Vacuum Cushion Research Articles

Does deformation of immobilization devices impact treatment accuracy in thoracic cancer radiotherapy?

Immobilization devices are essential for maintaining accurate and repeatable patient positioning in radiotherapy. This study aimed to evaluate the setup errors and dosimetric deviation induced by the deformation of immobilization devices in thoracic cancer radiotherapy using CT-linac. A retrospective analysis was conducted on 40 thoracic cancer patients who underwent radiotherapy, using vacuum cushion (VC) and thermoplastic mask (TM) for immobilization. A total of 206 weekly Fan-beam CT (FBCT) images (4-7 per patient) were analyzed to manually delineate immobilization devices and assess their geometric deformations against setup errors. Dosimetric deviations between the clinical plan (CT-plan) and the delivered plan (FBCT-plan) were compared for planning target volume (PTV) and organs at risk (OARs). Correlations between dose variations and setup errors were analyzed in lateral (LAT), longitudinal (LNG), and vertical (VRT) axes. The conformity of the VC (Nup) and TM (Ndown) with the patient in simulation CT exhibited moderate to strong correlations with VRT setup errors (Ndown: r=-0.484, p<0.01;Nup: r=-0.697, p<0.01). However, intra-fraction deformation of immobilization devices (in FBCT) showed no significant correlation with setup errors. In the dosimetric analysis of OARs, lung dose parameters (Dmean, V5, V20) and heart Dmean exhibited a consistent absolute difference with increasing setup errors. Dose variation decreased significantly when errors exceeded 5 mm, particularly in the VRT direction for most PTV indices, with the exception of CI and HI. Spinal cord Dmax variation correlated significantly with setup accuracy along the LNG axis, but not along other axes. The conformity of immobilization devices in simulation CT exhibits a stronger correlation with setup accuracy than the deformation of these devices in intra-fraction FBCT. FBCT is recommended for improving treatment precision through dosimetric assessment and planning adjustments.

MRgFUS ablation of a recurrent tenosynovial giant cell tumor in the foot using ExAblate 2100 system in combination with patient immobilization device

IntroductionMagnetic Resonance–guided Focused Ultrasound (MRgFUS) treatment for certain anatomy locations can be extremely challenging due to patient positioning and potential motion. This present study describes the treatment of a recurrent tenosynovial giant cell tumor of the plantar forefoot using the ExAblate 2100 system in combination with patient immobilization device. MethodsPrior to the treatment, several patient immobilization devices were investigated. Vacuum cushions were selected and tested for safety and compatibility with the treatment task and the MR environment. ResultsDuring the treatment, one vacuum cushion immobilized the patient's right leg in knee flexion and allowed the bottom of the foot to be securely positioned on the treatment window. Another vacuum cushion supported the patient upper body extended outside the scanner bore. 19 sonications were successfully executed. The treatment was judged to be successful. No immediate complications were observed. ConclusionsMRgFUS treatment of a recurrent tenosynovial giant cell tumor of the right plantar forefoot was successful with the use of patient immobilization vacuum cushions. Implications for practiceThe immobilization system could be utilized to aid future MRgFUS treatment of lesions in challenging anatomic locations. Various sizes of the vacuum cushions are available to potentially better accommodate other body parts and treatment configurations.

Intrafractional motion detection for spine SBRT via X-ray imaging using ExacTrac Dynamic

PurposeDue to its close vicinity to critical structures, especially the spinal cord, standards for safety for spine stereotactic body radiotherapy (SBRT) should be high. This study was conducted, to evaluate intrafractional motion during spine SBRT for patients without individualized immobilization (e.g., vacuum cushions) using high accuracy patient monitoring via orthogonal X-ray imaging. MethodsIntrafractional X-ray data were collected from 29 patients receiving 79 fractions of spine SBRT. No individualized immobilization devices were used during the treatment. Intrafractional motion was monitored using the ExacTrac Dynamic (ETD) System (Brainlab AG, Munich, Germany). Deviations were detected in six degrees of freedom (6 DOF). Tolerances for repositioning were 0.7 mm for translational and 0.5° for rotational deviations. Patients were repositioned when the tolerance levels were exceeded. ResultsOut of the 925 pairs of stereoscopic X-ray images examined, 138 (15 %) showed at least one deviation exceeding the predefined tolerance values. In all 6 DOF together, a total of 191 deviations out of tolerance were recorded. The frequency of deviations exceeding the tolerance levels varied among patients but occurred in all but one patient. Deviations out of tolerance could be seen in all 6 DOF. Maximum translational deviations were 2.6 mm, 2.3 mm and 2.8 mm in the lateral, longitudinal and vertical direction. Maximum rotational deviations were 1.8°, 2.6° and 1.6° for pitch, roll and yaw, respectively. Translational deviations were more frequent than rotational ones, and frequency and magnitude of deviations showed an inverse correlation. ConclusionIntrafractional motion detection and patient repositioning during spine SBRT using X-ray imaging via the ETD System can lead to improved safety during the application of high BED in critical locations. When using intrafractional imaging with low thresholds for re-positioning individualized immobilization devices (e.g. vacuum cushions) may be omitted.

Stereotactic body radiation therapy (SBRT) for spinal metastases: 12years of a single center experience.

To assess the clinical outcomes of patients with spine metastases treated with SBRT at our institution. Patients with spine metastases treated with SBRT (1 fraction/18Gy or 5 fractions/7Gy) during the last 12years have been analyzed. All patients were simulated supine in a vacuum cushion or with a shoulder mask. CT scans and MRI image registration were performed. Contouring was based on International Spine-Radiosurgery-Consortium-Consensus-Guidelines. Highly conformal-techniques (IMRT/VMAT) were used for treatment planning. Intra and interfraction (CBCT or X-Ray-ExacTrac) verification were mandatory. From February 2010 to January 2022, 129 patients with spinal metastases were treated with SBRT [1 fraction/18Gy (75%) or 5 fractions/7Gy] (25%). For patients with painful metastases (74/129:57%), 100% experienced an improvement in pain after SBRT. With a median follow-up of 14.2months (average 22.9; range 0.5-140) 6 patients (4.6%) experienced local relapse. Local progression-free survival was different, considering metastases's location (p < 0.04). The 1, 2 and 3years overall survival (OS) were 91.2%, 85.1% and 83.2%, respectively. Overall survival was significantly better for patients with spine metastases of breast and prostate cancers compared to other tumors (p < 0.05) and significantly worse when visceral metastases were present (p < 0.05), when patients were metastatic de novo (p < 0.05), and in those patients receiving single fraction SBRT (p: 0.01). According to our experience, SBRT for patients with spinal metastases was effective in terms of local control and useful to reach pain relief. Regarding the intent of the treatment, an adequate selection of patients is essential to propose this ablative approach.

Comparison between supine and prone patient setup for lumbosacral spinal stereotactic body radiosurgery with CyberKnife.

The aim of this study is to analyze which tracking modality is more suitable for stereotactic body radiosurgery of lumbosacral spinal tumors by comparing prone and supine patient treatment setup. Eighteen patients with lumbosacral spinal tumors were selected. CT simulation was performed in the supine position (fixed with a vacuum cushion) and prone position (fixed with a thermoplastic mask and prone plate), respectively. The plans in the supine and prone positions were designed using the xsight spine tracking (XST) and xsight spine prone tracking (XSPT) modalities, respectively. The dose-volume histogram (DVH) parameters, namely, V100%, D95%, Dmean, conformity index (CI), and heterogeneity index (HI) in planning target volume (PTV), as well as Dmax, D0.1cc, D1cc, and D5cc in the cauda equina and bowel were recorded. The supine plans were simulation plans and were not used for treatment, which were only used to record the alignment errors. The spinal tracking correction errors (alignment error) and correlation errors of the synchrony respiratory model in the prone position were recorded during the treatment. After treatment, the simulation plan of the supine position was implemented and the spinal tracking correction errors were recorded. The parameters of correction error and DVH parameters for the two positions were analyzed using the paired t-test to compare the difference in positioning accuracy and dose distribution. In addition, the correlation errors of the synchrony respiratory model in the prone position were analyzed to evaluate the prediction accuracy of the synchrony model. For patient setup, the correction error of the supine position in interior/posterior was (0.18 ± 0.16) mm and the prone position was (0.31 ± 0.26) mm (P< 0.05). The correction error of the supine position in inferior/superior was (0.27 ± 0.24) mm, and the prone position was (0.5 ± 0.4) mm (P< 0.05). The average correlation errors of the synchrony model for left/right, inferior/superior, and anterior/posterior in the prone position were (0.21 ± 0.11) mm, (0.41 ± 0.38) mm, and (0.68 ± 0.42) mm, respectively. For the dose distribution, compared with prone plans, the average CI in supine plans was increased by 4.5% (P< 0.05). There was no significant difference in HI, PTV V100%, D95%, and Dmean between the prone and supine plans. Compared with supine plans, average D1cc and D5cc for the cauda equina was significantly decreased by 4.7 and 15.3% in the prone plan (P< 0.05). For the bowel, average Dmax, D0.1cc, D1cc, and D5cc were reduced by 8.0, 7.7, 5.2, and 26.6% in prone plans (P< 0.05) compared with supine plans. Compared with the supine setup, the prone setup combined with XSPT modality for the lumbosacral spinal stereotactic body radiosurgery can spare the bowel and cauda equina of the middle and low dose irradiation, and decrease the number of beams and monitor units.

Feasibility of marker-less stereotactic body radiotherapy for hepatocellular carcinoma

Background The feasibility of marker-less stereotactic body radiotherapy (SBRT) for hepatocellular carcinoma (HCC) has not yet been established, and, thus, was examined in the present study. Material and methods We retrospectively investigated patients who received marker-less SBRT for locally untreated HCC tumors between July 2005 and December 2018. Radiotherapy planning CT was performed under fixation with vacuum cushions and abdominal compression. The clinical target volume (CTV) was equivalent to the gross tumor volume (GTV). The internal target volume (ITV) margin to CTV was determined from calculations based on the motion of the diaphragm. The planning target volume (PTV) margin to ITV was 5–6 mm. In the set-up, radiotherapy planning CT and linac-integrated cone-beam CT performed in the same imaging and fixation settings were merged by referring to the anatomical components surrounding target tumors. The primary endpoint was the 3-year cumulative local tumor progression rate. The upper limit of the 95% confidence interval for the 3-year cumulative local tumor progression rate was less than 7.0%, which was interpreted as favorable local control and feasible for marker-less SBRT. Local tumor progression was assessed by mRECIST. Results We reviewed 180 patients treated with 35–40 Gy/5 fractions. The median follow-up time for the local tumor progression of censored tumors was 32.3 months (range, 0.3–104). The 3-year cumulative local tumor progression rate was 3.0% (95% CI, 1.1–6.5%). The 3-year overall survival rate was 71.6% (95% CI, 63.5–78.2%). Regarding acute hematologic toxicities, grade 3 hypoalbuminemia and thrombocytopenia were detected in 1 (0.6%) and 5 (2.9%) patients, respectively. Treatment-related death from SBRT was not observed. SBRT was initiated within 7 days after radiotherapy planning CT for 84% (152/180) of patients. Conclusions Marker-less SBRT for HCC achieved favorable local control that fulfilled the threshold. This result suggests that marker-less SBRT with appropriate settings is a feasible treatment strategy.

Influence of Clinical and Tumor Factors on Interfraction Setup Errors With Rotation Correction for Vacuum Cushion in Lung Stereotactic Body Radiation Therapy.

PurposeTo explore the influence of clinical and tumor factors over interfraction setup errors with rotation correction for non-small cell lung cancer (NSCLC) stereotactic body radiation therapy (SBRT) patients immobilized in vacuum cushion (VC) to better understand whether patient re-setup could further be optimized with these parameters.Materials and MethodsThis retrospective study was conducted on 142 NSCLC patients treated with SBRT between November 2017 to July 2019 in the local institute. Translation and rotation setup errors were analyzed in 732 cone-beam computed tomography (CBCT) scans before treatment. Differences between groups were analyzed using independent sample t-test. Logistic regression test was used to analyze possible correlations between patient re-setup and clinical and tumor factors.ResultsMean setup errors were the largest in anterior–posterior (AP) direction (3.2 ± 2.4 mm) compared with superior–inferior (SI) (2.8 ± 2.1 mm) and left–right (LR) (2.5 ± 2.0 mm) directions. The mean values were similar in pitch, roll, and rtn directions. Of the fractions, 83.7%, 90.3%, and 86.6% satisfied setup error tolerance limits in AP, SI, and LR directions, whereas 95% had rotation setup errors of <2° in the pitch, roll, or rtn directions. Setup errors were significantly different in the LR direction when age, body mass index (BMI), and “right vs. left” location parameters were divided into groups. Both univariate and multivariable model analyses showed that age (p = 0.006) and BMI (p = 0.002) were associated with patient re-setup.ConclusionsAge and BMI, as clinical factors, significantly influenced patient re-setup in the current study, whereas all other clinical and tumor factors were not correlated with patient re-setup. The current study recommends that more attention be paid to setup for elderly patients and patients with larger BMI when immobilized using VC, especially in the left–right direction.

Evaluation of inter- and intra-fraction 6D motion for stereotactic body radiation therapy of spinal metastases: influence of treatment time

BackgroundThe objective of this study was to analyze the amplitude of translational and rotational movements occurring during stereotactic body radiotherapy (SBRT) of spinal metastases in two different positioning devices. The relevance of intra-fractional imaging and the influence of treatment time were evaluated.MethodsTwenty patients were treated in the supine position either (1) on a body vacuum cushion with arms raised and resting on a clegecel or (2) on an integrated SBRT solution consisting of a SBRT table top, an Orfit™ AIO system, and a vacuum cushion. Alignments between the cone beam computed tomography (CBCT) and the planning computed tomography allowed corrections of inter- and intra-fraction positional shifts using a 6D table. The absolute values of the translational and rotational setup errors obtained for 329 CBCT were recorded. The translational 3D vector, the maximum angle, and the characteristic times of the treatment fractions were calculated.ResultsAn improvement in the mean (SD) inter-fraction 3D vector (mm) from 7.8 (5.9) to 5.9 (3.8) was obtained by changing the fixation devices from (1) to (2) (p < 0.038). The maximum angles were less than 2° for a total of 87% for (1) and 96% for (2). The mean (SD) of the intra-fraction 3D vectors (mm) was lower for the new 1.1 (0.8) positioning fixation (2) compared to the old one (1) 1.7 (1.7) (p = 0.004). The angular corrections applied in the intra-fraction were on average very low (0.4°) and similar between the two systems. A strong correlation was found between the 3D displacement vector and the fraction time for (1) and (2) with regression coefficients of 0.408 (0.262–0.555, 95% CI) and 0.069 (0.010–0.128, 95% CI), respectively. An accuracy of 1 mm would require intra-fraction imaging every 5 min for both systems. If the expected accuracy was 2 mm, then only system (2) could avoid intra-fractional imaging.ConclusionsThis study allowed us to evaluate setup errors of two immobilization devices for spine SBRT. The association of inter- and intra-fraction imaging with 6D repositioning of a patient is inevitable. The correlation between treatment time and corrections to be applied encourages us to move toward imaging modalities which allow a reduction in fraction time.

Invention and Evaluation of a Novel Air Leak Check System for Vacuum-type Patient Immobilization Device

We developed a novel system to measure air leakage in vacuum cushions, which are used in high-precision radiation therapy. The purpose of this study was to verify the usefulness of this system by evaluating the accuracy and the capability for detecting air leakage. The novel system was used to measure pressure in the cushion using a manometer. The advantage of this system was that we can measure the pressure without deformation of the cushion and check the pressure immediately. We confirmed that the pressure measured using this system is proportional to the reading in the reference manometer by the coefficient of 1.0. This system had a higher capability in the leak detection than the capability by checking softness in our sense of touch. We checked the leakage using this system against 18 cushions without air leakage (NL group) and 7 cushions that had problems regarding usage in patients due to the leakage (CW group). Average pressure variations in the NL group and the CW group were 22 kPa and 46 kPa, respectively. This was a significant difference in both groups. We could decide the criteria of pressure in the cushions that may cause troubles in the future use. We concluded that this system can detect air leakage in the cushions with a higher detectivity than our tactile sense.

Impact of a vacuum cushion on intrafraction motion during online adaptive MR-guided SBRT for pelvic and para-aortic lymph node oligometastases

Background and purposeVacuum cushion immobilization is commonly used during stereotactic body radiotherapy (SBRT) to reduce intrafraction motion. We investigated target and bony anatomy intrafraction motion (translations and rotations) during online adaptive SBRT on an MR-linac for pelvic/para-aortic lymph node metastases with and without vacuum cushion. Materials and methodsThirty-nine patients underwent 5x7 Gy SBRT on a 1.5T MR-linac, 19 patients were treated with vacuum cushion, 19 without and 1 patient sequentially with and without. Intrafraction motion was calculated for target lymph nodes (GTVs) and nearby bony anatomy, for three time intervals (pre-position verification (PV), pre-post, PV-post, relating to the online MRI scans) per treatment fraction. ResultsVacuum cushion immobilization significantly reduced anterior-posterior translations for the pre-PV and pre-post intervals, for bony anatomy and pre-post interval for GTV (p < 0.05). Mean GTV intrafraction motion reduction in posterior direction was 0.7 mm (95% confidence interval 0.3–1.1 mm) for pre-post interval (mean time = 32 min). Shifts in other directions were not significantly reduced. More motion occurred in pre-PV interval than in PV-post interval (mean time = 16 min for both); vacuum cushion immobilization did not reduce intrafraction motion during the beam-on period. ConclusionA vacuum cushion reduces GTV and bony anatomy intrafraction motion in posterior direction during pelvic/para-aortic lymph node SBRT. This motion reduction was found for the first 16 min per session. For single targets this motion can be corrected for directly with an MR-linac. Intrafraction motion was not reduced during the second half of the session, the period of radiotherapy delivery on an MR-linac. Vacuum cushion immobilization may not be necessary for patients with single lymph node oligometastases undergoing SBRT on an MR-linac.

Automated patient positioning in CT using a 3D camera for body contour detection: accuracy in pediatric patients

ObjectiveTo assess the accuracy of a 3D camera for body contour detection in pediatric patient positioning in CT compared with routine manual positioning by radiographers.Methods and materialsOne hundred and ninety-one patients, with and without fixation aid, which underwent CT of the head, thorax, and/or abdomen on a scanner with manual table height selection and with table height suggestion by a 3D camera were retrospectively included. The ideal table height was defined as the position at which the scanner isocenter coincides with the patient’s isocenter. Table heights suggested by the camera and selected by the radiographer were compared with the ideal height.ResultsFor pediatric patients without fixation aid like a baby cradle or vacuum cushion and positioned by radiographers, the median (interquartile range) absolute table height deviation in mm was 10.2 (16.8) for abdomen, 16.4 (16.6) for head, 4.1 (5.1) for thorax-abdomen, and 9.7 (9.7) for thorax CT scans. The deviation was less for the 3D camera: 3.1 (4.7) for abdomen, 3.9 (6.3) for head, 2.2 (4.3) for thorax-abdomen, and 4.8 (6.7) for thorax CT scans (p < 0.05 for all body parts combined).ConclusionA 3D camera for body contour detection allows for automated and more accurate pediatric patient positioning than manual positioning done by radiographers, resulting in overall significantly smaller deviations from the ideal table height. The 3D camera may be also useful in the positioning of patients with fixation aid; however, evaluation of possible improvements in positioning accuracy was limited by the small sample size.Key Points• A 3D camera for body contour detection allows for automated and accurate pediatric patient positioning in CT.• A 3D camera outperformed radiographers in positioning pediatric patients without a fixation aid in CT.• Positioning of pediatric patients with fixation aid was feasible using the 3D camera, but no definite conclusions were drawn regarding the positioning accuracy due to the small sample size.

Analyzing the Positional uncertainties in 3dcrt ca breast Patients with Free Breathing and Active Breath Coordinator Gating Immobilization Devices

Aim: The aim of this study is to rule out the difference in positional setup errors when using immobilization device such as thermoplastic mould for free breathing and vacloc with ABC gating in ca breast patient treating with 3DCRT technique. Objective: The study is to compare the patient setup uncertainties using two different immobilization device, one with standard thermoplastic mould and other with vacuum cushion with active breath control gating in our clinical setup. Methodology: fourteen patients with ca breast are taken for the study. seven patients are undergone immobilization using standard thermoplastic moulding and remaining seven patients undergone, vacuum cushion with active breath control DIBH (deep inspiration breath hold) gating. CT was taken and 3dcrt plan were done according to the standard protocol. Prior to the treatment CBCT was taken, matching was done in XVI with the reference images, to rule out any positional shifts. Positional Shifts on all 3 axes such x, y, z is noted with rotational shift. Comparison were done on systematic error (?), random error (?), mean displacement vector (R), mean setup error (M). Result: immobilization device used by vacloc with DIBH ABC gating shows very less shifts in all direction, especially longitudinal direction compared with mould one, which we are using routinely in our department.

Development of an Immobilization Device for Total Marrow Irradiation

PurposeA body frame dedicated to total marrow (lymph node) irradiation (TMI/TMLI) could minimize patient motion during the potentially extended beam-on time with this technique. We present the development of a dedicated immobilization system for TMI/TMLI using volumetric modulated arc therapy. Methods and MaterialsSince 2010, 59 adult patients were treated with TMI/TMLI using a multi-isocenter volumetric modulated arc therapy technique. Two computed tomographies (CTs) were required (1 head-first supine and 1 feet-first supine) to cover the whole volume. For the first 10 patients, 2 standard commercial frames with personalized masks (with/without personalized vacuum cushion for the lower extremities) were used without specific interfixation (frame A). For the next 49 patients a homemade 3-frame immobilization system was adopted (frame B), where each frame was interlocked with the next one and thermoplastic masks used to fix the patient. The effectiveness of the 2 immobilization systems was assessed by offline/online matching between daily cone beam CT of each isocenter and the simulation CTs. ResultsMean offline shifts for frame A were 3 to 12 mm in anterior–posterior, 2 to 5 mm in cranilal–caudal, and 2 to 6 mm in left–right directions. Larger shifts were found for feet-first supine series (shifts up to 23 mm). In frame B, mean offline shifts were 1 to 4 mm in anterior–posterior, 1 to 4 mm in cranial–caudal, and 1 to 4 mm in left–right directions. Mean online adjustments were –1 ± 4 mm in anterior–posterior, 0 ± 2 mm in cranial–caudal, and 0 ± 4 mm in left–right directions. ConclusionsThe patient positioning shifts for TMI/TMLI irradiation were mitigated by a homemade immobilization system and the use of individualized masks.

Longitudinal body composition assessment in healthy term-born infants until 2 years of age using ADP and DXA with vacuum cushion.

Accelerated gain in fat mass (FM) in early life increases the risk for adult diseases. Longitudinal data on infant body composition are crucial for clinical and research use, but very difficult to obtain due to limited measurement tools and unsuccessful measurements between age 6-24 months. We compared FM% by dual-energy X-ray absorptiometry (DXA), with cushion to reduce movement artifacts, with FM% by air-displacement plethysmography (ADP) and evaluated the reliability of this cushion during DXA by comparing FM% with and without cushion. Subsequently, we constructed sex-specific longitudinal body composition charts from 1-24 months. In 692 healthy, term-born infants (Sophia Pluto Cohort), FM% was measured by ADP from 1-6 months and DXA with cushion from 6-24 months. At 6 months, FM% was measured in triplicate by ADP and DXA with and without cushion(n = 278), later on in smaller numbers. At 6 months, mean FM% by DXA with cushion was 24.1 and by ADP 25.0, mean difference of 0.9% (Bland-Altman p = 0.321, no proportional bias). Mean FM% by DXA without cushion was 12.5% higher compared to ADP (Bland-Altman p < 0.001). DXA without cushion showed higher mean FM% compared to DXA with cushion (+11.6%, p < 0.001) at 6 months. Longitudinally, FM% increased between 1-6 months and decreased from 6-24 months(both p < 0.001). In infants, DXA scan with cushion limits movement artifacts and shows reliable FM%, comparable to ADP. This allowed us to construct longitudinal body composition charts until 24 months. Our study shows that FM% increases from 1-6 months and gradually declines until 24 months.

VACUUM AND THERMOPLASTIC MOULD-BASED IMMOBILIZATION SYSTEMS USED IN PATIENT UNDERGOING PELVIC RADIATION THERAPY: A COMPARATIVE STUDY

Introduction: The aim of the present study was to compare two immobilization systems for comparison of setup errors in targeted radiotherapy.&#x0D; Methods: Retrospective analysis was done for the patients undergoing radiotherapy from May 2012 to December 2018 at our institution. Immobilization was performed on 30 patients sessions (Vacuum cushion i.e., Vac-Lok™ = 15; Thermoplastic mould i.e., Pelvicast pelvic masks = 15). A total of 763 cone-beams were analysed. The target lesion location was verified by cone-beam computed tomography (CBCT) prior to each session, with displacements assessed by CBCT simulation prior to each treatment session. Systematic setup errors, random setup errors, isocenter deviations in the Medio-lateral (ML), Supero-inferior (SI), Antero-posterior (AP), Rotation (yaw) directions of the patient position was calculated.&#x0D; Results: On comparing the Vac-Lok™ and Pelvicast pelvic masks group with respect to Systematic and random error in the lateral, longitudinal, vertical and YAW direction, no statistically significant difference was seen except the random error in YAW direction (P=0.037, Unpaired t-test). There was no difference observed in comparing the isocentric deviation.&#x0D; Conclusion: It was inferred and concluded that using a vacuum cushion for pelvic radiotherapy provides no added benefit compared to using a thermoplastic mould. Thermoplastic mould is recommended for patients receiving pelvic radiotherapy to improve overall reproducibility.Keywords: Rotational therapy; Radiotherapy; Systematic, random error; Thermoplastic mould; Vacuum cushion.

Retrospective Dosimetric analysis of Bone marrow sparing vs non bone marrow sparing Image Guided Volumetric Modulated Arc Therapy in intact Carcinoma Cervix patients

ABSTRACT Aim: Aim of this study was to compare dosimetric parameters of bone marrow (BM) and non bone marrow sparing with state of the art technique image guided volumetric modulated arc therapy in the treatment of Carcinoma Cervix. Methods and Materials: The retrospective Dosimetric study was conducted on 10 consecutive patients of biopsy-proven invasive cervical cancer attending the outpatient department of Geetanjali cancer centre. For treatment planning, patients were scanned on a GE Optima-520, 16 slice fan-beam CT (FBCT) scanner with 2.5 mm slice thickness in the supine position on a customized vacuum cushion with simulation tattoos and alignment lasers. All the simulation scans were taken after following a bladder and bowel preparation protocol, aimed at an empty rectum and full bladder, starting prior to the initial planning scan and continuing throughout the treatment. The prescribed dose to PTV was 50Gy in 25 fractions (2Gy/fraction) and from second week of radiotherapy 50mg/m2/week cisplatin chemotherapy was administered for five weeks. Two sets of plans were generated for all the 10 patients using Volumetric Arc Radiotherapy (VMAT) in Monaco v 5.11.02(Elekta, Crawley, UK) treatment planning system. Keeping all constraints in mind planning optimization was performed with no compromise in coverage of PTV. Results: In the present study V5, V10, V20, V30 were all significantly lower in BMS-IG/VMAT plan . Maximum significance was noted at V20. Value of V40 is lower in BM-IG/VMAT plan, but statistically not significant. Conclusion: Treatment of carcinoma cervix is restricted as a result of toxicity of the surrounding normal structures and HT. HT could be significantly reduced by bone marrow sparing, which could be aided by IGRT/VMAT. This modality could allow completion of treatment with prescribed dose and concurrent chemotherapy in allotted stipulated time. More prospective randomized control trials are needed, to prove its efficacy. key words: bone marrow sparing, hematological toxicity, Image Guidance/Volumetric Modulated Arc Therapy

Real-time Magnetic Resonance-guided Liver Stereotactic Body Radiation Therapy: An Institutional Report Using a Magnetic Resonance-Linac System.

BackgroundStereotactic body radiation therapy (SBRT) is a proven and effective modality for treatment of hepatic primary and metastatic tumors. However, these lesions are challenging for planning and treatment execution due to natural anatomic changes associated with respiration. Magnetic resonance imaging (MRI) offers superior soft tissue contrast resolution and the ability for real-time image-guided treatment delivery and lesion tracking.ObjectiveTo evaluate the plan quality, treatment delivery, and tumor response of a set of liver SBRT cancer treatments delivered with magnetic resonance (MR)-guided radiotherapy on a MR-linear accelerator (MR-linac).MethodsTreatment data from 29 consecutive patients treated with SBRT were reviewed. All treatments were performed using a step and shoot technique to one or more liver lesions on an MR-linac platform. Patients received 45 to 50 Gy prescribed to at least 95% of the planning target volume (PTV) in five fractions except for two patients who received 27-30 Gy in three fractions. Computed tomography and MRI simulation were performed in the supine position prior to treatment in the free-breathing, end exhalation, and end inhalation breath-hold positions to determine patient tolerability and potential dosimetric advantages of each technique. Immobilization consisted of using anterior and posterior torso MRI receive coils embedded in a medium-sized vacuum cushion. Gating was performed using sagittal cine images acquired at 4 frames/second. Gating boundaries were defined in the three major axes to be 0.3 to 0.5 cm. An overlapping region of interest, defined as the percentage volume allowed outside the boundary for beam-on to occur, was set between 1 and 10%. The contoured target was assigned a 5-mm PTV expansion. Organs at risk constraints adopted by the American Association of Physicists in Medicine Task Group 101 were used during optimization.ResultsTwenty-nine patients, with a total of 34 lesions, successfully completed the prescribed treatment with minimal treatment breaks or delays. Twenty-one patients were treated at end-exhale, and six were treated at end-inhale. Two patients were treated using a free-breathing technique due to poor compliance with breath-hold instructions. The reported mean liver dose was 5.56 Gy (1.39 - 10.43; STD 2.85) and the reported mean liver volume receiving the prescribed threshold dose was 103.1 cm3 (2.9 - 236.6; STD 75.2). Follow-up imaging at one to 12 months post treatment confirmed either stable or decreased size of treated lesions in all but one patient. Toxicities were mild and included nausea/vomiting, abdominal pain and one case of bloody diarrhea. Four patients died due to complications from liver cirrhosis unrelated to radiation effect.ConclusionSBRT treatment using a gated technique on an MR-linac has been successfully demonstrated. Potential benefits of this modality include decreased liver dose leading to decreased toxicities. Further studies to identify the benefits and risks associated with MR-guided SBRT are necessary.

Comparison of geometrical uncertainties in the radiotherapy for various treatment sites with two different immobilization marking methods

The skin marking method (SMM) and bow-form-ruler marking method (BFRM) are two commonly used patient marking methods in mainland China. This study aims to evaluate SMM and BFRM by comparing the inter-fraction setup errors from using these two methods together with vacuum cushion immobilization in patients underwent radiotherapy for different treatment sites. Eighteen patients diagnosed with pelvic, abdominal and thoracic malignant tumors (with 6 patients per treatment site) were enrolled in this prospective study. All patients were immobilized with vacuum cushion. Each patient was marked by both SMM and BFRM before computed tomography (CT) simulation. Target location was verified by cone beam CT images with displacements assessed prior to each sampled treatment session. The localization errors in three translational and three rotational directions were recorded and analyzed. Images from 108 fractions in 18 patients produced 324 translational and 324 rotational comparisons for SMM and BFRM. The setup errors of all treatment sites showed no difference in two marking methods in any directions (p > 0.05). In subgroups of treatment site analysis, SMM significantly lessened the lateral and yaw setup errors compared to BFRM in the pelvic sites (0.39±1.85 mm vs -1.28±1.13 mm, p < 0.01 and -0.19±0.59° vs -0.61±0.59°, p < 0.05). However, in the abdominal subgroup, BFRM was superior to SMM for reduced vertical errors (0.17±2.73 mm vs 2.28±3.16 mm, p < 0.05). For the underweight or obese patients (with Body Mass Index, BMI < 18.5 or BMI≥24), SMM resulted in less yaw errors compared to BFRM (-0.05±0.38° vs -0.43±0.48°, p < 0.05). No significant difference between SMM and BFRM in setup errors of normal weighted patients (18.5≤BMI < 24) was observed for all three studied treatment sites. This study shows no significant difference in patient setup errors for various treatment sites between SMM and BFRM in general. SMM may be suitable for the pelvic tumor and patients with BMI < 18.5 or BMI≥24, while BFRM is recommended for the abdominal tumor sites.

A Novel 3D-Printed Patient Positioning Platform to Accommodate Curved Couch of MR Scanner Optimizes Precision Treatment Planning Workflow for Abdominal Radiotherapy.

Magnetic Resonance Imaging (MR) is increasingly used in treatment planning (TP) owing to superior soft tissue contrast versus computed tomography (CT). Organ deformation in patient positioning on a curved MR couch versus a flat CT couch causes registration difficulties. This may lead to contour errors and tumor volume misjudgment, particularly in organs poorly visualized on CT (i.e. liver). MR-based simulation systems (MR-BSS) address this issue but are not widely available. In this study, we fabricated a 3D-printed platform (3D-PP) adapted to the MR couch and body array to enable scans in the TP position and optimize MR-guided TP in the absence of a dedicated MR-BSS. We demonstrate that a 3D-PP is low cost, does not interfere with image quality, and is easily implemented by radiology staff. The 3D-PP was drafted with computer-aided design to fit the table arc and 12 channel body array coil of a 1.5 T, 70 cm wide bore, MR scanner. The 3D-PP creates a flat surface to position an immobilization vacuum bag typically used in treatment. The 3D-PP consists of ¼” thick deck and 3/32” thick alignment wings mounted on ten risers. The deck and alignment wings are polyoxymethylene homopolymer laser-cut with a contact-free CO2 beam. Risers are fabricated from polylactide in a thermoplastic 3D printer. A urethane immobilization vacuum cushion (88 x 55 cm, 15 L fill) was fabricated for an 8-channel upper annular MR phantom. CT was acquired in an 85 cm bore simulation CT (120kVp, 512x512 in-plane dimensions, 0.11cm x 0.11cm pixel size, 2mm thickness). Standard body MR sequences were done including single shot fast spin echo (SS-FSE), 3D fast spoiled gradient echo with fat suppression(FSPGR FS), T2 fat suppression(T2 FS), balanced steady-state free precession (BSSFP), dual echo fast spin echo(DE FSE), and diffusion weight imaging (DWI). MR and CT scans were exported to a treatment planning system and fused using a local correlation algorithm capable of both rigid and deformable registration. An anthropomorphic phantom and quality control devices were employed for MR scans. SS-FSE, FSPGR, FSPGR FS, T2 FS, BSSFP, DEFSE, and DWI were analyzed to determine the effect of any artifacts contributed by the 3D-PP. Neither appreciable signal loss nor artifact were observed on any scan. Each MR-CT fusion required negligible computation time (< 2 seconds). In-plane registration was within sub-pixel accuracy for every slice in each sequence. We report a new, low cost approach to optimize MR-guided TP. A 3D-PP enables MR scans in the simulated TP position without appreciable loss of image quality or interruption of radiology workflow. A 3D-PP in a 70 cm wide bore MR system accommodates most treatment positions, including wing board. We are implementing this process into our abdominal SBRT workflow. The 3D-PP design and fabrication can be modified for the workflow of most clinics.

Research progress on target delineation for radiotherapy in hepatocellular carcinoma with

Modern medical imaging techniques, such as computed tomorgraphy (CT), magnetic resonance imaging (MRI) and position emission tomorgraphy/computed tomorgraphy (PET-CT) can accurately delineate the gross target volume (GTV) of hepatocellular carcinoma (HCC). Comparison of postoperative pathological subclinical lesions, imaging and clinical parameters contributes to the precise delineation of clinical target volume (CTV). Moreover, radiotherapy-assisted techniques, such as four-dimensional computed tomography (4DCT), compression of abdomen, active breathing control and respiratory gating, can minimize the internal target volume (ITV). In addition, immobilization with vacuum cushion and body membrane can reduce the set-up error, minimize the planning target volume (PTV) and avoid or decrease the irradiation error or missing irradiation. All these approach can minimize the target volume, elevate the dose and reduce the complications during radiotherapy for HCC. In this article, the research progress on the target delineation for external beam radiotherapy in HCC patients was reviewed. Key words: Hepatocellular neoplasm/radiotherapy; Target delineation; Progress