Appropriate margin for planning target volume for breast radiotherapy during deep inspiration breath-hold by variance component analysis

BACKGROUND: This study aimed to quantify errors by using a cine electronic portal imaging device (cine EPID) during deep inspiration breath-hold (DIBH) for left-sided breast cancer and to estimate the planning target volume (PTV) by variance component analysis. METHODS: This study included 25 consecutive left-sided breast cancer patients treated with whole-breast irradiation (WBI) using DIBH. Breath-holding was performed while monitoring abdominal anterior-posterior (AP) motion using the Real-time Position Management (RPM) system. Cine EPID was used to evaluate the chest wall displacements in patients. Cine EPID images of the patients (309, 609 frames) were analyzed to detect the edges of the chest wall using a Canny filter. The errors that occurred during DIBH included differences between the chest wall position detected by digitally reconstructed radiographs and that of all cine EPID images. The inter-patient, inter-fraction, and intra-fractional standard deviations (SDs) in the DIBH were calculated, and the PTV margin was estimated by variance component analysis. RESULTS: The median patient age was 55 (35-79) years, and the mean irradiation time was 20.4 ± 1.7 s. The abdominal AP motion was 1.36 ± 0.94 (0.14-5.28) mm. The overall mean of the errors was 0.30 mm (95% confidence interval: - 0.05-0.65). The inter-patient, inter-fraction, and intra-fractional SDs in the DIBH were 0.82 mm, 1.19 mm, and 1.63 mm, respectively, and the PTV margin was calculated as 3.59 mm. CONCLUSIONS: Errors during DIBH for breast radiotherapy were monitored using EPID images and appropriate PTV margins were estimated by variance component analysis

Factual survey of the clinical use of deformable image registration software for radiotherapy in Japan

Deformable image registration (DIR) has recently become commercially available in the field of radiotherapy. However, there was no detailed information regarding the use of DIR software at each medical institution. Thus, in this study, we surveyed the status of the clinical use of DIR software for radiotherapy in Japan. The Japan Society of Medical Physics and the Japanese Society for Radiation Oncology mailing lists were used to announce this survey. The questionnaire was created by investigators working under the research grant of the Japanese Society for Radiation Oncology (2017–2018) and intended for the collection of information regarding the use of DIR in radiotherapy. The survey was completed by 161 institutions in Japan. The survey results showed that dose accumulation was the most frequent purpose for which DIR was used in clinical practice (73%). Various commissioning methods were performed, although they were not standardized. Qualitative evaluation with actual patient images was the most commonly used method (28%), although 30% of the total number of responses (42% of institutions) reported that they do not perform commissioning. We surveyed the current status of clinical use of DIR software for radiotherapy in Japan for the first time. Our results indicated that a certain number of institutions used DIR software for clinical practice, and various commissioning methods were performed, although they were not standardized. Taken together, these findings highlight the need for a technically unified approach for commissioning and quality assurance for the use of DIR software in Japan

Independent calculation-based verification of volumetric-modulated arc therapy–stereotactic body radiotherapy plans for lung cancer

This study aimed to investigate the feasibility of independent calculation‐based verification of volumetric‐modulated arc therapy (VMAT)–stereotactic body radiotherapy (SBRT) for patients with lung cancer using a secondary treatment planning system (sTPS). In all, 50 patients with lung cancer who underwent VMAT‐SBRT between April 2018 and May 2019 were included in this study. VMAT‐SBRT plans were devised using the Collapsed‐Cone Convolution in RayStation (primary TPS: pTPS). DICOM files were transferred to Eclipse software (sTPS), which utilized the Eclipse software, and the dose distribution was then recalculated using Acuros XB. For the verification of dose distribution in homogeneous phantoms, the differences among pTPS, sTPS, and measurements were evaluated using passing rates of a dose difference of 5% (DD5%) and gamma index of 3%/2 mm (γ3%/2 mm). The ArcCHECK cylindrical diode array was used for measurements. For independent verification of dose‐volume parameters per the patient’s geometry, dose‐volume indices for the planning target volume (PTV) including D95% and the isocenter dose were evaluated. The mean differences (± standard deviations) between the pTPS and sTPS were then calculated. The gamma passing rates of DD5% and γ3%/2 mm criteria were 99.2 ± 2.4% and 98.6 ± 3.2% for pTPS vs. sTPS, 92.9 ± 4.0% and 94.1 ± 3.3% for pTPS vs. measurement, and 93.0 ± 4.4% and 94.3 ± 4.1% for sTPS vs. measurement, respectively. The differences between pTPS and sTPS for the PTVs of D95% and the isocenter dose were −3.1 ± 2.0% and −2.3 ± 1.8%, respectively. Our investigation of VMAT‐SBRT plans for lung cancer revealed that independent calculation‐based verification is a time‐efficient method for patient‐specific quality assurance

An α-synuclein decoy peptide prevents cytotoxic α-synuclein aggregation caused by fatty acid binding protein 3

α-synuclein (αSyn) is a protein known to form intracellular aggregates during the manifestation of Parkinson’s disease. Previously, it was shown that αSyn aggregation was strongly suppressed in the midbrain region of mice that did not possess the gene encoding the lipid transport protein fatty acid binding protein 3 (FABP3). An interaction between these two proteins was detected in vitro, suggesting that FABP3 may play a role in the aggregation and deposition of αSyn in neurons. In order to characterize the molecular mechanisms that underlie the interactions between FABP3 and αSyn that modulate the cellular accumulation of the latter, in this report, we used in vitro fluorescence assays combined with fluorescence microscopy, transmission electron microscopy, and quartz crystal microbalance assays to characterize in detail the process and consequences of FABP3-αSyn interaction. We demonstrated that binding of FABP3 to αSyn results in changes in the aggregation mechanism of the latter; specifically, a suppression of fibrillar forms of αSyn, and also the production of aggregates with an enhanced cytotoxicity toward mice neuro2A cells. Since this interaction involved the C-terminal sequence region of αSyn, we tested a peptide derived from this region of αSyn (αSynP130-140) as a decoy to prevent the FABP3-αSyn interaction. We observed that the peptide competitively inhibited binding of αSyn to FABP3 in vitro and in cultured cells. We propose that administration of αSynP130-140 might be used to prevent the accumulation of toxic FABP3-αSyn oligomers in cells, thereby preventing the progression of Parkinson’s disease

Monthly Variation and Ultraviolet Stability of Mycosporine-like Amino Acids from Red Alga Dulse Palmaria palmata in Japan

Mycosporine-like amino acids (MAAs) are the natural ultraviolet (UV)-absorbing compounds from micro- and macro-algae. The MAAs in algae change with the environmental conditions and seasons. We previously determined an efficient extraction method of MAAs from red alga dulse in Usujiri (Hokkaido, Japan) and revealed monthly variation of MAA in 2019. Dulse samples in 2019 for MAA preparation were suitable from late February to April. In this study, to confirm the suitable timings to extract MAAs from Usujiri dulse, we also investigated the monthly (from January to May) variation of MAA content in 2020. There were the most MAAs in the sample on 18 March (6.696 µmol g−1 dry weight) among the samples from January to May 2020. From two years of investigation, we deduce that samples of Usujiri dulse from late February to early April were suitable for MAA preparation. The UV stability of the two major purified MAAs in Usujiri dulse—palythine and porphyra-334—was tested. The two MAAs and 2-hydroxy-4-methoxybenzophenone were stable for up to 12 h under a 312 nm lamp at 200 µW cm−2, but 2-ethylhexyl-4-methoxycinnamate formed a cis/trans-mixture in a short time. The data in this study show the suitable sampling period for Usujiri dulse and the possible application for UV protection from food and cosmetics

Quality assurance of non-coplanar, volumetric-modulated arc therapy employing a C-arm linear accelerator, featuring continuous patient couch rotation

Purpose: To perform quality assurance of non-coplanar, volumetric-modulated arc therapy featuring continuous couch rotation (CCR-VMAT) using a C-arm linear accelerator. Methods: We planned and delivered CCR-VMAT using the TrueBeam Developer Mode. Treatment plans were created for both a C-shaped phantom and five prostate cancer patients using seven CCR trajectories that lacked collisions; we used RayStation software (ver. 4.7) to this end. Subsequently, verification plans were generated. The mean absolute error (MAE) between the center of an MV-imaged steel ball and the radiation field was calculated using the Winston–Lutz test. The MAEs between planned and actual irradiation values were also calculated from trajectory logs. In addition, correlation coefficients (r values) among the MAEs of gantry angle, couch angle, and multi-leaf collimator (MLC) position, and mechanical parameters including gantry speed, couch speed, MLC speed, and beam output, were estimated. The dosimetric accuracies of planned and measured values were also assessed using ArcCHECK. Results: The MAEs ±2 standard deviations as revealed by the Winston–Lutz test for all trajectories were 0.3 ± 0.3 mm in two dimensions. The MAEs of the gantry, couch, and MLC positions calculated from all trajectory logs were within 0.04°, 0.08°, and 0.02 mm, respectively. Deviations in the couch angle (r = 0.98, p < 0.05) and MLC position (r = 0.86, p < 0.05) increased significantly with speed. The MAE of the beam output error was less than 0.01 MU. The mean gamma passing rate ± 2 SD (range) of the 3%/3 mm, 3%/1 mm, and 5%/1 mm was 98.1 ± 1.9% (95.7–99.6%), 87.2 ± 2.8% (80.2–96.7%), and 96.3 ± 2.8% (93.9–99.6%), respectively. Conclusions: CCR-VMAT delivered via the TrueBeam Developer Mode was associated with high-level geometric and mechanical accuracy, thus affording to high dosimetric accuracy. The CCR-VMAT performance was stable regardless of the trajectory chosen

Feasibility evaluation of a new irradiation technique: three-dimensional unicursal irradiation with the Vero4DRT (MHI-TM2000).

The Vero4DRT (MHI-TM2000) is a newly designed unique image-guided radiotherapy system consisting of an O-ring gantry. This system can realize a new irradiation technique in which both the gantry head and O-ring continuously and simultaneously rotate around the inner circumference of the O-ring and the vertical axis of the O-ring, respectively, during irradiation. This technique creates three-dimensional (3D) rotational dynamic conformal arc irradiation, which we term '3D unicursal irradiation'. The aim of this study was to present the concept and to estimate feasibility and potential advantages of the new irradiation technique. Collision maps were developed for the technique and a 3D unicursal plan was experimentally created in reference to the collision map for a pancreatic cancer case. Thereafter, dosimetric comparisons among the 3D unicursal, a two-dimensionally rotational dynamic conformal arc irradiation (2D-DCART), and an intensity-modulated radiation therapy (IMRT) plan were conducted. Dose volume data of the 3D unicursal plan were comparable or improved compared to those of the 2D-DCART and IMRT plans with respect to both the target and the organs at risk. The expected monitor unit (MU) number for the 3D unicursal plan was only 7% higher and 22.1% lower than the MUs for the 2D-DCART plan and IMRT plan, respectively. It is expected that the 3D unicursal irradiation technique has potential advantages in both treatment time and dose distribution, which should be validated under various conditions with a future version of the Vero4DRT fully implemented the function

Investigation of 4D dose in volumetric modulated arc therapy-based stereotactic body radiation therapy: does fractional dose or number of arcs matter?

The aim of this study was to assess the impact of fractional dose and the number of arcs on interplay effects when volumetric modulated arc therapy (VMAT) is used to treat lung tumors with large respiratory motions. A three (fractional dose of 4, 7.5 or 12.5 Gy) by two (number of arcs, one or two) VMAT plan was created for 10 lung cancer cases. The median 3D tumor motion was 17.9 mm (range: 8.2–27.2 mm). Ten phase-specific subplans were generated by calculating the dose on each respiratory phase computed tomography (CT) scan using temporally assigned VMAT arcs. We performed temporal assignment of VMAT arcs using respiratory information obtained from infrared markers placed on the abdomens of the patients during CT simulations. Each phase-specific dose distribution was deformed onto exhale phase CT scans using contour-based deformable image registration, and a 4D plan was created by dose accumulation. The gross tumor volume dose of each 4D plan (4D GTV dose) was compared with the internal target volume dose of the original plan (3D ITV dose). The near-minimum 4D GTV dose (D99%) was higher than the near-minimum 3D internal target volume (ITV) dose, whereas the near-maximum 4D GTV dose (D1%) was lower than the near-maximum 3D ITV dose. However, the difference was negligible, and thus the 4D GTV dose corresponded well with the 3D ITV dose, regardless of the fractional dose and number of arcs. Therefore, interplay effects were negligible in VMAT-based stereotactic body radiation therapy for lung tumors with large respiratory motions