Radiological, dosimetric and mechanical properties of a deformable breast phantom for radiation therapy and surgical applications

Implementation of a Breast Intraoperative Oncoplastic Form to Aid Management of Oncoplastic Surgery

INTRODUCTION

Oncoplastic breast conservation surgery (BCS) uses concurrent reduction and/or mastopexy with lumpectomy to improve aesthetic outcomes. However, tissue rearrangement can shift the original tumor location site in relation to external breast landmarks, resulting in difficulties during re-excision for a positive margin and accurate radiation targeting. We developed the Breast Intraoperative Oncoplastic (BIO) form to help depict the location of the tumor and breast reduction specimen. This study seeks to assess physician perspectives of the implementation outcomes.

METHODS

From February 2021 to April 2021, the BIO form was used in 11 oncoplastic BCS cases at a single institution. With institutional review board approval, surgical oncologists (SOs), plastic surgeons (PSs), and radiation oncologists (ROs) were administered a 12-question validated survey on Acceptability of Intervention Measure (AIM), Intervention Appropriateness Measure (IAM), and Feasibility of Intervention Measure (FIM), using a 5-point Likert scale during initial implementation and at 6-month reassessment.

RESULTS

Twelve physicians completed the survey initially (4 SOs, 4 PSs, and 4 ROs). The mean scores for Acceptability of Intervention Measure, Intervention Appropriateness Measure, and Feasibility of Intervention Measure were high (4.44, 4.56, and 4.56, respectively). Twelve completed the second survey (5 SOs, 3 PSs, and 4 ROs). The mean scores were marginally lower (4.06, 4.21, and 4.25). There were no significant differences when stratified by number of years in practice or specialty. Free text comments showed that 75% of physicians found the form helpful in oncoplastic BCS.

CONCLUSIONS

The data indicate high feasibility, acceptability, and appropriateness of the BIO form. Results of this study suggest multidisciplinary benefits of implementing the BIO form in oncoplastic BCS.

Promoting simulation-based training in radiology: a homemade phantom for the practice of ultrasound-guided procedures

OBJECTIVE

Ultrasound-guided intervention is an essential skill for many radiologists and critical for accurate diagnosis and treatment in many radiology subspecialties. Simulation using phantoms have demonstrated statistically significant benefits for trainees within the literature. We propose a novel phantom model which the authors feel is ideal for training clinical radiology trainees in the performance of ultrasound-guided procedures.

METHODS

The recipe to prepare a homemade phantom is described. Results of a local survey from trainees preparing and using the phantom are also presented.

RESULTS

This realistic training simulation model can be adapted to suit a variety of biopsy devices and procedures including soft tissue biopsy and cyst aspiration. The phantom mimics the sonographic appearances of soft tissue and biopsy targets can be concealed within. The phantom was easily prepared by 22 trainees (Likert score 4.5) and it functioned well (Likert score of 4.7).

CONCLUSION

In summary, our phantom model is ideal for training clinical radiology trainees in the performance of ultrasound-guided core biopsy. The availability and low cost of the model, combined with the ease of preparation and reproducibility, make this an efficient and effective addition to the training process.

ADVANCES IN KNOWLEDGE

A low cost easily handmade phantom recipe is described that could be easily implemented in training schemes.

Dosimetric considerations for moldable silicone composites used in radiotherapy applications

Due to their many favorable characteristics, moldable silicone (MS) composites have gained popularity in medicine and recently, in radiotherapy applications. We investigate the dosimetric properties of silicones in radiotherapy beams and determine their suitability as water substitutes for constructing boluses and phantoms. Two types of silicones were assessed (ρ= 1.04 g/cm³ and ρ= 1.07 g/cm³). Various dosimetric properties were characterized, including the relative electron density, the relative mean mass energy‐absorption coefficient, and the relative mean mass restricted stopping power. Silicone slabs with thickness of 1.5 cm and 5.0 cm were molded to mimic a bolus setup and a phantom setup, respectively. Measurements were conducted for Co‐60 and 6 MV photon beams, and 6 MeV electron beams. The doses at 1.5 cm and 5.0 cm depths in MS were measured with solid water (SW) backscatter material (D_MS–SW), and with a full MS setup (D_MS–MS), then compared with doses at the same depths in a full SW setup (D_SW–SW). Relative doses were reported as D_MS–SW/D_MS–SW and D_MS–MS/D_SW–SW. Experimental results were verified using Monaco treatment planning system dose calculations and Monte Carlo EGSnrc simulations. Film measurements showed varying dose ratios according to MS and beam types. For photon beams, the bolus setup D_MS–SW/D_SW–SW exhibited a 5% relative dose reduction. The dose for 6 MV beams was reduced by nearly 2% in a full MS setup. Up to 2% dose increase in both scenarios was observed for electron beams. Compared with dose in SW, an interface of MS–SW can cause relatively high differences. We conclude that it is important to characterize a particular silicone's properties in a given beam quality prior to clinical use. Because silicone compositions vary between manufacturers and differ from water/SW, accurate dosimetry using these materials requires consideration of the reported differences.

Low-Cost and Easily Fabricated Ultrasound-Guided Breast Phantom for Breast Biopsy Training

We aimed to develop an inexpensive and easy-to-fabricate gelatin-based training phantom for improving the breast biopsy skill and confidence level of residents. Young’s modulus and acoustic properties of the gelatin tissue phantom and simulated tumors were investigated. Six residents were requested to evaluate the effectiveness of the breast phantom. The results showed that 83% (n = 5) of the participants agreed that the ultrasound image quality produced by the breast phantom was excellent or good. Only 17% (n = 1) of the participants claimed that there was room for improvement for the haptic feedback they received during the placement of the core needle into the breast phantom. The mean pre-instructional score was 17% (SD 17%) for all participants. The mean post-instructional score was 83% (SD 17%), giving an overall improvement of 67%. In conclusion, the mean needle biopsy skill and confidence levels of the participants substantially increased through simulation training on our breast phantom. The participants’ feedback showed the phantom is sufficiently realistic in terms of ultrasound imaging and haptic feedback during needle insertion; thus, the training outcome can be linked to the performance of residents when they perform a live biopsy.

Can we rely on surgical clips placed during oncoplastic breast surgery to accurately delineate the tumor bed for targeted breast radiotherapy?

PURPOSE

Oncoplastic breast surgery (OBS) is gaining popularity among surgeons for breast-conserving surgery treatments. OBS relies on complex relocation and deformation of breast tissue involving the tumor bed (TB). In this study, we investigate the validity of using surgical clips with OBS for accurate TB delineation in adjuvant, targeted breast radiotherapy.

METHODS

Different OBS techniques were simulated on realistic breast phantoms. Surgical clips were used to demarcate the TB. Following tumor resection and closure, the true TB (TB_True) was extracted. Each phantom was CT imaged at several phases of surgery in order to record pre- and post-OBS closure surgical clip displacements. Two senior radiation oncologists (ROs) were asked to delineate TBs on CTs by relying on surgical clips placed as per standard protocol, and by referring to operative notes. Their original contours, as well as those expanded using 5-15 mm margins, were compared with the accurate TB_True using the dice similarity coefficient (DSC), Hausdorff Distance (HD), and over- and under-contoured volumes. Inter- and intra-RO contour agreements were also evaluated.

RESULTS

Post-OBS surgical clips were significantly displaced outside the original breast quadrant. Inter- and Intra-RO TB contours were consistent, yet systematically differed from TB_True (DSC values range = 0.38 to 0.69, and maximum HD range = 17.8 mm to 38.0 mm). Using expansion margins did not improve contour congruence and caused significant over-contoured volumes.

CONCLUSION

Following OBS, surgical clips alone are not reliable radiographic surrogates of TB locations and accurate TB delineation is challenging. For complex OBS cases, indication of any type of partial breast irradiation is very questionable.