Shielding of the Contralateral Breast During Tangential Irradiation

2018

The purpose of this study was to evaluate a methodology to reduce scatter and leakage radiations to patients’ surface and shallow depths during conventional and advanced external beam radiotherapy. Superflab boluses of different thicknesses were placed on top of a stack of solid water phantoms, and the bolus effect on surface and shallow depth doses for both open and intensity-modulated radiotherapy (IMRT) beams was evaluated using thermoluminescent dosimeters and ion chamber measurements. Contralateral breast dose reduction caused by the bolus was evaluated by delivering clinical post-mastectomy radiotherapy (PMRT) plans to an anthropomorphic phantom. For the solid water phantom measurements, surface dose reduction caused by the Superflab bolus was achieved only in out-of-field area and on the incident side of the beam, and the dose reduction increased with bolus thickness. The dose reduction caused by the bolus was more significant at closer distances from the beam. Most of the dose reductions occurred in the first 2-cm depth and stopped at 4-cm depth. For clinical PMRT treatment plans, surface dose reductions using a 1-cm Superflab bolus were up to 31% and 62% for volumetric modulated arc therapy and 4-field IMRT, respectively, but there was no dose reduction for Tomotherapy. A Superflab bolus can be used to reduce surface and shallow depth doses during external beam radiotherapy when it is placed out of the beam and on the incident side of the beam. Although we only validated this dose reduction strategy for PMRT treatments, it is applicable to any external beam radiotherapy and can potentially reduce patients’ risk of developing radiation-induced side effects.

Section: Introductionmentioning

confidence: 99%

Evaluation of surface and shallow depth dose reductions using a Superflab bolus during conventional and advanced external beam radiotherapy

Yoon

Xie

2018

“…Unfortunately, lead shielding at these thicknesses is too heavy to use safely, and the lead shield does not reduce the SRD to normal tissues in the rest of the body. Researchers have proposed that thinner lead shielding is likely to have a significant protective effect on normal tissue . Therefore, we developed a body‐shielding device (BSD) to reduce SRD in the OFR and reduce the risk of radiation‐induced cancers.…”

Section: Introductionmentioning

confidence: 99%

“…Researchers have proposed that thinner lead shielding is likely to have a significant protective effect on normal tissue. 19,21 Therefore, we developed a body-shielding device (BSD) to reduce SRD in the OFR and reduce the risk of radiation-induced cancers. SRD at distances from the field edge were measured and analyzed before and after shielding.…”

Section: Introductionmentioning

confidence: 99%

“…It is well known that low-energy rays are easily shielded by high-atomic-number materials, such as lead and tungsten. Several groups have used lead as a shield to reduce SRD to the contralateral breast during tangential irradiation; 19,20 55% and 65% of the relative dose can be reduced by 13 mm and 25 mm of lead shielding, respectively, when the contralateral breast is shielded. Unfortunately, lead shielding at these thicknesses is too heavy to use safely, and the lead shield does not reduce the SRD to normal tissues in the rest of the body.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Reduction in stray radiation dose using a body‐shielding device during external radiation therapy

Jiang

et al. 2017

With the purpose of reducing stray radiation dose (SRD) in out‐of‐field region (OFR) during radiotherapy with 6 MV intensity‐modulated radiation therapy (IMRT), a body‐shielding device (BSD) was prepared according to the measurements obtained in experimental testing. In experimental testing, optimal shielding conditions, such as 1 mm lead, 2 mm lead, and 1 mm lead plus 10 mm bolus, were investigated along the medial axis of a phantom using thermoluminescent dosimeters (TLDs). The SRDs at distances from field edge were then measured and analyzed for a clinical IMRT treatment plan for nasopharyngeal carcinoma before and after shielding using the BSD. In addition, SRDs in anterior, posterior, left and right directions of phantom were investigated with and without shielding, respectively. Also, the SRD at the bottom of treatment couch was measured. SRD decreased exponentially to a constant value with increasing distance from field edge. The shielding rate was 50%–80%; however, there were no significant differences in SRDs when shielded by 1 mm lead, 2 mm lead, or 1 mm lead plus 10 mm bolus (P>0.05). Importantly, the 10 mm bolus absorbed back‐scattering radiation due to the interaction between photons and lead. As a result, 1 mm lead plus 10 mm bolus was selected to prepare the BSD. After shielding with BSD, total SRDs in the OFR decreased to almost 50% of those without shielding when irradiated with IMRT beams. Due to the effects of treatment couch and gantry angle, SRDs at distances were not identical in anterior, posterior, left and right direction of phantom without BSD. As higher dose in anterior and lower dose in posterior, SRDs were substantial similarities after shielding. There was no significant difference in SRDs for left and right directions with or without shielding. Interestingly, SRDs in the four directions were similar after shielding. From these results, the BSD developed in this study may significantly reduce SRD in the OFR during radiotherapy, thus decreasing the risk of secondary cancers.

“…If a supine treatment is used, to reduce contralateral breast dose, different types of shielding devices, and delivery techniques have been used 12, 13, 14, 15, 16. These included mobile high‐density lead shields placed between the treatment machine and the patient.…”

Section: Introductionmentioning

confidence: 99%

Characterization of a novel scale maille contralateral breast shield: SMART Armor

Butson¹,

Carroll

Butson

et al. 2017

During breast radiotherapy treatment, the contralateral breast receives radiation doses to the skin and subcutaneous tissue caused mainly from incident electron contamination and low energy photon scatter radiation. Measurements have shown that for a typical hybrid tangential treatment, these dose levels can be up to 17% of maximum applied prescription dose if no shielding is used during the treatment process. This work examined the use of different shielding metals, aluminum, copper, and lead to reduce peripheral radiation dose to evaluate the optimal metal to form the basis of a contralateral breast radiation shield. This work also shows a simple but novel method to substantially reduce this unwanted radiation dose with the use of a copper scale maille sheet which can be easily and accurately draped over a patient's contralateral breast during treatment. The copper scale maille is flexible and can thus conform around typical breast shapes. It can also form irregular shaped edges to match those outlined by typical tangential treatment fields. As the shield is made from copper, it is nontoxic and can potentially be used directly on patients for treatment. The designed copper scale maille has shown to reduce contralateral breast skin and subcutaneous dose by up to 80% for typical radiation fields used in breast radiotherapy.