射波刀金标追踪优化的临床应用价值

目的:评价射波刀金标追踪优化方法的临床应用价值.方法:112例胸腹部肿瘤患者采用金标追踪放疗,对不符合金标追踪要求金标分别采取减小金标间距、加大金标刚体误差和采用单纯旋转误差监测模式及脊柱追踪辅助定位模式进行优化处理,比较优化前后可用金标数目≥3、等于2和1变化情况,统计采用单纯旋转误差监测模式及脊柱追踪辅助定位模式病例数目.结果:优化前后可用金标数目≥3、等于2和1病例分别由49例(43.8%)、47例(42.0%)、16例(14.3%)变化为68例(60.7%)、33例(29.5%)、11例(9.8%),差异具有统计学意义(P=0.035).其中8例(7.1%)采用单纯旋转误差监测次优模式,44例(39.2%)采用脊柱追踪辅助定位方式,患者的体位旋转误差处于可控和可接受范围,无治疗意外发生.结论:综合采用金标追踪优化措施,有利于提高金标利用率和降低射波刀治疗风险.     

射波刀立体定向放疗中金标利用率统计与弃用原因分析

目的 统计射波刀VSI治疗中金标的利用率并分析金标弃用的原因,为金标植入、放疗计划设计和操作提供参考数据。方法 2017年3—8月间植入或粘贴金标患者47人次,植入金标42人次,其中CT引导3D共面模板辅助植入金标32人次,CT引导3D非共面模板辅助植入金标1人次,不使用模板辅助单纯CT引导下植入1人次,超声引导下金标植入8人次。利用射波刀共治疗44人次肿瘤患者,有2人次肿瘤患者金标不能使用改为脊柱追踪,有3人次患者未行射波刀放疗。统计患者在射波刀治疗时使用的金标和弃用金标的数量,得到金标的利用率和弃用率。对弃用金标的原因进行分析并分类统计。结果 44人次患者植入体内和粘贴体表的134颗金标有111颗被使用,利用率为82.8%;弃用23颗,弃用率为17.2%。造成金标弃用的主要因素有刚性误差大(26.1%)、植入金标不符合要求(17.4%)、金标移位(26.1%)、其他因素(30.4%)。结论 应用CT引导3D共面或非共面模板辅助植入金标,较单纯CT引导徒手植入和超声引导下植入金标,每次金标植入只需要使用2根穿刺针,单根穿刺针植入2颗金标,减少了穿刺针数目,降低了患者穿刺造成的风险和创伤,降低金标植入手术术后并发症的发生率;多种方式植入的金标在治疗中不是全部都能被使用,会因各种原因造成弃用,因此要在金标植入等环节中考虑到此情况。     

射波刀治疗前植入与治疗中追踪的金标数量统计与评价

目的：统计射波刀治疗前植入到肝脏肿瘤患者体内的,与治疗中用于追踪的金标数量并加以评价.方法：2011年6月至2012年6月我中心利用射波刀为437例肝脏肿瘤患者实施了立体定向体部放射治疗（SBRT）,治疗前在这些患者体内共植入1584颗金标,每名患者植入的金标数量为2-9颗.对治疗中使用不同数量金标追踪的病例分别进行统计,并与植入时的病例进行对比.结果：植入2颗金标的例数为25例,占总例数的5.72％;植入3颗和3颗以上的金标的例数为412例,占总例数的94.28％.治疗中利用2颗金标追踪的例数为97例,占总例数的22.20％;利用3颗和3颗以上金标追踪的例数为340例,占总例数的77.80％.金标的移位率为1.70％,利用率为90.62％.结论：在治疗中使用2颗金标追踪的比例为22.20％,9.38％的金标在追踪没有使用,应不断提高金标植入的质量和数量,最大限度降低2颗金标追踪的比例,提高金标利用率.     

立体定向体部放疗肿瘤金标追踪数量及影响因素分析

目的 分析射波刀立体定向体部放疗(SBRT)腹部肿瘤金标追踪数量及影响因素。
方法 选取利用金标追踪的 254例腹部肿瘤患者资料,分别统计<3个和≥3个金标追踪资料,分析造成金标数量<3个的原因。
结果 254例患者中植入数量与显示数量相等的 22例;不相等的 232例,其中显示<3个的 49例(21.1%),≥3个的 183例(78.9%)。显示<3个金标追踪的49 例患者中 9 例金标移位、1例金标无法识别、23例植入质量不合格、16例刚性误差超过阈值。
结论 78.9% 患者达到了≥3个金标追踪要求,而不合格原因主要是金标植入数量不足、质量不合格和刚性误差超阈值。     

CBCT配合6D治疗床对食管癌放疗摆位偏差的纠正

目的:探讨食管癌影像引导的放射治疗(Image Guided Radiation Therapy,IGRT)6个自由度(Six-degree,6D)摆位误差的纠正和再纠正.方法:2008年6月到2009年6月我院用ELEKTA公司的具有六维调节床的Synergy IGRT治疗机治疗胸部肿瘤患者14例.所有患者在每次的治疗前(IGRT纠正前)、IGRT六维床纠正后和治疗后用KV级的锥形束CT(Cone Beam CT,CBCT)扫描获取患者的3种容积CT图像.结果:IGRT纠正前、纠正后六维误差有4项的摆位偏差经纠正后差异有统计学意义.纠正前后摆位边界的减少幅度,平移为0.67 cm～1.27cm,旋转为1.6度～2.3度.患者在IGRT治疗后的体位变化对六维误差影响仅Z轴平移和Y轴旋转变化差异有统计学意义,但患者治疗中体位的平移均小于0.04cm,体位旋转均小于0.2度.IGRT纠正后的平移误差均小于1mm,旋转误差均小于0.5度.结论:IGRT对胸部肿瘤放疗的摆位误差纠正有明显的作用,且能较大幅度减少摆位边界,缩小计划靶区而减少正常组织的受量.胸部肿瘤IGRT治疗过程虽然体位有所变动,但六维变化范围均很小不影响治疗.当IGRT纠正前的六维偏差有渐大趋势时要注意热塑体模是否有变形的可能.为提高和保证胸部肿瘤放疗的精确性,当平移误差大于1mm,旋转误差大于0.5度时要重新配准纠正六维误差.     

肺癌患者体内组织瞬间平移和旋转对立体定向放射治疗摆位的影响

目的 在体部立体定向放射治疗(SBRT)中,利用锥形束CT(CBCT)比较软组织匹配及骨解剖匹配的精度,评估组织内部和组织之间瞬间平移在肺癌病人肿瘤中心位置的旋转误差,实现在线校正。方法 选用美国瓦里安公司的具有机载影像系统(On-borad-imager,OBI)的clinac-ix直线加速器治疗机治疗的肺癌患者8例。通过CBCT对SBRT每位患者治疗前后进行比较,评价体内组织瞬间的平移和旋转导致患者体位和肿瘤中心位置数值的变化。结果 骨解剖匹配和软组织匹配的区别在于体位变化是3.0mm(0~8.3mm),病人的肿瘤位置变化是1.4mm(0~12.2mm)和2.2mm(0~13.2mm)。这个中心偏移中位数是2.2mm(0~4.7mm),其余系统误差和随机误差约1°。结论 在肺癌的立体SBRT的转换改进治疗过程中,肿瘤中心位置的改变主要是受机体内部组织瞬间平移和旋转所影响。     

应用EPID分析头颈部肿瘤调强放疗的摆位误差

目的 通过对头颈部肿瘤患者群体的射野图像回顾性分析,了解患者群体的摆位误差分布情况,为治疗计划设计设置计划靶体积(PTV)时提供依据.方法 通过配准数字重建图像(DRR)和电子射野影像装置(EPID)拍摄的正、侧位验证像的骨性解剖结构,计算平移和旋转误差.结果 平移误差左右方向为(1.40±1.27)mm,头脚方向为(1.34±1.37)mm,腹背方向为(1.34±1.30)mm;旋转误差冠状面为(0.791±0.976).,矢状面为(0.531±0.750)..结论 对于头颈部肿瘤调强放疗(IMRT),临床靶体积(cTV)到PTV的外放边界在左右方向宜为3.7 mm,头脚及腹背方向宜为3.6 mm.考虑到旋转误差,当靶区比较长时靶区两端外放要更大一些.     

子宫颈癌俯卧位调强放射治疗摆位误差分析

目的研究子宫颈癌俯卧位调强放射治疗的摆位误差大小,为子宫颈癌调强放疗计划设计临床靶区体积（CTV）外放计划靶区体积（PTV）时提供参考数据。方法选取行俯卧位调强放射治疗的子宫颈癌患者6例,所有病例治疗时身下垫有孔泡沫板,热塑成形固定膜固定。连续5d治疗时用电子射野影像装置（EPID）拍射正侧位验证片各1张,共60张验证片,通过配准数字化重建图像（DRR）和EPID拍摄的验证片的骨性解剖结构,计算平移和旋转误差。结果平移误差：左右方向为（3．1±1．8）mm、头脚方向为（3．9±3．3）mm、腹背方向为（4．2±2．6）mm;旋转误差冠状面为（0．8±0．9）°、矢状面为（1．2±1）°。结论对于子宫颈癌俯卧位调强放射治疗,CTV到PTV的外放应为左右7．1mm、腹背10．8mm、头脚10.4mm,在患者身体上做摆位的标记线有助于减少摆位误差。     

机载影像系统分析体部肿瘤放疗摆位误差的临床观察

目的通过直线加速器机载影像系统分析体部肿瘤放疗期间产生的摆位误差,测量临床靶体积(CTV)到计划靶体积(PTV)边界的大小。方法应用直线加速器治疗55例体部肿瘤。放疗前获取锥形束CT(CBCT)图像,将该图像与计划CT图像相匹配,计算平移和旋转误差。结果胸部肿瘤平移误差在左右(x)方向、头脚(y)方向、前后(z)方向分别为(-0.309 8±3.706 7)mm、(0.500 1±5.958 7)mm、(0.161 0±4.512 6)mm;腹部肿瘤分别为(-0.392 7±2.601 2)mm、(0.872 1±5.600 1)mm、(0.110 3±3.297 8)mm;旋转误差在胸部和腹部肿瘤分别为(0.218 3±1.502 8)°、(-0.198 9±1.596 6)°。结论 CTV到PTV胸部肿瘤外放边界值在x方向、y方向、z方向分别为7 mm、11 mm、8 mm为宜;腹部肿瘤分别为5 mm、10mm、6 mm为宜,可以包括90%的摆位误差。     

应用锥形束CT对盆腔肿瘤放疗计划靶区外放距离的研究

目的 利用锥形束CT(CBCT)在线研究盆腔肿瘤摆位误差的大小,推算CTV与PTV 之间外放的间隙.方法 应用医科达Synergy IGRT加速器治疗12例盆腔肿瘤患者,通过CBCT影像技术获得患者左右(x)、头脚(y)、前后(z)方向线性摆位误差以及分别以x、y、z轴旋转形成相应的u、v、w旋转摆位误差,分析其摆位误差.结果 12例患者共行229次CBCT,x、y、z、u、v、w轴自由度的系统误差±随机误差分别为(0.49±1.18)mm、(-0.11±3.45)mm、(-2.00±1.59)mm、1.14°±0.67°、0.42°±0.94°、-0.32°±0.68°.其中y方向摆位误差最大、z方向次之、x方向摆位误差最小.x、y、z方向的摆位扩边值分别为4.6、12.5、6.2 mm.结论 盆腔肿瘤放疗时不可避免存在一定程度摆位误差,为减少摆位误差影响CTV外放PTV时考虑x方向5 mm、y方向15 mm,z方向10 mm.     

Evaluation of an infrared camera and X-ray system using implanted fiducials in patients with lung tumors for gated radiation therapy

PURPOSE: To report on the initial clinical use of a commercially available system to deliver gated treatment using implanted fiducials, in-room kV X-rays, and an infrared camera tracking system. METHODS AND MATERIALS: ExacTrac Adaptive Gating from BrainLab is a localization system using infrared cameras and X-rays. Gating signals are the patient's breathing pattern obtained from infrared reflectors on the patient. kV X-rays of an implanted fiducial are synchronized to the breathing pattern. After localization and shift of the patient to isocenter, the breathing pattern is used to gate the radiation. Feasibility tests included localization accuracy, radiation output constancy, and dose distributions with gating. Clinical experience is reported on treatment of patients with small lung lesions. RESULTS: Localization accuracy of a moving target with gating was 1.7 mm. Dose constancy measurements showed insignificant change in output with gating. Improvements of dose distributions on moving targets improved with gating. Eleven patients with lung lesions were implanted with 20 mmx0.7 mm gold coil (Visicoil). The implanted fiducial was used to localize and treat the patients with gating. Treatment planning and repeat computed tomographic scans showed that the change in center of gross target volume (GTV) to implanted marker averaged 2.47 mm due in part to asymmetric tumor shrinkage. CONCLUSION: ExacTrac Adaptive Gating has been used to treat lung lesions. Initial system evaluation verified its accuracy and usability. Implanted fiducials are visible in X-rays and did not migrate.     

Correlation between internal fiducial tumor motion and external marker motion for liver tumors imaged with 4D-CT

PURPOSE: We investigated the correlation between the motions of an external marker and internal fiducials implanted in the liver for 8 patients undergoing respiratory-based computed tomography (four-dimensional CT [4D-CT]) procedures. METHODS AND MATERIALS: The internal fiducials were gold seeds, 3 mm in length and 1.2 mm in diameter. Four patients each had one implanted fiducial, and the other four had three implanted fiducials. The external marker was a plastic box, which is part of the Real-Time Position Management System (RPM) used to track the patient's respiration. Each patient received a standard helical CT scan followed by a time-correlated CT-image acquisition (4D-CT). The 4D-CT images were reconstructed in 10 separate phases covering the entire respiratory cycle. RESULTS: The internal fiducial motion is predominant in the superior-inferior direction, with a range of 7.5-17.5 mm. The correlation between external respiration and internal fiducial motion is best during expiration. For 2 patients with their three fiducials separated by a maximum of 3.2 cm, the motions of the fiducials were well correlated, whereas for 2 patients with more widely spaced fiducials, there was less correlation. CONCLUSIONS: In general, there is a good correlation between internal fiducial motion imaged by 4D-CT and external marker motion. We have demonstrated that gating may be best performed at the end of the respiratory cycle. Special attention should be paid to gating for patients whose fiducials do not move in synchrony, because targeting on the correct respiratory amplitude alone would not guarantee that the entire tumor volume is within the treatment field.     

Electromagnetic Transponder Based Tracking and Gating in the Radiotherapeutic Treatment of Thoracic Malignancies

PurposeThis report details our institutional workflow and technique for use of the Calypso electromagnetic transponder system with respiratory gating for localization and tracking of lung tumors during stereotactic radiation therapy for early stage thoracic malignancies.Methods and MaterialsSixteen patients underwent bronchoscopic fiducial placement of 3 transponders in small airways in proximity to the primary tumor. Transponders were placed <19 cm from the most anterior skin location of the patient for appropriate tracking functionality. Patients underwent simulation with 4-dimensional assessment and were treated with transponder based positional gating if tumors moved >5 mm in any direction. Tumor motion <5 mm was not gated and treated using an internal target volume approach. A 5 mm uniform planning target volume was used. Before treatment, fiducial placement and tumor location were verified by daily kilovoltage (kV) and cone beam computed tomography image guidance. Tracking limits were placed based on the movement of the transponders from the centroid of the structures on the maximum intensity projection image. The Calypso treatment system paused treatment automatically if beacons shifted beyond the predefined tracking limits.ResultsAll 16 patients underwent successful implantation of the electromagnetic transponders. Eight patients exhibited tumor motion sufficient to require respiratory gating, and the other 8 patients were treated using a free breathing internal target volume technique. Difficulty with transponder sensing was experienced in 3 patients as a result of anatomic interference with the placement of the sensing arrays; each of these cases was successfully treated after making setup modifications. Triggered imaging of fiducials during treatment was consistent with real-time positioning determined by the Calypso tracking system.ConclusionsRespiratory gated electromagnetic based transponder guided stereotactic body radiation therapy using the workflow described is feasible and well tolerated in selected patients with early stage lung malignancies.     

Daily electronic portal imaging of implanted gold seed fiducials in patients undergoing radiotherapy after radical prostatectomy

PURPOSE: The aim of this study was to measure interfraction prostate bed motion, setup error, and total positioning error in 10 consecutive patients undergoing postprostatectomy radiotherapy. METHODS AND MATERIALS: Daily image-guided target localization and alignment using electronic portal imaging of gold seed fiducials implanted into the prostate bed under transrectal ultrasound guidance was used in 10 patients undergoing adjuvant or salvage radiotherapy after prostatectomy. Prostate bed motion, setup error, and total positioning error were measured by analysis of gold seed fiducial location on the daily electronic portal images compared with the digitally reconstructed radiographs from the treatment-planning CT. RESULTS: Mean (+/- standard deviation) prostate bed motion was 0.3 +/- 0.9 mm, 0.4 +/- 2.4 mm, and -1.1 +/- 2.1 mm in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) axes, respectively. Mean set-up error was 0.1 +/- 4.5 mm, 1.1 +/- 3.9 mm, and -0.2 +/- 5.1 mm in the LR, SI, and AP axes, respectively. Mean total positioning error was 0.2 +/- 4.5 mm, 1.2 +/- 5.1 mm, and -0.3 +/- 4.5 mm in the LR, SI, and AP axes, respectively. Total positioning errors >5 mm occurred in 14.1%, 38.7%, and 28.2% of all fractions in the LR, SI, and AP axes, respectively. There was no significant migration of the gold marker seeds. CONCLUSIONS: This study validates the use of daily image-guided target localization and alignment using electronic portal imaging of implanted gold seed fiducials as a valuable method to correct for interfraction target motion and to improve precision in the delivery of postprostatectomy radiotherapy.     

脊柱追踪相关参数对射波刀定位误差影响

目的 探讨脊柱ROI、追踪范围和实时影像对比度系数与射波刀定位误差的关系。方法 利用肺追踪体模制定脊柱追踪计划并进行治疗,通过目标定位系统进行体模预置,获得体模实时预置影像及定位误差;以实时预置影像为基础,改体模脊柱ROI大小、追踪范围和实时影像对比度系数,观察体模定位误差及相关参数的改变。采用Pearson法相关分析。结果 追踪范围的改变不会引起脊柱追踪定位误差的改变,追踪范围与脊柱追踪定位误差无关联(R=0,P=1);ROI大小和影像对比度系数的改变对脊柱追踪平移误差无影响,但对脊柱追踪旋转误差有影响,主要表现在左右旋转误差改变(R=0.533、0.693,P=0.002、0.026),其中尤以实时影像对比度的影响最为明显,其变化幅度高达2.2°。结论 除追踪范围的改变不会影响脊柱追踪的定位误差外,ROI大小和影像对比度系数的改变均会导致脊柱追踪的定位误差不同程度的变化,在射波刀治疗中应引起足够重视。     

Evaluation of the Visibility and Artifacts of 11 Common Fiducial Markers for Image Guided Stereotactic Body Radiation Therapy in the Abdomen

PurposeThe purpose of this study was to quantitatively evaluate the visibility and artifacts of commercially available fiducial markers to optimize their selection for image guided stereotactic body radiation therapy.Methods and MaterialsFrom 6 different vendors, we selected 11 fiducials commonly used in image guided radiation therapy. The fiducials varied in material composition (e.g., gold, platinum, carbon), shape (e.g., cylindrical, notched/linear, coiled, ball-like, step), and size measured in terms of diameter (0.28-1.0 mm) and length (3.0-20.0 mm). Each fiducial was centered in 4-mm bolus within a 13-cm-thick water-equivalent phantom. Fiducials were imaged with the use of a simulation computed tomography (CT) scanner, a CT-on-rails system, and an onboard cone beam CT system. Acquisition parameters were set according to clinical protocols. Visibility was assessed in terms of contrast (Δ Hounsfield unit [HU]) and the Michelson visibility metric. Artifacts were quantified in terms of relative standard deviation and relative streak artifacts level (rSAL). Twelve radiation oncologists ranked each fiducial in terms of clinical usefulness.ResultsContrast and artifacts increased with fiducial size. For CT imaging, maximum contrast (2722 HU) and artifacts (rSAL = 2.69) occurred for the largest-diameter (0.75 mm) platinum fiducial. Minimum contrast (551 HU) and reduced artifacts (rSAL = 0.65) were observed for the smallest-diameter (0.28 mm) gold fiducial. Carbon produced the least severe artifacts (rSAL = 0.29). The survey indicated that physicians preferred gold fiducials with a 0.35- to 0.43-mm diameter, 5- to 10-mm length, and coiled or cylindrical shape that balanced contrast and artifacts.ConclusionsWe evaluated 11 different fiducials in terms of visibility and artifacts. The results of this study may assist radiation oncologists who seek to maximize contrast, minimize artifacts, or balance contrast versus artifacts by fiducial selection.     

Ultrasonography and fluoroscopic fusion for prostate brachytherapy dosimetry

: To investigate the feasibility of performing postimplant and intraoperative dosimetry for prostate brachytherapy by fusing transrectal ultrasound (TRUS) and fluoroscopic data.

: Registration of ultrasound (prostate boundary) and fluoroscopic (seed) data requires spatial markers that are detectable by both imaging modalities. In this study, the needle tips were considered as such fiducials. Prostate phantoms were implanted with the seeds, and four localization needles were inserted. In the TRUS frame of reference, the longitudinal coordinate of the needle tip was determined by advancing the needle until the echo from its tip just registered at a known probe depth. The tip’s transverse coordinates were determined from the associated TRUS slice. The three-dimensional needle tip positions were also calculated in the fluoroscopic coordinate system using a seed reconstruction method. The transformation between the TRUS and fluoroscopy coordinate systems was established by the least-squares solution using the singular value decomposition.

: With three of four needle tips as fiducials and the one remaining needle as a test target, the mean fiducial registration error was 0.8 mm and the test target registration error was 2.5 mm. When all four points were used for registration, the errors decreased to 1.1 mm. A comparison between the proposed method and CT-based dosimetry yielded a percentage of prostate volume receiving 100% and 150% of the prescribed minimal peripheral dose and minimal dose received by 90% of the prostate gland that agreed within 0.4%, 2.7%, and 4.2%, respectively.

: The combination of TRUS and fluoroscopy is a feasible alternative to the currently used CT-based postimplant dosimetry. Furthermore, because of online imaging capability, the method lends itself to real-time intraoperative applications.     

Target localization and real-time tracking using the Calypso 4D localization system in patients with localized prostate cancer

PURPOSE: The Calypso 4D Localization System is being developed to provide accurate, precise, objective, and continuous target localization during radiotherapy. This study involves the first human use of the system, to evaluate the localization accuracy of this technique compared with radiographic localization and to assess its ability to obtain real-time prostate-motion information. METHODS AND MATERIALS: Three transponders were implanted in each of 20 patients. Eleven eligible patients of the 20 patients participated in a study arm that compared radiographic triangulated transponder locations to electromagnetically recorded transponder locations. Transponders were tracked for 8-min periods. RESULTS: The implantations were all successful, with no major complications. Intertransponder distances were largely stable. Comparison of the patient localization on the basis of transponder locations as per the Calypso system with the radiographic transponder localization showed an average (+/-SD) 3D difference of 1.5 +/- 0.9 mm. Upon tracking during 8 min, 2 of the 11 patients showed significant organ motion (>1 cm), with some motion lasting longer that 1 min. CONCLUSION: Calypso transponders can be used as magnetic intraprostatic fiducials. Clinical evaluation of this novel 4D nonionizing electromagnetic localization system with transponders indicates a comparable localization accuracy to isocenter, (within 2 mm) compared with X-ray localization.     

A complementary dual-modality verification for tumor tracking on a gimbaled linac system

Background and purpose

For dynamic tracking of moving tumors, robust intra-fraction verification was required, to assure that tumor motion was properly managed during the course of radiotherapy. A dual-modality verification system, consisting of an on-board orthogonal kV and planar MV imaging device, was validated and applied retrospectively to patient data.

Methods and materials

Real-time tumor tracking (RTTT) was managed by applying PAN and TILT angular corrections to the therapeutic beam using a gimbaled linac. In this study, orthogonal X-ray imaging and MV EPID fluoroscopy was acquired simultaneously. The tracking beam position was derived from respectively real-time gimbals log files and the detected field outline on EPID. For both imaging modalities, the moving target was localized by detection of an implanted fiducial. The dual-modality tracking verification was validated against a high-precision optical camera in phantom experiments and applied to clinical tracking data from a liver and two lung cancer patients.

Results

Both verification modalities showed a high accuracy (<0.3 mm) during validation on phantom. Marker detection on EPID was influenced by low image contrast. For the clinical cases, gimbaled tracking showed a 90th percentile error (E90) of 3.45 (liver), 2.44 (lung A) and 3.40 mm (lung B) based on EPID fluoroscopy and good agreement with XR-log file data by an E90 of 3.13, 1.92 and 3.33 mm, respectively, during beam on.

Conclusion

Dual-modality verification was successfully implemented, offering the possibility of detailed reporting on RTTT performance.