Custom Bolus Research Articles

Total scalp irradiation: A study comparing multiple types of bolus and VMAT optimization techniques.

To investigate bolus design and VMAT optimization settings for total scalp irradiation. Three silicone bolus designs (flat, hat, and custom) from .decimal were evaluated for adherence to five anthropomorphic head phantoms. Flat bolus was cut from a silicone sheet. Generic hat bolus resembles an elongated swim cap while custom bolus is manufactured by injecting silicone into a 3D printed mold. Bolus placement time was recorded. Air gaps between bolus and scalp were quantified on CT images. The dosimetric effect of air gaps on target coverage was evaluated in a treatment planning study where the scalp was planned to 60Gy in 30 fractions. A noncoplanar VMAT technique based on gEUD penalties was investigated that explored the full range of gEUD alpha values to determine which settings achieve sufficient target coverage while minimizing brain dose. ANOVA and the t-test were used to evaluate statistically significant differences (threshold=0.05). The flat bolus took 32±5.9min to construct and place, which was significantly longer (p<0.001) compared with 0.67±0.2min for the generic hat bolus or 0.53±0.10min for the custom bolus. The air gap volumes were 38±9.3cc, 32±14cc, and 17±7.0cc for the flat, hat, and custom boluses, respectively. While the air gap differences between the flat and custom boluses were significant (p=0.011), there were no significant dosimetric differences in PTV coverage at V57Gy or V60Gy. In the VMAT optimization study, a gEUD alpha of 2 was found to minimize the mean brain dose. Two challenging aspects of total scalp irradiation were investigated: bolus design and plan optimization. Results from this study show opportunities to shorten bolus fabrication time during simulation and create high quality treatment plans using a straightforward VMAT template with simple optimization settings.

PO-1555 Treatment of lower limb Kaposi sarcoma (KS) with radiotherapy (RT) and 3D printed custom bolus

PO-1555 Treatment of lower limb Kaposi sarcoma (KS) with radiotherapy (RT) and 3D printed custom bolus

Synthetic cranial MRI from 3D optical surface scans using deep learning for radiation therapy treatment planning

BackgroundOptical scanning technologies are increasingly being utilised to supplement treatment workflows in radiation oncology, such as surface-guided radiotherapy or 3D printing custom bolus. One limitation of optical scanning devices is the absence of internal anatomical information of the patient being scanned. As a result, conventional radiation therapy treatment planning using this imaging modality is not feasible. Deep learning is useful for automating various manual tasks in radiation oncology, most notably, organ segmentation and treatment planning. Deep learning models have also been used to transform MRI datasets into synthetic CT datasets, facilitating the development of MRI-only radiation therapy planning.AimsTo train a pix2pix generative adversarial network to transform 3D optical scan data into estimated MRI datasets for a given patient to provide additional anatomical data for a select few radiation therapy treatment sites. The proposed network may provide useful anatomical information for treatment planning of surface mould brachytherapy, total body irradiation, and total skin electron therapy, for example, without delivering any imaging dose.MethodsA 2D pix2pix GAN was trained on 15,000 axial MRI slices of healthy adult brains paired with corresponding external mask slices. The model was validated on a further 5000 previously unseen external mask slices. The predictions were compared with the “ground-truth” MRI slices using the multi-scale structural similarity index (MSSI) metric. A certified neuro-radiologist was subsequently consulted to provide an independent review of the model’s performance in terms of anatomical accuracy and consistency. The network was then applied to a 3D photogrammetry scan of a test subject to demonstrate the feasibility of this novel technique.ResultsThe trained pix2pix network predicted MRI slices with a mean MSSI of 0.831 ± 0.057 for the 5000 validation images indicating that it is possible to estimate a significant proportion of a patient’s gross cranial anatomy from a patient’s exterior contour. When independently reviewed by a certified neuro-radiologist, the model’s performance was described as “quite amazing, but there are limitations in the regions where there is wide variation within the normal population.” When the trained network was applied to a 3D model of a human subject acquired using optical photogrammetry, the network could estimate the corresponding MRI volume for that subject with good qualitative accuracy. However, a ground-truth MRI baseline was not available for quantitative comparison.ConclusionsA deep learning model was developed, to transform 3D optical scan data of a patient into an estimated MRI volume, potentially increasing the usefulness of optical scanning in radiation therapy planning. This work has demonstrated that much of the human cranial anatomy can be predicted from the external shape of the head and may provide an additional source of valuable imaging data. Further research is required to investigate the feasibility of this approach for use in a clinical setting and further improve the model’s accuracy.

Development and dosimetric verification of 3D customized bolus in head and neck radiotherapy

The commercial flat bolus cannot form perfect contact with the irregular surface of the patient’s skin, resulting in an air gap. The purpose of this study was to evaluate the feasibility of using a 3D customized bolus from silicone rubber. The silicone rubber boluses were studied in basic characteristics. The 3D customized bolus was fabricated at the nose, cheek and neck regions. The point dose and planar dose differences were evaluated by comparing with virtual bolus. The hardness, thickness, density, Hounsfield unit (HU) and dose attenuation of the customized bolus were quite similar to a commercial bolus. When a 3D customized bolus was placed on the RANDO phantom, it can significantly increase buildup region doses and perfectly fit against the irregular surface shape. The average point dose differences of 3D customized bolus were −1.1%, while the commercial bolus plans showed −1.7%. The average gamma results for planar dose differences comparison of 3D customized bolus were 93.9%, while the commercial bolus plans were reduced to 91.9%. Overall, A silicone rubber bolus produced the feasible dosimetric properties and could save cost compared to a commercial bolus. The 3D printed customized bolus is a good buildup material and could potentially replace and improve treatment efficiency.

Technical note: Evaluation of a silicone-based custom bolus for radiation therapy of a superficial pelvic tumor.

PurposeUse of standard‐of‐care radiation therapy boluses may result in air‐gaps between the target surface and bolus, as they may not adequately conform to each patient's unique topography. Such air‐gaps can be particularly problematic in cases of superficial pelvic tumor radiation, as the density variation may result in the radiation delivered to the target site being inconsistent with the prescribed dose. To increase bolus fit and thereby dose predictability and homogeneity, we designed and produced a custom silicone bolus for evaluation against the clinical standard.MethodsA custom bolus was created for the pelvic regions of both an anthropomorphic phantom and a pelvic patient with squamous cell carcinoma of the penile shaft. Molds were designed using computed tomography (CT) scans, then 3D‐printed and cast with silicone rubber to yield the boluses. Air‐gap measurements were performed on custom and standard‐of‐care Superflab gel sheet boluses by analyzing total volume between the bolus and target surface, as measured from CT scans. Therapeutic doses of radiation were delivered to both boluses. Radiation dose was measured and compared to the expected dose using nine optically stimulated luminescent dosimeters (OSLDs) placed on the phantom.ResultsMean air‐gap volume between the bolus and phantom was decreased from 314 ± 141 cm3 with the standard bolus to 4.56 ± 1.59 cm3 using the custom device. In the case of the on‐treatment patient, air‐gap volume was reduced from 169 cm3 with the standard bolus to 46.1 cm3 with the custom. Dosimetry testing revealed that the mean absolute difference between expected and received doses was 5.69%±4.56% (15.1% maximum) for the standard bolus and 1.91%±1.31% (3.51% maximum) for the custom device. Areas of greater dose difference corresponded to areas of larger air‐gap.ConclusionsThe custom bolus reduced air‐gap and increased predictability of radiation dose delivered compared to the standard bolus. The custom bolus could increase the certainty of prescribed dose‐delivery of radiation therapy for superficial tumors.

A three-dimensional printed customized bolus: adapting to the shape of the outer ear.

The skin-sparing effect of megavoltage-photon beams in radiotherapy (RT) reduces the target coverage of superficial tumours. Consequently, a bolus is widely used to enhance the target coverage for superficial targets. This study evaluates a three-dimensional (3D)-printed customized bolus for a very irregular surface, the outer ear. We fabricated a bolus using a computed tomography (CT) scanner and evaluated its efficacy. The head of an Alderson Rando phantom was scanned with a CT scanner. Two 3D boluses of 5- and 10-mm thickness were designed to fit on the surface of the ear. They were printed by the Stratasys Objet260 Connex3 using the malleable "rubber-like" photopolymer Agilus. CT simulations of the Rando phantom with and without the 3D and commercial high density boluses were performed to evaluate the dosimetric properties of the 3D bolus. The prescription dose to the outer ear was 50 Gy at 2 Gy/fraction. We observed that the target coverage was slightly better with the 3D bolus of 10mm compared with the commercial one (D98% 98.2% vs. 97.6%).The maximum dose was reduced by 6.6% with the 3D bolus and the minimum dose increased by 5.2% when comparing with the commercial bolus. In addition, the homogeneity index was better for the 3D bolus (0.041 vs. 0.073). We successfully fabricated a customized 3D bolus for a very irregular surface. The target coverage and dosimetric parameters were at least comparable with a commercial bolus. Thus, the use of malleable materials can be considered for the fabrication of customized boluses in cases with complex anatomy.

A novel approach to embed eye shields in customized bolus on nasal dorsum treatment for electron radiotherapy

We aim to demonstrate the unique use of embedded lead eye shields in an electron wax bolus when treating the nasal dorsum. A patient presented to the clinic with squamous cell carcinoma of the nasal dorsum requiring treatment with en face electrons. A 3D customized wax bolus was designed and imported into the treatment planning system (TPS) to calculate the dose distribution. Due to high lens dose, the bolus was customized further to create 2 milled open slots in the wax, over the lens of eye, to allow lead sheets totaling 4 mm to be slid into the wax. The patient was brought back to the clinic to be scanned with the wax bolus fitting snugly over the nose, eyes, and cheek regions. The 3D milled insert holes were contoured on the CT in the TPS, assigned HU of 2758, to mimic the lead insertion. The lens dose with lead inserts was compared to the plan without lead insert. To further confirm the lens dose, EBT3 films were placed on the right and left eye under the bolus, and nose dorsum on the first day of treatment. The maximum dose of right lens, as calculated in the TPS with the simulated lead shields in place, decreased from 989.5cGy to 457cGy. The maximum dose of left lens decreased from 1085.4cGy to 501cGy. The dose readings from EBT3 films were in good agreement with the TPS, with deviation of 3.32%, 0.26%, and 3.44% for right lens, left lens, and nose, respectively. Daily positioning deviations compared to the plan were 0.65 ± 0.16cm and 0.63 ± 0.29cm for right eye and left eye, respectively. This novel device demonstrated the feasibility, in terms of dose calculation accuracy in the TPS and fabrication, of using customized bolus with lead inserts to conveniently shield the lens of the eyes in an electron treatment for the nose, enabling a streamlined daily setup.

Investigation of elastomeric materials for bolus using stereolithography printing technology in radiotherapy

Purpose: An investigation was conducted of an elastomeric material, VisiJet M2 (3D systems, USA) for use as 3D bolus within high energy photon beams for radiotherapy. Personalized conformal bolus material on complex structures like the nose can be challenging. This material was evaluated for its clinical feasibility due to its pliability and comfort compared to alternatives. Method: Regular slabs of bolus were created of various thicknesses for dosimetric and non-dosimetric characterization. Verification culminated with the creation of a custom nose bolus for an end to end verification using an anthropomorphic head phantom. In vivo dosimetry using Gafchromic EBT3 (Ashland, USA) film validated delivered doses from a 6 MV conformal field and a pair of 6 MV volumetric modulated arc therapy (VMAT) beams. Results & Conclusion: Non-dosimetric and dosimetric tests were conducted to assess clinical suitability. The bolus was precisely created using stereolithographic (SLA) methods and presented a compliant and uniform water equivalent material with elastic memory. Measurement yielded a physical density of 1.10 g cm−3 and 1.06 relative to water electron density, and the bolus to skin distance was measured to be a maximum of 3 mm. A maximum measured dose difference of <2% was observed for dynamic treatment. Based on the investigation conducted, and the benefits presented for patient comfort while being uniform and water equivalent, and correctly represented within the treatment planning system (TPS), this material has the potential for clinical use for patient specific custom bolus.

128 3D Printer Technology for Custom Bolus and Immobilization Device Fabrication in the Management of Palmar or Plantar Fibromatosis with Radiotherapy: Technical and Dosimetry Aspects

128 3D Printer Technology for Custom Bolus and Immobilization Device Fabrication in the Management of Palmar or Plantar Fibromatosis with Radiotherapy: Technical and Dosimetry Aspects

Simple and Rapid Creation of Customized 3D Printed Bolus Utilizing iPhone X True Depth Camera

Three-dimensional (3D) printing has effectively produced patient-specific bolus materials during radiation treatment for superficial tumors along irregular skin surfaces. Traditional bolus materials in comparison, are often difficult to manipulate for proper fit, and can be difficult to reproduce. Current 3D printed boluses are made from either pre-existing computed tomography (CT) scans or complex surface scanning methods. Here, we introduce an inexpensive, convenient approach to generating 3D printed bolus from surface scanning technology available in common smartphones. 3D printed bolus was designed using surface scans from iphone X true depth cameras and a low cost 3D printer. The percentage density infill was adjusted to achieve tissue equivalence. To evaluate the clinical feasibility, fit against skin surface and radiation dose distribution was compared to traditional bolus. We fabricated customized 3D printed bolus for different areas of the face utilizing an iphone X camera and an inexpensive commercially available 3D printer. When printed at 100% density this bolus material approximated soft tissue/water and provided an equivalent dose distribution to that found with standard bolus materials on direct comparison. The bolus material was inexpensive and produces an ideal fit with the scanned anatomy. We present a simplified method of highly customized bolus production that requires minimal experience with computer modeling programs and can be accomplished with an iphone true depth camera.

Simple and Rapid Creation of Customized 3-dimensional Printed Bolus Using iPhone X True Depth Camera

PurposeThree-dimensional printing has produced customized bolus during radiation therapy for superficial tumors along irregular skin surfaces. In comparison, traditional bolus materials are often difficult to manipulate for a proper fit. Current 3-dimensional printed boluses are made from either preexisting computed tomography scans or complex surface scanning methods. Herein, we introduce an inexpensive, convenient approach to generate a 3-dimensional printed bolus from surface scanning technology available in common smartphones. Methods and materialsA three-dimensional printed bolus was designed using surface scans from iPhone X true depth cameras and a low-cost 3-dimensional printer. The percentage density infill was adjusted to achieve tissue equivalence. To evaluate the clinical feasibility, fit against the skin surface and radiation dose distribution were compared with those of the traditional bolus. ResultsWe fabricated a customized 3-dimensional printed bolus for different areas of the face using an iPhone X camera and inexpensive commercially available 3-dimensional printer. When printed at 100% density, the bolus material approximated soft tissue/water and provided an equivalent dose distribution to that found with standard bolus materials on direct comparison. The bolus material is inexpensive and produces an ideal fit with the scanned anatomy. ConclusionsWe present a simplified method of highly customized bolus production that requires minimal experience with computer modeling programs and can be accomplished with an iPhone true depth camera.

Using 3D printer technology to advance and optimize the use of bolus in the radiotherapy workflow

Bolus is commonly used in Radiotherapy to escalate the dose to the skin surface for the treatment of shallow tumours and to improve dose uniformity in the region of irregular body contours. There are many different commercial solutions currently available, each of which has their own disadvantages as an all-round bolus solution. One solution which does not have these shortcomings is 3D printed bolus, which can be generated directly from a contoured structure drawn on the patient’s CT dataset and then printed accurately using readily available 3D printing technology. Recent advancements in 3D printing technology have resulted in printer technology and materials that can be easily integrated into the radiotherapy workflow. In our clinic, we have opted to use the 3DBolus system which integrates with our existing TPS. 3DBolus uses the contours generated during the planning process and leverages the TPS dose calculation algorithms to create custom bolus that represents the planned bolus dose distribution accurately. Our experience of integrating 3D printed bolus into our radiotherapy workflow found that 3D printed bolus offers four main advantages over traditional bolus methods. First, it conforms to difficult patient anatomy where traditional bolus would typically fail. Second, it can be quickly recreated or adapted if required using patient’s treatment imaging. Third, it offers the clinicians a consistent and accurate representation of the planned dose distribution on the treatment unit. Finally, it was found to be more efficient on the treatment units compared to current bolus techniques. Bolus is commonly used in Radiotherapy to escalate the dose to the skin surface for the treatment of shallow tumours and to improve dose uniformity in the region of irregular body contours. There are many different commercial solutions currently available, each of which has their own disadvantages as an all-round bolus solution. One solution which does not have these shortcomings is 3D printed bolus, which can be generated directly from a contoured structure drawn on the patient’s CT dataset and then printed accurately using readily available 3D printing technology. Recent advancements in 3D printing technology have resulted in printer technology and materials that can be easily integrated into the radiotherapy workflow. In our clinic, we have opted to use the 3DBolus system which integrates with our existing TPS. 3DBolus uses the contours generated during the planning process and leverages the TPS dose calculation algorithms to create custom bolus that represents the planned bolus dose distribution accurately. Our experience of integrating 3D printed bolus into our radiotherapy workflow found that 3D printed bolus offers four main advantages over traditional bolus methods. First, it conforms to difficult patient anatomy where traditional bolus would typically fail. Second, it can be quickly recreated or adapted if required using patient’s treatment imaging. Third, it offers the clinicians a consistent and accurate representation of the planned dose distribution on the treatment unit. Finally, it was found to be more efficient on the treatment units compared to current bolus techniques.

EP-2174: Fabrication of three-dimensional printed customized bolus for the irregular shape of the outer ear

EP-2174: Fabrication of three-dimensional printed customized bolus for the irregular shape of the outer ear

Customized Bolus for Orbital Tumors Created with 3D Photogrammetry and Rapid Prototyping

Children with orbital tumors, such as retinoblastoma or sarcoma, are often treated with radiotherapy. There are many techniques, including en face electron beams, conformal and intensity-modulated radiation therapy. For tumors close to the skin, bolus is overlaid to avoid underdosing the superficial portions of the target. If bolus is separated from the skin by an air gap, this may lead to treatment inaccuracy, which is magnified by larger gaps and smaller field sizes. Commercial tissue equivalent bolus is difficult to conform around the eyes and bridge of the nose, and custom impression material requires experience to create a uniform bolus without air cavities. We describe a technique with 3D photogrammetry at consultation to rapidly prototype a custom bolus prior to simulation. Children with orbital tumors, such as retinoblastoma or sarcoma, are often treated with radiotherapy. There are many techniques, including en face electron beams, conformal and intensity-modulated radiation therapy. For tumors close to the skin, bolus is overlaid to avoid underdosing the superficial portions of the target. If bolus is separated from the skin by an air gap, this may lead to treatment inaccuracy, which is magnified by larger gaps and smaller field sizes. Commercial tissue equivalent bolus is difficult to conform around the eyes and bridge of the nose, and custom impression material requires experience to create a uniform bolus without air cavities. We describe a technique with 3D photogrammetry at consultation to rapidly prototype a custom bolus prior to simulation. The 3D printed bolus was manufactured within a day after completing the STL file. The conformality of the 3D bolus to the phantom was compared to SuperFlab and the VPS bolus with computed tomography. SuperFlab was the least conformal and the 3D bolus was intermediate. Ridges on the surface of the 3D bolus from manufacturing increased the bolus-phantom gap. The VPS bolus material was the most malleable and conformal, but was not uniformly thick and had some internal air voids. Photogrammetry is an old technique to obtain patient contours, which we modernized to create a 3D file for rapid prototyping. The resulting bolus was created quickly and fit with excellent conformality, but was the most expensive. Over time, as rapid prototyping innovates, this method will become easier, more efficient, and increasingly available with a greater choice of materials and vendors. Until then, this process is useful now for a few small and irregular sites in the head and neck region, but routine and widespread application will not benefit most patients.

Fabrication of malleable three-dimensional-printed customized bolus using three-dimensional scanner.

A three-dimensional (3D)-printed customized bolus (3D bolus) can be used for radiotherapy application to irregular surfaces. However, bolus fabrication based on computed tomography (CT) scans is complicated and also delivers unwanted irradiation. Consequently, we fabricated a bolus using a 3D scanner and evaluated its efficacy. The head of an Alderson Rando phantom was scanned with a 3D scanner. The 3D surface data were exported and reconstructed with Geomagic Design X software. A 3D bolus of 5-mm thickness designed to fit onto the nose was printed with the use of rubber-like printing material, and a radiotherapy plan was developed. We successfully fabricated the customized 3D bolus, and further, a CT simulation indicated an acceptable fit of the 3D bolus to the nose. There was no air gap between the bolus and the phantom surface. The percent depth dose (PDD) curve of the phantom with the 3D bolus showed an enhanced surface dose when compared with that of the phantom without the bolus. The PDD of the 3D bolus was comparable with that of a commercial superflab bolus. The radiotherapy plan considering the 3D bolus showed improved target coverage when compared with that without the bolus. Thus, we successfully fabricated a customized 3D bolus for an irregular surface using a 3D scanner instead of a CT scanner.

EP-1488: Evaluation of the Efficacy and Accuracy of Customized bolus by using a 3-dimensional printer

EP-1488: Evaluation of the Efficacy and Accuracy of Customized bolus by using a 3-dimensional printer

An Innovative Risk-Reducing Approach to Postmastectomy Radiation Delivery after Autologous Breast Reconstruction.

Introduction:Postmastectomy radiation therapy (PMRT) has known deleterious side effects in immediate autologous breast reconstruction. However, plastic surgeons are rarely involved in PMRT planning. Our institution has adopted a custom bolus approach for all patients receiving PMRT. This offers uniform distribution of standard radiation doses, thereby minimizing radiation-induced changes while maintaining oncologic safety. We present our 8-year experience with the custom bolus approach for PMRT delivery in immediate autologous breast reconstruction.Methods:All immediate autologous breast reconstruction patients requiring PMRT after 2006 were treated with the custom bolus approach. Retrospective chart review was performed to compare the postirradiation complications, reconstruction outcomes, and oncologic outcomes of these patients with those of previous patients at our institution who underwent standard bolus, and to historical controls from peer-reviewed literature.Results:Over the past 10 years, of the 29 patients who received PMRT, 10 were treated with custom bolus. Custom bolus resulted in fewer radiation-induced skin changes and less skin tethering/fibrosis than standard bolus (0% vs 10% and 20% vs 35%, respectively), and less volume loss and contour deformities compared with historical controls (10% vs 22.8% and 10% vs 30.7%, respectively).Conclusions:Custom bolus PMRT minimizes radiation delivery to the internal mammary vessels, anastomoses, and skin; uniformly doses the surgical incision; and provides the necessary radiation dose to prevent recurrence. Because custom bolus PMRT may reduce the deleterious effects of radiation on reconstructive outcomes while maintaining safe oncologic results, we encourage all plastic surgeons to collaborate with radiation oncologists to consider this technique.

Use of 3D printing for construction of custom bolus in external beam radiotherapy

Aim To create a patient specific mould of a treatment area for bolus fitting using a 3D printer and compare it with conventional bolus. Methods A patient with a right medial Basal Cell Carcinoma (BCC) lesion on the forehead extending to the upper nose was presented for electron external beam radiotherapy (50 Gy in 20#). A conventional custom bolus 0.5 cm thick using Aquaplast™ thermoplastic pellets was made on the treatment area. Following this, a CT simulation using 2.5 mm slice thickness was performed. DICOM image files from the CT simulation for the treatment area were processed using 3D printing software to allow for a solid plastic mould of the patient’s contour to be printed using a 3D printer. The mould was used to fashion form fitting bolus, 1cm thick, with custom lead lens shielding included. The mould and bolus were CT scanned to ensure there were no air gaps and that the lead shielding was in the correct position. Comparison of the dosimetric performance of the conventional bolus and the bolus designed on the 3D printed mould will be presented. A 6 MeV electron plan for each bolus will be performed using electron Monte Carlo algorithm. Conclusion This work has demonstrated the feasibility of the use of 3D printing to assist in the construction of patient specific bolus for the treatment of superficial lesions. The bolus created on the 3D printed mould demonstrated less air gaps which improved the dosimetric performance when compared with a conventional bolus. To create a patient specific mould of a treatment area for bolus fitting using a 3D printer and compare it with conventional bolus. A patient with a right medial Basal Cell Carcinoma (BCC) lesion on the forehead extending to the upper nose was presented for electron external beam radiotherapy (50 Gy in 20#). A conventional custom bolus 0.5 cm thick using Aquaplast™ thermoplastic pellets was made on the treatment area. Following this, a CT simulation using 2.5 mm slice thickness was performed. DICOM image files from the CT simulation for the treatment area were processed using 3D printing software to allow for a solid plastic mould of the patient’s contour to be printed using a 3D printer. The mould was used to fashion form fitting bolus, 1cm thick, with custom lead lens shielding included. The mould and bolus were CT scanned to ensure there were no air gaps and that the lead shielding was in the correct position. Comparison of the dosimetric performance of the conventional bolus and the bolus designed on the 3D printed mould will be presented. A 6 MeV electron plan for each bolus will be performed using electron Monte Carlo algorithm. This work has demonstrated the feasibility of the use of 3D printing to assist in the construction of patient specific bolus for the treatment of superficial lesions. The bolus created on the 3D printed mould demonstrated less air gaps which improved the dosimetric performance when compared with a conventional bolus.

TU‐H‐CAMPUS‐TeP1‐05: Fast Processed 3D Printing‐Aided Urethane Resin (PUR) Bolus in Radiation Therapy

Purpose:3D printed custom bolus is regularly used in radiation therapy clinic as a compensator. However, usual method of bolus printing with 100% filling is very time‐consuming. The purpose of this study is to evaluate the feasibility and benefit of 3D printed bolus filled with UR.Methods:Two boluses were designed on nose (9e electrons) and ear (6× photons) for a head phantom in treatment planning system (TPS) to achieve dose coverage to the skin. The bolus structures (56–167cc) were converted to STereoLithographic (STL) model using an in‐house developed algorithm and sent to a commercial fused deposition modeling (FDM) printer. Only shells were printed with polylactic acid (PLA) material. Liquid UR was then placed in a vacuum pump and slowly poured into the hollow bolus from its top opening. Liquid UR hardened in around half an hour. The phantom was rescanned with custom boluses attached and the dosimetry was compared with original design in TPS. Basic CT and dose properties were investigated. GaF films were irradiated to measure dose profile and output of several open photon and electron beams under solid water and UR slabs of same thicknesses.Results:CT number was 11.2±7.3 and 65.4±7.8, respectively for solid water(∼1.04g/cc) and UR(∼1.08g/cc). The output measurement at dmax for 6× was within 2% for the two materials. The relative dose profiles of the two materials above dmax show 94–99% Gamma analysis passing rates for both photons and electrons. Dose distributions with 3D PUR boluses maintained great coverage on the intended skin regions and resembled that with computer generated boluses. Manufacturing 3D PUR boluses was 3–4 times faster than 100% printed boluses. The efficiency significantly improves for larger boluses.Conclusion:The study suggests UR has similar dose responses as solid water. Making custom bolus with UR greatly increases clinical workflow efficiency.

Abstract P2-13-01: An innovative risk-reducing approach to post-mastectomy radiation delivery following autologous breast reconstruction

Abstract Introduction: There is no consensus among radiation oncologists regarding delivery of post-mastectomy radiation therapy (PMRT) after immediate autologous breast reconstruction, and plastic surgeons rarely participate in this decision-making process. However, radiation-induced changes markedly influence flap outcomes and affect the flap permanently. We present an innovative approach for PMRT delivery, through the use of custom bolus. This technique provides individualized, targeted PMRT to the reconstructed breast to minimize flap-related complications. Methods: All patients who underwent mastectomy with immediate autologous reconstruction between 2005 and 2014 at our institution were identified. Radiation was delivered to the reconstructed autologous breast in 29 patients. Post-irradiation complications and reconstruction outcomes were compared for patients treated with custom bolus, standard PMRT, and historical controls. Results: Over the past 10 years, 157 patients (226 breasts) underwent immediate autologous tissue breast reconstruction following mastectomy. Of the 29 patients who received PMRT, 10 were treated with custom bolus. The custom bolus uses perforated Aquaplast and a nearly tissue-equivalent wax to form a cast which conforms to the irregular contours of the chest wall, allowing for easy application through the duration of treatment. Pre-irradiation computed tomography was used to optimize dose distribution, evaluate the internal mammary vessels, and target the deeper tissues adjacent to the chest wall (minimizing dose inhomogeneity to the skin). Custom bolus resulted in fewer radiation-induced skin changes and less skin tethering/fibrosis than standard bolus (0% vs 10% and 20% vs 35%, respectively), and less volume loss and contour deformities compared with historical controls (10% vs 22.8% and 10% vs 30.7%, respectively). Conclusion: The use of custom bolus tailors radiation delivery to the internal mammary vessels, anastomoses, and skin; uniformly doses the surgical incision; and provides the necessary radiation dose to prevent recurrence, thus not compromising oncologic safety. It is easily fabricated, cost-effective and placement is straightforward and reproducible. Because radiation has negative effects on autologous breast reconstruction and often results in vascular intimal fibrosis and fat necrosis, plastic surgeons should participate in radiation planning. Our custom bolus PMRT technique reduces the incidence of these radiation effects. Citation Format: Piper ML, Evangelista M, Amara D, Daar DA, Foster RD, Fowble B, Sbitany H. An innovative risk-reducing approach to post-mastectomy radiation delivery following autologous breast reconstruction. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-13-01.