Scalp Irradiation Research Articles

Scalp Irradiation with 3D-Milled Bolus: Dosimetric, Toxicity, and Oncologic Outcomes

Scalp Irradiation with 3D-Milled Bolus: Dosimetric, Toxicity, and Oncologic Outcomes

A Comparative Evaluation of Dosal Usefulness in Total Scalp Irradiation according to Treatment Plans and Methods

Objective: The purpose of this study is to choose a treatment plan and equipment to maximize tangential irradiation to protect the normal brain tissues as much as possible during total scalp irradiation. Subjects and Methods: After zoning the total scalp of a phantom and selecting a target area for treatment, the study made a Helical Tomo Therapy (HT) plan, a Helical Tomo Therapy with a Complete Block (HTCB) plan, and a Volumetric Modulated Arc Therapy (VMAT) plan. All of these plans made sure that the volume of a treatment plan with 95% of a prescription dose (40 Gy) would not exceed 95% of the entire volume and that Dmax would not be more than 110% of the prescription dose. The plans compared doses among organs at risk of damage including the brain. Doses in the brain tissues were assessed based on the volumetric criteria for normal tissues in Emami et al. Results: HT, HTCB, and VMAT had a dose of 21.68 Gy, 13.75 Gy, and 20.89 Gy, respectively, in brain tissues at D33%, a dose of 7.06 Gy, 3.21 Gy, and 7.84 Gy, respectively, at D67%, and a dose of 3.14 Gy, 1.75 Gy, and 3.84 Gy, respectively, at D100%. They recorded a Dmean of 16.64 Gy, 11.78 Gy, and 16.64 Gy, respectively. These results show that the overall dose was low in the HTCB plan. When the volume of a low dose was calculated based on 5 Gy, they recorded 87%, 49%, and 96%, respectively, in V5Gy. In addition, the maximum dose in the remaining organ (brain stem, hippocampus, and both lenses) except for the optic pathway was the lowest in HTCB Conclusion: The findings demonstrate that Tomo Therapy with a complete block minimized a dose in organs at risk of damage including the brain and hippocampus on both sides and accordingly reduced the probability of side effects such as radiation-induced brain injuries and a resulting decrease in neurocognitive functions. In addition to total scalp irradiation, if additional studies on ring targets treated in various areas are conducted to establish the benefits of tangential irradiation, it is believed that Tomo Therapy using Complete Block can be used to maximize tangential irradiation in treatment planning.

Scalp Irradiation with 3D-Milled Bolus: Initial Dosimetric and Clinical Experience.

A bolus is required when treating scalp lesions with photon radiation therapy. Traditional bolus materials face several issues, including air gaps and setup difficulty due to irregular, convex scalp geometry. A 3D-milled bolus is custom-formed to match individual patient anatomy, allowing improved dose coverage and homogeneity. Here, we describe the creation process of a 3D-milled bolus and report the outcomes for patients with scalp malignancies treated with Volumetric Modulated Arc Therapy (VMAT) utilizing a 3D-milled bolus. Twenty-two patients treated from 2016 to 2022 using a 3D-milled bolus and VMAT were included. Histologies included squamous cell carcinoma (n = 14, 64%) and angiosarcoma (n = 8, 36%). A total of 7 (32%) patients were treated in the intact and 15 (68%) in the postoperative setting. The median prescription dose was 66.0 Gy (range: 60.0-69.96). The target included the entire scalp for 8 (36%) patients; in the remaining 14 (64%), the median ratio of planning target volume to scalp volume was 35% (range: 25-90%). The median dose homogeneity index was 1.07 (range: 1.03-1.15). Six (27%) patients experienced acute grade 3 dermatitis and one (5%) patient experienced late grade 3 skin ulceration. With a median follow-up of 21.4 months (range: 4.0-75.4), the 18-month rates of locoregional control and overall survival were 75% and 79%, respectively. To our knowledge, this is the first study to report the clinical outcomes for patients with scalp malignancies treated with the combination of VMAT and a 3D-milled bolus. This technique resulted in favorable clinical outcomes and an acceptable toxicity profile in comparison with historic controls and warrants further investigation in a larger prospective study.

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.

Feasibility of Customized Thermoplastic Patient-Specific Helmet Bolus for Scalp Irradiation Using Volumetric-Modulated Arc Therapy Planning.

Introduction: In this study, we sought to develop a thermoplastic patient-specific helmet bolus that could deliver a uniform therapeutic dose to the target and minimize the dose to the normal brain during whole-scalp treatment with a humanoid head phantom. Methods: The bolus material was a commercial thermoplastic used for patient immobilization, and the holes in the netting were filled with melted paraffin. We compared volumetric-modulated arc therapy treatment plans with and without the bolus for quantitative dose distribution analysis. We analyzed the dose distribution in the region of interest to compare dose differences between target and normal organs. For quantitative analysis of treatment dose, OSLD chips were attached at the vertex (VX), posterior occipital (PO), right (RT), and left temporal (LT) locations. Results: The average dose in the clinical target volume was 6553.8 cGy (99.3%) with bolus and 5874 cGy (89%) without bolus, differing by more than 10% from the prescribed dose (6600 cGy) to the scalp target. For the normal brain, it was 3747.8 cGy (56.8%) with bolus and 5484.6 cGy (83.1%) without bolus. These results show that while the dose to the treatment target decreased, the average dose to the normal brain, which is mostly inside the treatment target, increased by more than 25%. With the bolus, the OSLD measured dose was 102.5 ± 1.2% for VX and 101.5 ± 1.9%, 95.9 ± 1.9%, and 81.8 ± 2.1% for PO, RT, and LT, respectively. In addition, the average dose in the treatment plan was 102%, 101%, 93.6%, and 80.7% for VX, PO, RT, and LT. When no bolus was administered, 59.6 ± 2.4%, 112.6 ± 1.8%, 47.1 ± 1.6%, and 53.1 ± 2.3% were assessed as OSLD doses for VX, PO, RT, and LT, respectively. Conclusion: This study proposed a method to fabricate patient-specific boluses that are highly reproducible, accessible, and easy to fabricate for radiotherapy to the entire scalp and can effectively spare normal tissue while delivering sufficient surface dose.

Total scalp irradiation using pencil beam scanning proton therapy for dermatofibrosarcoma protuberans: case study and photon dosimetric comparison—a case report

Total scalp irradiation using pencil beam scanning proton therapy for dermatofibrosarcoma protuberans: case study and photon dosimetric comparison—a case report

Dosimetric Comparison of Automated Non-Coplanar Volumetric-Modulated Arc Therapy and Intensity-Modulated Proton Therapy in Angiosarcoma of the Scalp

Angiosarcoma of the scalp (AS) is a rare tumor and has often been treated by total scalp irradiation (TSI). TSI is a challenging technique because of the target close to the organs at risks (OARs), located in the skin surface, and helmet-shape of the target. We performed the dosimetric comparison of automated non-coplanar volumetric-modulated arc therapy (HA) and intensity-modulated proton therapy (IMPT) in TSI for AS. A planning study was performed on 20 patients with AS. The clinical target volume (CTV) 1 and CTV2 were defined as gross tumor volume with margin and entire scalp, respectively. For HA, planning target volume (PTV) 1 and PTV2 were defined as CTV1 and CTV2 with 5-mm margins, respectively. For IMPT, robust optimization was utilized which accounted for a 5-mm setup and a 3.5% range uncertainty and dose was prescribed to CTV1 robust and CTV2 robust. The prescription doses were 70 Gy and 56 Gy in 35 fractions to PTV1 (CTV1 robust) and PTV2 (CTV2 robust), respectively, using the simultaneous integrated boost technique. The HA plan was performed using a 6-MV photon beam machine and a 1-cm thick virtual bolus. The HA plan included three half non-coplanar and one full coplanar arc fields. The HA plan used collimator angles of 15°, 60°, 15°, and 120° in the beam with couch rotations of 0°, 45°, 90°, and 315°, respectively. The IMPT plan was performed using a compact proton beam machine dedicated to pencil beam scanning. The IMPT plan used gantry angles of 70°, 150°, 70°, 150°, and 30° in the beam with couch rotations of 0°, 0°, 180°, 180°, and 270°, respectively. The IMPT plan was optimized assuming a relative biological effectiveness of 1.1. The dose distribution and dosimetric parameters for each plan were evaluated. All plans met the goals within the acceptable range in target volume coverage, conformity, and homogeneity. Table shows the dosimetric parameters of OARs in HA and IMPT plans. The doses receiving 0.1 cc of the volume for hippocampus, optic passway, eye, and lens in the IMPT plan were significantly lower than those in the HA plan. The IMPT plan showed a significant reduction in the percentage of brain volume receiving at least 5 Gy (V5 Gy) compared to the HA plan, while the HA plan showed a significant reduction of V10 Gy - V60 Gy and mean brain dose compared to the IMPT plan. The HA plan provided a shorter beam-on time (184 ± 9 s) than did the IMPT plan (446 ± 49 s). The HA and IMPT plans demonstrated different strengths with respect to OARs sparing.

Dosimetric Comparison of Helical Tomotherapy and HyperArc Treatment Plans for Angiosarcoma of the Scalp.

Angiosarcoma of the scalp (AS) is a rare tumor that has often been treated by total scalp irradiation (TSI). TSI has technical and dosimetric challenges. This study aimed to compare the dosimetric performance of helical tomotherapy (HT) plans with that of HyperArc (HA) plans for TSI in AS. A planning study was conducted for 11 patients with AS (70 Gy/35 fr). HT and HA planning was performed using TomoHDA and TrueBeam Edge systems, respectively. The performance of three different plans were compared: HT, HA, and HA with half-field beams (HF-HA). The dose distribution and dosimetric parameters for each plan were evaluated. All constraint parameters for the target and organs at risk (OARs) met the goals within acceptable limits for the three techniques. The HA and HF-HA plans provided significantly lower mean brain dose (12.46±2.48 Gy and 8.02±1.48 Gy) than did the HT plan (17.59±3.47 Gy). The doses receiving 0.1 cc of the volume for brainstem and chiasm were significantly lower in the HA and HF-HA plans than those in the HT plan. The HA and HF-HA plans provided a shorter beam-on time (155±3 s and 181±14 s) than did the HT plan (962±221 s). The HA plan provided significantly better OARs sparing than the HT plan for TSI in AS and had an advantage to using half-field beams.

Dermoscopic Description of Scarring Alopecia after Scalp Irradiation

Dermoscopic Description of Scarring Alopecia after Scalp Irradiation

Two Novel Irradiation Methods for Angiosarcoma of Total Scalp Irradiation

<h3>Purpose/Objective(s)</h3> Due to large, irregular and superficial spread of the complex target, conventional radiotherapy via photon and electron beams matching technique for angiosarcoma of total scalp irradiation (TSI) presents major technical and dosimetric challenges. To increase superficial target coverage, reduce normal brain dose, and eliminate the difficulty of patient set up and fields matching, we propose two novel irradiation methods: fully-automated non-coplanar HyperArc VMAT and co-planar Halcyon delivery platform utilizing a 3D-printed 1 cm scalp bolus. <h3>Materials/Methods</h3> The technical and dosimetric performance of the proposed two novel methods was simulated using nine previously treated TSI patients in our institution. HyperArc plans utilized 6MV-FFF beam (800 MU/min) on SBRT-dedicated Linac with fully-automated HyperArc module and 1 cm 3D-printed scalp bolus for dose build up to the superficial target to deliver a prescription dose of 70 Gy in 35 fractions. For comparison, these plans were re-planned via 4 full-arcs on recently installed fast rotating co-planar Halcyon Linac equipped with 6MV-FFF (800 MU/min) with lower mean energy of 1.3 MeV and nominal depth of maximum dose at 1.3 cm. Identical isocenter location and similar planning parameters and objectives, were used on both Linac platforms. Plan quality, including BED10 and treatment delivery accuracy and efficacy, was compared. <h3>Results</h3> Both platforms generated highly conformal, homogenous TSI plans and showed statistically insignificant differences on target coverage, mean target dose, conformity, and dose homogeneity. The average BED10 of the mean target dose was 92.0 ± 1.4 Gy (HyperArc) vs 93.4 ± 0.9 Gy (Halcyon) (p = 0.06). HyperArc provided mean brain dose and V60Gy of 8.1 ± 1.5 Gy and 0.8 ± 0.9 cc respectively, compared to 8.5 ± 1.4 Gy (p > 0.05) and 1.4 ± 0.7 cc (p = 0.04), on Halcyon. For both platforms, significantly lower maximal dose of < 5 Gy was observed in organs at risk (OARs), including spinal cord, brainstem, optic pathway, hippocampi, eyes and lenses, and cochlea (p > 0.05 for all OARs). Halcyon plan complexity slightly decreased as seen in the average decreases of total monitor units, modulation factor and beam-on time by 119, 0.6, and 0.6 min respectively, and the estimated overall treatment time was reduced by an average of 2.4 min. Treatment time for both platforms was less than 15 minutes. Portal dosimetry quality assurance results of HyperArc and the corresponding Halcyon plans were 99.8% and 100%, demonstrating comparable treatment delivery accuracy. <h3>Conclusion</h3> We demonstrated that both Halcyon and HyperArc platforms can deliver an accurate and efficient treatment of greater than 90 Gy BED10 to large, complex and superficial angiosarcoma of the scalp and face with significantly lower mean brain dose of less than 10 Gy. Clinical use of these platforms is underway in our center and highly recommended to other centers, including community centers, expanding the use of Halcyon Linac to underserved patient cohort.

35. Human Adipose-derived Stem Cells Decrease Skin Damage in Mice After Scalp Irradiation: A Pilot Experiment

Purpose: The treatment for radiation dermatitis ulcers is surgical reconstruction. We aimed to characterize the effects of human adipose-derived stem cells (hAdMSCs) to prevent complications of radiation dermatitis of the scalp in an immunocompetent mouse model. Methods: Two 4-week-old female C57BL/6 mice were delivered a dose of 60 Gy to a skin area between the coronal and lambdoid sutures using a 5 mm circular collimator. On day 12 after irradiation, 600,000 luciferase- and green fluorescent protein-labeled hAdMSCs in 300 µL of PBS were injected subcutaneously into the scalp of one mouse. Mice were photographed under standardized conditions and weighted daily. Bioluminescence imaging (BLI) was performed daily from the day after injection until there was no detectable signal. Both were euthanized on day 27 after irradiation, and the scalp tissue was collected. Staining with hematoxylin and eosin, Masson’s trichrome, and immunohistochemistry for CD31 were performed. The histological slides were digitalized and analyzed using ImageJ (NIH). Statistical analyses were performed using Excel 2010 (Microsoft Corp., United States). Results: Bioluminescence images showed that hAdMSCs survived in vivo for five days. While desquamation and ulceration appeared on day 14 and lasted for 12 days in the treated mouse, the control mouse did not show signs of improvement by the time of euthanasia. The treated mouse had a greater mean erythematous area than the control mouse (0.38 cm2 vs. 0.23 cm2, p<0.05). The mean ulceration areas did not differ between the treated and control mouse (0.12 cm2 vs. 0.14 cm2, p>0.05). The epidermis, total skin thickness, and hypodermis of the irradiated regions were significantly thicker than the non-irradiated regions in both the treatment and control mice. The vessel size (treated = 67.25 µm2, control = 72.27 µm2, p>0.05) and the difference in tissue area occupied by vessels (treated = 2.58%, control = 2.42%, p>0.05) of the radiated regions did not differ between mice. Collagen deposition in the irradiated region was decreased in the treated mouse compared to the control mouse (11% vs. 42%). Conclusion: Human adipose-derived stem cells decrease the duration of ulceration and improve the macroscopic quality of the skin, survive for only 5 days after transplantation, decrease collagen deposition in the irradiated area, increase micro vessel area and size, and decrease the thickness of the irradiated area of the skin compared to controls two weeks after transplantation.

109. Vitamin E Treated Fat Grafts Maintain Volume to Improve Grafting Effects on Radiation-induced Fibrosis

Introduction: Fat grafts and vitamin E administration have both previously been described to mitigate radiation-induced skin fibrosis. Fat graft retention continues to hinder its long-term functionality affected mainly by two factors: initial inflammatory response and chronic necrosis secondary to hypovascularity. Thus, we aimed to simultaneously improve fat graft retention along with radiation-induced fibrosis. Methods: Ten adult CD-1 nude male mice at 6-8 weeks of age underwent scalp irradiation with 5 Gy every other day for 12 days, totaling in 30 Gy. Mice recovered for four weeks to allow chronic fibrosis to develop. After recovery, mice received 1000μL of donor human fat graft to the scalp. Mice were separated into 4 conditions: ungrafted irradiated, untreated fat graft, fat graft treated with pentoxifylline (PTX), fat graft treated with vitamin E (VE). Fat graft volume retention was monitored in-vivo using microCT scans with 3-dimensional reconstruction and analysis at weeks 0, 1, 2, 4, 6, and 8 after grafting. Fat graft and overlying skin were harvested and underwent histological and cytokine analysis. Results: Histological analysis demonstrated improvement in radiation-induced fibrosis, CD31+ expression, and 8-isoprostane expression in the vitamin E group. Cytokine analysis revealed decreased cell differentiation markers and inflammatory markers. Fat graft volume retention significantly improved as early as 1 week post-grafting with local vitamin E administration compared to control. Conclusion: Radiation-induced fibrosis and fat graft volume retention are both simultaneously improved with novel, local administration of vitamin E, improving both cosmesis and functionality of fat grafting in chronically irradiated fields.

Fat Grafts Augmented With Vitamin E Improve Volume Retention and Radiation-Induced Fibrosis.

Treatments for radiation-induced fibrosis range from vitamin E (VE) and pentoxifylline (PTX) systemically to deferoxamine and fat grafting locally. Regarding fat grafting, volume retention hinders its long-term functionality and is affected by 2 factors: inflammation and necrosis secondary to hypovascularity. The authors aimed to simultaneously improve fat graft retention and radiation-induced fibrosis by integrating VE and PTX into fat grafts locally. Forty adult CD-1 nude male mice, 6 weeks old, underwent scalp irradiation and recovered for 4 weeks to allow for development of fibrosis. Mice received 200 μL of donor human fat graft to the scalp. Mice were separated into 4 conditions: no grafting, fat graft without treatment, graft treated with PTX, and graft treated with VE. Fat graft volume retention was monitored in vivo with micro-computed tomography scans at weeks 0, 1, 2, 4, 6, and 8 after grafting. Histological and cytokine analysis of the scalp skin and fat grafts were performed. VE-treated grafts had significant improvement in dermal thickness and collagen density of overlying skin compared with all other groups. VE decreased 8-isoprostane and increased CD31+ staining compared with the other grafted groups. Cytokine analysis revealed decreased inflammatory and increased angiogenic markers in both the fat graft and overlying skin of the VE group. Fat graft volume retention was significantly improved in the VE group starting at 1 week post grafting. Radiation-induced fibrosis and fat graft volume retention are both simultaneously improved with local administration of VE.

Dermal Regeneration Template and Staged Skin Grafting for Extirpative Scalp Wound Reconstruction: A 14‐Year Experience

Dermal regeneration template and staged split-thickness skin grafting may mitigate the need for flap coverage of postoncologic scalp defects. This technique has been studied previously in small case series. We examine the effect of risk factors, surgical technique, irradiation, and dressing modalities on reconstructive outcomes in a highly comorbid patient cohort. Retrospective review. Academic medical center. Full- and partial-thickness extirpative scalp wounds reconstructed with dermal regeneration template and staged skin grafting were reviewed over a 14-year period. Stage 1 consisted of template application following burr craniectomy in cases lacking periosteum. Stage 2 consisted of skin grafting. Negative pressure wound therapy (NPWT) was variably used to support adherence. In total, 102 patients were analyzed (average age 74, mean follow-up 18 months). Eighty-one percent were American Society of Anesthesiologists class 3 or 4. Defect size averaged 56 cm2. Average skin graft take was 94.5% in full-thickness wounds. Seven patients failed this method. Preoperative scalp irradiation was associated with major complication and delayed graft healing. Comorbidities, wound size, and burring were not associated with complication. Patients were more likely to heal with NPWT compared to bolster (hazard ratio, 1.67; 95% CI 1.01-2.77; P = .046). Time between stages was 6.6 days shorter when NPWT was applied (P < .001). Dermal template and staged skin grafting is a reliable option for postcancer scalp reconstruction in poor flap candidates. Radiotherapy is associated with adverse outcomes. Negative pressure wound therapy simplifies postoperative wound care regimens and may accelerate healing.

Development of a transparent and flexible patient-specific bolus for total scalp irradiation

A commercially available flat bolus (commercial bolus) would not fully fit the irregular surfaces of the scalp. We developed a transparent and flexible material with good fitting properties, analyzed its physical characteristics, and evaluated the clinical feasibility of the bolus fabricated using a three-dimensional (3D) printer (3D bolus). To evaluate the physical characteristics of the new material, treatment plans with virtual, 3D, and commercial boluses were created for water-equivalent phantoms using a radiation treatment planning system (RTPS). Using a head phantom and the dose volume histogram calculated with RTPS, dose distributions for total scalp irradiation were compared between the three treatment plans. To evaluate the clinical feasibility, the fitness and reproducibility of the 3D bolus were compared with the head phantom and clinical cases using dice similarity coefficient (DSC) measurements. A good agreement was observed between the percentage depth dose (PDD) curves for the virtual, 3D, and commercial boluses. The homogeneity indexes of the planning target volume (PTV) for the 3D and commercial boluses were 0.083 and 0.153, respectively, proving that the former achieved a better dose uniformity of PTV than the latter. Good fitness and reproducibility with the 3D bolus were observed in both the head phantom and two clinical cases, with mean DSC values of 0.854, 0.829, and 0.843, respectively. These results successfully demonstrated and verified the utility of the 3D bolus for total scalp irradiation.

Novel strategy with the automatic non-coplanar volumetric-modulated arc therapy for angiosarcoma of the scalp

BackgroundTotal scalp irradiation presents technical and dosimetric challenges. While reports suggest that HyperArc, a new stereotactic radiosurgery planning technique applied to non-coplanar volumetric-modulated arc therapy (VMAT) technique, is associated with high conformity and rapid dose fall-off, the performance of HyperArc for total scalp irradiation has not been explored. The current study aimed to compare the dosimetric performance of HyperArc plans with those of non-coplanar VMAT plans in angiosarcoma of the scalp.MethodsTen patients with angiosarcoma of the scalp were included in this study. The performance of three different plans administered using TrueBeam Edge were compared: non-coplanar VMAT using flattening filter (FF) beams (VMAT-FF), HyperArc using FF beams (HyperArc-FF), and HyperArc using flattening filter free (FFF) beams (HyperArc-FFF). The dose distribution, dosimetric parameters, and dosimetric accuracy for each of these plans were evaluated.ResultsThe three plans showed no statistically significant differences in target volume coverage, conformity, and homogeneity. The HyperArc-FF and HyperArc-FFF plans provided significantly lower mean brain doses (12.63 ± 3.31 Gy and 12.71 ± 3.40 Gy) than did the VMAT-FF plans (17.11 ± 5.25 Gy). There were almost no differences in sparing the organs at risk between the HyperArc-FF and HyperArc-FFF plans. The HyperArc-FF and HyperArc-FFF plans provided a shorter beam-on time than did the VMAT-FF plan. The 3%/2 mm gamma test pass rates were above 95% for all three plans.ConclusionsOur results suggest that the HyperArc plan can be potentially used for radiation therapy of target regions with large and complicated shapes, such as the scalp, and that there are no advantages of using FFF beams.

Scalp and Skull Reconstruction in Patients Irradiated for Tinea Capitis in Childhood: The Scalp Exchange Procedure

AbstractBackground Approximately 70,000 Israelis underwent scalp irradiation for tinea capitis infection during their childhood, as did many other children worldwide. Long-term follow-up data showed that these children had an increased risk of aggressive and multiple nonmelanoma skin cancers, meningiomas, and other malignancies. Resection of these lesions creates a defect of soft tissue, bone, and dura, and requires scalp and skull reconstruction with local or free flaps in the irradiated field.Methods Sixteen patients with a history of childhood scalp irradiation underwent scalp and skull reconstruction in our department (2000–2018). Data on demographics, oncological status, operative details, and postoperative outcome were retrospectively collected and analyzed.Results The study group included 11 males and 5 females (average age at surgery, 70 years). The most common lesions were meningiomas (n = 9) and basal cell carcinomas (n = 8), and the most common indication for reconstruction was chronic exposure of deep structures (skull, dura, brain tissue, and titanium mesh; n = 9). Thirteen patients underwent primary free flap reconstruction and three underwent primary local flap reconstruction. Flap failure requiring reoperation occurred in one patient of the free flap reconstruction group (7%) and in all three patients of the local flap reconstruction group.Conclusion Long-term consequences of childhood depilatory treatments of the scalp by irradiation are now surfacing. Our experience showed that in such cases, surgeons should aim for a more aggressive approach with wide resection and primary free flap reconstruction, and that favorable long-term functional and aesthetic results can safely be achieved using this reconstruction approach.

Abstract 151: Fat Grafting Mitigates Radiation-induced Scalp Fibrosis And Decreases The Abundance Of Profibrotic Engrailed1-positive Fibroblasts In The Overlying Skin

Purpose: Radiotherapy (RT) is used to treat thousands of patients every year, however it can result in significant damage to collateral healthy soft tissue within the radiation field. Radiation-induced soft tissue fibrosis may be severe and debilitating, but despite the frequency of this complication, there are few effective treatment strategies. Fat grafting is emerging as a popular technique able to address volume deficiencies and regenerate fibrotic scar tissue. The mechanisms of improved tissue quality after fat transfer remains poorly understood. We recently identified the Engrailed-1(En1)-positive fibroblast lineage in dorsal skin and scalp of mice responsible for the majority of collagen production in acute and chronic fibrosis. Here we asked whether grafted fat could alter the composition of this profibrotic fibroblast subtype in the irradiated scalp skin of recipient mice. Methods: Adult (60-day old) En1Cre;R26mTmG transgenic reporter mice (n=9) underwent full body lethal irradiation with 9 Gy for hematopoietic depletion. Mice were then immediately transplanted with 2 million nucleated bone-derived cells from donor NSG (NOD.CB17-Prkdcsscid/J) mice via retro-orbital sinus injection. Fluorescence-activated cell sorting (FACS) analysis of peripheral blood was used to assess the success of reconstitution. After 4 weeks, the calvarial region was then irradiated with a total of 30 Gy, fractionated into six 5 Gy doses delivered on alternative days across 12 days. A 4-week recovery period followed to allow for chronic radiation-induced skin fibrosis to develop. The irradiated site was then grafted with 200ul of fresh human lipoaspirate. Graft retention was measured radiographically over the subsequent 8 weeks. The calvarial skin was then harvested for histological assessment of fibrosis as well as for the abundance of En1-positive fibroblasts. Results: FACS analysis revealed that >90% of the hematopoietic cells (CD45+) in the peripheral blood ofEn1Cre;R26mTmG mice were membrane tomato (mT-) negative and membrane GFP negative (mG-) 2 weeks after bone marrow transplantation, indicating successful reconstitution. Scalp irradiation induced a significant expansion of the GFP+ profibrotic En1-positive fibroblasts 4 weeks following scalp irradiation. While reduced volume retention of grafted fat was observed over 8 weeks, this was associated with significant remodelling of the overlying skin; histological evidence of decreased collagen as well as a reduction in the profibrotic En1-positive fibroblast subpopulations was observed compared to irradiated but not grafted sites. Conclusion: Here, we show that fat grafting reduces radiation-induced scalp skin fibrosis by reducing the skin collagen content, remodelling collagen fiber networks, and by altering the composition of dermal fibroblast subpopulations. Specifically, we show that fat grafting reduces the abundance of the profibrotic En1-positive fibroblasts. Greater exploration of how radiation alters the function of this fibroblast subpopulation may lead to refinedtherapies for patients suffering from radiation-induced tissue fibrosis.

Improvement of the robustness to set up error by a virtual bolus in total scalp irradiation with Helical TomoTherapy.

Intensity-modulated radiation therapy has recently been used for total scalp irradiation. In inverse planning, the treatment planning system increases the fluence of tangential beam near the skin surface to counter the build-up region. Consequently, the dose to the skin surface increases even with small setup errors. Replacing the electron density of the surrounding air of some thickness with a virtual bolus during optimization could suppress the extremely high fluence near the skin. We confirmed the usefulness of a virtual bolus in total scalp irradiation. For each patient, two beams were planned, one with and the other without a virtual bolus. The dose distribution was calculated using computed tomography images that were shifted to simulate setup errors. The hot spot dose was suppressed in the plans using a virtual bolus. In conclusion, using a virtual bolus improved the robustness to setup errors.

Remote afterloading patient-specific brachytherapy with liquid radioisotope for irradiation of extensive scalp lesions: A Monte Carlo study.

The aim of this study is to propose a remote afterloading patient-specific brachytherapy technique for total scalp irradiation by utilizing liquid radioisotope as well as a three-dimensional (3D) printer and to find an optimal radioisotope for the suggested technique. We designed a brachytherapy device composed of liquid radioisotope tank, tube, patient-specific applicator, and a thin flexible pouch. The liquid radioisotope tank, tube, and the flexible pouch are interconnected one another to constitute a closed loop system. The pouch is located inside the solid patient-specific applicator; therefore, when the liquid radioisotope is injected into the pouch, the pouch is inflated and fills the space inside the applicator. The 3D-printed patient-specific applicator keeps the uniform thickness of the liquid radioisotope conforming patient's contour. To investigate an optimum condition for the suggested system, we performed Monte Carlo simulation with the GEANT4 simulation toolkit. To find the optimal radioisotope, percent depth doses (PDDs) of P-32, Sr-89, Y-90, and I-125 solutions were acquired in a rectangular parallelepiped phantom. For the selected radiation source, PDDs as well as dose rates in spherical phantoms with radii of 7.7cm (infant head size) and 9.1cm (adult head size) were acquired. To deliver prescription doses at 4-mm depth regions (scalp region), 1-mm-thick Y-90 and 5-mm-thick I-125 in liquid form were found to be feasible for the suggested technique. For both spherical phantoms with radii of 7.7 and 9.1cm, when delivering 2Gy at the 4-mm depth region with the 1-mm-thick Y-90 and 5-mm-thick I-125 sources, 53.3 and 3.8Gy were delivered at the surface regions, respectively (delivery time=111.1 and 3.5min with 1GBq/ml solutions). The PDDs of Y-90 and I-125 became less than 1% at depths greater than 8 and 50mm, respectively. The remote afterloading patient-patient specific brachytherapy with I-125 or Y-90 in liquid form seems feasible for total scalp irradiation.