Assessing alimentary tract radiation in liver cancer treatment with proton beam therapy: a PET/CT imaging study.

BACKGROUND: Proton beams deposit energy along their path, abruptly stopping and generating various radioactive particles, including positrons, along their trajectory. In comparison with traditional proton beam therapy, scanning proton beam therapy is effective in delivering proton beams to irregularly shaped tumors, reducing excessive radiation exposure to the alimentary tract during the treatment of liver cancer. METHODS: In this study, we utilized positron emission tomography/computed tomography (PET/CT) imaging to assess the total amount of radiation to the alimentary tract during liver cancer treatment with proton beam therapy, involving the administration of complex irradiation in 13 patients. RESULTS: This approach resulted in the prevention of excess radiation. The planned radiation restraint doses for the colon exhibited a significant correlation with the PET values of the colon (correlation coefficient 0.8384, P = .0003). Likewise, the scheduled radiation restraint doses for the gastroduodenum were correlated with the PET values of the gastroduodenum (correlation coefficient 0.5397, P = .0569). CONCLUSIONS: PET/CT conducted after proton beam therapy is useful for evaluating excess radiation in the alimentary tract. Proton beam therapy in liver cancer, assessed via PET/CT, effectively reduced alimentary tract radiation, which is vital for optimizing treatments and preventing excess exposure.

Carbon-ion radiotherapy for oligometastatic liver disease: A national multicentric study by the Japan Carbon-Ion Radiation Oncology Study Group (J-CROS).

Reports on the therapeutic efficacy and safety of carbon-ion radiotherapy (C-ion RT) for oligometastatic liver disease are limited, with insufficient evidence. This study aimed to evaluate the clinical outcomes of C-ion RT for oligometastatic liver disease at all Japanese facilities using the nationwide cohort data. We reviewed the medical records to obtain the nationwide cohort registry data on C-ion RT between May 2016 and June 2020. Patients (1) with oligometastatic liver disease as confirmed by histological or diagnostic imaging, (2) with ≤3 synchronous liver metastases at the time of treatment, (3) without active extrahepatic disease, and (4) who received C-ion RT for all metastatic regions with curative intent were included in this study. C-ion RT was performed with 58.0-76.0 Gy (relative biological effectiveness [RBE]) in 1-20 fractions. In total, 102 patients (121 tumors) were enrolled in this study. The median follow-up duration for all patients was 19.0 months. The median tumor size was 27 mm. The 1-year/2-year overall survival, local control, and progression-free survival rates were 85.1%/72.8%, 90.5%/78.0%, and 48.3%/27.1%, respectively. No patient developed grade 3 or higher acute or late toxicity. C-ion RT is a safe and effective treatment for oligometastatic liver disease and may be beneficial as a local treatment option in multidisciplinary treatment.

Event Collapse in Contrast Maximization Frameworks.

Contrast maximization (CMax) is a framework that provides state-of-the-art results on several event-based computer vision tasks, such as ego-motion or optical flow estimation. However, it may suffer from a problem called event collapse, which is an undesired solution where events are warped into too few pixels. As prior works have largely ignored the issue or proposed workarounds, it is imperative to analyze this phenomenon in detail. Our work demonstrates event collapse in its simplest form and proposes collapse metrics by using first principles of space-time deformation based on differential geometry and physics. We experimentally show on publicly available datasets that the proposed metrics mitigate event collapse and do not harm well-posed warps. To the best of our knowledge, regularizers based on the proposed metrics are the only effective solution against event collapse in the experimental settings considered, compared with other methods. We hope that this work inspires further research to tackle more complex warp models.

Carbon ion radiotherapy for patients with hepatocellular carcinoma in the caudate lobe carbon ion radiotherapy for hepatocellular carcinoma in caudate lobe.

AIM: The treatment of hepatocellular carcinoma in the caudate lobe (HCCCL) is technically challenging. We aimed to investigate the efficacy and toxicity of carbon ion radiotherapy (C-ion RT) for HCCCL. METHODS: Patients with HCCCL treated with C-ion RT at our hospital between January 2011 and December 2018 were evaluated. The total dose was 52.8 or 60 Gy (relative biological effectiveness) in four or 12 fractions depending on the distance between the tumor and the gastrointestinal tract. The survival outcome, the presence or absence of recurrence (local recurrence, intrahepatic recurrence outside the irradiation field, or extrahepatic recurrence), and acute/late adverse events were evaluated. RESULTS: Nine patients were included. The median tumor size was 3.4 cm, and the median follow-up duration was 18.3 months for all patients. No patient developed local recurrence during follow-up. Five patients subsequently developed intrahepatic recurrence outside the irradiation field and two had extrahepatic metastasis. Five patients died of hepatocellular carcinoma. No acute adverse events of grade ≥2 were observed. Two patients experienced grade 2 or 3 late adverse events, including obstructive jaundice, hepatic encephalopathy, ascites, and edema. CONCLUSION: Carbon ion radiotherapy for HCCCL achieved excellent local control with acceptable adverse events and can thus be a curative treatment option for HCCCL.

FGFR Signaling as a Candidate Therapeutic Target for Cancers Resistant to Carbon Ion Radiotherapy.

Radiotherapy is an essential component of cancer therapy. Carbon ion radiotherapy (CIRT) promises to improve outcomes compared with standard of care in many cancers. Nevertheless, clinicians often observe in-field recurrence after CIRT. This indicates the presence of a subset of cancers that harbor intrinsic resistance to CIRT. Thus, the development of methods to identify and sensitize CIRT-resistant cancers is needed. To address this issue, we analyzed a unique donor-matched pair of clinical specimens: a treatment-naïve tumor, and the tumor that recurred locally after CIRT in the same patient. Exon sequencing of 409 cancer-related genes identified enrichment of somatic mutations in FGFR3 and FGFR4 in the recurrent tumor compared with the treatment-naïve tumor, indicating a pivotal role for FGFR signaling in cancer cell survival through CIRT. Inhibition of FGFR using the clinically available pan-FGFR inhibitor LY2874455 sensitized multiple cancer cell lines to carbon ions at 3 Gy (RBE: relative biological effectiveness), the daily dose prescribed to the patient. The sensitizer enhancement ratio was 1.66 ± 0.17, 1.27 ± 0.09, and 1.20 ± 0.18 in A549, H1299, and H1703 cells, respectively. Our data indicate the potential usefulness of the analytical pipeline employed in this pilot study to identify targetable mutations associated with resistance to CIRT, and of LY21874455 as a sensitizer for CIRT-resistant cancers. The results warrant validation in larger cohorts.

Carbon ion radiotherapy for 80 years or older patients with hepatocellular carcinoma.

BACKGROUND: To evaluate the safety and efficacy of carbon ion radiotherapy (C-ion RT) for 80 years or older patients with hepatocellular carcinoma (HCC). METHODS: Eligibility criteria of this retrospective study were: 1) HCC confirmed by histology or typical hallmarks of HCC by imaging techniques of four-phase multidetector-row computed tomography or dynamic contrast-enhanced magnetic resonance imaging; 2) no intrahepatic metastasis or distant metastasis; 3) no findings suggesting direct infiltration of the gastrointestinal tract; 4) performance status ≤2 by Eastern Cooperative Oncology Group classification; and 5) Child-Pugh classification A or B. Patients received C-ion RT with 52.8 Gy (RBE) or 60.0 Gy (RBE) in four fractions for usual cases and 60.0 Gy (RBE) in 12 fractions for close-to-gastrointestinal tract cases. Toxicities were classified using the National Cancer Institute's Common Terminology Criteria for Adverse Events (Version 4.0). RESULTS: Between March 2011 and November 2015, 31 patients were treated. The median follow-up period of all patients was 23.2 months (range: 8.4-55.3 months). Median age at the time of registration of C-ion RT was 83 years (range: 80-95 years). Child-Pugh grade A and B were 27 patients and 4 patients, respectively. The 2-year estimated overall survival, local control, and progression-free survival rates were 82.3%, 89.2%, and 51.3%, respectively. No patients had Grade 2 or higher acute toxicities (within 3 months after C-ion RT). One patient experienced progression in Child-Pugh classification from A to B within 3 months after C-ion RT. In late toxicities, Grade 3 encephalopathy was observed in 3 patients, and 2 improved with medication. CONCLUSIONS: C-ion RT was effective with minimal toxicities for 80 years or older patients with hepatocellular carcinoma. TRIAL REGISTRATION: UMIN000020571 : date of registration, 14 January 2016, retrospectively registered.

The prognostic value of rectal invasion for stage IVA uterine cervical cancer treated with radiation therapy.

BACKGROUND: The prognostic value of rectal invasion is still unclear in stage IVA cervical cancer. The objective of this study is to evaluate patient outcome and prognostic factors in stage IVA cervical cancer treated with radiation therapy. METHODS: A retrospective review of the medical records of patients treated with definitive photon radiation therapy for pathologically proven stage IVA cervical cancer between 1980 and 2010 was performed. Eligible patients for the present study were diagnosed with clinical stage IVA cervical cancer by cystoscopy or/and proctoscopy, and they received definitive radiation therapy consisting of a combination of external beam radiotherapy and high-dose-rate brachytherapy. All patients underwent CT scans of the abdomen and pelvis. RESULTS: Among the 67 stage IVA patients studied, 53 patients were stage IVA on the basis of bladder invasion, 7 according to rectal mucosal invasion, and 7 because of both bladder and rectal mucosal invasion. Median follow-up of all patients and surviving patients was 19 months (range, 2-235 months) and 114 months (range, 14-223 months), respectively. The 5-year local control (LC), disease-free survival (DFS), and overall survival (OS) rate were 55, 17, and 24%, respectively. Rectal invasion had significant impact on DFS, but bladder invasion had the opposite effect (p = 0.00006 and 0.005, respectively). There were significant differences of LC, DFS and OS rates between patients with and without rectal invasion (p = 0.006, 0.00006 and 0.05, respectively). CONCLUSIONS: Patients with stage IVA cervical cancer had poor prognosis, with 5-year survival of only 24%. Furthermore, in stage IVA, rectal invasion might be a worse prognostic factor than bladder invasion.

Effects of background noise on acoustic characteristics of Bengalese finch songs.

Online regulation of vocalization in response to auditory feedback is one of the essential issues for vocal communication. One such audio-vocal interaction is the Lombard effect, an involuntary increase in vocal amplitude in response to the presence of background noise. Along with vocal amplitude, other acoustic characteristics, including fundamental frequency (F0), also change in some species. Bengalese finches (Lonchura striata var. domestica) are a suitable model for comparative, ethological, and neuroscientific studies on audio-vocal interaction because they require real-time auditory feedback of their own songs to maintain normal singing. Here, the changes in amplitude and F0 with a focus on the distinct song elements (i.e., notes) of Bengalese finches under noise presentation are demonstrated. To accurately analyze these acoustic characteristics, two different bandpass-filtered noises at two levels of sound intensity were used. The results confirmed that the Lombard effect occurs at the note level of Bengalese finch song. Further, individually specific modes of changes in F0 are shown. These behavioral changes suggested the vocal control mechanisms on which the auditory feedback is based have a predictable effect on amplitude, but complex spectral effects on individual note production.

Event-Based Background-Oriented Schlieren.

Schlieren imaging is an optical technique to observe the flow of transparent media, such as air or water, without any particle seeding. However, conventional frame-based techniques require both high spatial and temporal resolution cameras, which impose bright illumination and expensive computation limitations. Event cameras offer potential advantages (high dynamic range, high temporal resolution, and data efficiency) to overcome such limitations due to their bio-inspired sensing principle. This article presents a novel technique for perceiving air convection using events and frames by providing the first theoretical analysis that connects event data and schlieren. We formulate the problem as a variational optimization one combining the linearized event generation model with a physically-motivated parameterization that estimates the temporal derivative of the air density. The experiments with accurately aligned frame- and event camera data reveal that the proposed method enables event cameras to obtain on par results with existing frame-based optical flow techniques. Moreover, the proposed method works under dark conditions where frame-based schlieren fails, and also enables slow-motion analysis by leveraging the event camera's advantages. Our work pioneers and opens a new stack of event camera applications, as we publish the source code as well as the first schlieren dataset with high-quality frame and event data.

Secrets of Event-based Optical Flow, Depth and Ego-motion Estimation by Contrast Maximization.

Event cameras respond to scene dynamics and provide signals naturally suitable for motion estimation with advantages, such as high dynamic range. The emerging field of event-based vision motivates a revisit of fundamental computer vision tasks related to motion, such as optical flow and depth estimation. However, state-of-the-art event-based optical flow methods tend to originate in frame-based deep-learning methods, which require several adaptations (data conversion, loss function, etc.) as they have very different properties. We develop a principled method to extend the Contrast Maximization framework to estimate dense optical flow, depth, and ego-motion from events alone. The proposed method sensibly models the space-time properties of event data and tackles the event alignment problem. It designs the objective function to prevent overfitting, deals better with occlusions, and improves convergence using a multi-scale approach. With these key elements, our method ranks first among unsupervised methods on the MVSEC benchmark and is competitive on the DSEC benchmark. Moreover, it allows us to simultaneously estimate dense depth and ego-motion, exposes the limitations of current flow benchmarks, and produces remarkable results when it is transferred to unsupervised learning settings. Along with various downstream applications shown, we hope the proposed method becomes a cornerstone on event-based motion-related tasks. Code is available at https://github.com/tub-rip/event_based_optical_flow.

Proton-beam Therapy for Locally Advanced Hepatocellular Carcinoma With Inferior Vena Cava Tumor Thrombus: Case Report.

BACKGROUND/AIM: We report on a case of locally advanced hepatocellular carcinoma (HCC) accompanied by an inferior vena cava tumor thrombus (IVCTT), treated successfully with proton-beam therapy (PBT). CASE REPORT: A 63-year-old male presented with a primary, single HCC with IVCTT, without metastasis to the intrahepatic region, lymph nodes, or distant organs. The clinical staging was identified as T4N0M0 Stage IIIB. The patient's liver function was classified as Child-Pugh class A (score: 6), with a modified albumin-bilirubin (mALBI) grade of 2a. The patient had liver cirrhosis due to non-alcoholic steatohepatitis. Magnetic resonance imaging revealed a nodular tumor measuring 13.2×8.9×9.8 cm across segments 1, 6, 7, and 8, along with IVCTT. The patient received PBT, with a total dose of 72.6 Gy (relative biological effectiveness) delivered in 22 fractions. Throughout the PBT treatment, the patient experienced no acute toxicities and completed the therapy as planned. Twelve months following PBT, the patient was alive without evidence of local recurrence, lymph node involvement, or distant organ metastasis. The only late toxicity observed was a mild worsening of the mALBI grade. CONCLUSION: We observed a favorable local response with manageable toxicities in a patient with locally advanced HCC and IVCTT treated with PBT. While this is a single case report, our findings suggest that PBT could be considered a viable treatment option for HCC with IVCTT.

Cost-Effectiveness Comparison of Carbon-Ion Radiation Therapy and Transarterial Chemoembolization for Hepatocellular Carcinoma.

Purpose: Carbon-ion radiation therapy (CIRT) is a treatment option for patients with hepatocellular carcinoma (HCC) that results in better outcomes with fewer side effects despite its high cost. This study aimed to evaluate the cost-effectiveness of CIRT for HCC from medical and economic perspectives by comparing CIRT and transarterial chemoembolization (TACE) in patients with localized HCC who were ineligible for surgery or radiofrequency ablation. Methods and Materials: This study included 34 patients with HCC who underwent either CIRT or TACE at Gunma University between 2007 and 2016. Patient characteristics were employed to select each treatment group using the propensity score matching method. Life years were used as the outcome indicator. The CIRT technical fee was ¥3,140,000; however, a second CIRT treatment on the same organ within 2 years was performed for free. Results: Our study showed that CIRT was dominant over TACE, as the CIRT group had a higher life year (point estimate, 2.75 vs 2.41) and lower total cost (mean, ¥4,974,278 vs ¥5,284,524). We conducted a sensitivity analysis to validate the results because of the higher variance in medical costs in the TACE group, which demonstrated that CIRT maintained its cost effectiveness with a high acceptability rate. Conclusions: CIRT is a cost-effective treatment option for localized HCC cases unsuitable for surgical resection.

Comparing Efficacy Between Robust and PTV Margin-based Optimizations for Interfractional Anatomical Variations in Prostate Tomotherapy.

BACKGROUND/AIM: Interfractional anatomical variations cause considerable differences between planned and actual radiotherapy doses. This study aimed to investigate the efficacy of robust and planning target volume (PTV) margin-based optimizations for the anatomical variations in helical tomotherapy for prostate cancer. PATIENTS AND METHODS: Ten patients underwent treatment-planning kilovolt computed tomography (kVCT) and daily megavolt computed tomography (MVCT). Two types of nominal plans, with a prescription of 60 Gy/20 fractions, were created using robust and PTV margin-based optimizations on kVCT for each patient. Subsequently, the daily estimated doses were recalculated using nominal plans, and all available MVCTs modified the daily patient-setup errors. Due to the difference in dose calculation accuracy between kVCT and MVCT, three scenarios with dose corrections of 1, 2, and 3% were considered in the recalculation process. The dosimetric metrics, including target coverage with the prescription dose, Paddick's conformity index, homogeneity index, and mean dose to the rectum, were analyzed. RESULTS: A dosimetric comparison of the nominal plans demonstrated that the robust plans had better dose conformity, lower target coverage, and dose homogeneity than the PTV plans. In the daily estimated doses of any dose-corrected scenario, the target coverage and dose sparing to the rectum in the robust plans were significantly higher than those in the PTV plans, whereas dose conformity and homogeneity were identical to those of the nominal case. CONCLUSION: Robust optimization is recommended as it accounts for anatomical variations during treatment regarding target coverage in helical tomotherapy plans for prostate cancer.

Evaluating optimal quality assurance and quality control conditions of activation measurements at the accelerator-based boron neutron capture therapy system employing a lithium target.

Evaluating neutron output is important to ensure proper dose delivery for patients in boron neutron capture therapy (BNCT). It requires efficient quality assurance (QA) and quality control (QC) while maintaining measurement accuracy. This study investigated the optimal measurement conditions for QA/QC of activation measurements using a high-purity germanium (HP-Ge) detector in an accelerator-based boron neutron capture therapy (AB-BNCT) system employing a lithium target. The QA/QC uncertainty of the activation measurement was evaluated based on counts, reproducibility, and standard radiation source uncertainties. Measurements in a polymethyl methacrylate (PMMA) cylindrical phantom using aluminum-manganese (Al-Mn) foils and aluminum-gold (Al-Au) foils and measurements in a water phantom using gold wire with and without cadmium cover were performed to determine the optimal measurement conditions. The QA/QC uncertainties of the activation measurements were 4.5% for Au and 4.6% for Mn. The optimum irradiation proton charge and measurement time were determined to be 36 C and 900 s for measurements in a PMMA cylindrical phantom, 7.0 C and 900 s for gold wire measurements in a water phantom, and 54 C and 900 s at 0-2.2 cm depth and 3,600 s at deeper depths for gold wire measurements with cadmium cover. Our results serve as a reference for determining measurement conditions when performing QA/QC of activation measurements using HP-Ge detectors at an AB-BNCT employing a lithium target.

Dose Distribution Degradation of Carbon-ion Radiotherapy Caused by Tumor Cell-specific Relative Biological Effectiveness of Osteosarcoma: A Simulation Study Using In Vitro Experimental Results.

BACKGROUND/AIM: Dose distributions of carbon-ion radiotherapy (C-ion RT) have been created with the relative biological effectiveness (RBE) of human salivary gland cells (HSG). However, no dose distributions have been created using various tumor cell-specific RBE values. Hence, we conducted in vitro experiments to determine the RBE of human osteosarcoma cells (U2OS) and used this RBE value (RBEU2OS) to calculate the dose distribution for C-ion RT. MATERIALS AND METHODS: To obtain RBE values for various linear energy transfer (LET) levels, we exposed U2OS cells to different doses of X-rays and varying doses and LET levels of C-ion beams (13, 30, 50, and 70 keV/µm). Subsequently, we converted the RBE of HSG (RBEHSG) to RBEU2OS in the treatment planning system and reconstructed the dose distribution for a typical osteosarcoma case. We performed a dose-volume histogram (DVH) analysis, evaluating the percentage of the minimum dose that covered 98%, 50%, and 2% (D98%, D50%, and D2%, respectively), as well as the homogeneity index [HI; calculated as (D2%-D98%)/D50%]. RESULTS: The RBEU2OS values for C-ion beams with LET of 13, 30, 50, and 70 keV/µm were 1.77, 2.25, 2.72, and 4.50, respectively. When comparing DVH parameters with the planning target volume, we observed the following values: D98%, D50%, D2%, and HI for RBEHSG were 64.1, 70.1, 72.4 Gy (RBE), and 0.12, respectively. For RBEU2OS, these values were 86.2, 95.0, 107.9 Gy (RBE), and 0.23, respectively. CONCLUSION: We utilized RBEU2OS to calculate the dose distribution of carbon ion radiotherapy, revealing potential degradation in dose distribution and particularly worsening of the HI.

Repeated Carbon-Ion Radiation Therapy for Intrahepatic Recurrent Hepatocellular Carcinoma.

PURPOSE: This retrospective study aimed to evaluate the safety and efficacy of repeated carbon-ion radiation therapy (CIRT) in patients with intrahepatic recurrent hepatocellular carcinoma (HCC). METHODS AND MATERIALS: We reviewed patients who underwent repeated CIRT for intrahepatic recurrent HCC between 2010 and 2020. RESULTS: Forty-one patients received multiple CIRT courses for HCC. During the second course, 17 (41.5%) and 24 (58.5%) of 41 patients underwent CIRT for local recurrence (LR) and intrahepatic recurrence after the first irradiation, respectively. The median age at the first course was 76 years, and the median tumor size in all the courses was 25 mm. Throughout all CIRT courses, the prescribed dose was 52.8 to 60.0 Gy (relative biological effectiveness), which was delivered in 4 to 12 fractions. The median follow-up period after the first and second CIRT was 40 and 21 months. Median overall survival (OS) after the first and second CIRT were 80 and 27 months, respectively. The 2- and 5-year OS after the first CIRT were 87.8% and 50.1%, and the 2-year OS rate after the second CIRT was 56.0%. The 1- and 2-year local control (LC) after the second CIRT was 93.4% and 83.0%, respectively. The median progression-free survival (PFS) after the second CIRT was 11 months. There were no significant differences in the LC and PFS between patients with LR and out-of-field recurrence (P = .83; 0.28, respectively). The albumin-bilirubin scores at 3 and 6 months after the second CIRT were not significantly different from those before irradiation. According to the Common Terminology Criteria for Adverse Events version 4.0, grade 4 or greater toxicities were not observed. CONCLUSIONS: Repeated CIRT for intrahepatic recurrent HCC was safe and effective, including reirradiation for LR. OS, LC, and PFS were satisfactory, and liver function was preserved. Repeated CIRT could be considered a treatment option for intrahepatic recurrent HCC.

Carbon-Ion Radiotherapy Combined with Concurrent Chemotherapy for Locally Advanced Pancreatic Cancer: A Retrospective Case Series Analysis.

Systemic chemotherapy has significantly improved in recent years. In this study. the clinical impact of carbon-ion radiotherapy (CIRT) with concurrent chemotherapy for locally advanced unresectable pancreatic cancer (URPC) was evaluated. METHODS: Patients with URPC who were treated with CIRT between January 2016 and December 2020 were prospectively registered and analyzed. The major criteria for registration were (1) diagnosed as URPC on imaging; (2) pathologically diagnosed adenocarcinoma; (3) no distant metastasis; (4) Eastern Cooperative Oncology Group performance status of 0-2; (5) tumors without gastrointestinal tract invasion; and (6) available for concurrent chemotherapy. Patients who received neoadjuvant chemotherapy (NAC) for more than one year prior to CIRT were excluded. RESULTS: Forty-four patients met the inclusion criteria, and thirty-seven received NAC before CIRT. The median follow-up period of living patients was 26.0 (6.0-68.6) months after CIRT. The estimated two-year overall survival, local control, and progression-free survival rates after CIRT were 56.6%, 76.1%, and 29.0%, respectively. The median survival time of all patients was 29.6 months after CIRT and 34.5 months after the initial NAC. CONCLUSION: CIRT showed survival benefits for URPC even in the multiagent chemotherapy era.

Impact of delivery time factor on treatment time and plan quality in tomotherapy.

Delivery time factor (DTF) is a new parameter introduced by the RayStation treatment planning system for tomotherapy treatment planning. This study investigated the effects of this factor on various tomotherapy plans. Twenty-five patients with cancer (head and neck, 6; lung, 9; prostate, 10) were enrolled in this study. Helical tomotherapy plans with a field width of 2.5 cm, pitch of 0.287, and DTF of 2.0 were created. All the initial plans were recalculated by changing the DTF parameter from 1.0 to 3.0 in increments of 0.1. Then, DTF's impact on delivery efficiency and plan quality was evaluated. Treatment time and modulation factor increased monotonically with increasing DTF. Increasing the DTF by 0.1 increased the treatment time and modulation factor by almost 10%. This relationship was similar for all treatment sites. Conformity index (CI), homogeneity index, and organ at risk doses were improved compared to plans with a DTF of 1.0, except for the CI in the lung cancer case. However, the improvement in most indices ceased at a certain DTF; nevertheless, treatment time continued to increase following an increase in DTF. DTF is a critical parameter for improving the quality of tomotherapy plans.

Initial evaluation of accelerator-based neutron source system at the Shonan Kamakura General Hospital.

An accelerator-based boron neutron capture therapy (AB-BNCT) system was installed at the Shonan Kamakura General Hospital (SKGH). We confirmed that a stable operation was possible for 1 h at a current of 30 mA. The evaluated thermal neutron flux was 2.8 × 109 cm-2 s-1 and in good agreement (±5%) with the calculated values. The daily variation was within ±2%. The ambient dose rate due to residual radioactivity after irradiation was approximately 5 µSv/h using a lead shutter.

Carbon-ion Radiotherapy for Inoperable Solitary Fibrous Tumor of the Skull Base: A Case Report.

BACKGROUND/AIM: The curative treatment for solitary fibrous tumors (SFTs) consists of surgery. However, surgery for SFTs in the skull base is difficult due to the anatomy and curative surgery may not be possible. Carbon-ion radiotherapy (C-ion RT) might be useful in the treatment of inoperable SFTs in the skull base because of its biological and physical nature. This study presents the clinical outcomes of C-ion RT for an inoperable SFT of the skull base. CASE REPORT: A 68-year-old female patient experienced hoarseness, deafness on the right side, right facial nerve paralysis, and dysphagia. Magnetic resonance imaging revealed a tumor located in the right cerebello-pontine angle with destruction of the petrous bone, and immunohistochemical studies of the biopsy specimen showed a grade 2 SFT. Firstly, the patient underwent tumor embolization and surgery. However, 5 months after surgery, magnetic resonance imaging revealed regrowth of residual tumor. Subsequently, the patient was referred to our hospital for C-ion RT because curative surgery was unsuitable. The patient received 64 Gy (relative biological effectiveness) of C-ion RT in 16 fractions. Two years after C-ion RT, the tumor showed a partial response. The patient was still alive at the last follow-up without evidence of local recurrence, distant metastasis, or late toxicities. CONCLUSION: These findings suggest that C-ion RT is a suitable treatment option for inoperable SFTs of the skull base.