A Simple and Cost-effective Technique for Deep Inspiration Breath-hold Radiotherapy in Left-sided Breast Cancer Patients: A Retrospective Study

Background: Deep inspiration breath-hold (DIBH) radiotherapy is effective but requires specific devices for tracking the respiratory cycle or surface motion. There are some reports of DIBH without such devices. However, to the best of our knowledge, no study has evaluated all three components which are: setup accuracy, dose assessment, and treatment time. We evaluated the accuracy, effect of dose reduction on organs at risk (OARs), and the treatment time of our DIBH technique, which avoids the use of such devices.Methods: We analyzed 64 left-sided early breast cancer patients. Three-dimensional conformal radiotherapy treatment plans of 42.56 Gy in 16 fractions were created in free-breathing (FB) and DIBH settings. Thirty patients were evaluated for inter- and intra-fractional displacement. The treatment room entry-to-exit times were measured and retrospectively compared with those of 44 right breast cancer patients who received FB radiotherapy (Right-FB) in the same period. The volumes and dose metrics of the clinical target volume (CTV) and contoured OARs (HEART, left anterior descending artery [LAD], and LUNG) were compared between FB and DIBH.Results: The average inter-fractional, intra-fractional, and overall setup displacement were 2.32 ± 1.30, 0.55 ± 0.43, and 2.46 ± 1.24 mm, respectively. Compared to Right-FB, the medians of entry-to-exit times slightly increased in DIBH (9 vs 7 minutes, P = 3.95e-23). The LUNG volume in DIBH was 1.58 times larger than that in FB, but other volumes were not statistically different. Compared to FB, the median HEART, LAD, and mean LUNG doses decreased significantly in DIBH: 1.67 vs 0.71 (P = 9.72e-15), 13.0 vs 2.3 (P = 6.65e-15), and 2.42 vs 2.03 (P = 6.80e-8) Gy, respectively. CTV doses were not statistically different.Conclusions: With only minor setup errors, this simple and cost-effective DIBH technique is a feasible method. It can be easily tested for new facilities and is expected to accelerate the further clinical implementation.Trial registration:

Motivation Strategies and Exiting Class by Students in Inquiry-Oriented Biology Labs

Experimental inquiry-oriented science labs can be designed to have students regulate their own learning and decide when they leave class or to have the teacher regulate student learning and determine when they leave class. In this study, grades were examined relative to student exit times in a student-regulated class design. Preliminary interviews revealed four motivation strategies likely to differentially influence exit times and grades: proficiency, grade-target-A, grade-target-C, and time-limited. Students were categorized into the four groups of motivation strategies with a survey. Twenty teaching assistants teaching three lab sections each taught the stand-alone lab class. Students recorded the time they left class each week. Grades were determined as the overall percentage of points a student received in class. Results of the survey showed that the four motivation strategies were well represented in the student population, and two additional strategies were also frequently seen: a hybrid-1 between proficiency and grade-target-A, and a hybrid-2 between time-limited and grade-target-C. Grades were significantly higher for grade-target-A and hybrid-1 students, followed by time-limited, proficiency, grade-target-C, and hybrid 2. Time spent in class was not significantly different among categories. Students who chose to stay in class longer had significantly higher grades. If a grade is the goal, these results support the idea of a teacher-controlled exit time for the students in these inquiry-oriented labs. Implications are discussed.