放射防護管理是保證放射診療質量和安全的重要手段。通過健全組織架構，規范制度流程，強化人員培訓，加強檔案建設，構建多部門聯動工作機制，完善監督考核等多種方式，全面規范放射防護管理，有效提升了醫院醫療服務品質，保障了醫療安全，其思路與方法可供大型醫院醫療管理參考借鑒。
【摘要】 目的 研究使用Bowtie濾線器（F1）后，保證加速器CBCT患者掃描圖像質量前提下，如何合理設置掃描條件，盡量降低輻射劑量。 方法 使用Piranha輻射測量儀測量CBCT在使用F1與未使用F1時射線的半價層。設定不同的掃描模式，使用直徑30 cm的有機玻璃模體測量掃描劑量，并使用XVI附帶的Catphan503模體測量客觀圖像質量。在此基礎上，研究掃描劑量以及圖像質量與掃描條件的關系，提出了適合臨床患者的胸部與腹部不同的掃描條件。 結果 使用F1后射束的半價層增加了0.77～0.92 mmAl，掃描劑量明顯減少，中心點減少了22%~29%，邊緣點減少了41%~45%，皮膚劑量減少顯著。圖像質量隨著掃描劑量的增大而提高。空間分辨力受FOV影響較大，但一般能識別1～2 mm的物體，完全能夠滿足分辨細小骨結構與標記點的臨床要求。圖像偽影在使用L20時的大mAs下明顯。胸部低劑量的CBCT圖像如100 kV，M20，0.5 mAs的掃描條件亦可滿足臨床要求。腹部則需要使用較大劑量的掃描模式，CBCT圖像才達到進行配準的要求。 結論 F1的使用在改善圖像質量的前提下降低了掃描劑量，使用新的掃描序列能平衡二者的關系。【Abstract】 Objective To explore the influence of bowtie filtration on absorb dose and half-value layer inaluminum (Al) of cone-beam CT, estimate the image dose under different scan protocol, and establish the relationship between the image quality and the scan protocol after using F1. Methods Piranha was used to measure the HVL. Dose measurements were performed with an 0.6 cc Farmer type ionization chamber with a 30 cm-diam cylindrical shaped water phantoms in 100 and 120 kV with a series of mAs and FOV. CNR, noise and uniformity were measured on the Catphan503 images. Results HVL increased 0.77-0.92 mmAl where XVI generally had more penetrating beams at the similar kV settings. Scanning dose significantly reduced, the center point decreased 22%-29%, the edge with a decrease of 41%-45% which meant a very significant reduction in skin dose. Image quality improved with mAs increase. The spatial resolution mainly changed with FOV. But generally can identify 1-2 mm-diam objects, fully meet the clinical requirements of identify small bone structure and marker. Through this clinical investigation, low-dose CBCT images in chest, such as 100 kV, M20, and 0.5 mAs scanning protocol appeared to be an optimal settings. Abdomen image needed a higher dose to reach the requirements of registration. Conclusion Using F1 under the premise of improving the image quality then reducing the scanning dose and using a new scanning sequence can balance the image quality and scanning dose.
Cone-beam computed tomography (CBCT) is widely used in dentistry, surgery, radiotherapy and other medical fields. However, repeated CBCT scans expose patients to additional radiation doses, increasing the risk of secondary malignant tumors. Low-dose CBCT image reconstruction technology, which employs advanced algorithms to reduce radiation dose while enhancing image quality, has emerged as a focal point of recent research. This review systematically examined deep learning-based methods for low-dose CBCT reconstruction. It compared different network architectures in terms of noise reduction, artifact removal, detail preservation, and computational efficiency, covering three approaches: image-domain, projection-domain, and dual-domain techniques. The review also explored how emerging technologies like multimodal fusion and self-supervised learning could enhance these methods. By summarizing the strengths and weaknesses of current approaches, this work provides insights to optimize low-dose CBCT algorithms and support their clinical adoption.
ObjectiveCompare the two-degrade collimator (MLC) angle selection's impact on plan quality and operational efficiency for volumetric intensity-modulated radiotherapy (VMAT) in the treatment planning system, and to explore the scheme for treatment plan optimization. MethodsTwenty patients with nasopharyngeal carcinoma underwent the treatment between March and December 2013 were randomly selected and planned for SIBVMAT treatment with different parameters set in the range of 0-60°with 15°interval for collimator angles. Planned dose distribution to the target volumes, organs at risk, and monitor units were compared. ResultsAs the MLC angle increased, target conformal index and homogeneity index had a trend to became deteriorated. The optimal plans were 0°and 15°, while 45°and 60°plans gave poor protection for the organ at risk compare to other angle plans and the monitor units were significantly increased. ConclusionChange the MLC angle had visible impact on treatment plans,there was a trend to deteriorate with the MLC angle increased, but small changes in MLC angle range can theoretically reduce the influence from leakage radiation on the human body.
ObjectiveTo compare the dosimetric differences among the double-arc volumetric-modulated arc therapy (VMAT), 7 field intensity-modulated radiotherapy (IMRT) and 3-dimensional conformal radiotherapy (3D-CRT) techniques in treatment planning for cervical cancer as adjuvant radiotherapy. MethodFifteen patients who underwent adjuvant chemotherapy for cervical cancer between March 1st and September 30th, 2013 were chosen to be our study subjects through random sampling. Under Pinnacle 9.2 planning system, the same CT image was designed through three different techniques:VMAT, IMRT and 3D-CRT. We then compared target zone fitness index, evenness index, D98%, D2%, D50% among those different techniques. Monitor unit (MU) and treatment time were also analyzed. ResultsThree techniques showed similar target dose coverage. The IMRT and VMAT plans achieved better target dose conformity, which reduced the V20 of the pelvic, the V50 of the rectum and bladder, as well as the V40/50 of the small intestine (P<0.05). The VMAT technique showed few dosimetric advantages over the IMRT technique. VMAT technique had the advantages of less MU (P>0.05) and shorter overall treatment time (P<0.01) compared with IMRT technique. ConclusionsThe IMRT and VMAT plans achieve similar dose distribution to the target, and are superior to the 3D-CRT plans, in adjuvant radiotherapy for cervical cancer. VMAT technique has the advantages of less MU and shorter overall treatment time.
While radiation treatment to patients with tumors in thorax and abdomen is being performed, further improvement of radiation accuracy is restricted by the tumor intra-fractional motion due to respiration. Real-time tumor tracking radiation is an optimal solution to tumor intra-fractional motion. A review of the progress of real-time dynamic multi-leaf collimator (DMLC) tracking is provided in the present review, including DMLC tracking method, time lag of DMLC tracking system, and dosimetric verification.
ObjectiveTo compare the dosimetric differences among flattening filter free intensity modulated radiotherapy (3FIMRT), flattening filter free volumetric modulated arc therapy (3FVMAT), filter free intensity modulated radiotherapy (IMRT), and filter free volumetric modulated arc therapy (VMAT) for hyperthyroidism exophthalmus patients.MethodsComputed tomography (CT) scans of 29 patients, who were diagnosed with hyperthyroidism exophthalmus and treated with radiation therapy between September 2016 and September 2017, were selected for study. Four treatment plans with the same dose prescription and objective constrains were designed for each patient based on their images, consisting of IMRT, VMAT, 3FIMRT, and 3FVMAT. The target dosimetric distribution, normal tissue radiation dose, monitor units, and treatment time of each plan were evaluated.ResultsFour types of plans were all able to satisfy the clinical treatment requirements, and there were no significant differences in maximum dose, mean dose (Dmean), homogeneity index of the targets (P>0.05). For the parameters minimum dose, V50%, conformity index (CI), gradient index of the targets, statistically significant differences were observed among the four kinds of technologies (F=10.920, 35.860, 11.320, 17.790; P<0.05). The CI of IMRT and 3FIMRT were superior to those of VMAT and 3FVMAT, but there was no significant difference between IMRT and 3FIMRT. In terms of Lens Dmean and Brain Dmean, statistically significant differences were observed among the four kinds of technologies (F=5.054, 83.780; P<0.05). For Lens Dmean and Brain Dmean, 3FVMAT achieved better sparing effects when compared with the other three plans. The total monitor units and treatment time did not significantly differ between 3FVMAT and VMAT. The mean monitor units of 3FVMAT were 65.07% and 70.22% less than that of IMRT and 3FIMRT respectively. The mean treatment time of 3FVMAT were 48.1% and 35.24% less than that of IMRT and 3FIMRT respectively.Conclusion3FVMAT can bring more dosimetric advantages for hyperthyroidism exophthalmus radiation therapy when compared with IMRT, 3FIMRT, and VMAT.
【摘要】 目的 調強放射治療（IMRT）能較好的保護危及器官并給予腫瘤足夠的致死劑量，基于多葉準直器（MLC）分步照射的IMRT技術對復雜病例需要更多子野。研究對直腸癌術后放射治療使用不同子野數目的IMRT計劃進行比對，選擇合理的子野數。 方法 選取2010年4-8月入院的直腸癌術后患者10例，保持射野入射角度及優化目標參數相同，僅改變MLC子野數目，設計不同IMRT對每一患者治療計劃的靶區適形指數（CI）、均勻性指數、最大劑量、最小劑量、平均劑量，危及器官關注體積的受照劑量，機器跳數及治療時間進行分析。 結果 所有治療計劃中靶區及危及器官的劑量學評估指標無統計學意義（Pgt;0.05），只有亞臨床計劃靶區（PTV）CI在15個子野的方案中（0.74±0.06）明顯差于25個子野方案（0.82±0.03）、40個子野方案（0.81±0.06）及60個子野方案（0.84±0.03），有統計學意義（Plt;0.05）；治療機器跳數（MU）隨子野數目增多明顯增大，15、20、40及60個子野方案所需MU分別為（458±56）、（559±62）、（614±74）、（622±82），有統計學意義（Plt;0.05），但40個子野方案與60個子野方案間無統計學意義。治療時間明顯隨子野數增加而增大。 結論 直腸癌術后IMRT計劃使用25個子野能滿足臨床劑量要求，同時能有效降低治療時間，可作為臨床應用參考值。【Abstract】 Objective The intensity modulated radiotherapy (IMRT) can deliver tumor enough doses and protect risk organs as much as possible at the same time. The MLC-based step and shoot IMRT(sIMRT) plan needs much more segment member to meet clinical aims. In this study, several sIMRT plans using different segment number for postoperative rectal cancer were compared to find out the most reasonable segment number setting. Methods Ten patients with rectal carcinoma underwent postoperative adjuvant radiotherapy for rectal cancer from April to August 2010 were selected. For each patient, the angle of field, the prescription expected and the physical parameters optimized were kept the same, while only the number of segments was changed in sIMRT plans. The dose volume histogram-based parameters [conformity index (CI) and homogeneous index (HI)] and other parameters concerned were compared and analyzed. Results The indexes of dosimetry associated with the targets and risk organs showed no significant statistical difference among the 4 sIMRT plans with different segment numbers. The index CI of PTV in the sIMRT plan with 15 segments (CI 0.74±0.06) was less than that in the sIMRT plan with 25 segments (CI 0.82±0.03), the sIMRT plan with 40 segments plan (CI 0.81±0.06), and the sIMRT plan with 60 segments (CI 0.84±0.03) (Plt;0.05). There were significant differences in MU among the sIMRT plans with 15 segments (average MU: 458±56) , with 25 segments (average MU: 559±62 ), and with 40 segments (average MU: 614±74)or with the 60 segments (average MU: 622±82 (Plt;0.05). The more segments meant more MU and more irradiation time. Conclusion The sIMRT plan for patients of rectal cancer to receive postoperative adjuvant radiotherapy may require at least 25 segments to balance the accepted dose results and efficient delivering.