Lợi ích xạ trị ung thư vú trái phối hợp hít sâu nín thở và hệ thống quản lý bề mặt quang học của máy Truebeam tại Bệnh viện Ung bướu Thành phố Hồ Chí Minh

TÓM TẮT Đối với ung thư vú (UTV) xạ trị là điều trị bổ túc cần thiết giúp giảm tái phát tại chỗ tại vùng, gia tăng sống còn. Tuy nhiên, xạ trị có tác dụng phụ lên tim mạch nhất là với UTV trái. Nhiều nghiên cứu đã chứng minh biến chứng và tử vong do tim mạch tăng tỉ lệ thuận với liều trung bình lên tim. Các kỹ thuật xạ trị mới trong xạ trị ung thư vú trái giúp tối ưu hóa liều vào thể tích xạ và bảo vệ tốt hơn cơ quan lành, càng đòi hỏi độ chính xác cao khi đặt bệnh. Các sai số do thiết bị hoặc đặt bệnh sẽ dẫn đến nguy cơ quá liều dung nạp hoặc thiếu liều và có nguy cơ tái phát. Vì vậy, xạ trị đòi hỏi sự chính xác cao trong suốt quá trình từ mô phỏng đến lập kế hoạch và tiến hành xạ trị. Xạ trị ung thư vú trái phối hợp hít sâu nín thở (DIBH - Deep Inspiration Breath - hold) và hệ thống quản lý bề mặt quang học (OSMS - Optical Surface Management System) làm cho tim di chuyển ra xa hơn khỏi vú, thành ngực trong quá trình xạ trị, giúp giảm liều tim một cách rõ rệt, vẫn đảm bảo được liều xạ lên thể tích đích. Ưu điểm của OSMS ngoài áp dụng cho đặt bệnh nhanh không cần xăm dấu trên da còn giám sát thời gian thực trong toàn bộ quá trình điều trị. Khi nhịp thở của bệnh nhân vượt quá một ngưỡng nhất định (0,3cm) chùm tia bức xạ sẽ bị tắt để ngăn ngừa độc tính. Do đó, hiểu và nắm rõ lợi ích quy trình đặt bệnh giúp đạt mục tiêu điều trị đồng thời giảm thời gian đặt bệnh để người bệnh có tâm lý thoải mái hơn, giảm áp lực về số lượng bệnh, nhất là đối với các trung tâm xạ trị lớn. ABSTRACT BENEFITS OF LEFT BREAST CANCER RADIATION COMBINATION OF DEEP INSPIRATION BREATH - HOLD AND OPTICAL SURFACE MANAGEMENT SYSTEM OF TRUEBEAM MACHINE AT CANCER HOSPITAL HO CHI MINH CITY Background: For breast cancer, radiation therapy is an essential adjuvant treatment to help reduce local recurrence and increase survival. However, radiation therapy has adverse effects on the cardiovascular systemespecially for left breast cancer. Several studies have demonstrated that cardiovascular morbidity and mortality increase in proportion to the mean cardiac dose. New radiotherapy techniques in radiation therapy for left breast cancer help optimize dose to radiation volume and better protect healthy organs, which requires high accuracy when patient set - up. Errors due to equipment or patient set - up will lead to the risk of overdosage or underdosage and risk of relapse. Therefore, radiation therapy requires high precision throughout the process from simulation to planning and conducting radiation therapy. Radiation therapy for left breast cancer combined with Deep Inspiration Breath - hold (DIBH) and Optical Surface Management System (OSMS)causes the heart to move further away from the breast and chest wall during radiation therapy, helping to reduce the cardiac dose significantly, still ensuring the radiation dose to the target volume. The advantage of OSMS is that in addition to being applied for fastpatient set - up, without tattooing on the skin, it also provides real - time monitoring during the entire treatment process. When the patient’s breathing rate exceeds a certain threshold (0,3cm) the radiation beam is turned off to prevent toxicity. Therefore, understanding and understanding the benefits of patient set - up helps to achieve treatment goals, while reducing patient set - up time for more comfort, reducing pressure on the number of patients, especially for patients large radiotherapy center. Keyword: Radiation therapy for left breast cancer, Deep Inspiration Breath - hold, Optical Surface Management System, cardiovascular risk.

Parametric Mid-Spatial Frequency Surface Error Synthesis

Standard mid-spatial frequency tooling mark errors were parameterized into a series of characteristic features and systematically investigated. Diffraction encircled and ensquared energy radii at the 90% levels from an unpowered optical surface were determined as a function of the root-mean-square surface irregularity, characteristic tooling mark parameters, fold mirror rotation angle, and incident beam f-number. Tooling mark frequencies on the order of 20 cycles per aperture or less were considered. This subset encompasses small footprints on single-point diamond turned optics or large footprints on sub-aperture tool polished optics. Of the characteristic features, off-axis fabrication distance held the highest impact to encircled and ensquared energy radii. The transverse oscillation of a tooling path was found to be the second highest contributor. Both impacts increased with radial tooling mark frequency.

Research and Experimental Verification on Topology-Optimization Design Method of Space Mirror Based on Additive-Manufacturing Technology

As one of the most-critical components in space optical cameras, the performance of space mirrors directly affects the imaging quality of space optical cameras, and the lightweight form of mirror blanks is a key factor affecting the structural quality and the surface-shape accuracy of mirrors. For the design requirements of lightweight and high surface-shape accuracy with space mirrors, this study proposes a design and manufacturing method that integrates topology-optimization with additive-manufacturing technology. This article firstly introduced the basic process and key technologies of space-mirror design and analyzed the superiority of combining a topology-optimized configuration design and additive-manufacturing technology; secondly, the topology-optimized design method of a back-open-structure mirror was used to complete the scheme design of a Φ260 mm aperture mirror; finally, the laser selective-melting manufacturing technology was used to complete the Φ260 mm aperture mirror blank. The mirror and its support structure were assembled and tested in a modal mode; the resonant frequencies of the mirror assembly were all over 600 Hz; and the deviation from the analytical results was within 2%. The optical surface of the mirror was turned by the single-point diamond-turning (SPDT) technique. The accuracy of the optical surface was checked by a Zygo interferometer. The RMS accuracy of the mirror surface was 0.041λ (λ is the wavelength; λ = 632 nm). In the test of the influence of gravity on the surface-shape accuracy, the mirror was turned over, which was equivalent to twice the gravity, and the RMS of the mirror surface-shape accuracy was 0.043λ, which met the requirement. The verification results show that the mirror designed and fabricated by the additive-manufacturing-based mirror-topology-optimization method can be prepared by the existing process, and the machinability and mechanical properties can meet the requirements, which provides an effective development method for improving the structural design and optimizing the manufacturing of space reflectors.

A comparison of traceable spatial angle autocollimator calibrations performed by PTB and VTT MIKES

Autocollimators are versatile devices for angle metrology used in a wide range of applications in engineering and manufacturing. A modern electronic autocollimator generally features two measuring axes and can thus fully determine the surface normal of an optical surface relative to it in space. Until recently, however, the calibration capabilities of the national metrology institutes were limited to plane angles. Although it was possible to calibrate both measuring axes independently of each other, it was not feasible to determine their crosstalk if angular deflections were present in both axes simultaneously. To expand autocollimator calibrations from plane angles to spatial angles, PTB and VTT MIKES have created dedicated calibration devices which are based on different measurement principles and accomplish the task of measurand traceability in different ways. Comparing calibrations of a transfer standard makes it possible to detect systematic measurement errors of the two devices and to evaluate the validity of their uncertainty budgets. The importance of measurand traceability via calibration for a broad spectrum of autocollimator applications is one of the motivating factors behind the creation of both devices and for this comparison of the calibration capabilities of the two national metrology institutes. The latter is the focus of the work presented here.

The Irradiation Instability of Protoplanetary Disks

The temperature in most parts of a protoplanetary disk is determined by irradiation from the central star. Numerical experiments of Watanabe and Lin suggested that such disks, also called “passive disks,” suffer from a thermal instability. Here we use analytical and numerical tools to elucidate the nature of this instability. We find that it is related to the flaring of the optical surface, the layer at which starlight is intercepted by the disk. Whenever a disk annulus is perturbed thermally and acquires a larger scale height, disk flaring becomes steeper in the inner part and flatter in the outer part. Starlight now shines more overhead for the inner part and so can penetrate into deeper layers; conversely, it is absorbed more shallowly in the outer part. These geometric changes allow the annulus to intercept more starlight, and the perturbation grows. We call this the irradiation instability. It requires only ingredients known to exist in realistic disks and operates best in parts that are both optically thick and geometrically thin (inside 30 au, but can extend to further reaches when, e.g., dust settling is considered). An unstable disk develops traveling thermal waves that reach order unity in amplitude. In thermal radiation, such a disk should appear as a series of bright rings interleaved with dark shadowed gaps, while in scattered light it resembles a moving staircase. Depending on the gas and dust responses, this instability could lead to a wide range of consequences, such as ALMA rings and gaps, dust traps, vertical circulation, vortices, and turbulence.

Heat transfer in laser passive and deformable mirrors

In work, the possibilities of using uncooled and cooled optical elements (including laser passive and deformable mirrors) with an increase in the power of laser facilities are analyzed. To increase the permissible light loads acting on the optical elements, the use of highly efficient cooling systems with minichannels (coplanar and multi-tiered), providing a high compactness of the heat exchange surface and the intensification of heat transfer, is considered. The advantages and efficiency of the proposed cooling systems for reducing the displacement of the optical surface of the mirror due to bending are estimated.