± 28.28%), 69.20% (± 30.46%), 60.80% (± 19.37%) and 73.2% (± 20.36%) for PTVs brain, chest, torso, limb and upper body respectively. The corresponding deviation in median D98% and D2% of all PTVs were 98% and D2%

Aim: The aim of the study was to find the most balanced plan with an optimal combination of planning parameters in helical tomotherapy (HT) for bilateral breast irradiation by evaluating dosimetric indices and time factors. In particular, we investigated the best combination of field width (FW), pitch, and modulation factor (MF). Materials and Methods: A total of 90 plans (18 plans for each patient) was created in this study, with different combination of planning parameters (FW: 2.5 cm [F1] and 5 cm [F2]; pitch: 0.215 [P1], 0.287 [P2], and 0.43 [P3]; and MF: 2.0 [M1], 2.5 [M2], and 3.0 [M3]). Plans were analyzed using several dosimetric indices: homogeneity index, conformity index, dose near minimum D98%, dose near maximum D2%, and the coverage by D95% of the target. Organ at risk (OAR) doses were evaluated by mean dose, V5Gy and V25Gy for the heart and mean dose V5Gy and V20Gy for both the lungs. Treatment time was also reported for all plans. Results: Reducing FW from 5 cm to 2.5 cm increased the treatment time by 40%–50% and improved homogeneity of the target. Tightening the pitch value from 0.43 to 0.215 improved target as well as OAR doses without increasing the treatment time. Increasing MF from 2 to 3 improved all the dosimetric indices and also increased treatment time. Conclusions: On the basis of our analysis, a plan with FW 5 cm, pitch 0.215, and MF 2.5 can be considered as an optimal combination of planning parameters for bilateral breast irradiation in HT technique.

We demonstrate terahertz single-pixel imaging is improved by using a photomodulator based on silicon passivated with SiO 2 . By exploring various SiO 2 thicknesses, we show that the modulation factor of the as-fabricated terahertz photomodulator can reach 0.9, three times that based on bare silicon. This improvement originates from chemical passivation, as well as anti-reflection. Single-pixel imaging experiments based on the compressed sensing method show that reconstructed images adopting the new photomodulator have better quality than the conventional terahertz modulator based on bare silicon. Since the passivation process is routine and low cost, we expect this work will reduce the cost of terahertz photomodulator and single-pixel THz imaging, and advance their applications.

Several studies have reported changes in dose distribution and delivery time based on the value of specific planning parameters [field width (FW), pitch, and modulation factor (MF)] in tomotherapy. However, the variation in the parameters between different facilities is unknown. The purpose of this study was to determine standard values of the above parameters for cases of head and neck cancer (HNC) and prostate cancer (PC) in Japan. In this survey, a web-based questionnaire was sent to 48 facilities performing radiation therapy with tomotherapy in March 2016. The deadline for data submission was April 2016. In the questionnaire, the values of the planning parameters usually used were requested and 23 responses were received, representing a response rate of 48% (23/48). The FW selected was 2.5 cm in most facilities, and facilities with a tomoEDGE license used dynamic FW rather than fixed FW. Facilities changed the pitch based on FW, dose per fraction, or target offset more frequently in HNC than in PC. In contrast, >50% of the facilities used the magic number proposed by Kissick et al. Median preset MFs (range, min to max) in HNC and PC were 2.4 (1.8-2.8) and 2.0 (1.8-3.0), respectively, and MF values showed large variations between the facilities. Our results are likely to be useful to several facilities designing treatment plans in tomotherapy.

A low modulation factor (MF) maintaining a good dose distribution contributes to the shortening of the delivery time and efficiency of the treatment plan in helical tomotherapy. The purpose of this study was to reduce the delivery time using initial values and the upper limit values of MF. First, patients with head and neck cancer (293 cases) or prostate cancer (181 cases) treated between June 2011 and July 2015 were included in the analysis of MF values. The initial MF value (MF initial) was defined as the average MF actual value, and the upper limit of the MF value (MFUL) was defined according the following equation: MFUL = 2 × standard deviation of MF actual value + the average MF actual Next, a treatment plan was designed for patients with head and neck cancer (62 cases) and prostate cancer (13 cases) treated between December 2015 and June 2016. The average MF actual value for the nasopharynx, oropharynx, hypopharynx, and prostate cases decreased from 2.1 to 1.9 (p = 0.0006), 1.9 to 1.6 (p < 0.0001), 2.0 to 1.7 (p < 0.0001), and 1.8 to 1.6 (p = 0.0004) by adapting the MF initial and the MFUL values, respectively. The average delivery time for the nasopharynx, oropharynx, hypopharynx, and prostate cases also decreased from 19.9 s cm−1 to 16.7 s cm−1 (p < 0.0001), 15.0 s cm−1 to 13.9 s cm−1 (p = 0.025), 15.1 s cm−1 to 13.8 s cm−1 (p = 0.015), and 23.6 s cm−1 to 16.9 s cm−1 (p = 0.008) respectively. The delivery time was shortened by the adaptation of MF initial and MFUL values with a reduction in the average MF actual for head and neck cancer and prostate cancer cases.

The workload for shielding purposes of modern linear accelerators (linacs) consists of primary and scatter radiation which depends on the dose delivered to isocenter (cGy) and leakage radiation which depends on the monitor units (MUs). In this study, we report on the workload for 10 treatment vaults in terms of dose to isocenter (cGy), monitor units delivered (MUs), number of treatment sessions (Txs), as well as, use factors (U) and modulation factors (CI) for different treatment techniques. The survey was performed for the years between 2006 and 2015 and included 16 treatment machines which represent different generations of Varian linear accelerators (6EX, 600C, 2100C, 2100EX, and TrueBeam) operating at different electron and x‐ray energies (6, 9, 12, 16 and 20 MeV electrons and, 6 and 15 MV x‐rays). An institutional review board (IRB) approval was acquired to perform this study. Data regarding patient workload, dose to isocenter, number of monitor units delivered, beam energies, gantry angles, and treatment techniques were exported from an ARIA treatment management system (Varian Medical Systems, Palo Alto, Ca.) into Excel spreadsheets and data analysis was performed in Matlab. The average (± std‐dev) number of treatment sessions, dose to isocenter, and number of monitor units delivered per week per machine in 2006 was 119 ± 39 Txs, (300 ± 116) × 102 cGys, and (78 ± 28) × 103 MUs respectively. In contrast, the workload in 2015 was 112 ± 40 Txs, (337 ± 124) × 102 cGys, and (111 ± 46) × 103 MUs. 60% of the workload (cGy) was delivered using 6 MV and 30% using 15 MV while the remaining 10% was delivered using electron beams. The modulation factors (MU/cGy) for IMRT and VMAT were 5.0 (± 3.4) and 4.6 (± 1.6) respectively. Use factors using 90° gantry angle intervals were equally distributed (~0.25) but varied considerably among different treatment techniques. The workload, in terms of dose to isocenter (cGy) and subsequently monitor units (MUs), has been steadily increasing over the past decade. This increase can be attributed to increased use of high dose hypo‐fractionated regimens (SBRT, SRS) and the increase in use of IMRT and VMAT, which require higher MUs per cGy as compared to more conventional treatment (3DCRT). Meanwhile, the patient workload in terms of treatment sessions per week remained relatively constant. The findings of this report show that variables used for shielding purposes still fall within the recommendation of NCRP Report 151.

This paper presents the design and implementation of a wideband power amplifier (PA) suitable for applications using signals with large peak-to-average-power-ratio (PAPR). The proposed design approach is based on reducing the load modulation factor compared to conventional Doherty PA. To demonstrate the principle, a PA that operates between 2.55 GHz and 3.8 GHz has been implemented and tested. In this frequency range, the measured peak output power is 49.3 ± 0.5 dBm and the measured drain efficiency is between 47-60 % for output power levels corresponding to 8 dB output back-off (OBO).

TomoDirect has been reported to have some advantages over TomoHelical in delivering total body irradiation (TBI). This study aimed to investigate the relationships between the number of ports and the dose evaluation indices in low‐dose TBI in TomoDirect mode using 2–12 ports and to compare these data with those for the TomoHelical mode in a simulation study. Thirteen patients underwent low‐dose TBI in TomoHelical mode from June 2015 to June 2016. We used the same computed tomography data sets for these patients to create new treatment plans for upper‐body parts using TomoDirect mode with 2–12 beam angles as well as TomoHelical mode. The prescription was 4 Gy in two equal fractions. For the TomoDirect data, we generated plans with 2–12 ports with approximately equally spaced angles; the modulation factor, field width, and pitch were 2.0, 5.0 cm, and 0.500, respectively. For the TomoHelical plans, the modulation factor, field width, and pitch were 2.0, 5.0 cm, and 0.397, respectively. D2, D98, D50, and the homogeneity index (HI) were evaluated to compare TomoDirect plans having 2–12 ports with the TomoHelical plan. Using TomoDirect plans, D2 with four ports or fewer, D98 with 10 ports or fewer, D50 with four ports or fewer and HI with five ports or fewer showed statistically significantly worse results than the TomoHelical plan. With the TomoDirect plans, D2 with seven ports or more, D50 with eight ports or more, and HI with eight ports or more showed statistically significant improvement compared with the TomoHelical plan. All of the dose evaluation indices of the TomoDirect plans showed a tendency to improve as the number of ports increased. TomoDirect plans showed statistically significant improvement of D2, D50, and HI compared with the TomoHelical plan. Therefore, we conclude that TomoDirect can provide better dose distribution in low‐dose TBI with TomoTherapy.

Nonlinear acoustic coefficients have a close relationship with structural cracks. A nonlinear ultrasonic modulation method for micro-crack quantitative evaluation is developed. The influence of phase threshold on the crack evaluation is discussed. Ultrasonic modulation using a unilateral incentive model is applied to the quantitative evaluation of micro-cracks for different specimens. The experimental results indicate that the method can be beneficially applied for micro-cracks detection. A proper phase threshold can improve the reliability of the method based on nonlinear ultrasonic modulation. The presented modulation factor can be used to quantitatively evaluate the structural cracks, and it is suitable for small-crack quantitative evaluation.

Background This study investigated planned MLC distribution and treatment region specific plan parameters to recommend optimal delivery parameters based on statistical process techniques. Methods A cohort of 28 head and neck, 19 pelvic and 23 brain pre-treatment plans were delivered on a helical tomotherapy system using 2.5 cm field width. Parameters such as gantry period, leaf open time (LOT), actual modulation factor, LOT sonogram, treatment duration and couch travel were investigated to derive optimal range for plans that passed acceptable delivery quality assurance. The results were compared against vendor recommendations and previous publications. Results No correlation was observed between vendor recommended gantry period and percentage of minimum leaf open times. The range of gantry period (min–max) observed was 16–21 s for head and neck, 15–22 s for pelvis and 13–18 s for brain plans respectively. It was also noted that the highest percentage (average ( X - ) ± SD) of leaf open times for a minimum time of 100 ms was seen for brain plans (53.9 ± 9.2%) compared to its corresponding head and neck (34.5 ± 4.2%) and pelvic (32.0 ± 9.4%) plans respectively. Conclusions We have proposed that treatment site specific delivery parameters be used during planning that are based on the treatment centre and have detailed recommendations and limitations for the studied cohort. This may enable to improve efficiency of treatment deliveries by reducing inaccuracies in MLC distribution.

Aim: To study the effect of various planning parameters viz field width (FW), pitch factor (PF) on breast tumor and evaluate the relation among these parameters and their influence on the quality of plan and the treatment time. Material and method: Nine plans for each of the ten breast cancer patients were created taking various combinations of field width (FW) and pitch keeping the Modulation factor (MF) constant 3. The reference plan selected for the study is field width of 1, pitch 0.215. Other plans were created keeping the same constraints and penalty as the reference plan and 1000 iterations. Target coverage was evaluated in terms of conformity index (CN) and homogeneity index (HI) while the sparing of organs at risk (OARs) were evaluated in terms of mean, maximum and relevant dose volumes. Low dose spillages in normal tissues were also evaluated. The plans are compared with the reference plan using the Wilcoxon Signed Ranks Test. Concept of plan Quality index is also used to evaluate the plans qualitatively. Results: The mean treatment delivery time for 5, 2.5 and 1.0 cm FW plans were 5.04 ± 0.4, 8.51 ± 0.87 and 20.67 ± 2.02 minutes respectively. There was no significant variation in doses for OARs and COIN and HI of targets for 1 cm and 2.5 cm plans except for 5 cmplans. But the low dose spillage increased by 9-14% and 23-43% for 2.5 and 5 cm respectively. Conclusion: Dose to the OARs was not significantly higher for 2.5_FW plans from the reference plan but, significantly higher for 5_FW. Larger the FW and higher the pitch, spillage were more. On the basis of our analysis, 2.5_0.215 plan with MF=3, can be considered as the optimum plan for unilateral breast treatment using Tomotherapy.

Purpose Hippocampal avoidance during irradiation is hypothesized to reduce the risk of memory function decline. This study is designed to evaluate the dosimetric and clinical results of Helical Tomotherapy (HT) whole brain radiotherapy with hippocampal avoidance (WBHA) and Simultaneous Integrated Boost (SIB). Methods A total of 19 patients with 1 to 4 brain metastases (BM), diameter ⩽3 cm, absent or controlled extracranial disease were planned for WBHA with SIB using HT, from September 2014 to November 2017. The hippocampus was contoured on diagnostic T1-weighted magnetic resonance imaging (MRI) which had been registered with the planning CT image set. The hippocampal Planning Risk Volume was generated using a 5 mm uniform margin around the hippocampi. The BM were contoured on T1-weighted MRI registered with the planning computed tomography (CT), and the BM-PTV was the BM expanded 3 mm in all directions. The whole-brain planning target volume (WB-PTV) was defined as the whole-brain tissue volume, expanded 3 mm in all directions, minus hippocampal PRV and BM-PTVs. HT plans were generated with the following parameters: field width set at 1.05 cm, pitch 0.287, modulation factor (MF) set in the range 2–3 leading to a final value of 2 on average (range 1.3–2.8). Prescription dose was 30 Gy for WB-PTV and 40 Gy for each BM-PTVs in 10 fractions. Results Dosimetric result were reported in Table 1: all the parameter analysed were very promising and in accord to the RTOG 0933 trial [1] . The mean treatment time was 8.7 min (range 6.5–12.6 min). Conclusions HT plans achieved three objectives: quite homogeneous whole brain dose distribution; conformal hippocampal avoidance; and high coverage to the BM. Download : Download high-res image (323KB) Download : Download full-size image

Quality assurance (QA) of the image quality for image‐guided localization systems is crucial to ensure accurate visualization and localization of regions of interest within the patient. In this study, the temporal stability of selected image parameters was assessed and evaluated for kV CBCT mode, planar radiographic k V, and MV modes. The motivation of the study was to better characterize the temporal variability in specific image‐quality parameters. The CATPHAN, QckV‐1, and QC‐3 phantoms were used to evaluate the image‐quality parameters of the imaging systems on a Varian Novalis Tx linear accelerator. The planar radiographic images were analyzed in PIPSpro with high‐contrast spatial resolution (f30,f40,f50lp/mm) being recorded. For OBI kV CBCT, high‐quality head full‐fan acquisition and pelvis half‐fan acquisition modes were evaluated for uniformity, noise, spatial resolution, HU constancy, and geometric distortion. Dose and X‐ray energy for the OBI were recorded using the Unfors RaySafe Xi system with the R/F High Detector for kV planar radiographic and the CT detector for kV CBCT. Dose for the MV EPID was recorded using a PTW975 Semiflex ion chamber, PTW UNIDOS electrometer, and CNMC Plastic Water. For each image‐quality parameter, values were normalized to the mean, and the normalized standard deviations were recorded to evaluate the parameter's temporal variability. For planar radiographic modes, the normalized standard deviations of the spatial resolution (f30,f40,& f50) were 0.015, 0.008, 0.004 lp/mm and 0.006, 0.009, 0.018 lp/mm for the kV and MV, respectively. The normalized standard deviation of dose for kV and MV were 0.010 mGy and 0.005 mGy, respectively. The standard deviations for full‐and half‐fan kV CBCT modes were averaged together. The following normalized standard deviations for each kV CBCT parameter were: 0.075 HU (uniformity), 0.071 HU (noise), 0.006 mm (AP‐geometric distortion), 0.005 mm (LAT‐geometric distortion), 0.058 mm (slice thickness), 0.124 (f50), 0.031 (HU constancy – Lung), 0.063 (HU constancy – Water), 0.020 (HU constancy – Bone), 0.006 mGy (Dose – Center), 0.004 mGy (Dose –Periphery). Using control chart analysis, institutional QA tolerances were reported as warning and action thresholds based on 1σ and 2σ thresholds. A study was performed to characterize the stability of image‐quality parameters recommended by AAPM Task Group‐142 for the Varian OBI and EPID imaging systems. Both imaging systems show consistent imaging and dosimetric properties over the evaluated time frame. PACS number: 87.10.‐e

Background and purpose To determine the optimum combination of treatment parameters between pitch, field width (FW) and modulation factor (MF) for extremity sarcomas in tomotherapy. Materials and methods Six patients previously treated for extremity sarcomas (3 arms and 3 legs) with tomotherapy were included in this study. 288 treatment plans were recalculated, corresponding to all combinations between 2 FW (2.5 and 5 cm), 4 MF (1.5, 2, 2.5 and 3) and 6 pitches (0.215, 0.287, 0.43 and 3 off-axis pitches). The treatment parameters (MF, FW or pitch) are modified between each plan, and the calculation is relaunched for 400 iterations, without modifying the optimisation constraints of the plan under which the patient has been treated. Results We suggest eliminating the 0.43 pitch and never combining a 0.215 pitch with an MF ≤ 2. We also do not recommend using an MF = 1.5 unless treatment time is an absolute priority over plan quality. We did not see any advantage in using Chen off-axis pitches, except for targets far from the axis (>15 cm) treated with a high pitch. A combination of MF = 2/FW = 5 cm/pitch = 0.287 gives plans of acceptable quality, combined with reduced treatment times. These conclusions are true only for extremity sarcomas treated in 2 Gy/fraction. Conclusions We have shown that the choice of pitch/MF/FW combination is crucial for the treatment of extremity sarcomas in tomotherapy: some produce good dosimetric quality with a reduced irradiation time, while others may increase the time without improving the quality.

Spiking Neural Network (SNN) acts as a part of the third generation of Artificial Neural Networks (ANNs). Evolving Spiking Neural Network (ESNN) is one of the most broadly utilized among in SNN models in numerous current research works. During the classification process, ESNN model acts as a classifier and three parameters are used in this article. However, the parameters are needed to set manually before the classification process. To solve the stated problems, ESNN required an optimizer that able to optimize the three parameters such as similarity value, modulation factor and proportion factor. The best estimations of parameters are adaptively chosen by Harmony Search Algorithm (HSA) to abstain from choosing appropriate values for specific issues through the trial-and-error approach. Therefore, this article proposed the integration of ESNN as a classifier and HSA as an optimizer for parameter optimization. The experimental results give favorable accuracy rates via the hybrid of ESNN and HSA.

A 55-year-old hypertensive patient presents atrial fibrillation after vasovagal syncope. Non-invasive cardiac workup is normal. Without antiarrhythmic therapy, the patient has no recurrence for the next 3years, then presents with a stroke. Echocardiography eventually reveals left atrial dilation. This sequence of events illustrates the well-known links between age, arterial hypertension, atrial fibrillation, atrial neuromyopathy and stroke. A frequently neglected common denominator in this equation is impaired sympathovagal balance. Contrary to what is often stated, autonomic imbalance is not a simple modulation factor of atrial fibrillation; both the trigger and the substrate of atrial fibrillation can be influenced by abnormal cardiac innervation. Here, we review the neurogenic theory of atrial fibrillation, based on literature and original data. We also provide evidence that this concept may help to improve atrial fibrillation prediction, early diagnosis and therapy.

We show that optimizing pre- and post-dispersion compensation can increase the section of low fourth-order modulation factor in the transmission link. In experiments, we demonstrate reach increase for 32 Gbaud PM-16QAM by using 25% to 50% pre-compensation of the dispersion.

This study presents an integration of Evolving Spiking Neural - Network (ESNN) with Dynamic Population Particle Swarm Optimization (DPPSO). The original ESNN framework does not automatically modulate its parameters’ optimum values. Thus, an integrated framework is proposed to optimize ESNN parameters namely, the modulation factor (mod), similarity factor (sim), and threshold factor (c). DPPSO improves the original PSO technique by implementing a dynamic particle population. Performance analysis is measured on classification accuracy in comparison with the existing methods. Five datasets retrieved from UCI machine learning are selected to simulate the classification problem. The proposed framework improves ESNN performance in regulating its parameters’ optimum values.

This work outlines the development of a robust method of calculating modulation factors used for the independent verification of MUs for IMRT and VMAT treatments, to replace onerous ion chamber measurements. Two‐dimensional fluence maps were calculated for dynamic MLC fields that include MLC interleaf leakage, transmission, and tongue‐and‐groove effects, as characterized from EPID‐acquired images. Monte Carlo‐generated dose kernels were then used to calculate doses for a modulated field and that field with the modulation removed at a depth specific to the calculation point in the patient using in‐house written software, Mod_Calc. The ratio of these two doses was taken to calculate modulation factors. Comparison between Mod_Calc calculation and ion chamber measurement of modulation factors for 121 IMRT fields yielded excellent agreement, where the mean difference between the two was −0.3%±1.2%. This validated use of Mod_Calc clinically. Analysis of 5,271 dynamic fields from clinical use of Mod_Calc gave a mean difference of 0.3%±1.0% between Mod_Calc and Eclipse‐generated factors. In addition, 99.3% and 96.5% fields pass 5% and 2% criteria, respectively, for agreement between these two predictions. The development and use of Mod_Calc at our clinic has considerably streamlined our QA process for IMRT and RapidArc fields, compared to our previous method based on ion chamber measurements. As a result, it has made it feasible to maintain our established and trusted current in‐house method of MU verification, without resorting to commercial software alternatives. PACS numbers: 87.55.km, 87.55.Qr, 87.55.kd, 87.57.uq

Background and aimThis study proposed a method to estimate the beam-on time for prostate cancer patients treated on Tomotherapy when FW (field width), PF (pitch factor), modulation factor (MF) and treatment length (TL) were given.Material and methodsThe study was divided into two parts: building and verifying the model. To build a model, 160 treatment plans were created for 10 patients. The plans differed in combination of FW, PF and MF. For all plans a graph of beam-on time as a function of TL was created and a linear trend function was fitted. Equation for each trend line was determined and used in a correlation model. Finally, 62 plans verified the treatment time computation model – the real execution time was compared with our estimation and irradiation time calculated based on the equation provided by the manufacturer.ResultsA linear trend function was drawn and the coefficient of determination R2 and the Pearson correlation coefficient r were calculated for each of the 8 trend lines corresponding to the adequate treatment plan. An equation to correct the model was determined to estimate more accurately the beam-on time for different MFs. From 62 verification treatment plans, only 5 disagreed by more than 60s with the real time from the HT software. Whereas, for the equation provided by the manufacturer the discrepancy was observed in 16 cases.ConclusionsOur study showed that the model can well predict the treatment time for a given TL, MF, FW and it can be used in clinical practice.

Helical tomotherapy plans using a combination of pitch and jaw width settings were developed for 3 patients previously treated for head and neck cancer. Three jaw widths (5, 2.5, and 1 cm) and 4 pitches (0.86, 0.43, 0.287, and 0.215) were used with a (maximum) modulation factor setting of 4. Twelve plans were generated for each patient using an identical optimization procedure (e.g., number of iterations, objective weights, and penalties, etc.), based on recommendations from TomoTherapy (Madison, WI). The plans were compared using isodose plots, dose volume histograms, dose homogeneity indexes, conformity indexes, radiobiological models, and treatment times. Smaller pitches and jaw widths showed better target dose homogeneity and sparing of normal tissue, as expected. However, the treatment time increased inversely proportional to the jaw width, resulting in delivery times of 24 ± 1.9 min for the 1-cm jaw width. Although treatment plans produced with the 2.5-cm jaw were dosimetrically superior to plans produced with the 5-cm jaw, subsequent calculations of tumor control probabilities and normal tissue complication probabilities suggest that these differences may not be radiobiologically meaningful. Because treatment plans produced with the 5-cm jaw can be delivered in approximately half the time of plans produced with the 2.5-cm jaw (5.1 ± 0.6 min vs. 9.5 ± 1.1 min), use of the 5-cm jaw in routine treatment planning may be a viable approach to decreasing treatment delivery times from helical tomotherapy units.

The development of new technology in micropattern gaseous detectors makes it possible to measure x-ray polarization for energies where the photoelectric effect is the main mechanism of interaction with matter. In a previous work, we showed that a modification of the Geant4 simulation code is a useful toolkit to simulate the photoelectric interaction of linearly polarized x-rays with micropattern gas detectors. In particular, by properly taking into account the direction of the photoelectron, we developed a new calculation of the final state. We simulated one experimental setup found in the literature and showed that the simulation results obtained are in agreement with the experimental data. In this work, we present new results on simulation of a mixture of two gases with different pressures and study the impact in the modulation factor. The simulations were done for both low and high Z mean mixture. With these gas mixtures, we observed that the modulation factor was greater for a low Z mixture than that with a high Z, but the efficiency was opposite. We also observed that the modulation factor for high Z was influenced by the absorption edge of the photoelectric cross section. Copyright © 2009 John Wiley & Sons, Ltd.

Helical tomotherapy (HT) can be used for the delivery of cranio-spinal axis irradiation (CSAI) without the need for beam matching of conventional linac-based external beam irradiation. The aim of this study is to retrospectively evaluate HT plans used for treatment in nine patients treated with CSAI. Helical tomotherapy cranio-spinal axis irradiation (HT-CSAI) plans were created for each patient. Average length along the cranio-spinal axis of the PTV was 65.6 cm with a range between 53 and 74 cm. Treatment planning optimization and plan evaluation parameters were obtained from the HT planning station for each of the nine patients. PTV coverage by the 95% isodose surface ranged between 98.0 to 100.0% for all nine patients. The clinically acceptable dose variation within the PTV or tolerance range was between 0.7 and 2.5% for all nine patients. Doses to the organs at risk were clinically acceptable. An increasing length along the longitudinal axis of the PTV did not consistently increase the beam-on time indicating that using a larger jaw width had a greater impact on treatment time. With a larger jaw width it is possible to substantially reduce the normalized beam-on treatment time without compromising plan quality and sparing of organs at risk. By using a larger jaw width or lower modulation factor or both, normalized beam-on times were decreased by up to 61% as compared to the other evaluated treatment plans. From the nine cases reported in this study the minimum beam-on time was achieved with a jaw width of 5.0 cm, pitch of 0.287 and a modulation factor of 2.0. Large and long cylindrical volumes can be effectively treated with helical tomotherapy with both clinically acceptable dose distribution and beam-on time.

著者人数: 20名, 資料番号: SA1000093000

determining the most desirable and achievable target dose and organ at risk (OAR) sparing using helical TomoTherapy planning system for mesothelioma treatment plans. A range of planning parameters was used. The reviewers' ranking assessment (Ranking in Groups: 1 = Good, 2 = Above Average, 3 = Average, 4 = Poor). The overall rankings revealed that a plan with a balanced trade-off among all planning objectives was preferred by most participants and reviewers. Other studies found low doses to the contralateral lung to be limiting. This was not the case in our study, with TomoTherapy we found the dose to contra lateral lung to be as low as V5Gy=0.87%. A pitch value of 0.287 or 0.43 would provide better result. A delivered modulation factor of above 1.7 and a treatment time around 500 sec will be beneficial consideration in planning.

Background: Modulation factor (MF) and pitch have an impact on Helical TomoTherapy (HT) plan quality and HT users mostly use vendor-recommended settings. This study analyses the effect of these two parameters on both plan quality and treatment time for plans made with TomoEdge planning software by using the concept of Pareto optimal fronts. Methods: More than 450 plans with different combinations of pitch [0.10-0.50] and MF [1.2-3.0] were produced. These HT plans, with a field width (FW) of 5 cm, were created for five head and neck patients and homogeneity index, conformity index, dose-near-maximum (D2), and dose-near-minimum (D98) were analysed for the planning target volumes, as well as the mean dose and D2 for most critical organs at risk. For every dose metric the median value will be plotted against treatment time. A Pareto-like method is used in the analysis which will show how pitch and MF influence both treatment time and plan quality. Results: For small pitches (≤0.20), MF does not influence treatment time. The contrary is true for larger pitches (≥0.25) as lowering MF will both decrease treatment time and plan quality until maximum gantry speed is reached. At this moment, treatment time is saturated and only plan quality will further decrease. Conclusion: The Pareto front analysis showed optimal combinations of pitch [0.23-0.45] and MF > 2.0 for a FW of 5 cm. Outside this range, plans will become less optimal. As the vendor-recommended settings fall within this range, the use of these settings is validated., SCOPUS: ar.j, info:eu-repo/semantics/published

We measured the X-ray polarization using our micro-pixel chamber with a strip readout, while changing the X-ray energy (5– 18 keV ) and gas mixtures (neon- and argon-based). As a result, modulation factors of 0.18 (at 9 keV ) and 0.12 (at 14 keV ) were obtained for neon- and argon-based mixtures, respectively. We also simulated this experiment utilizing a Monte-Carlo code, EGS4, which reproduced the experimental results quite well. According to the Monte-Carlo simulation, the modulation factor should be improved by a pixel-readout detector. The simulated modulation factors are 0.25 (for X-ray with energy at >6 keV ) with a neon-based gas mixture and 0.18 (for X-ray at >10 keV ) with an argon-based one.

In this paper, differential evolution DE has been utilised to solve the problem of tuning the parameters of evolving spiking neural network ESNN manually. As ESNN is sensitive to its parameters as other models, optimal integration of parameters leads to better classification accuracy. A hybrid differential evolution for parameter tuning of evolving spiking neural network DEPT-ESNN is presented for parameter optimisation for determining the optimal number of evolving spiking neural network ESNN parameters: modulation factor Mod, similarity factor Sim and threshold factor C. The best values of parameters are adaptively selected by differential evolution DE to avoid selecting suitable values for a particular problem by trial-and-error approach. Several standard datasets from UCI machine learning are used for evaluating the performance of this hybrid model. It has been found that the classification accuracy and other performance measures can be increased by using hybrid method with differential evolution DEPT_ESNN.

Purpose: The overall aim was to conduct an analytical study of the impact of the modulation factor (MF) on the quality of the head and neck treatment plans and their execution time on Tomotherapy. Materials and Methods: In-phantom (RANDO® Alderson) planning study of the head and neck cancer was performed. Thirteen different plans in terms of MF were prepared. Other optimization parameters were the same for all plans. Results: Analysis of treatment plans in terms of quality shows that MF < 1.4 does not provide an accepted dose distribution (physician decision). Statistically significant differences were observed for plans with an MF < 1.6. No differences were obtained for plans with MF from 6.0 to 1.8. Decreasing of MF leads to a shorter time of irradiation. The maximum rotational speed has been reached for an MF = 3.0. Further reducing this however produces no decrease in the time of irradiation. The actual and planned values of the MF were compared. The optimal range of MF for head and neck was determined as 3.0 > MF > 1.8. The lower limit increases to 2.4 when hard reduction of the dose in critical organs is required. Conclusions: It was showed that the final MF value is less than the value calculated after each loop of optimization. The computer system reduces MF by shortening the longest time and increasing the average time of leaves opening. Increase in the average time is obtained by eliminating the use of leafs with the shortest times of opening, thereby reducing the dose in critical organs that are outside the direct irradiation area.

Measurements of the linear polarisation dependence of the X-ray photocurrent from gold were made at the Daresbury Synchrotron Radiation Source using a novel rotating chamber and the tuneable linear polarisation of the undulator beamline 5U.1. The overall energy range was 65–1000 eV. At a grazing angle of 8°, significant polarisation sensitivity was observed (modulation factor 0.02 M

X-ray polarimetry with CCD has been performed using a polarized X-ray beam from an electron impact X-ray source. The standard data reduction method employing double-pixel events yields the modulation factor M of 0.14 at 27 keV and 0.24 at 43 keV for the 12 lm pixel size CCD chip. We develop a new data reduction method, in which multi-pixel events are employed, and which approximates the charge spread as an oval shape. We optimize the reduction parameters, so that we improve the P .*/ (minimum detectable polarization degree) by factor of three from the value obtained through the usual double-pixel event method. ( 1999 Elsevier Science B.V. All rights reserved.

Purpose To report potential dose heterogeneity leading to underdosing at different skeletal sites in total marrow irradiation (TMI) with helical tomotherapy due to the thread effect and provide possible solutions to reduce this effect. Methods and Materials Nine cases were divided into 2 groups based on patient size, defined as maximum left-to-right arm distance (mLRD): small mLRD (≤47 cm) and large mLRD (>47 cm). TMI treatment planning was conducted by varying the pitch and modulation factor while a jaw size (5 cm) was kept fixed. Ripple amplitude, defined as the peak-to-trough dose relative to the average dose due to the thread effect, and the dose–volume histogram (DVH) parameters for 9 cases with various mLRD was analyzed in different skeletal regions at off-axis (eg, bones of the arm or femur), at the central axis (eg, vertebrae), and planning target volume (PTV), defined as the entire skeleton plus 1-cm margin. Results Average ripple amplitude for a pitch of 0.430, known as one of the magic pitches that reduce thread effect, was 9.2% at 20 cm off-axis. No significant differences in DVH parameters of PTV, vertebrae, or femur were observed between small and large mLRD groups for a pitch of ≤0.287. Conversely, in the bones of the arm, average differences in the volume receiving 95% and 107% dose (V95 and V107, respectively) between large and small mLRD groups were 4.2% ( P =.016) and 16% ( P =.016), respectively. Strong correlations were found between mLRD and ripple amplitude ( r s=.965), mLRD and V95 ( r s=−.742), and mLRD and V107 ( r s=.870) of bones of the arm. Conclusions Thread effect significantly influences DVH parameters in the bones of the arm for large mLRD patients. By implementing a favorable pitch value and adjusting arm position, peripheral dose heterogeneity could be reduced.

We examined the adequacy of existing shielding guidelines using five‐year clinical data from a busy CyberKnife center. From June 2006 through July 2011, 1,370 patients were treated with a total of 4,900 fractions and 680,691 radiation beams using a G4 CyberKnife. Prescription dose and total monitor units (MU) were analyzed to estimate the shielding workload and modulation factor. In addition, based on the beam's radiation source position, targeting position, MU, and beam collimator size, the MATLAB program was used to project each beam toward the shielding barrier. The summation of the projections evaluates the distribution of the shielding load. On average, each patient received 3.6 fractions, with an average 9.1 Gy per fraction prescribed at the 71.1% isodose line, using 133.7 beams and 6,200 MU. Intracranial patients received an average of 2.7 fractions, with 8.6 Gy per fraction prescribed at the 71.4% isodose line, using 133 beams and 5,083 MU. Extracranial patients received an average of 3.94 fractions, with 9.2 Gy per fraction prescribed at the 71% isodose line, using 134 beams and 6,514 MU. Most‐used collimator sizes for intracranial patients were smaller (7.5 to 20 mm) than for extracranial patients (20 to 40 mm). Eighty‐five percent of the beams exited through the floor, and about 40% of the surrounding wall area received no direct beam. For the rest of the wall, we found “hot” areas that received above‐average MU. The locations of these areas were correlated with the projection of the nodes for extracranial treatments. In comparison, the beam projections on the wall were more spread for intracranial treatments. The maximum MU any area received from intracranial treatment was less than 0.25% of total MU used for intracranial treatments, and was less than 1.2% of total MU used for extracranial treatments. The combination of workload, modulation factor, and use factor in our practice are about tenfold less than recommendations in the existing CyberKnife shielding guidelines. The current guidelines were found to be adequate for shielding, even in a busy center. There may be a potential to reduce shielding in areas with no or few direct beams in the current G4 model. Since a newer model CyberKnife (M6) has recently been introduced, the patterns of usage reported here may be changed in the future. The uneven distribution of use factor we have found may, however, be considered in the vault design. PACS number: 87.55.N

Purpose: To develop and validate a computational method to simulate craniocaudal respiratory motion in a VMAT treatment plan. Methods: Three 4DCTs of the QUASAR respiratory motion phantom were acquired with a 2cm water-density spherical tumour embedded in cedar to simulate lung. The phantom was oscillating sinusoidally with an amplitude of 2cm and periods of 3, 4, and 5 seconds. An ITV was contoured and 5mm PTV margin was added. High and a low modulation factor VMAT plans were created for each scan. An in-house program was developed to simulate respiratory motion in the treatment plans by shifting the MLC leaf positions relative to the phantom. Each plan was delivered to the phantom and the dose was measured using Gafchromic film. The measured and calculated plans were compared using an absolute dose gamma analysis (3%/3mm). Results: The average gamma pass rate for the low modulation plan and high modulation plans were 91.1% and 51.4% respectively. The difference between the high and low modulation plans gamma pass rates is likely related to the different sampling frequency of the respiratory curve and the higher MLC leaf speeds in the high modulation plan. A high modulation plan has a slower gantry speed and therefore samples the breathing cycle at a coarser frequency leading to inaccuracies between the measured and planned doses. Conclusion: A simple program, including a novel method for increasing sampling frequency beyond the control point frequency, has been developed to simulate respiratory motion in VMAT plans by shifting the MLC leaf positions.

Purpose: To report cranio-spinal irradiation (CSI) planning experience, compare dosimetric quality and delivery efficiency with Tomotherapy from different institutions, and to investigate effect of planning parameters on plan quality and treatment time. Methods: Clinical helical tomotherapy IMRT plans for thirty-nine CSI cases from three academic institutions were retrospectively evaluated. The planning parameters: field width (FW), pitch, modulation factor (MF), and achieved dosimetric endpoints were cross-compared. A fraction-dose-delivery-timing index (FDTI), defined as treatment time per fraction dose per PTV length, was utilized to evaluate plan delivery efficiency. A lower FDTI indicates higher delivery efficiency. We studied the correlation between planning quality, treatment time and planning parameters by grouping the plans under specific planning parameters. Additionally, we created new plans using 5cm jaw for a subset of plans that used 2.5cm jaw to exam if treatment efficiency can be improved without sacrificing plan quality. Results: There were significant dosimetric differences for organ at risks (OARs) among different institutions (A,B,C). Using the lowest average MF (1.9±0.4) and 5cm field width, C had the highest lung, heart, kidney, liver mean doses and maximum doses for lens. Using the same field width of 5cm, but higher MF (2.6±0.6), B had lower doses to the OARs in the thorax and abdomen area. Most of A's plans were planned with 2.5cm jaw, the plans yielded better PTV coverage, higher OAR doses and slightly shorter FDTI compared to institution B. The replanned 5cm jaw plans achieved comparable PTV coverage and OARs sparing, while saving up to 44.7% treatment time. Conclusion: Plan quality and delivery efficiency could vary significantly in CSI planning on Tomotheapy due to choice of different planning parameters. CSI plans using a 5cm jaw, with proper selection of pitch and MF, can achieve comparable/ better plan quality with shorter delivery time compared to 2.5cm jaw plans.

Purpose: A new development in linac-based intracranial radiosurgery is treatment of multiple targets using single isocenter VMAT, which dramatically reduces treatment time while maintaining high conformality and dose gradient. Our purpose is to translate this technique to extracranial SBRT of oligometastases and address additional challenges such as interplay from motion and setup uncertainties. Methods: We propose SIDO (Single Isocenter with Distinct Optimizations) planning in which all VMAT arcs share an isocenter but each arc treats only one target. Setup uncertainties from rotations and deformations are mitigated by applying a couch translation between VMAT arcs, while interplay is minimized by using dynamic conformal arcs (DCAs) as the starting point for VMAT optimization. We compared SIDO to single (VMAT) and dual (VMAT & DCA) isocenter plans for phantom and patient (N=2) cases. Dose statistics included conformity index (CI), gradient index (GI), and modulation factor (MLC opening & total MU). Finally, we determined likelihood of needing a translational shift between SIDO arcs to correct rotational uncertainties using CBCTs from eleven previous SBRT cases. Results: For phantoms with target separations of 5–15cm, CI was 0.87±0.02, 0.89±0.05, and 0.91±0.02, for SIDO, single, and dual-isocenter VMAT respectively. GI was 6.83±1.0, 7.45±1.0 and 5.94±0.7 respectively. SIDO conformity did not trend with increasing distance between PTVs, while gradient decreased for all planning techniques. Using DCAs as the starting point of VMAT optimization decreased modulation, with a 39.4% reduction in monitor units. SIDO had 4.9% and 39% less MU than single and dual-isocenter VMAT respectively. A translational shift between SIDO arcs would be required in 10–28% of cases due to rotational uncertainties to stay within a 5mm margin, for targets separated by ≥10cm. Conclusion: SIDO for extracranial oligometastases has comparable dosimetry to traditional VMAT with low modulation similar to DCAs. Future work will quantify decrease in dosimetric interplay.

Helical TomoTherapy(HT) planning depends on optimize parameters including field width (FW), pitch factor (PF) and modulation factor (MF). These optimize parameters are effect to quality of plans and treatment time. The aim of this study was to find the optimized parameters which compromise between plan quality and treatment times. Six nasopharyngeal cancer patients were used. For each patient data set, 18 treatment plans consisted of different optimize parameters combination (FW=5.0, 2.5, 1.0 cm; PF=0.43, 0.287, 0.215; MF2.0, 3.0) were created. The identical optimization procedure followed ICRU83 recommendations. The average D50 of both parotid glands and treatment times per fraction were compared for all plans. The study show treatment plan with FW1.0 cm showed the lowest average D50 of both parotid glands. The treatment time increased inversely to FW. The FW1.0 cm the average treatment time was 4 times longer than FW5.0 cm. PF was very little influence on the average D50 of both parotid glands. Finally, MF increased from 2.0 to 3.0 the average D50 of both parotid glands was slightly decreased. However, the average treatment time was increased 22.28%. For routine nasopharyngeal cancer patients with HT, we suggest the planning optimization parameters consist of FW=5.0 cm, PF=0.43 and MF=2.0.

The driver active assistances have gained recently in importance and become usual features in commercialized vehicles. Nevertheless, the sharing of the vehicle control with the driver, especially for the steering assistances, is an open issue. The rear wheels steering could be an answer to this question. This study contains the development of a control law for the rear steering able to provide lane departure avoidance and lane keeping. The design of the control law is casted as a LMI (Linear Matrix Inequality) optimization problem in order to take into account constraints, as the rear steering actuator limitation. A modulation factor is added to allow a flexible activation strategy of the rear steering assistance. Preliminary simulation results are presented to explain the concept.

A quantized probability distribution is defined for a sequence of digital data produced by a Bernoulli source. From it, both a grouped distribution and a histogram are obtained. Their entropies are considered, and relationships between them are derived. Some applications are described, and a commentary about microscopic uncertainty versus macroscopic information is presented, with a related entropic modulation factor.