Incidental Axillary Dose of Tomotherapy in Hypofractionated Whole Breast Radiotherapy for Early Breast Cancer: A Dosimetrical Analysis.

Background and Objectives: Intensity-modulated radiation therapy (IMRT) is becoming a more common method of performing whole breast irradiation (WBI) for early breast cancer. This study aimed to examine the incidental dose to the axillary region using tomotherapy, a unique form of IMRT. Patients and Methods: This study included 30 patients with early-stage breast cancer who underwent adjuvant WBI using TomoDirect IMRT. A hypofractionation scheme of 42.4 Gy delivered in 16 fractions was prescribed. The plan comprised of two parallel-opposed beams, along with two additional beams positioned anteriorly at gantry angles of 20° and 40° from the medial beam. The incidental dose received at axillary levels I, II, and III was evaluated using several dose-volume parameters. Results: The study participants had a median age of 51 years, and 60% had left-sided breast cancer. The mean dose of the axilla for levels I, II, and III were 15.5 ± 4.8 Gy, 14.9 ± 4.2 Gy, and 1.5 ± 1.6 Gy, respectively. Adequate coverage of the axilla, defined as V95%[%], was achieved for 4.7 ± 3.9%, 4.8 ± 3.7%, and 0 ± 0% for levels I, II, and III, respectively. The results were compared with those of previously published studies, and the axillary mean dose and V95%[%] of TomoDirect IMRT were low, comparable to other IMRT techniques, and lower than those of traditional tangential therapy. Conclusions: While incidental axillary radiation during WBI has been proposed to assist in regional disease control, the TomoDirect plan was demonstrated to decrease this dose, and a hypofractionation scheme would further lower its biological effectiveness. Future clinical studies should incorporate dosimetrical analysis of incidental axillary dose, in order to facilitate hypofractionated IMRT planning with risk-adjusted axilla coverage in early breast cancer.

Exploiting Zirconium-Based Metallic Glass Thin Films for Anode-Free Lithium-Ion Batteries and Lithium Metal Batteries With Ultra-Long Cycling Life.

Coating Zr-based metallic glass, Zr53 Cu31 Ni11 Al5 (Zr-MG), on a Cu current collector (CC) and Li metal anode (LMA) significantly improves the cycle performance of both types of Li-ion batteries, namely, anode-free Li-ion batteries (AFLBs) and Li metal batteries (LMB). The inherent isotropy and homogeneity of the Zr-MG significantly improve the surface uniformity of the CC and LMA. A 12 nm-thick Zr-MG thin film coating on the CC reduces the overpotential in the AFLB, leading to a more uniform Li plating morphology. The Li film covers almost the entire surface of the Zr-CC, whereas it only covers ≈75% of the bare CC during charging. An LFP||Zr-CC full-cell exhibits a capacity retention of 63.6% after the 100th cycle, with an average CE of 99.55% at a 0.2 C rate. In the case of the LMB, a 12 nm-thick Zr-MG thin film-coated LMA (Zr-LMA) exhibits a stable capacity of up to 1500 cycles. An LFP||Zr-LMA full-cell exhibits capacity retention and CE after 1500 cycles of 66.6% and 99.97%, respectively, at a 1 C rate. Zirconium-MG thin films with atomic-level uniformity, outstanding corrosion resistance, lithiophilic characteristics, and high diffusivity result in superior AFLB and LMB performances.

Stereotactic body radiotherapy using helical tomotherapy for hepatocellular carcinoma: clinical outcome and dosimetric comparison of Hi-ART vs. Radixact.

Background: Helical tomotherapy (HT), a unique rotational dose delivery machine, has been updated from Hi-ART to Radixact. We retrospectively evaluated the treatment outcomes of stereotactic body radiotherapy (SBRT) using HT for hepatocellular carcinoma (HCC) and compared the dosimetric details of Hi-ART and Radixact. Methods: Between April 2014 and November 2020, 28 patients with HCC were treated with SBRT using HT for a cure at Soonchunhyang University College of Medicine, Bucheon. According to the Barcelona Clinic Liver Cancer classification, 9 patients had stage 0 disease, 12 had stage A, 4 had stage B, and 3 had stage C. The tumor size ranged from 1 cm to 8 cm (median, 2 cm). The SBRT dose ranged from 40 to 60 Gy (median, 48 Gy) with 4 fractions. Twenty-three patients were treated with Hi-ART and 5 patients were treated with Radixact. To compare the dosimetric parameters between Hi-ART and Radixact, we created treatment plans with the same constraints, pitch, modulation factor, and field width for the same patient in pairs. Results: The median follow-up time from the date of SBRT administration was 24 months (range, 3-67 months). The local failure-free survival and intrahepatic failure-free survival rates were 96% and 58% at 1 year, 84% and 36% at 2 years, and 76% and 18% at 3 years, respectively. The overall survival rate was 93% at 1 year, 93% at 2 years, and 53% at 3 years, respectively. When the paired treatment plans were reviewed, the beam-on time and intermediate dose-spillage were found to be significantly reduced in Radixact than Hi-ART (P<0.001). With regard to normal organ sparing, the irradiated dose to the total liver, normal liver, heart, and kidney was significantly lower with Radixact (P<0.001). Conclusions: SBRT using HT for HCC showed favorable treatment outcomes. Radixact, the latest version, physically improved treatment efficiency by reducing treatment time and provided better organ sparing than Hi-ART.

Treatment outcomes of helical tomotherapy for hepatocellular carcinoma in terms of intermediate-dose spillage.

BACKGROUND: Although helical tomotherapy (HT) tends to increase intermediate-dose spillage by increasing of low-dose region, this has not been fully determined in the clinical setting. Therefore, we investigated treatment outcomes of HT for hepatocellular carcinoma (HCC) with respect to intermediate-dose spillage. METHODS: We retrospectively reviewed 20 HCC patients, who received high-dose radiotherapy (RT) using HT with radical intent between April 2014 and September 2017. In accordance with the Barcelona Clinic Liver Cancer (BCLC) classification, stage was 0 in 7 patients, A in 3 patients, B in 5 patients, and C in 5 patients. Baseline Child-Pugh class was A in 18 patients and B in 2 patients. The median tumor size was 2.5 cm (range, 1-11 cm). Helical intensity-modulated radiotherapy (IMRT) technique was applied in all patients: among these, 13 patients were treated with stereotactic body radiotherapy (SBRT). The median fraction size was 12 Gy (range, 2-15 Gy), and the median total dose was 50 Gy (range, 44-60 Gy). Intermediate-dose spillage was assessed by the Radiation Therapy Oncology Group recommendation from 22 HT planning data, as follows: R50% means the ratio of the 50% prescription isodose volume to the planning target volume (PTV). RESULTS: The median follow-up period after HT was 22 months. The local progression-free survival (LPFS) and progression-free survival (PFS) rates were 89% and 59% at 1 year, and 82% and 30% at 2 years, respectively. The overall survival rate was 100% at 1 year and 85% at 2 years, respectively. In terms of intermediate-dose spillage, minor or major deviations were noted in the R50% of 20 HT plans (91%). However, 1 patient (5%) experienced classic radiation-induced liver disease, and severe toxicity ≥ grade 3 was not reported. CONCLUSIONS: Although HT for HCC tends to increase intermediate-dose spillage, the treatment results were favorable with that reported in other published studies.

Endorectal balloon (ERB) in helical tomotherapy (HT) for localized prostate cancer: a case report of dosimetric analysis.

Radiation therapy (RT) for localized prostate cancer yields oncological outcomes similar to those following radical prostatectomy, but is associated with more anorectal toxicity. An endorectal balloon (ERB) has been utilized to decrease the incidental dose to the rectal wall. However, few studies analyzed whether the ERB can further spare the rectum in helical tomotherapy (HT), which by itself can be used to treat prostate cancer while minimizing irradiation of surrounding critical tissues. Here, we report a 64-year-old man with pathologically proven prostate adenocarcinoma (stage T2cN0M0). He underwent definitive RT using HT with a hypofractionated scheme of 70 Gy in 28 fractions. Simulation CT was performed twice: with and without ERB application. The ERB was filled with 70 mL of air. Two intensity-modulated RT (IMRT) plans were generated for each CT image set (with and without ERB) and compared about the dose to the anorectum. The rectal volume receiving ≥40 Gy (V40Gy) was reduced from 43.4% to 34.6% with ERB use (20.3% reduction). This reduction rate increased continuously up to V70Gy (48.2% reduction). The anal volume reduction was approximately 50% from V5Gy to V15Gy. The patient tolerated all ERB insertions well and there were no severe acute toxicities. ERB had a further anorectal-sparing effect in this case of prostate cancer treated by highly conformal HT, beyond the generally recommended dose-volume constraints of hypofractionated IMRT.

Controlling Residual Lithium in High-Nickel (>90 %) Lithium Layered Oxides for Cathodes in Lithium-Ion Batteries.

The rampant generation of lithium hydroxide and carbonate impurities, commonly known as residual lithium, is a practical obstacle to the mass-scale synthesis and handling of high-nickel (>90 %) layered oxides and their use as high-energy-density cathodes for lithium-ion batteries. Herein, we suggest a simple in situ method to control the residual lithium chemistry of a high-nickel lithium layered oxide, Li(Ni0.91 Co0.06 Mn0.03 )O2 (NCM9163), with minimal side effects. Based on thermodynamic considerations of the preferred reactions, we systematically designed a synthesis process that preemptively converts residual Li2 O (the origin of LiOH and Li2 CO3 ) into a more stable compound by injecting reactive SO2 gas. The preformed lithium sulfate thin film significantly suppresses the generation of LiOH and Li2 CO3 during both synthesis and storage, thereby mitigating slurry gelation and gas evolution and improving the cycle stability.

Dose Estimation Curves Following In Vitro X-ray Irradiation Using Blood From Four Healthy Korean Individuals.

Cytogenetic dosimetry is useful for evaluating the absorbed dose of ionizing radiation based on analysis of radiation-induced chromosomal aberrations. We created two types of in vitro dose-response calibration curves for dicentric chromosomes (DC) and translocations (TR) induced by X-ray irradiation, using an electron linear accelerator, which is the most frequently used medical device in radiotherapy. We irradiated samples from four healthy Korean individuals and compared the resultant curves between individuals. Aberration yields were studied in a total of 31,800 and 31,725 metaphases for DC and TR, respectively, obtained from 11 X-ray irradiation dose-points (0, 0.05, 0.1, 0.25, 0.5, 0.75, 1, 2, 3, 4, and 5 Gy). The dose-response relationship followed a linear-quadratic equation, Y=C+αD+ßD², with the coefficients C=0.0011 for DC and 0.0015 for TR, α=0.0119 for DC and 0.0048 for TR, and ß=0.0617 for DC and 0.0237 for TR. Correlation coefficients between irradiation doses and chromosomal aberrations were 0.971 for DC and 0.6 for TR, indicating a very strong and a moderate correlation, respectively. This is the first study implementing cytogenetic dosimetry following exposure to ionizing X-radiation.

Quality assurance for a multicenter Phase II study of stereotactic ablative radiotherapy for hepatocellular carcinoma ≤5 cm: a planning dummy run.

OBJECTIVE: The Korean Radiation Oncology Group (12-02) investigated the outcome of stereotactic ablative radiotherapy for hepatocellular carcinoma ≤5 cm using 60 Gy in three fractions. To evaluate dosimetric differences and compliance in a multicenter trial, a planning dummy run procedure was performed. METHODS: All six participating institutions were provided the contours of two dummy run cases. Plans were performed following the study protocol to cover the planning target volume with a minimum of 90% of the prescription dose and to satisfy the constraints for organs at risk. We assessed the institutional variations in plans using dose-volume histograms. RESULTS: Different planning techniques were applied: static intensity-modulated radiotherapy in two institutions, CyberKnife in two institutions and RapidArc in two institutions. The conformity index of all 12 plans was ≤1.2. In terms of the planning target volume coverage, all participants followed our study protocol. For the second dummy run case, located in Segment 8 near the heart, the minimum dose of the planning target volume (D99%: dose covering 99% of the planning target volume) was variable because there was no mention of constraints of D99% of the planning target volume in the study protocol. As an important organ at risk, the normal liver volumes receiving <17 Gy in all 12 plans were >700 ml. CONCLUSIONS: Dosimetric parameters showed acceptable compliance with the study protocol. However, we found the possibility of underdose to the planning target volume if the hepatocellular carcinoma lesion was located near organs at risk such as the heart. Based on this dummy run, we will conduct individual case reviews to minimize the effects of study protocol deviation.

Development of a 3D optical scanner for evaluating patient-specific dose distributions.

PURPOSE: This paper describes the hardware and software characteristics of a 3D optical scanner (P3DS) developed in-house. The P3DS consists of an LED light source, diffuse screen, step motor, CCD camera, and scanner management software with 3D reconstructed software. MATERIALS AND METHOD: We performed optical simulation, 2D and 3D reconstruction image testing, and pre-clinical testing for the P3DS. We developed the optical scanner with three key characteristics in mind. First, we developed a continuous scanning method to expand possible clinical applications. Second, we manufactured a collimator to improve image quality by reducing scattering from the light source. Third, we developed an optical scanner with changeable camera positioning to enable acquisition of optimal images according to the size of the gel dosimeter. RESULTS: We confirmed ray-tracing in P3DS with optic simulation and found that 2D projection and 3D reconstructed images were qualitatively similar to the phantom images. For pre-clinical tests, the dose distribution and profile showed good agreement among RTP, optical CT, and external beam radiotherapy film data for the axial and coronal views. The P3DS has shown that it can scan and reconstruct for evaluation of the gel dosimeter within 1 min. We confirmed that the P3DS system is a useful tool for the measurement of 3D dose distributions for 3D radiation therapy QA. Further experiments are needed to investigate quantitative analysis for 3D dose distribution.

Feasibility and response of helical tomotherapy in patients with metastatic colorectal cancer.

PURPOSE: To investigate the treatment outcome and the toxicity of helical tomotherapy (HT) in patients with metastatic colorectal cancer (mCRC). MATERIALS AND METHODS: We retrospectively reviewed 18 patients with 31 lesions from mCRC treated with HT between 2009 and 2013. The liver (9 lesions) and lymph nodes (9 lesions) were the most frequent sites. The planning target volume (PTV) ranged from 12 to 1,110 mL (median, 114 mL). The total doses ranged from 30 to 70 Gy in 10-30 fractions. When the α/ß value for the tumor was assumed to be 10 Gy for the biologically equivalent dose (BED), the total doses ranged from 39 to 119 Gy10 (median, 55 Gy10). Nineteen lesions were treated with concurrent chemotherapy (CCRT). RESULTS: With a median follow-up time of 16 months, the median overall survival for 18 patients was 33 months. Eight lesions (26%) achieved complete response. The 1- and 3-year local progression free survival (LPFS) rates for 31 lesions were 45% and 34%, respectively. On univariate analysis, significant parameters influencing LPFS rates were chemotherapy response before HT, aim of HT, CCRT, PTV, BED, and adjuvant chemotherapy. On multivariate analysis, PTV ≤113 mL and BED >48 Gy10 were associated with a statistically significant improvement in LFPS. During HT, four patients experienced grade 3 hematologic toxicities, each of whom had also received CCRT. CONCLUSION: The current study demonstrates the efficacy and tolerability of HT for mCRC. To define optimal RT dose according to tumor size of mCRC, further study should be needed.

Oxide-based platform for reconfigurable superconducting nanoelectronics.

We report quasi-1D superconductivity at the interface of LaAlO3 and SrTiO3. The material system and nanostructure fabrication method supply a new platform for superconducting nanoelectronics. Nanostructures having line widths w ~ 10 nm are formed from the parent two-dimensional electron liquid using conductive atomic force microscope lithography. Nanowire cross-sections are small compared to the superconducting coherence length in LaAlO3/SrTiO3, placing them in the quasi-1D regime. Broad superconducting transitions versus temperature and finite resistances in the superconducting state well below Tc ≈ 200 mK are observed, suggesting the presence of fluctuation- and heating-induced resistance. The superconducting resistances and V-I characteristics are tunable through the use of a back gate. Four-terminal resistances in the superconducting state show an unusual dependence on the current path, varying by as much as an order of magnitude. This new technology, i.e., the ability to 'write' gate-tunable superconducting nanostructures on an insulating LaAlO3/SrTiO3 'canvas', opens possibilities for the development of new families of reconfigurable superconducting nanoelectronics.

Effect of jaw size in megavoltage CT on image quality and dose.

PURPOSE: Recently, the jaw size for the TomoTherapy Hi-Art II(®) (TomoTherapy Inc., Madison, WI) was reduced from 4 mm (J4) to 1 mm (J1) to improve the longitudinal (IEC-Y) resolution in megavoltage computed tomography (MVCT) images. This study evaluated the effect of jaw size on the image quality and dose, as well as the dose delivered to the lens of the eye, which is a highly radiosensitive tissue. METHODS: MVCT image quality (image noise, uniformity, contrast linearity, high-contrast resolution, and full width at half-maximum) and multiple scan average dose (MSAD) were measured at different jaw sizes. A head phantom and photoluminescence glass dosimeters (PLDs) were used to measure the exposed lens dose (cGy). Different MVCT scan modes (pitch = 1, 2, and 3) and scan lengths (108 mm, 156 mm, and 204 mm) were applied in the MSAD and PLDs measurements. RESULTS: The change in jaw size from J4 to J1 produced no change or only a slight improvement in image noise, uniformity, contrast linearity, and high-contrast resolution. However, the full-width at half-maximum reduced from approximately 7.2 at J4 to 4.5 mm at J1, which represents an enhancement in the longitudinal resolution. The MSAD at the center point changed from approximately 0.69-2.32 cGy (peripheral: 0.83-2.49 cGy) at J4 to 0.85-2.81 cGy (peripheral: 1.05-2.86 cGy) at J1. The measured lens dose increased from 0.92-3.36 cGy at J4 to 1.06-3.91 cGy at J1. CONCLUSIONS: The change in jaw size improved longitudinal resolution. The MVCT imaging dose of approximately 3.86 cGy, 1.92 cGy, and 1.22 cGy was delivered at a pitch of 1, 2, and 3, respectively, per fraction in the head and neck treatment plans. Therefore, allowance for an approximately 15% increase in lens dose over that with J4 should be provided with J1.

Rectum dose analysis employing a multi-purpose brachytherapy phantom.

PURPOSE: It is difficult to reproduce a brachytherapy measurement because of changes in the rectal shape during inter-fraction. We constructed a multi-purpose brachytherapy phantom (MPBP) and reproduced the same conditions found in actual therapy. We further attempted to apply the measured optimal dose to reduce rectal complications. METHODS: A measured dose was administered at rectal reference point R1 using a diode detector in four patients who used a tandem and ovoid in brachytherapy for carcinoma of the cervix. A total number of 20 rectal dose measurements were performed five times per patient. In addition, discrepancies in the set-up of the diode detector were analyzed with each repetitive measurement. After reproducing the same conditions as found in actual therapy using a multi-function applicator (MFA) in the multi-purpose brachytherapy phantom constructed for this study, the dose was measured at reference points in the rectum using a thermoluminescence dosimeter (TLD). RESULTS: According to the discrepancies measured in the set-up using a diode detector, Patient 1 showed a maximum value of 11.25 +/- 0.95 mm in the Y direction, Patients 2 and 3 exhibited 9.90 +/- 2.40 mm and 20.85 +/- 4.50 mm in the Z direction, respectively. Patient 4 showed 19.15 +/- 3.33 mm in the Z direction. In addition, values of the mean dose according to the position of the diode detector were recorded as 122.82 +/- 7.96-323.78 +/- 11.16 cGy. In the measured results for TLD in an MPBP, relative error for Patients 1 and 4 at the rectal reference point R2 were a maximum of 8.6 and 7.7%, respectively. For Patients 2 and 3 they were 1.7 and 1.2%, respectively. Furthermore, the dose measured at point R1 and R2 exhibited values approximately 1.7-8.6% higher than the dose calculated in advance, excluding point R1 in Patient 2. The discrepancies in the set-up owing to repetitive measurements and alterations in dosage according to these changes were not analyzed. It was evident that the relative error between the calculated and measured value was within 15%, which was allowable according to the recommendations by the American Association of Physicists in Medicine (AAPM). CONCLUSIONS: The multi-purpose brachytherapy phantom constructed for this study successfully reproduced an optimal dose measured under the same conditions found in actual therapy in which the dose was precisely analyzed at a rectal reference point. In addition, these results were considered reliable and applicable for dose optimization before applying therapy using the measured data from the phantom in order to reduce rectal complications.