Frequency of errors in the transfer of treatment parameters from the treatment planning system to the oncology information system in a multi-vendor environment.

BACKGROUND: Technological advancements have made it possible to improve patient outcomes in radiotherapy, sparing both normal tissues and increasing tumour control. However, these advancements have resulted in an increase in the number of software systems used, which each require data inputs to function. For institutions with multiple vendors for their treatment planning systems and oncology information systems, the transfer of data between them is potentially error prone and can lead to treatment errors. PURPOSE: The goal of this work was to determine the frequency of errors in data transfers between the Varian Eclipse treatment planning system and the Elekta Mosaiq oncology information system. METHODS: An in-house program was used to quantify the number of errors for 2700 unique plans over an 8-month period. Using this information, the frequency of the errors were calculated. A risk priority number was calculated using the calculated frequencies to determine the impact on the clinic. RESULTS: The most common errors discovered were backup timer settings (10.7%), Field label (8.5%), DRR associations (3.3%), imaging field types (3.1%), dose rate (1%), Field Id (0.8%), imaging isocenter (0.7% and SSD (0.7%). Based on the risk priority numbers, the DRR association error was ranked as having the highest potential impact on the patient. CONCLUSIONS: The results of the work show that the most effort should be focused on checking the manual steps performed in the transfer process, while items that are imported directly from DICOM-RT without modification are highly likely to be transferred accurately. The data can be used to help guide the implementation of future automated tools and process improvement in the clinic.

Dynamic Modulated Brachytherapy (DMBT) Balloon Applicator for Accelerated Partial Breast Irradiation.

PURPOSE: To propose a novel high-dose-rate brachytherapy applicator for balloon-based dynamic modulated brachytherapy (DMBT) for accelerated partial breast irradiation (APBI) and to demonstrate its dosimetric advantage compared to the widely used Contura applicator. METHODS AND MATERIALS: The DMBT balloon device consists of a fixed central channel enabling real-time, in vivo dosimetry and an outer motion-dynamic, adjustable-radius channel capable of moving to any angular position within the balloon. This design allows placement of dwell positions anywhere within the balloon volume, guaranteeing optimal placement and generation of the applicator and treatment plan, respectively. Thirteen clinical treatment plans for patients with early-stage breast cancer receiving APBI after lumpectomy using Contura were retrospectively obtained under institutional review board approval. New treatment plans were created by replacing the Contura with the DMBT device. DMBT plans were limited to 4 angular positions and an outer channel radius of 1.5 cm. The new plans were optimized to limit dose to ribs and skin while maintaining target coverage similar to that of the clinical plan. RESULTS: Similar target coverage was obtained for the DMBT plans compared with clinical Contura plans. Across all patients the mean (standard deviation) reductions in D0.1 cc to the ribs and skin were 6.70% (6.28%) and 5.13% (6.54%), respectively. A threshold separation distance between the balloon surface and the organ at risk (OAR), below which dosimetric changes of greater than 5% were obtained, was observed to be 12 mm for ribs and skin. When both OARs were far from the balloon, DMBT plans were of similar quality to Contura plans, as expected. CONCLUSIONS: This study demonstrates the superior ability of the APBI DMBT applicator to spare OARs while achieving target coverage comparable to current treatment plans, especially when in close proximity. The DMBT balloon may enable new modes of dynamic high-dose-rate treatment delivery and allow for ultrahypofractionated dose regimens to be safely used.

Optimizing beam models for dosimetric accuracy over a wide range of treatments.

This work presents a systematic approach for testing a dose calculation algorithm over a variety of conditions designed to span the possible range of clinical treatment plans. Using this method, a TrueBeam STx machine with high definition multi-leaf collimators (MLCs) was commissioned in the RayStation treatment planning system (TPS). The initial model parameters values were determined by comparing TPS calculations with standard measured depth dose and profile curves. The MLC leaf offset calibration was determined by comparing measured and calculated field edges utilizing a wide range of MLC retracted and over-travel positions. The radial fluence was adjusted using profiles through both the center and corners of the largest field size, and through measurements of small fields that were located at highly off-axis positions. The flattening filter source was adjusted to improve the TPS agreement for the output of MLC-defined fields with much larger jaw openings. The MLC leaf transmission and leaf end parameters were adjusted to optimize the TPS agreement for highly modulated intensity-modulated radiotherapy (IMRT) plans. The final model was validated for simple open fields, multiple field configurations, the TG 119 C-shape target test, and a battery of clinical IMRT and volumetric-modulated arc therapy (VMAT) plans. The commissioning process detected potential dosimetric errors of over 10% and resulted in a final model that provided in general 3% dosimetric accuracy. This study demonstrates the importance of using a variety of conditions to adjust a beam model and provides an effective framework for achieving high dosimetric accuracy.

Direction modulated brachytherapy (DMBT) tandem applicator for cervical cancer treatment: Choosing the optimal shielding material.

PURPOSE: To investigate the dose modulation capability of a novel MRI-compatible direction modulated brachytherapy (DMBT) tandem applicator design with various high-density shielding materials for brachytherapy treatment of cervical cancer. The shield materials that have been evaluated are tantalum (Ta), pure tungsten (W), gold (Au), rhenium (Re), osmium (Os), platinum (Pt), iridium (Ir), and W' tungsten alloy (95%W, 3.5%Ni, 1.5%Cu). MATERIALS AND METHODS: The recently proposed six-channel DMBT tandem is composed of nonmagnetic tungsten alloy (W') rod with diameter of 5.4 mm and coated with 0.3-mm thick bio-safe plastic sheath. The tandem shielding material can, however, be individually replaced with various other shields to create directional radiation. Monte Carlo N-Particle (MCNP) code was used to calculate the three-dimensional (3D) dose distributions in a water phantom for an HDR 192 Ir (mHDR-v2) source inside each DMBT tandem with various shields and a plastic conventional tandem (Con.T). Then, the 3D dose distributions were imported into an in-house-coded inverse planning optimization algorithm to obtain optimal plans for 12 clinical cases chosen at random from the international RetroEMBRACE dataset involving conventional tandem and ring (Con.T&R) applicators. All plans generated by the DMBT tandem and ring (DMBT&R) with the tungsten alloy [DMBT(W')&R] were compared with the corresponding Con.T&R plans, to generate benchmark results. These benchmark results were then considered as reference plans for other shields performances. Plans were normalized to receive the same high-risk clinical target volume (CTVHR ) D90 . The D100 , D10 , and V100 for CTVHR , and D2cm3 for organs at risk (OARs) of bladder, sigmoid, and rectum were calculated and compared. RESULTS: Transmission factor (TF), that is, the dose in the backside of the DMBT shield over that in the front opening, at a 5 cm distance, were 36.6%, 34.8%, 31.9%, 28.9%, 27.9%, 26.2%, 26.2%, and 25.5%, for Ta, W', W, Re, Au, Os, Pt, and Ir shields, respectively. On average, the CTVHR values for D100 , V100 , D10 were not significantly different across all DMBT&R shields and the Con.T&R plans (P > 0.219). For the D2cm3 , the benchmark results showed significant reductions (P < 0.03), that is, on average, -8.3% for bladder, -10.7% for rectum, and -10.1% for sigmoid, compared to the Con.T&R plans. However, the various shields showed little improvement from the tungsten alloy (W'), where on average, rectum (bladder) [sigmoid] D2cm3 were reduced by -1.32% (-0.85%) [-1.01%], -1.25% (-0.78%) [-0.91%], -1.22% (-0.75%) [-0.86%], -0.94% (-0.60%) [-0.70%], -0.84% (-0.51%) [-0.59%], and -0.38% (-0.24%) [-0.23%] for Ir, Pt, Os, Au, Re, and W shields, relative to the benchmark W' DMBT plans, respectively. These corresponding values for Ta increased by +0.28% (+0.08%) [+0.25%], respectively. CONCLUSION: The Ir, Pt, Os, Au, Re, and W shielding materials, respectively, in descending order, lead to better OAR sparing than the DMBT(W')&R plans. However, the amount of improvement is limited and clinically insignificant. This finding suggests that the initial W' shield remains a suitable choice given the proven MR compatibility, for use in MR-guided adaptive brachytherapy of cervical cancer.

Quantitative CT assessment of a novel direction-modulated brachytherapy tandem applicator.

PURPOSE: The purpose of this study was to quantitatively assess the CT metal-induced artifacts from a novel direction-modulated brachytherapy (DMBT) tandem applicator prototype, recently designed for cervical cancer treatments. METHODS AND MATERIALS: A water-based pelvic phantom was constructed for CT scanning. The DMBT applicator was imaged using our institutional protocol, one with higher kVp and mAs settings, and repetition of these protocols using 3-mm slices. A conventional stainless steel applicator was also scanned. In addition to the standard reconstructed images, applicator images were reconstructed using a commercial metal artifact-reduction (MAR) algorithm and an in-house-developed research algorithm. Subsequently, image quality and artifact severity were evaluated. RESULTS: Artifact severity, measured in terms of SDs in CT numbers, decreased asymptotically to background water levels with the distance away from the applicator. Artifact-reduction algorithms lead to significant and visible improvements in image quality, with >50% and >20% decrease in artifact severity achieved at a 10-mm distance for the DMBT and stainless steel applicators, respectively. Differences in artifact severity were minimal between the four imaging protocols. DMBT dimensions were the same on images with and without the commercial MAR algorithm, within <1 mm of the theoretical value. Both the commercial and in-house algorithms restored the CT numbers outside the applicator, albeit a better performance was achieved by the in-house algorithm. CONCLUSIONS: The artifacts produced by both applicators were minimized with the use of MAR algorithms. Adoption of the DMBT and stainless steel applicators for CT-guided brachytherapy is anticipated as MAR algorithms are widely available on CT scanners.

Real-time electromagnetic tracking-based treatment platform for high-dose-rate prostate brachytherapy: Clinical workflows and end-to-end validation.

PURPOSE: New technologies were integrated into a novel treatment platform combining electromagnetically (EM) tracked catheters, a 3D ultrasound (3DUS) imaging device, and a new treatment planning system to provide a real-time prostate high-dose-rate (HDR) brachytherapy treatment system. This work defines workflows for offline CT and online 3DUS planning scenarios and preclinical end-to-end validation of the platform. METHODS AND MATERIALS: The platform is composed of an EM-tracked stylet, a EM-tracked 3DUS probe, and an EM-tracked template guide, all used with the NDI Aurora field generator (NDI, Ontario, Canada). The treatment planning system performs continuous position and angular readings from all three EM sensors into a streamlined environment that allows for (1) contouring; (2) planning; (3) catheter insertion guidance and reconstruction; (4) QA of catheter path and tip position; and (5) exporting to an afterloader. Data were gathered on the times required for the various key steps of the 3DUS-based workflow. RESULTS: The complete 3DUS-based workflow on 16-catheter implant phantoms took approximately 15 min. This time is expected to increase for actual patients. Plan generation is fast (7.6 ± 2.5s) and the initial catheter reconstruction with updated dose distribution is obtained at no (time) cost as part of the insertion process. Subsequent catheter reconstruction takes on average 10.5 ± 3.1s per catheter, representing less than 3 min for a 16-catheter implant. CONCLUSIONS: This preclinical study suggests that EM technology could help to significantly streamline real-time US-based high-dose-rate prostate brachytherapy.

Direction modulated brachytherapy (DMBT) for treatment of cervical cancer: A planning study with 192 Ir, 60 Co, and 169 Yb HDR sources.

PURPOSE: To evaluate plan quality of a novel MRI-compatible direction modulated brachytherapy (DMBT) tandem applicator using 192 Ir, 60 Co, and 169 Yb HDR brachytherapy sources, for various cervical cancer high-risk clinical target volumes (CTVHR ). MATERIALS AND METHODS: The novel DMBT tandem applicator has six peripheral grooves of 1.3-mm diameter along a 5.4-mm thick nonmagnetic tungsten alloy rod. Monte Carlo (MC) simulations were used to benchmark the dosimetric parameters of the 192 Ir, 60 Co, and 169 Yb HDR sources in a water phantom against the literature data. 45 clinical cases that were treated using conventional tandem-and-ring applicators with 192 Ir source (192 Ir-T&R) were selected consecutively from intErnational MRI-guided BRAchytherapy in CErvical cancer (EMBRACE) trial. Then, for each clinical case, 3D dose distribution of each source inside the DMBT and conventional applicators were calculated and imported onto an in-house developed inverse planning optimization code to generate optimal plans. All plans generated by the DMBT tandem-and-ring (DMBT T&R) from all three sources were compared to the respective 192 Ir-T&R plans. For consistency, all plans were normalized to the same CTVHR D90 achieved in clinical plans. The D2 cm3 for organs at risk (OAR) such as bladder, rectum, and sigmoid, and D90, D98, D10, V100, and V200 for CTVHR were calculated. RESULTS: In general, plan quality significantly improved when a conventional tandem (Con.T) is replaced with the DMBT tandem. The target coverage metrics were similar across 192 Ir-T&R and DMBT T&R plans with all three sources (P > 0.093). 60 Co-DMBT T&R generated greater hot spots and less dose homogeneity in the target volumes compared with the 192 Ir- and 169 Yb-DMBT T&R plans. Mean OAR doses in the DMBT T&R plans were significantly smaller (P < 0.0084) than the 192 Ir-T&R plans. Mean bladder D2 cm3 was reduced by 4.07%, 4.15%, and 5.13%, for the 192 Ir-, 60 Co-, and 169 Yb-DMBT T&R plans respectively. Mean rectum (sigmoid) D2 cm3 was reduced by 3.17% (3.63%), 2.57% (3.96%), and 4.65% (4.34%) for the 192 Ir-, 60 Co-, and 169 Yb-DMBT T&R plans respectively. The DMBT T&R plans with the 169 Yb source generally resulted in the greatest OAR sparing when the CTVHR were larger and irregular in shape, while for smaller and regularly shaped CTVHR (<30 cm3 ), OAR sparing between the sources were comparable. CONCLUSIONS: The DMBT tandem provides a promising alternative to the Con.T design with significant improvement in the plan quality for various target volumes. The DMBT T&R plans generated with the three sources of varying energies generated superior plans compared to the conventional T&R applicators. Plans generated with the 169 Yb-DMBT T&R produced best results for larger and irregularly shaped CTVHR in terms of OAR sparing. Thus, this study suggests that the combination of the DMBT tandem applicator with varying energy sources can work synergistically to generate improved plans for cervical cancer brachytherapy.

Direction Modulated Brachytherapy for Treatment of Cervical Cancer. II: Comparative Planning Study With Intracavitary and Intracavitary-Interstitial Techniques.

PURPOSE: To perform a comprehensive comparative planning study evaluating the utility of the proposed direction modulated brachytherapy (DMBT) tandem applicator against standard applicators, in the setting of image guided adaptive brachytherapy of cervical cancer. METHODS AND MATERIALS: A detailed conceptual article was published in 2014. The proposed DMBT tandem applicator has 6 peripheral grooves of 1.3-mm width, along a 5.4-mm-thick nonmagnetic tungsten alloy rod of density 18.0 g/cm(3), capable of generating directional dose profiles. We performed a comparative planning study with 45 cervical cancer patients enrolled consecutively in the prospective observational EMBRACE study. In all patients, MRI-based planning was performed while utilizing various tandem-ring (27 patients) and tandem-ring-needles (18 patients) applicators, in accordance with the Groupe Européen de Curiethérapie-European Society for Radiotherapy and Oncology recommendations. For unbiased comparisons, all cases were replanned with an in-house-developed inverse optimization code while enforcing a uniform set of constraints that are reflective of the clinical practice. All plans were normalized to the same high-risk clinical target volume D90 values achieved in the original clinical plans. RESULTS: In general, if the standard tandem was replaced with the DMBT tandem while maintaining all other planning conditions the same, there was consistent improvement in the plan quality. For example, among the 18 tandem-ring-needles cases, the average D2cm(3) reductions achieved were -2.48% ± 11.03%, -4.45% ± 5.24%, and -5.66% ± 6.43% for the bladder, rectum, and sigmoid, respectively. An opportunity may also exist in avoiding use of needles altogether for when the total number of needles required is small (approximately 2 to 3 needles or less), if DMBT tandem is used. CONCLUSIONS: Integrating the novel DMBT tandem onto both intracavitary and intracavitary-interstitial applicator assembly enabled consistent improvement in the sparing of the OARs, over a standard "single-channel" tandem, though individual variations in benefit were considerable. Although at an early stage of development, the DMBT concept design is demonstrated to be useful and pragmatic for potential clinical translation.

Quantitative MRI assessment of a novel direction modulated brachytherapy tandem applicator for cervical cancer at 1.5T.

BACKGROUND AND PURPOSE: The purpose of this work is to quantitatively investigate the artifacts and image distortions induced in the MR images by a recently proposed direction modulated brachytherapy (DMBT) tandem applicator prototype. This new MRI-compatible applicator allows better sparing of organs-at-risk (OAR) for cervical cancer patients, while providing conformal dose distributions to target volumes. MATERIALS AND METHODS: Specific phantom and tools were designed and manufactured for this study. The phantom was filled with a tissue-like solution and MR images were acquired with clinical protocols as per GEC-ESTRO recommendations. Images were obtained at 6 different orientations that mimic possible clinical settings and full-width-at-half-maximum (FWHM) was recorded at multiple locations/angles. The accuracy of detecting the centerline of the tandem was assessed using a novel radial-fiducials mount. RESULTS: FWHM from all line profiles at all angles and all orientations was 6.14±0.7mm (compared to 6mm of the actual DMBT tandem diameter). The in-plane spatial-shift observed at para-axial and para-sagittal views was less than 0.5mm. CONCLUSIONS: This work demonstrated that the novel DMBT tandem applicator prototype has minimal artifact in T2-weighted images employed in clinical practice, suggesting the applicator might be a good candidate for MRI-guided adaptive brachytherapy.

Direction-modulated brachytherapy for high-dose-rate treatment of cervical cancer. I: theoretical design.

PURPOSE: To demonstrate that utilization of the direction-modulated brachytherapy (DMBT) concept can significantly improve treatment plan quality in the setting of high-dose-rate (HDR) brachytherapy for cervical cancer. METHODS AND MATERIALS: The new, MRI-compatible, tandem design has 6 peripheral holes of 1.3-mm diameter, grooved along a nonmagnetic tungsten-alloy rod (ρ = 18.0 g/cm(3)), enclosed in Delrin tubing (polyoxymethylene, ρ = 1.41 g/cm(3)), with a total thickness of 6.4 mm. The Monte Carlo N-Particle code was used to calculate the anisotropic (192)Ir dose distributions. An in-house-developed inverse planning platform, geared with simulated annealing and constrained-gradient optimization algorithms, was used to replan 15 patient cases (total 75 plans) treated with a conventional tandem and ovoids (T&O) applicator. Prescription dose was 6 Gy. For replanning, we replaced the conventional tandem with that of the new DMBT tandem for optimization but left the ovoids in place and kept the dwell positions as originally planned. All DMBT plans were normalized to match the high-risk clinical target volume V100 coverage of the T&O plans. RESULTS: In general there were marked improvements in plan quality for the DMBT plans. On average, D2cc for the bladder, rectum, and sigmoid were reduced by 0.59 ± 0.87 Gy (8.5% ± 28.7%), 0.48 ± 0.55 Gy (21.1% ± 27.2%), and 0.10 ± 0.38 Gy (40.6% ± 214.9%) among the 75 plans, with best single-plan reductions of 3.20 Gy (40.8%), 2.38 Gy (40.07%), and 1.26 Gy (27.5%), respectively. The high-risk clinical target volume D90 was similar, with 6.55 ± 0.96 Gy and 6.59 ± 1.06 Gy for T&O and DMBT, respectively. CONCLUSIONS: Application of the DMBT concept to cervical cancer allowed for improved organ at risk sparing while achieving similar target coverage on a sizeable patient population, as intended, by maximally utilizing the anatomic information contained in 3-dimensional imaging. A series of mechanical and clinical validations are to be followed.

HDR brachytherapy of rectal cancer using a novel grooved-shielding applicator design.

PURPOSE: The aim of this work was to design a novel high-dose rate (HDR) ((192)Ir) brachytherapy applicator for treatment of rectal carcinomas that uses tungsten shielding for possibly improved dosimetric results over commercial brachytherapy applicator(s). METHODS: A set of 15 single-depth applicators and one dual-depth applicator were designed and simulated using Monte Carlo (MCNPX). All applicators simulated were high-density tungsten alloy cylinders, 16-mm in diameter, and 60-mm long, with longitudinal grooves within which an (192)Ir source can be placed. The single-depth designs varied regarding the number and depth of these grooves, ranging from 8 to 16 and 1-mm to 3-mm, respectively. The dual-depth design had ten channels, each of which had two depths at which the source could be placed. Optimized treatment plans were generated for each design on data from 13 treated patients (36 fractions) with asymmetrical clinical target volumes (CTVs). All results were compared against the clinically treated plans which used intracavitary mold applicator (ICMA), as well as a recently designed, highly automated, and collimated intensity modulation device named dynamic modulated brachytherapy (DMBT) device. RESULTS: All applicator designs outperformed the ICMA in every calculated dosimetric criteria, except the total dwell times (∼30% increase). There were clear, but relative, tradeoffs regarding both the number of channels and the depth of each channel. Overall, the 12-channel, 1-mm depth, and 14-channel 2-mm depth designs had the best results of the simpler designs, sparing the healthy rectal tissues the most while achieving comparable CTV coverage with the dose heterogeneity index and lateral spill doses improving by over 10% and the contralateral healthy rectum dose dropping over 30% compared to ICMA. The ten-channel dual-depth design outperformed each single-depth design, yielding the best coverage and sparing. CONCLUSIONS: New grooved tungsten HDR-brachytherapy devices have been designed and simulated. The results of this work attest to the capability of these new, highly anisotropic, intelligently shielded applicators to limit dose to healthy tissues while maintaining a conformal prescription dose to the CTV.

SU-E-T-317: Dynamic Modulated Brachytherapy (DMBT): Robotic Applicator Design.

PURPOSE: To investigate the hardware necessary for implementing our Dynamic Modulated Brachytherapy (DMBT) treatment concept for rectal cancer. METHODS: The DMBT robot has three major parts: 1) shield and shield delivery module, 2) controlling module, and 3) DMBT controlling and monitoring software. The shield is a tungsten alloy cylinder (r=0.95cm, l=4.5cm) with a 5.5mm rectangular-shaped opening. The shield is controlled by an aluminum pipe with gear set (1:3) and linear actuator (2mm/turn). An Ir-192 radiation source will be placed through the aluminum pipe. The power source is a Nema-17 stepping motor with EvoDrive ST-17 (EVA Robotics, Queensland, Australia) and USB-6009 DAQ (National Instrument, Austin, TX). With our in-house operating program through LabView (National Instrument, Austin, TX), we can make and load plans for treatment as well as testing. Checking the shield position is also possible through the operating program. For safety, a lexan sheath tube and emergency buttons are built-in. RESULTS: The DMBT robot has 2 degrees of freedom, which are linear translation and rotation. With our power delivery system, the spatial resolutions are 0.0125mm (linear stage) and 0.012Ës (rotation). In 0.5s, motors achieve the desired position with the maximum speeds 450 step/s (1Ës), 7,500 step/s (30Ës), and 12,000 step/s (5mm). Four registers are triggered with USB-6009 DAQ signals. The operating program includes gages for checking shield position, loading treatment plans, and safety buttons. CONCLUSIONS: In all, we have designed the hardware components of the DMBT system for rectal cancer. For treatment, the system needs more elements to support the DMBT robot; lexan sheath tube holder, DMBT robot security joint, and a system for reducing friction between the tube and shield. We will also refine our system to be more compact by using DC servomotors instead of the larger Nema-17 stepping motors.