Comparison of Electronic Portal Imaging and Cone Beam Computed Tomography for Position Verification in Children

AimTo compare the accuracy of radiotherapy set-up using an electronic portal imaging device (EPID) versus megavoltage cone beam computed tomography (MV-CBCT) in paediatric patients.Materials and methodsIn total, 204 pairs of EPID and MV-CBCT were carried out for 72 patients in the first 3 treatment days and weekly thereafter.ResultsFor the whole group, the mean systematic EPID set-up errors were 1.8 (±1.7), 1.6 (±1.3), 1.4 (±1.5) mm and 2.3 (±1.7), 1.6 (±1.3), 2.4 (±1.6) mm for MV-CBCT in the longitudinal, lateral and vertical directions, respectively, whereas the mean EPID random errors were 2.0 (±1.7), 1.4 (±1.5), 1.2 (±1.6) and 1.9 (±1.5), 1.5 (±1.3), 2.1 (±1.7) mm for MV-CBCT in the longitudinal, lateral and vertical directions, respectively. For systematic errors of head and neck patients, there was a statistically significant difference in the lateral and vertical directions (P = 0.027, 0.003), whereas in the non-head and neck patients there was a statistically significant difference in the lateral direction only (P = 0.031). In head and neck patients, the mean random errors were significantly different in the vertical and lateral directions, whereas in non-head and neck patients, they were significantly different in the vertical direction only. The larger values alternate between the two modalities. The systematic and random errors (detected by EPID and MV-CBCT) were significantly correlated in almost all direction in all tumour sites.ConclusionsThe comparison between set-up error in EPID and MV-CBCT was not in favour of any of the two modalities. However, the two modalities were strongly correlated but fairly agreed and the differences between the shifts reported were small and hardly influenced the recommended planning target volume margin.     

Feasibility evaluation of prone breast irradiation with the Sagittilt© system including residual-intrafractional error assessment

PurposeFeasibility evaluation of the Sagittilt^© prone breast board system (Orfit Industries, Wijnegem, Belgium) for radiotherapy focusing on patient and staff satisfaction, treatment time, treatment reproducibility with the assessment of residual-intrafractional errors.Material and methodsThirty-six patients underwent whole-breast irradiation in prone position. Seventeen received a sequential boost (breast: 42.56 Gy in 16 fractions, boost: 10 Gy in five fractions), while 19 patients received a concomitant boost protocol (breast/boost: 45.57/55.86 Gy in 21 fractions). Treatment verification included a daily online cone-beam CT (CBCT). In order to assess the residual and residual-intrafractional errors post-treatment CBCTs were performed systematically at the first five treatment sessions. Treatment time, patient comfort, staff satisfaction were also evaluated.ResultsThe pretreatment CBCT resulted in a population systematic error of 4.5/3.9/3.3 mm in lateral/longitudinal/vertical directions, while the random error was 5.4/3.8/2.8 mm. Without correction these would correspond to a clinical to planning target volume margin of 15.0/12.3/10.3 mm. The population systematic and random residual-intrafractional errors were 1.5/0.9/1.7 mm and 1.7/1.9/1.6 mm. Patient and staffs’ satisfaction were considered good and average. The mean treatment session time was 21 minutes (range: 13–40 min).ConclusionThe Sagittilt^© system seems to be feasible for breast irradiation and well-tolerated by patients, acceptable to radiographers and reasonable in terms of treatment times. Set-up accuracy was comparable with other prone systems; residual errors need further investigations.     

Intrafraction variations in linac-based image-guided radiosurgery of intracranial lesions

PurposeThis study investigated image-guided patient positioning during frameless, mask-based, single-fraction stereotactic radiosurgery of intracranial lesions and intrafractional translational and rotational variations in patient positions.Patients and methodsA non-invasive head and neck thermoplastic mask was used for immobilization. The Exactrac/Novalis Body system (BrainLAB AG, Germany) was used for kV X-ray imaging guided positioning. Intrafraction displacement data, obtained by imaging after each new table position, were evaluated.ResultsThere were 269 radiosurgery treatments performed on 190 patients and a total of 967 setups within different angles. The first measured error after each table rotation (mean 2.6) was evaluated (698 measurements). Intrafraction translational errors were (1 standard deviation [SD]) on average 0.8, 0.8, and 0.7 mm for the left–right, superior–inferior, and anterior–posterior directions, respectively, with a mean 3D-vector of 1.0 mm (SD 0.9 mm) and a range from –5 mm to +5 mm. On average, 12%, 3%, and 1% of the translational deviations exceeded 1, 2, and 3 mm, respectively, in the three directions.ConclusionThe range of intrafraction patient motion in frameless image-guided stereotactic radiosurgery is often not fully mapped by pre- and post-treatment imaging. In the current study, intrafraction motion was assessed by performing measurements at several time points during the course of stereotactic radiosurgery. It was determined that 12% of the intrafraction values in the three dimensions are above 1 mm, the usual safety margin applied in stereotactic radiosurgery.     

On-board patient positioning for head-and-neck IMRT: comparing digital tomosynthesis to kilovoltage radiography and cone-beam computed tomography

PURPOSE: High-precision intensity-modulated radiotherapy demands high patient positioning accuracy. On-board digital tomosynthesis (DTS) provides three-dimensional (3D) image guidance for daily positioning with a lower imaging dose, faster acquisition, and more geometric flexibility than 3D cone-beam computed tomography (CBCT). This clinical study evaluated DTS as a daily imaging technique for patient positioning and compared the results with 3D CBCT and two-dimensional (2D) radiography. METHODS AND MATERIALS: Head and neck cancer patients undergoing intensity-modulated radiotherapy were studied. For each session, the patient was positioned using laser marks. On-board imaging data sets, including 2D kilovoltage radiographs, DTS, and CBCT, were obtained to measure the daily patient positioning variations. The mean and standard deviations of the positioning variations in the translational and rotational directions were calculated. The positioning differences among 2D radiography, DTS, and CBCT were analyzed. RESULTS: Image data sets were collected from 65 treatment fractions for 10 patients. The systematic patient positioning variation was <0.10 cm and 1.0 degrees one dimensionally. The random variations were 0.27-0.34 cm in the translational and 0.93 degrees -1.99 degrees in the rotational direction. The mean vector isocenter variation was 0.48 cm. DTS with 40 degrees and 20 degrees scan angles in the coronal or sagittal directions yielded the same results for patient positioning. DTS performance was comparable to that of CBCT, with positioning differences of <0.1 cm and 0.5 degrees . The positioning difference between 2D radiography and DTS was approximately 0.1 cm and 0.2 cm in the vertical/longitudinal and lateral directions. CONCLUSION: Our results have demonstrated that DTS is a comparable 3D imaging technique to CBCT for daily patient positioning of head-and-neck patients as determined by manual registration of bony anatomy.     

Inter-observer Variability of Prostate Delineation on Cone Beam Computerised Tomography Images

AimTo determine the inter-observer variability of defining the prostate gland on cone beam computerised tomography images for the purposes of image-guided radiotherapy.Materials and methodsFive genitourinary oncologists contoured the prostate gland on five cone beam computerised tomography datasets. The variations in prostate boundary delineation and consequent isocentre placement between observers were measured. Variations in volume and centre of mass were calculated. The variation in boundary definition was determined with finite element modelling.ResultsThe average standard deviation for centre of mass displacements was small, measuring 0.7, 1.8 and 2.8 mm in the left–right, anterior–posterior and superior–inferior directions, respectively. The standard deviation for volume determination was 8.93 cm³ with large variability (3.98–19.00 cm³). The mean difference between the computerised tomography-derived volume and the mean cone beam-derived volume was 16% (range 0–23.7%). The mean standard deviations for left–right, anterior–posterior and superior–inferior boundary displacements were, respectively, 1.8, 2.1 and 3.6 mm. The maximum deviation seen was 9.7 mm in the superior direction.ConclusionExpert observers had difficulty agreeing upon the location of the prostate peri-prostatic interface on the images provided. The effect on the centre of mass determination was small, and inter-observer variability for prostate detection on cone beam computerised tomography images is not prohibitive to the use of soft tissue guidance protocols. Potential exists for significant systematic matching errors, and points to the need for rigorous therapist image recognition training and development of guidance protocols before clinical implementation of soft tissue cone beam image guidance.     

Daily setup uncertainty analysis for craniospinal irradiation using helical tomotherapy

PurposeSetup deviations of a craniospinal irradiation (CSI) patient cohort previously treated with helical tomotherapy were used to derive the optimal planning target volume (PTV) margin for CSI patients treated in the supine position.Methods and MaterialsThe daily setup shifts of 27 CSI tomotherapy patients as determined using pretreatment megavoltage computed tomography verification for a total of 454 fractions were evaluated. Translational displacements in the mediolateral (ML), craniocaudal (CC), and anteroposterior (AP) directions were used to assess the systematic and random setup errors, and to derive the PTV margin required when daily image guidance is unavailable.ResultsThe individual patient mean shifts and the corresponding standard deviations in the ML, CC, and AP directions were ? 0.5 ± 2.1 mm, 1.0 ± 2.7 mm, and 0.7 ± 1.1 mm, respectively. The random errors in the corresponding directions were 1.9 mm, 1.9 mm, and 2.2 mm. The PTV margins required in the absence of daily imaging were 3.7 mm to the right, 4.7 mm to the left, 4.4 mm inferior, 6.4 mm superior, 1.6 mm posterior, and 3.0 mm anterior.ConclusionsThe current PTV margin of 3.0 mm is sufficient to ensure clinical target volume coverage for CSI tomotherapy patients treated with daily megavoltage computed tomography imaging. When pretreatment verification imaging is not used to lower the setup uncertainty, a larger PTV margin of up to 6.4 mm in the CC direction will be needed.     

Comparison of Contrast-to-Noise Ratios of Transmission and Dark-Field Signal in Grating-Based X-ray Imaging for Healthy Murine Lung Tissue

PurposeAn experimental comparison of the contrast-to-noise ratio (CNR) between transmission and dark-field signals in grating-based X-ray imaging for ex-vivo murine lung tissue.Materials and MethodsLungs from three healthy mice were imaged ex vivo using a laser-driven compact synchrotron X-ray source. Background noise of transmission and dark-field signal was quantified by measuring the standard deviation in a region of interest (ROI) placed in a homogeneous area outside the specimen. Image contrast was quantified by measuring the signal range in rectangular ROIs placed in central and peripheral lung parenchyma. The relative contrast gain (RCG) of dark-field over transmission images was calculated as CNR_DF / CNR_T.ResultsIn all images, there was a trend for contrast-to-noise ratios of dark-field images (CNR_DF) to be higher than for transmission images (CNR_T) for all ROIs (median 61 vs. 38, p = 0.10), but the difference was statistically significant only for peripheral ROIs (61 vs. 32, p = 0.03). Median RCG was >1 for all ROIs (1.84). RCG values were significantly smaller for central ROIs than for peripheral ROIs (1.34 vs. 2.43, p = 0.03).ConclusionThe contrast-to-noise ratio of dark-field images compares more favorably to the contrast-to-noise ratio of transmission images for peripheral lung regions as compared to central regions. For any specific specimen, a calculation of the RCG allows comparing which X-ray modality (dark-field or transmission imaging) produces better contrast-to-noise characteristics in a well-defined ROI.     

Assessment of patient setup errors in IGRT in combination with a six degrees of freedom couch

PurposeThe range of patient setup errors in six dimensions detected in clinical routine for cranial as well as for extracranial treatments, were analyzed while performing linear accelerator based stereotactic treatments with frameless patient setup systems. Additionally, the need for re-verification of the patient setup for situations where couch rotations are involved was analyzed for patients treated in the cranial region.Methods and MaterialsA total of 2185 initial (i.e. after pre-positioning the patient with the infrared system but before image guidance) patient setup errors (1705 in the cranial and 480 in the extracranial region) obtained by using ExacTrac (BrainLAB AG, Feldkirchen, Germany) were analyzed. Additionally, the patient setup errors as a function of the couch rotation angle were obtained by analyzing 242 setup errors in the cranial region. Before the couch was rotated, the patient setup error was corrected at couch rotation angle 0° with the aid of image guidance and the six degrees of freedom (6DoF) couch. For both situations attainment rates for two different tolerances (tolerance A: ±0.5 mm, ±0.5°; tolerance B: ±1.0 mm, ±1.0°) were calculated.ResultsThe mean (± one standard deviation) initial patient setup errors for the cranial cases were -0.24 ± 1.21°, -0.23 ± 0.91° and -0.03 ± 1.07° for the pitch, roll and couch rotation axes and 0.10 ± 1.17 mm, 0.10 ± 1.62 mm and 0.11 ± 1.29 mm for the lateral, longitudinal and vertical axes, respectively. Attainment rate (all six axes simultaneously) for tolerance A was 0.6% and 13.1% for tolerance B, respectively. For the extracranial cases the corresponding values were -0.21 ± 0.95°, -0.05 ± 1.08° and -0.14 ± 1.02° for the pitch, roll and couch rotation axes and 0.15 ± 1.77 mm, 0.62 ± 1.94 mm and -0.40 ± 2.15 mm for the lateral, longitudinal and vertical axes. Attainment rate (all six axes simultaneously) for tolerance A was 0.0% and 3.1% for tolerance B, respectively. After initial setup correction and rotation of the couch to treatment position a re-correction has to be performed in 77.4% of all cases to fulfill tolerance A and in 15.6% of all cases to fulfill tolerance B.ConclusionThe analysis of the data shows that all six axes of a 6DoF couch are used extensively for patient setup in clinical routine. In order to fulfill high patient setup accuracies (e.g. for stereotactic treatments), a 6DoF couch is recommended. Moreover, re-verification of the patient setup after rotating the couch is required in clinical routine.     

Intensity-modulated whole pelvic radiotherapy provides effective dosimetric outcomes for cervical cancer treatment with lower toxicities

PurposeTo compare the efficacy of intensity-modulated radiotherapy, three-dimensional conformal radiotherapy, and conventional radiotherapy for cervical cancer treatment.Materials and methodsWhole pelvis intensity-modulated radiotherapy, three-dimensional conformal radiotherapy, and conventional radiotherapy plans were designed for 16 patients with stage IIB cervical cancer, each using the prescribed dose of 50.4 Gy/28 fractions. Dose–volume histograms of the target volume and organs at risk were evaluated.ResultsCompared to the 3D conformal and conventional radiotherapy plans, the intensity-modulated radiotherapy plan demonstrated superior conformal treatment. The mean planning target volume dose of all three plans reached the target effective therapeutic dose. The planning target volume dose of the intensity-modulated radiotherapy plan was significantly higher than that of either the three-dimensional conformal radiotherapy or conventional radiotherapy plan (P < 0.05). When more than 30 Gy was administered in intensity-modulated radiotherapy, organs at risk including the small intestine, rectum, bladder, and bone marrow received a significantly reduced volume of radiation. In comparison of the average planning target volume doses, significant volume reductions in irradiation of organs at risk were obtained with full bladders.ConclusionsAn intensity-modulated radiotherapy plan with appropriate margins encompassing the primary tumour and potential microscopic pelvic disease reduces the dose to organs at risk without compromising target coverage. Intensity-modulated radiotherapy is an appropriate definitive treatment for patients with cervical cancer.     

A comparative study of locoregionally advanced nasopharyngeal carcinoma treated with intensity modulated irradiation and platinum-based chemotherapy

PurposeTo investigate the prognosis of three subgroups of locoregionally advanced nasopharyngeal carcinoma treated with intensity-modulated radiotherapy and platinum-based chemotherapy.Patients and methodsHundred and eighty-one consecutive patients with locoregionally advanced untreated nasopharyngeal carcinoma were retrospectively divided into three subgroups: locally advanced group (T3-4N0-1M0), regionally advanced group (T1-2N2-3M0) and the mixed group (T3-4N2-3M0). They were all treated with definitive intensity-modulated radiotherapy and platinum-based chemotherapy. Their prognosis were investigated and compared. Multivariate analysis was applied to identify the independent risk factors of study endpoints.ResultsThe 3-year locoregional control rates for locally advanced group, regionally advanced group, and the mixed group were 91.5%, 90.6% and 84.3% respectively, no significant difference was observed (P = 0.656, P = 0.429). The 3-year distant metastasis-free survival rates were 89.6%, 75.7% and 76.3%, respectively. The distant metastasis-free survival rate of the locally advanced group was significantly higher than the other two subgroups (P = 0.028, P = 0.028). The 3-year progression-free survival rates were 85.5%, 67.9% and 67.1% respectively with significance also favoring the locally advanced group (P = 0.043, P = 0.023). Nodal stage and the performance status were the independent risk factors of distant metastasis in the observed period.ConclusionsIn the context of intensity-modulated radiotherapy and platinum-based chemotherapy, the locally advanced group had a better prognosis compared with the regionally advanced group and the mixed group. Treatment stratification may be based on nodal stage.     

Automatic delineation of on-line head-and-neck computed tomography images: toward on-line adaptive radiotherapy

PURPOSE: To develop and validate a fully automatic region-of-interest (ROI) delineation method for on-line adaptive radiotherapy. METHODS AND MATERIALS: On-line adaptive radiotherapy requires a robust and automatic image segmentation method to delineate ROIs in on-line volumetric images. We have implemented an atlas-based image segmentation method to automatically delineate ROIs of head-and-neck helical computed tomography images. A total of 32 daily computed tomography images from 7 head-and-neck patients were delineated using this automatic image segmentation method. Manually drawn contours on the daily images were used as references in the evaluation of automatically delineated ROIs. Two methods were used in quantitative validation: (1) the dice similarity coefficient index, which indicates the overlapping ratio between the manually and automatically delineated ROIs; and (2) the distance transformation, which yields the distances between the manually and automatically delineated ROI surfaces. RESULTS: Automatic segmentation showed agreement with manual contouring. For most ROIs, the dice similarity coefficient indexes were approximately 0.8. Similarly, the distance transformation evaluation results showed that the distances between the manually and automatically delineated ROI surfaces were mostly within 3 mm. The distances between two surfaces had a mean of 1 mm and standard deviation of <2 mm in most ROIs. CONCLUSION: With atlas-based image segmentation, it is feasible to automatically delineate ROIs on the head-and-neck helical computed tomography images in on-line adaptive treatments.     

Patient participation to patient safety in radiotherapy: a reality to be developed

BackgroundPatient safety during radiotherapy has become a central priority for public policy further to the various accidents arisen at Epinal, Toulouse and Grenoble for the most symbolic. In this context, patients’ involvement in the management of their own safety can be a way to improve the quality of care in general.Objective and methodThis study was carried out in the radiotherapy department of the Georges-Pompidou European Hospital and aimed at analyzing the role of patients in the management of patient safety. Interviews have been conducted with patients and with professionals in order to understand if patients could have a role in the safety of their treatment and to describe the possible forms of participation.ResultsThe results describe two main forms of patient participation. On one hand, active participation, which refers to preventive and corrective actions carried out spontaneously by the patients. On the other hand, compliance, which consists in the respect of the recommended or prescribed behavior.ConclusionPatient participation is a reality which remains almost invisible for professionals and which needs to be encouraged insofar as it is a means to improve healthcare safety by a cooperative risk management. However, it must be a possibility offered to the patients and not an obligation, a source of additional stress     

Set-Up Errors,Organ Motion,Tumour Regression and its Implications on Internal Target Volume–Planning Target Volume During Cervical Cancer Radiotherapy: Results From a Prospective Study

AimsUterocervical motions and organ filling during cervical cancer conformal radiotherapy is complex. This prospective, observational study investigated set-up margins (clinical target vo, ume [CTV] to planning target volume [PTV]) for pelvic nodal CTV and internal margin (CTV to internal target volume [ITV]) expansions for uterocervical movements during cervical cancer radiotherapy.Materials and methodsDuring cervical cancer radiotherapy, a daily kilovoltage, cone-beam computed tomography (CBCT) scan was acquired. Bony anatomy-based rigid co-registration and matching to vessels/pelvic nodal region was carried out to document shifts, errors (systematic and random) and to calculate CTV to PTV margins. Subsequently, soft-tissue matching was carried out at the mid-cervical region and uterine fundus to record shifts, errors and to calculate CTV to ITV margins.ResultsIn 67 patients, 1380 CBCT scans were analysed. The mean (±standard deviation) couch shifts for CTV pelvic nodal region in all directions were within 4.5–5.3 mm, systematic and random errors 3.0–3.6 mm and set-up margins of within 10 mm (except anterior margin 10.3 mm). For the mid-cervical region, mean shifts were 4.5–5.5 mm, systematic and random errors 2–4 mm amounting to <10 mm internal margins (CTV–ITV for cervix) and for uterine fundus mean (±standard deviation) shifts were larger in the superior direction (12.1 mm) but 4.0–7.5 mm in other directions, systematic and random errors 2–7 mm amounting to anisotropic margins in various directions (10 mm in anterior–posterior and lateral directions, 12–20 mm in superior–inferior directions) (CTV–ITV for uterine fundus).ConclusionOur study suggests anisotropic CTV to ITV and CTV to PTV margins for cervical cancer radiotherapy.     

自制“倾倒式”治疗床减小胸腹部肿瘤放疗摆位误差可行性与有效性

目的 CT模拟定位和放疗过程中均使用自制“倾倒式”治疗床进行摆位,探讨其减小摆位误差的可行性和有效性。方法 选取 2016年3-9月于肿瘤医院进行放疗的 22例胸腹部肿瘤患者,根据是否使用“倾倒式”治疗床随机分为2个组,每组 11例。试验组使用“倾倒式”治疗床实现患者由直立位转换至仰卧位,对照组采用常规的患者自主仰卧位。所有患者均在自主呼吸的状态下接受定位CT扫描,根据IGRT协作组的规范化建议进行图像配准。记录并分析CBCT扫描平移误差和旋转误差配准数据,根据“四参数模型”计算2个组摆位误差。结果 试验组x、y、z轴向平移误差和范围分别为(-0.012±0.128)、(0.272±0.123)、(0.089±0.105) cm和 0.29~0.70、0.23~0.70、0.14~0.53 cm,对照组的分别为(0.006±0.198)、(-0.108±0.396)、(-0.096±0.176) cm和 0.27~0.75、0.56~2.08、0.34~0.89 cm。结论 自制“倾倒式”治疗床可以提高胸腹部肿瘤放疗的摆位重复性,减少摆位误差,尤其是y轴向上的摆位误差。     

A new strategy for online adaptive prostate radiotherapy based on cone-beam CT

PurposeInterfractional organ motion and patient positioning errors during prostate radiotherapy can have deleterious clinical consequences. It has become clinical practice to re-position the patient with image-guided translational position correction before each treatment to compensate for those errors. However, tilt errors can only be corrected with table corrections in six degrees of freedom or “full” adaptive treatment planning strategies. Organ shape deformations can only be corrected by “full” plan adaptation. This study evaluates the potential of instant treatment plan adaptation (fast isodose line adaptation with real-time dose manipulating tools) based on cone-beam CT (CBCT) to further improve treatment quality.Methods and MaterialsUsing in-house software, CBCTs were modified to approximate a correct density calibration. To evaluate the dosimetric accuracy, dose distributions based on CBCTs were compared with dose distributions calculated on conventional planning CTs (PCT) for four datasets (one inhomogeneous phantom, three patient datasets).To determine the potential dosimetric benefit of a “full” plan adaptation over translational position correction, dose distributions were re-optimized using graphical “online” dose modification tools for three additional patients’ CT-datasets with a substantially distended rectum while the original plans have been created with an empty rectum (single treatment fraction estimates).ResultsAbsolute dose deviations of up to 51% in comparison to the PCT were observed when uncorrected CBCTs were used for replanning. After density calibration of the CBCTs, 97% of the dose deviations were ?3% (gamma index: 3%/3 mm).Translational position correction restored the PTV dose (D₉₅) to 73% of the corresponding dose of the reference plan. After plan adaptation, larger improvements of dose restoration to 95% were observed. Additionally, the rectal dose (D₃₀) was further decreased by 42 percentage points (mean of three patient datasets).ConclusionsAn accurate dose calculation based on CBCT-datasets is possible when density distributions are corrected. The presented adaptive strategy has the potential to reduce dose delivery errors due to organ deformations to a minimum.     

实时图像引导系统对乳腺癌保乳术后放疗摆位误差的影响

目的：探讨基于图像引导系统的乳腺癌保乳术后行容积旋转调强放疗(volumetric modulated arc therapy, VMAT)患者在投照过程中摆位误差的实时校正及剂量学参数变化。方法：选取2020年10月至2021年12月天津医科大学肿瘤医院收治的20例保乳术后行VMAT患者,随机分为对照组10例和试验组10例,放疗时行图像引导,对误差数据进行统计学分析,将摆位误差引入治疗计划重新计算,比较两组剂量学差异。结果：对照组和试验组在左右(LR)、腹背(AP)、头脚(SI)方向的摆位误差校正前分别为(3.58±2.35)mm和(3.51±2.08)mm、(4.44±3.62)mm和(4.23±2.17)mm、(2.85±2.36)mm和(2.99±1.90)mm。对照组在治疗后摆位误差分别为(2.64±1.62)、(3.15±1.50)、(2.49±1.70)mm;试验组在治疗中与治疗后摆位误差分别为(2.07±1.65)mm与(1.85±1.22)mm、(2.29±1.93) mm与(1.78±1.26)mm、(1.98±1.49)mm与(1.67±1.27) mm。LR、A...     

Lung tumor reproducibility with active breath control (ABC) in image-guided radiotherapy based on cone-beam computed tomography with two registration methods

Purpose

To study the inter- and intrafraction tumor reproducibility with active breath control (ABC) utilizing cone-beam computed tomography (CBCT), and compare validity of registration with two different regions of interest (ROI).

Methods and materials

Thirty-one lung tumors in 19 patients received conventional or stereotactic body radiotherapy with ABC. During each treatment, patients had three CBCT scanned before and after online position correction and after treatment. These CBCT images were aligned to the planning CT using the gray scale registration of tumor and bony registration of the thorax, and tumor position uncertainties were then determined.

Results

The interfraction systematic and random translation errors in the left-right (LR), superior-inferior (SI) and anterior-posterior (AP) directions were 3.6, 4.8, and 2.9 mm; 2.5, 4.5, and 3.5 mm, respectively, with gray scale alignment; 1.9, 4.3, 2.0 mm and 2.5, 4.4, 2.9 mm, respectively, with bony alignment. The interfraction systematic and random rotation errors with gray scale and bony alignment groups ranged from 1.4° to 3.0° and 0.8° to 2.3°, respectively. The intrafraction systematic and random errors with gray scale registration in LR, SI, AP directions were 0.9, 2.0, 1.8 mm and 1.5, 1.7, 2.9 mm, respectively, for translation; 1.5°, 0.9°, 1.0° and 1.2°, 2.2°, 1.8°, respectively, for rotation. The translational errors in SI direction with bony alignment were significantly larger than that of gray scale (p < 0.05).

Conclusions

With CBCT guided online correction the interfraction positioning errors can be markedly reduced. The intrafraction errors were not diminished by the use of ABC. Rotation errors were not very remarkable both inter- and intrafraction. Gray scale alignment of tumor may provide a better registration in SI direction.     

Set-up improvement in head and neck radiotherapy using a 3D off-line EPID-based correction protocol and a customised head and neck support.

PURPOSE: First, to investigate the set-up improvement resulting from the introduction of a customised head and neck (HN) support system in combination with a technologist-driven off-line correction protocol in HN radiotherapy. Second, to define margins for planning target volume definition, accounting for systematic and random set-up uncertainties. METHODS AND MATERIALS: In 63 patients 498 treatment fractions were evaluated to develop and implement a 3D shrinking action level correction protocol. In the comparative study two different HN-supports were compared: a flexible 'standard HN-support' and a 'customised HN-support". For all three directions (x, y and z) random and systematic set-up deviations (1 S.D.) were measured. RESULTS: The customised HN-support improves the patient positioning compared to the standard HN-support. The 1D systematic errors in the x, y and z directions were reduced from 2.2-2.3 mm to 1.2-2.0 mm (1 S.D.). The 1D random errors for the y and z directions were reduced from 1.6 and 1.6 mm to 1.1 and 1.0 mm (1S.D.). The correction protocol reduced the 1D systematic errors further to 0.8-1.1 mm (1 S.D.) and all deviations in any direction were within 5 mm. Treatment time per measured fraction was increased from 10 to 13 min. The total time required per patient, for the complete correction procedure, was approximately 40 min. CONCLUSIONS: Portal imaging is a powerful tool in the evaluation of the department specific patient positioning procedures. The introduction of a comfortable customised HN-support, in combination with an electronic portal imaging device-based correction protocol, executed by technologists, led to an improvement of overall patient set-up. As a result, application of proposed recipes for CTV-PTV margins indicates that these can be reduced to 3-4 mm.     

应用真空负压垫联合热塑体膜对小儿肾母细胞瘤放疗价值

目的 探讨真空负压垫联合热塑体膜在小儿肾母细胞瘤放疗中的临床应用价值。 方法 选取 42例肾母细胞瘤术后接受放疗的小儿患者,依据体位固定方式的不同将其等分成A、B组,A组患者在放疗实施时采用真空负压垫固定体位,B组患者则采用真空负压垫联合热塑体膜固定体位。对比两组患者在治疗时的摆位误差、近期效果、不良反应以及预后。对计数资料行χ²检验,计量资料行t检验。 结果 在平移误差、旋转误差、≤3 mm和≤5 mm的对比中B组均小于A组(P=0.04、0.04、0.04、0.03、0.00、0.04、0.04、0.00、0.04);B组的完全缓解率、有效率均好于A组(P=0.02、0.04);A组和B组的不良反应发生率相近(P=0.75);A组和B组在2、3年OS率相近(P=0.68、0.74)。A组和B组在左右、头脚、腹背向外放值分别为5.74、5.93、5.94 mm和4.21、5.71、4.61 mm。 结论 对小儿肾母细胞瘤患者放疗时采取真空负压垫联合热塑体膜体位固定技术可降低摆位误差,提高放疗效果,值得在临床工作中推广和应用。     

The prognostic value of 18F-FDG PET/CT taken immediately after completion of radiotherapy for lung cancer treated with concurrent chemoradiotherapy: A pilot study

PurposeThe prognostic value of F-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) taken immediately after completion of radiotherapy in lung cancer patients is not well known. The purpose of this study is to assess the prognostic value of PET/CT taken immediately after completion of radiotherapy in lung cancer patients.Materials and methodsPatients with primary lung cancer planned to undergo concurrent chemoradiotherapy were enrolled. Patients underwent PET/CT scans at 3 time points: before radiotherapy, within 24 hours of completing radiotherapy (im-PET/CT), and 2–9 months after radiotherapy (post-PET/CT). Maximum standardized uptake value (SUV_max) was obtained. A post-PET/CT-SUV_max cut-off of 2.5 was determined as radiotherapy success.ResultsNineteen patients were enrolled. im-PET/CT-SUV_max for patients in the high post-PET/CT-SUV_max group was significantly higher than that of the low group (P = 0.004). Receiver operator curve analysis indicated that im-PET/CT-SUV_max of 4.35 was an optimal cut-off value to discriminate between the two groups. Multivariable analysis showed that a high im-PET/CT-SUV_max was significantly associated with a high post-PET/CT-SUV_max (P = 0.003).ConclusionPET/CT-SUV_max taken immediately following radiotherapy was associated with that evaluated 2–9 months after radiotherapy.