Research Spotlight

Morrow, A., Trisnadi, N. and Chung, H. (2021). “Multi-level multi-leaf collimators: Optimization of layer thicknesses and a feasibility study.” Med Phys Dec 27. [Epub ahead of print].

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PURPOSE: The function of multi-leaf collimators (MLC) is to modulate and shape the intensity of a radiotherapy beam by either blocking or unblocking beamlets. A variation on this functionality is tested in this work wherein the MLC is split into layers, with each layer attenuating the beam by a different amount. In this design, full blocking of a beamlet occurs only if all layers are blocked. This work suggests that such a device, a multi-layer MLC (MLMLC), can deliver dose distributions like a single layer MLC can deliver while requiring less time and monitor units (MU) METHODS: Optimal fluences were made for prostate plans using the Eclipse v13.6. An algorithm was developed to create step-and-shoot MLMLC patterns to match these optimal fluences when using up to six layers of MLC. Twelve MLMLC plans were made in total. These patterns were imported back into Eclipse as equivalent tungsten compensators and doses were calculated. Dose-volume histogram (DVH) values, total monitor units (MU), and total time to deliver were compared between arc-style MLMLC plans and nine-field step and shoot IMRT plans created completely in Eclipse using a single layer MLC. RESULTS: When using three or more layers, specified DVH values between the two sets agreed to within 5% while requiring roughly half as much time to deliver and about 20% fewer MU. CONCLUSIONS: Demonstrated that having multi-layer MLC can deliver dose distributions like a single layer MLC with less time and monitor units.

Monticciolo, D.L. (2022). “Invited Commentary: The Challenges of Early-Onset Breast Cancer.” Radiographics 42(1): E16-e17.

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In their outstanding review article, Gao et al. remind us that breast cancer affects young women as well. Although much of the focus of early-onset breast cancer has been on women with a genetic predisposition, Gao et al. correctly point out that the overwhelming majority of breast cancer diagnoses in women younger than 40 years, similar to those in their older counterparts, occur in those without a known germline genetic mutation or first-degree family history of breast cancer. [No abstract; excerpt from commentary].

Lopez, N.E., Nguyen, N.H., Hull, T.L., Peters, W.R., Singh, S. and Ramamoorthy, S.L. (2021). “Gender Related Differences in Surgeon Compensation: Survey Results from the American Society of Colon and Rectal Surgeons.” Ann Surg Dec 28. [Epub ahead of print].

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OBJECTIVE: We sought to understand the effect of gender on compensation among colorectal surgeons and to determine which factors contribute to gender-based differences in compensation. SUMMARY BACKGROUND DATA: The gender-based wage gap in the medical profession is among the most pronounced wage gaps in the U.S. Data regarding the wage gap among colorectal surgeons and the underlying reasons for this disparity remain unclear. METHODS: The Healthcare Economics Committee of The American Society of Colon and Rectal Surgeons (ASCRS) conducted a survey to evaluate surgeon demographics, compensation, and practice characteristics. To evaluate the effect of sex on compensation, we performed multivariable linear regression with backward selection. We used a two-sided p-value with a significance threshold <0.05. RESULTS: The mean difference in normalized total compensation between men and women was $46,250, and when salary was adjusted for FTEs, the difference was $57,000. Women were more likely to perform anorectal surgery, less likely to perform general surgery and less likely to hold positions in leadership. After adjustments, women reported significantly lower compensation (aOR, 0.88; 95% CI, 0.80-0.97). Time spent doing abdominal surgery (aOR, 1.13; 95% CI 1.03-1.23), professor status (aOR, 1.17; 95% CI, 1.03-1.32) and instructor status (aOR, 1.49; 95% 1.28-1.73) were independently associated with compensation. CONCLUSIONS: We found a 12% adjusted gender wage gap among colorectal surgeons. Gender-based differences in leadership positions and allocation of effort may contribute. Further research will be necessary to clarify sources of wage inequalities. Still, our results should prompt expedient actions to support closing the gap.

Liu, Y., Brinjikji, W., Abbasi, M., Dai, D., Arturo Larco, J.L., Madhani, S.I., Shahid, A.H., Mereuta, O.M., Nogueira, R.G., Kvamme, P., Layton, K.F., Delgado Almandoz, J.E., Hanel, R.A., Mendes Pereira, V., Almekhlafi, M.A., Yoo, A.J., Jahromi, B.S., Gounis, M.J., Patel, B., Fitzgerald, S., Doyle, K., Haussen, D.C., Al-Bayati, A.R., Mohammaden, M., Pisani, L., Rodrigues, G.M., Thacker, I.C., Kayan, Y., Copelan, A., Aghaebrahim, A., Sauvageau, E., Demchuk, A.M., Bhuva, P., Soomro, J., Nazari, P., Cantrell, D.R., Puri, A.S., Entwistle, J., Kadirvel, R., Cloft, H.J., Kallmes, D.F. and Savastano, L. (2021). “Quantification of clot spatial heterogeneity and its impact on thrombectomy.” J Neurointerv Surg Dec 15;neurintsurg-2021-018183. [Epub ahead of print].

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BACKGROUND: Compositional and structural features of retrieved clots by thrombectomy can provide insight into improving the endovascular treatment of ischemic stroke. Currently, histological analysis is limited to quantification of compositions and qualitative description of the clot structure. We hypothesized that heterogeneous clots would be prone to poorer recanalization rates and performed a quantitative analysis to test this hypothesis. METHODS: We collected and did histology on clots retrieved by mechanical thrombectomy from 157 stroke cases (107 achieved first-pass effect (FPE) and 50 did not). Using an in-house algorithm, the scanned images were divided into grids (with sizes of 0.2, 0.3, 0.4, 0.5, and 0.6 mm) and the extent of non-uniformity of RBC distribution was computed using the proposed spatial heterogeneity index (SHI). Finally, we validated the clinical significance of clot heterogeneity using the Mann-Whitney test and an artificial neural network (ANN) model. RESULTS: For cases with FPE, SHI values were smaller (0.033 vs 0.039 for grid size of 0.4 mm, P=0.028) compared with those without. In comparison, the clot composition was not statistically different between those two groups. From the ANN model, clot heterogeneity was the most important factor, followed by fibrin content, thrombectomy techniques, red blood cell content, clot area, platelet content, etiology, and admission of intravenous tissue plasminogen activator (IV-tPA). No statistical difference of clot heterogeneity was found for different etiologies, thrombectomy techniques, and IV-tPA administration. CONCLUSIONS: Clot heterogeneity can affect the clot response to thrombectomy devices and is associated with lower FPE. SHI can be a useful metric to quantify clot heterogeneity.

Kobashigawa, J.A., Hall, S., Farr, M., Blumberg, E., Michael Borkon, A., Colvin, M., Copeland, H., Eisen, H., Johnson, M., Jorde, U., Khush, K., Kirklin, J.K., Patel, J., Pinney, S., Saadaeijahromi, H., Schold, J.D. and Stehlik, J. (2021). “Proceedings from the metrics forum in heart transplantation for performance monitoring.” Am J Transplant Dec 6. [Epub ahead of print].

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Regulatory oversight for heart transplant programs is currently under review by the United Network for Organ Sharing (UNOS). There is concern whether 1-year patient and graft survival truly represent heart transplant center performance. Thus, a forum was organized by the Thoracic and Critical Care Community of Practice (TCC COP) of the American Society of Transplantation (AST) for the heart transplant community to voice their opinions on matters involving program performance monitoring by UNOS. A TCC COP work group was formed to review outcome metrics for adult heart transplantation and culminated in a virtual community forum (72 participants representing 61 heart transplant programs) on November 12-13, 2020. One-year posttransplant survival is still considered an appropriate and important measure to assess program performance. Waitlist mortality and offer acceptance rate as pretransplant metrics could also be useful measures of program performance, recognizing that outside factors may influence these metrics. In depth discussion of these metrics and other issues including auditing thresholds, innovations to reduce risk-averse behavior and personally designed program scorecards are included in this meeting proceedings.