肝癌千伏级CBCT引导放疗配准方法比较

目的 比较肝癌千伏级CBCT图像与计划CT图像配准的不同方法。方法 离线下由4位观测者在加速器控制室内分别完成121幅CBCT图像与计划CT图像的配准,配准方法包括手动配准、常规软组织配准、常规骨性配准、肝脏配准、椎体配准,其中后4种方法均使用配准软件自动配准。对配准软件的稳定性进行检测,然后比较4位观测者使用同种自动配准方法结果,以此评估使用该方法可重复性。以4位观测者手动配准肝脏外轮廓结果平均值为基准,与其他配准方法结果比较。使用McNemar检验差异。结果 若保持配准条件不变,自动配准结果完全一致。常规软组织、骨性配准方法可重复性较好,椎体配准次之,肝脏配准最差。但肝脏配准结果与手动配准结果最接近,差值在3 mm内百分率分别为左右方向84.3%、上下方向 77.7%、前后方向92.6%。结论 使用配准软件自动肝脏配准可用于肝癌图像引导,但每次图像引导时均需有经验医师、技师共同参与,自动配准完成之后应根据肝脏外轮廓手动校正。     

Adaptive radiotherapy for prostate cancer using kilovoltage cone-beam computed tomography: first clinical results

PURPOSE: To evaluate the first clinical results of an off-line adaptive radiotherapy (ART) protocol for prostate cancer using kilovoltage cone-beam computed tomography (CBCT) in combination with a diet and mild laxatives. METHODS AND MATERIALS: Twenty-three patients began treatment with a planning target volume (PTV) margin of 10 mm. The CBCT scans acquired during the first six fractions were used to generate an average prostate clinical target volume (AV-CTV), and average rectum (AV-Rect). Using these structures, a new treatment plan was generated with a 7-mm PTV margin. Weekly CBCT scans were used to monitor the CTV coverage. A diet and mild laxatives were introduced to improve image quality and reduce prostate motion. RESULTS: Twenty patients were treated with conform ART protocol. For these patients, 91% of the CBCT scans could be used to calculate the AV-CTV and AV-Rect. In 96% of the follow-up CBCT scans, the CTV was located within the average PTV. In the remaining 4%, the prostate extended the PTV by a maximum of 1 mm. Systematic and random errors for organ motion were reduced by a factor of two compared with historical data without diet and laxatives. An average PTV reduction of 29% was achieved. The volume of the AV-Rect that received >65 Gy was reduced by 19%. The mean dose to the anal wall was reduced on average by 4.8 Gy. CONCLUSIONS: We safely reduced the high-dose region by 29%. The reduction in irradiated volume led to a significant reduction in the dose to the rectum. The diet and laxatives improved the image quality and tended to reduce prostate motion.     

Image-guided radiotherapy using megavoltage cone-beam computed tomography for treatment of paraspinous tumors in the presence of orthopedic hardware

PURPOSE: This report describes a new image-guided radiotherapy (IGRT) technique using megavoltage cone-beam computed tomography (MV-CBCT) to treat paraspinous tumors in the presence of orthopedic hardware. METHODS AND MATERIALS: A patient with a resected paraspinous high-grade sarcoma was treated to 59.4 Gy with an IMRT plan. Daily MV-CBCT imaging was used to ensure accurate positioning. The displacement between MV-CBCT and planning CT images were determined daily and applied remotely to the treatment couch. The dose-volume histograms of the original and a hypothetical IMRT plan (shifted by the average daily setup errors) were compared to estimate the impact on dosimetry. RESULTS: The mean setup corrections in the lateral, longitudinal, and vertical directions were 3.6 mm (95% CI, 2.6-4.6 mm), 4.1 mm (95% CI, 3.2-5.0 mm), and 1.0 mm (95% CI, 0.6-1.3 mm), respectively. Without corrected positioning, the dose to 0.1 cc of the spinal cord increased by 9.4 Gy, and the doses to 95% of clinical target volumes 1 and 2 were reduced by 4 Gy and 4.8 Gy, respectively. CONCLUSIONS: Megavoltage-CBCT provides a new alternative image-guided radiotherapy approach for treatment of paraspinous tumors in the presence of orthopedic hardware by providing 3D anatomic information in the treatment position, with clear imaging of metallic objects and without compromising soft-tissue information.     

Examining margin reduction and its impact on dose distribution for prostate cancer patients undergoing daily cone-beam computed tomography

PURPOSE: To examine the dosimetric impact of margin reduction and quantify residual error after three-dimensional (3D) image registration using daily cone-beam computed tomography (CBCT) for prostate cancer patients. METHODS AND MATERIALS: One hundred forty CBCTs from 5 prostate cancer patients were examined. Two intensity-modulated radiotherapy plans were generated on CT simulation on the basis of two planning target volume (PTV) margins: 10 mm all around the prostate and seminal vesicles except 6 mm posteriorly (10/6) and 5 mm all around except 3 mm posteriorly (5/3). Daily CBCT using the Varian On-Board Imaging System was acquired. The 10/6 and 5/3 simulation plans were overlaid onto each CBCT, and each CBCT plan was calculated. To examine residual error, PlanCT/CBCT intensity-based 3D image registration was performed for prostate localization using center of mass and maximal border displacement. RESULTS: Prostate coverage was within 2% between the 10/6 and 5/3 plans. Seminal vesicle coverage was reduced with the 5/3 plan compared with the 10/6 plan, with coverage difference within 7%. The 5/3 plan allowed 30-50% sparing of bladder and rectal high-dose regions. For residual error quantification, center of mass data show that 99%, 93%, and 96% of observations fall within 3 mm in the left-right, anterior-posterior, and superior-inferior directions, respectively. Maximal border displacement observations range from 79% to 99%, within 5 mm for all directions. CONCLUSION: Cone-beam CT dosimetrically validated a 10/6 margin when soft-tissue localization is not used. Intensity-based 3D image registration has the potential to improve target localization and to provide guidelines for margin definition.     

Cone-beam computed tomography for on-line image guidance of lung stereotactic radiotherapy: localization, verification, and intrafraction tumor position

PURPOSE: Cone-beam computed tomography (CBCT) in-room imaging allows accurate inter- and intrafraction target localization in stereotactic body radiotherapy of lung tumors. METHODS AND MATERIALS: Image-guided stereotactic body radiotherapy was performed in 28 patients (89 fractions) with medically inoperable Stage T1-T2 non-small-cell lung carcinoma. The targets from the CBCT and planning data set (helical or four-dimensional CT) were matched on-line to determine the couch shift required for target localization. Matching based on the bony anatomy was also performed retrospectively. Verification of target localization was done using either megavoltage portal imaging or CBCT imaging; repeat CBCT imaging was used to assess the intrafraction tumor position. RESULTS: The mean three-dimensional tumor motion for patients with upper lesions (n = 21) and mid-lobe or lower lobe lesions (n = 7) was 4.2 and 6.7 mm, respectively. The mean difference between the target and bony anatomy matching using CBCT was 6.8 mm (SD, 4.9, maximum, 30.3); the difference exceeded 13.9 mm in 10% of the treatment fractions. The mean residual error after target localization using CBCT imaging was 1.9 mm (SD, 1.1, maximum, 4.4). The mean intrafraction tumor deviation was significantly greater (5.3 mm vs. 2.2 mm) when the interval between localization and repeat CBCT imaging (n = 8) exceeded 34 min. CONCLUSION: In-room volumetric imaging, such as CBCT, is essential for target localization accuracy in lung stereotactic body radiotherapy. Imaging that relies on bony anatomy as a surrogate of the target may provide erroneous results in both localization and verification.     

千伏级CBCT图像引导椎体肿瘤放疗摆位误差分析

目的:研究千伏级CBCT图像引导椎体肿瘤放疗摆位误差的研究。方法:采用瓦里安IX直线加速器机载影像系统对37例椎体肿瘤患者调强放疗前行CBCT,系统自动重建图像并与治疗计划CT图像相匹配,获得患者X轴(左右）、Y轴（头脚）、Z轴（前后）方向摆位误差。结果:椎体肿瘤37例行114次扫描,只考虑误差大小时X轴、Y轴、Z轴方向误差分别为（2.69±2.46） mm、(5.37±4.57) mm、(4.02±3.5) mm。其中胸椎（2.02±2.07） mm、（4.80±4.59） mm、（4.00±3.92） mm,腰椎（3.35±2.65） mm、（5.83±4.54） mm、（4.03±3.08） mm。结论:腰椎患者与胸椎患者相比,摆位误差左右方向较大,在摆位中应加以注意,以减少治疗摆位误差。     

Comparison of radiotherapy treatment plans for left-sided breast cancer patients based on three- and four-dimensional computed tomography imaging

Aims

The target volume for breast radiotherapy after conservative surgery for breast cancer may be affected by breathing motion. We investigated differences between conventional and four-dimensional computed tomography-based treatment planning and whether gating could improve dose volume parameters.

Materials and methods

Ten patients with left-sided breast cancer and surgical clips at the excision site had conventional treatment planning computed tomography and four-dimensional computed tomography. Treatment plans using two tangential beams (6 MV X-rays) were optimised for target coverage and homogeneity using a field in field technique for the three-dimensional scan. This plan was applied directly to four-dimensional datasets representing individual phases of the breathing cycle and combinations thereof (average and maximum intensity projection). Optimised plans were generated for the maximum inhalation scan to study what could potentially be achieved in gated radiotherapy.

Results

Four-dimensional computed tomography with effective doses of around 10 mSv proved to be adequate for treatment planning in all patients. The average motion of the surgical clips was 3.7 mm (range 1.7–6.5 mm), which was similar to the movement of the chest wall. With a margin of 7 mm for the whole breast to planning target volume, conventional three-dimensional computed tomography-based planning was found to adequately cover the target as seen on four-dimensional computed tomography without significant differences in normal tissue sparing. Improved sparing of the heart and lung could only be achieved by reducing the posterior margin of the target volume, which may be justified if four-dimensional computed tomography is used to determine the target and its motion.

Conclusion

No significant benefit has been shown for the use of four-dimensional computed tomography-based planning if motion management is not implemented concurrently with a reduced posterior margin between clinical and planning target volumes.     

Assessment of residual error in liver position using kV cone-beam computed tomography for liver cancer high-precision radiation therapy

PURPOSE: To evaluate the residual error in liver position using breath-hold kilovoltage (kV) cone-beam computed tomography (CT) following on-line orthogonal megavoltage (MV) image-guided breath-hold liver cancer conformal radiotherapy. METHODS AND MATERIALS: Thirteen patients with liver cancer treated with 6-fraction breath-hold conformal radiotherapy were investigated. Before each fraction, orthogonal MV images were obtained during exhale breath-hold, with repositioning for offsets>3 mm, using the diaphragm for cranio-caudal (CC) alignment and vertebral bodies for medial-lateral (ML) and anterior posterior (AP) alignment. After repositioning, repeat orthogonal MV images, orthogonal kV fluoroscopic movies, and kV cone-beam CTs were obtained in exhale breath-hold. The cone-beam CT livers were registered to the planning CT liver to obtain the residual setup error in liver position. RESULTS: After repositioning, 78 orthogonal MV image pairs, 61 orthogonal kV image pairs, and 72 kV cone-beam CT scans were obtained. Population random setup errors (sigma) in liver position were 2.7 mm (CC), 2.3 mm (ML), and 3.0 mm (AP), and systematic errors (Sigma) were 1.1 mm, 1.9 mm, and 1.3 mm in the superior, medial, and posterior directions. Liver offsets>5 mm were observed in 33% of cases; offsets>10 mm and liver deformation>5 mm were observed in a minority of patients. CONCLUSIONS: Liver position after radiation therapy guided with MV orthogonal imaging was within 5 mm of planned position in the majority of patients. kV cone-beam CT image guidance should improve accuracy with reduced dose compared with orthogonal MV image guidance for liver cancer radiation therapy.     

Cone-beam CT localization of internal target volumes for stereotactic body radiotherapy of lung lesions

PURPOSE: In this study, we investigate a technique of matching internal target volumes (ITVs) in four-dimensional (4D) simulation computed tomography (CT) to the composite target volume in free-breathing on-board cone-beam (CB) CT. The technique is illustrated by using both phantom and patient cases. METHODS AND MATERIALS: A dynamic phantom with a target ball simulating respiratory motion with various amplitude and cycle times was used to verify localization accuracy. The dynamic phantom was scanned using simulation CT with a phase-based retrospective sorting technique. The ITV was then determined based on 10 sets of sorted images. The size and epicenter of the ITV identified from 4D simulation CT images and the composite target volume identified from on-board CBCT images were compared to assess localization accuracy. Similarly, for two clinical cases of patients with lung cancer, ITVs defined from 4D simulation CT images and CBCT images were compared. RESULTS: For the phantom, localization accuracy between the ITV in 4D simulation CT and the composite target volume in CBCT was within 1 mm, and ITV was within 8.7%. For patient cases, ITVs on simulation CT and CBCT were within 8.0%. CONCLUSION: This study shows that CBCT is a useful tool to localize ITV for targets affected by respiratory motion. Verification of the ITV from 4D simulation CT using on-board free-breathing CBCT is feasible for the target localization of lung tumors.     

Computed tomography and radiotherapy in the treatment of cancer

Computed tomography (CT) has shown to be of great value in the treatment of cancer with radiation therapy. It is used more and more in the estimation of tumor volume and for treatment planning, with the aid of the computerized treatment unit. At the James Graham Brown Cancer Center, Department of Radiation Oncology, CT has been used routinely for the treatment planning. From October 1, 1981 to June 30, 1982, we performed 180 CT scans for the treatment planning, 380 simple dose calculations, 237 complex treatment plans, and 42 intracavitary dosimetry using the treatment planning unit. This is a review of our experience with some illustrations. Accurate tumor dose can be delivered with reducing the complications with the use of CT and the computerized treatment unit.     

Image-guided radiotherapy via daily online cone-beam CT substantially reduces margin requirements for stereotactic lung radiotherapy

PURPOSE: To determine treatment accuracy and margins for stereotactic lung radiotherapy with and without cone-beam CT (CBCT) image guidance. METHODS AND MATERIALS: Acquired for the study were 308 CBCT of 24 patients with solitary peripheral lung tumors treated with stereotactic radiotherapy. Patients were immobilized in a stereotactic body frame (SBF) or alpha-cradle and treated with image guidance using daily CBCT. Four (T1) or five (T2/metastatic) 12-Gy fractions were prescribed to the planning target volume (PTV) edge. The PTV margin was >or=5 mm depending on a pretreatment estimate of tumor excursion. Initial daily setup was according to SBF coordinates or tattoos for alpha-cradle cases. A CBCT was performed and registered to the planning CT using soft tissue registration of the target. The initial setup error/precorrection position, was recorded for the superior-inferior, anterior-posterior, and medial-lateral directions. The couch was adjusted to correct the tumor positional error. A second CBCT verified tumor position after correction. Patients were treated in the corrected position after the residual errors were 相似文献   

Quantification of mediastinal and hilar lymph node movement using four-dimensional computed tomography scan: implications for radiation treatment planning

PURPOSE: To quantitatively describe mediastinal and hilar lymph node movement in patients with lymph node-positive lung cancer. METHODS AND MATERIALS: Twenty-four patients with lung cancer who underwent four-dimensional computed tomography scanning at Massachusetts General Hospital were included in the study. The maximum extent of superior motion of the superior border was measured, as well as the maximum inferior movement of the inferior border. The average of these two values is defined as the peak-to-peak movement. This process was repeated for mediolateral (ML) and anterior-posterior (AP) movement. Linear regression was used to determine lymph node characteristics associated with peak-to-peak movement. Various uniform expansions were investigated to determine the expansion margins necessary to ensure complete internal target volume (ITV) coverage. RESULTS: The mean peak-to-peak displacements of paratracheal lymph nodes were 4 mm (craniocaudal [CC]), 2 mm (ML), and 2 mm (AP). For subcarinal lymph nodes, the mean peak-to-peak movements were 6 mm (CC), 4 mm (ML), and 2 mm (AP). The mean peak-to-peak displacements of hilar lymph nodes were 7 mm (CC), 1 mm (ML), and 4 mm (AP). On multivariate analysis, lymph node station and lymph node size were significantly related to peak-to-peak movement. Expansions of 8 mm for paratracheal nodes and 13 mm for subcarinal and hilar nodes would have been necessary to cover the ITV of 95% of these nodal masses. CONCLUSIONS: Subcarinal and hilar lymph nodes may move substantially throughout the respiratory cycle. In the absence of patient-specific information on nodal motion, expansions of at least 8 mm, 13 mm, and 13 mm should be considered to cover the ITV of paratracheal, subcarinal, and hilar lymph nodes, respectively.     

应用4D-CT技术确定肝癌内靶体积及相关剂量学研究

背景与目的:由于肝脏肿瘤的位移受呼吸运动的影响显著,三维适形放射治疗(three-dimensionaI confomal radiotherapy,3D CRT)难以准确定位靶区.本研究应用4D-CT技术确定个体化肝癌内靶体积(internal target volume,ITV),比较3D计划与4D计划的计划靶体积(planning target volume,PTV)及相关剂量学差异,并评价4D-CT的优势.方法:选择7例原发性肝癌患者,行4D-CT门控扫描,在10个相位的CT图像中分别勾画大体肿瘤体积(gross tumor volume,GTV)和临床靶体积(clinical target volume,CTV).在20%呼吸时相CT图像中利用三维治疗计划系统根据PTV-3D、PTV-4D为每例患者设计两套放疗计划:3D计划与4D计划.PTV-3D由CTV外扩常规的安全边界得到;PTV-4D由10个时相的CTV融合形成的ITV-4D外扩摆位边界(SM)得到.两套计划的处方剂量、射野方式均相同.比较两套计划中靶区体积、靶区与危及器官的剂量学、正常组织并发症概率的差异.结果:PTV-3D、PTV-4D的体积分别为(417.60±197.70)cm3、(331.90±183.10)cm3,后者体积减少20.50%(12.60%～34.40%);两者靶区覆盖率与剂量分布均匀性无显著性差异;4D计划中危及器官(肝、肾、胃、小肠)的受照剂量均较3D计划降低,以肝最为显著.肝V30、V40分别由38.77%、27.32%降至33.59%、22.62%;正常肝平均剂量由24.13 Gy下降为21.50 Gy;肝并发症概率由21.57%下降为15.86%;在不增加正常组织并发症的前提下,4D计划的处方剂量可由(50.57±1.51)Gy提升至(54.86±2.79)Gy,平均提高9.72%(4.00%～16.00%).结论:3D计划存在遗漏靶区或过度扩大靶区的缺陷.应用4D-CT技术可在3D CRT的基础上准确定位肝癌靶区,进一步减少正常组织的受照剂量,并提升靶区剂量.     

Impact of IMRT and leaf width on stereotactic body radiotherapy of liver and lung lesions

PURPOSE: The present study explored the impact of intensity-modulated radiotherapy (IMRT) on stereotactic body RT (SBRT) of liver and lung lesions. Additionally, because target dose conformity can be affected by the leaf width of a multileaf collimator (MLC), especially for small targets and stereotactic applications, the use of a micro-MLC on "uniform intensity" conformal and intensity-modulated SBRT was evaluated. METHODS AND MATERIALS: The present study included 10 patients treated previously with SBRT in our institution (seven lung and three liver lesions). All patients were treated with 3 x 12 Gy prescribed to the 65% isodose level. The actual MLC-based conformal treatment plan served as the standard for additional comparison. In total, seven alternative treatment plans were made for each patient: a standard (actual) plan and an IMRT plan, both calculated with Helax TMS (Nucletron) using a pencil beam model; and a recalculated standard and a recalculated IMRT plan on Helax TMS using a point dose kernel approach. These four treatment plans were based on a standard MLC with 1-cm leaf width. Additionally, the following micro-MLC (central leaf width 3 mm)-based treatment plans were calculated with the BrainSCAN (BrainLAB) system: standard, IMRT, and dynamic arc treatments. For each treatment plan, various target parameters (conformity, coverage, mean, maximal, and minimal target dose, equivalent uniform doses, and dose-volume histogram), as well as organs at risk parameters (3 Gy and 6 Gy volume, mean dose, dose-volume histogram) were evaluated. Finally, treatment efficiency was estimated from monitor units and the number of segments for IMRT solutions. RESULTS: For both treatment planning systems, no significant difference could be observed in terms of target conformity between the standard and IMRT dose distributions. All dose distributions obtained with the micro-MLC showed significantly better conformity values compared with the standard and IMRT plans using a regular MLC. Dynamic arc plans were characterized by the steepest dose gradient and thus the smallest V(6 Gy) values, which were on average 7% smaller than the standard plans and 20% lower than the IMRT plans. Although the Helax TMS IMRT plans show about 18% more monitor units than the standard plan, BrainSCAN IMRT plans require approximately twice the number of monitor units relative to the standard plan. All treatment plans optimized with a pencil beam model but recalculated with a superposition method showed significant qualitative, as well as quantitative, differences, especially with respect to conformity and the dose to organs at risk. CONCLUSION: Standard conformal treatment techniques for SBRT could not be improved with inversely planned IMRT approaches. Dose calculation algorithms applied in optimization modules for IMRT applications in the thoracic region need to be based on the most accurate dose calculation algorithms, especially when using higher energy photon beams.     

Current status of stereotactic body radiotherapy for lung cancer

Stereotactic radiotherapy (SRT) for extracranial tumors has been recently performed to treat lung and liver cancers, and has subsequently been named stereotactic body radiotherapy (SBRT). The advantages of hypofractionated radiotherapy for treating lung tumors are a shortened treatment course that requires fewer trips to the clinic than a conventional program, and the adoption of a smaller irradiated volume allowed by greater setup precision. This treatment is possible because the lung and liver are considered parallel organs at risk. The preliminary clinical results, mostly reported on lung cancer, have been very promising, including a local control rate of more than 90%, and a relatively low complication rate. The final results of a few clinical trials are awaited. SBRT may be useful for the treatment of stage I lung tumors.     

Comparative study of respiratory motion correction techniques in cone-beam computed tomography

Background and purpose

To validate the clinical usefulness of motion-compensated (MC) cone-beam (CB) computed tomography (CT) for image-guided radiotherapy (IGRT) in comparison to four-dimensional (4D) CBCT and three-dimensional (3D) CBCT.

Material and methods

Forty-eight stereotactic body radiation therapy (SBRT) patients were selected. Each patient had 5-12 long CB acquisitions (4 min) and 1-7 short CB acquisitions (1 min), with a total of 349 and 150 acquisitions, respectively. 3D, 4D and MC CBCT images of every acquisition were reconstructed. Image quality, tumor positioning accuracy and tumor motion amplitude were quantified.

Results

The mean image quality of long short acquisitions, measured using the correlation ratio with the planning CT, was 74%/70%, 67%/47% and 79%/74% for 3D, 4D and MC CBCT, respectively; both 4D and MC CBCT were corrected for respiratory motion artifacts but 4D CBCTs suffered from streak artifacts. Tumor positioning with MC CBCT was significantly closer to 4D CBCT than 3D CBCT (p < 0.0001). Detailed patient analysis showed that motion correction was not required for tumors with less than 1 cm motion amplitude.

Conclusions

4D and MC CBCT both allow accurate tumor position analysis under respiratory motion but 4D CBCT requires longer acquisition time than MC CBCT for adequate image quality. MC CBCT can therefore advantageously replace 4D CBCT in clinical protocols for patients with large motion to improve image quality and reduce acquisition time.