Innovative Education Method for a More Effective, Faster, and Valued Training in Radiation Therapy Treatment Planning.

Purpose: Because of the automation of radiation therapy, competencies of radiation technologists (RTTs) change, and training methods are challenged. This study aims to develop, and pilot test an innovative training method based on lean management principles. Methods and Materials: A new training method was developed for lung cancer treatment planning (TP). The novelty is summarized by including a stable environment and an increased focus on the how and why of key decision making. Trainees have to motivate their decisions during TP process, and to argue their choices with peers. Six students and 6 RTTs completed this training for lung cancer TP. Effects of the training were measured by (1) quality of TP, using doses in organs at risk and target volumes, (2) perceived experiences (survey), measured at baseline (T0); after peer session (T1); and 6 months later (T2). Finally, training throughput time was measured. Results: At T0, RTTs showed a larger intragroup interquartile range (IIR) (2.63Gy vs 1.51Gy), but lower mean doses to heart and esophagus than students (6.79Gy vs 8.49Gy; 20.87Gy vs 24.62Gy). At T1, quality of TPs was similar between RTTs and students (IIR: 1.39Gy vs 1.33Gy) and no significant differences in mean dose to heart and esophagus (4.48Gy vs 4.69Gy; 17.75Gy vs 18.47Gy). At T2, students still performed equal to RTTs (IIR: 1.07Gy vs 1.45Gy) and achieved lower maximum dose to esophagus (44.75Gy vs 46.45Gy). The training method and peer sessions were experienced positive: at baseline (T0): 8 score on a scale 1-10, directly after the peer sessions; (T1): 8 by the students and 7 by the RTTs, after 9 months; (T2): 9 by the students and 7 by the RTTs. Training throughput time decreased from 12 to 3 months. Conclusions: This training method based on lean management principles was successfully applied to training of RTTs for lung cancer TP. Training throughput time was reduced dramatically and TP quality sustained after 6 months. This method can potentially improve training efficiency in diverse situations with complex decision-making.

Forward intensity-modulated radiotherapy planning in breast cancer to improve dose homogeneity: feasibility of class solutions.

PURPOSE: To explore forward planning methods for breast cancer treatment to obtain homogeneous dose distributions (using International Commission on Radiation Units and Measurements criteria) within normal tissue constraints and to determine the feasibility of class solutions. METHODS AND MATERIALS: Treatment plans were optimized in a stepwise procedure for 60 patients referred for postlumpectomy irradiation using strict dose constraints: planning target volume (PTV)(95%) of >99%; V(107%) of <1.8 cc; heart V(5 Gy) of <10% and V(10 Gy) of <5%; and mean lung dose of <7 Gy. Treatment planning started with classic tangential beams. Optimization was done by adding a maximum of four segments before adding beams, in a second step. A breath-hold technique was used for heart sparing if necessary. RESULTS: Dose constraints were met for all 60 patients. The classic tangential beam setup was not sufficient for any of the patients; in one-third of patients, additional segments were required (<3), and in two-thirds of patients, additional beams (<2) were required. Logistic regression analyses revealed central breast diameter (CD) and central lung distance as independent predictors for transition from additional segments to additional beams, with a CD cut-off point at 23.6 cm. CONCLUSIONS: Treatment plans fulfilling strict dose homogeneity criteria and normal tissue constraints could be obtained for all patients by stepwise dose intensity modification using limited numbers of segments and additional beams. In patients with a CD of >23.6 cm, additional beams were always required.

Reducing interobserver variation of boost-CTV delineation in breast conserving radiation therapy using a pre-operative CT and delineation guidelines.

AIMS: To investigate whether using a pre-operative CT scan (Preop-CT) (1) decreases interobserver variation of boost-CTV delineation in breast conserving therapy (BCT), and (2) influences the size of the delineated volumes. PATIENTS AND METHODS: Thirty cT1-2N0-1 breast cancer patients underwent a CT-scan in radiation treatment position, prior to and after lumpectomy. Five observers delineated a boost-CTV, both with and without access to the Preop-CT. For each patient and for each observer pair, the conformity index (CI) and the distance between the centres of mass (COMd) for both boost volumes were calculated. In addition, all delineated volumes including the standard deviation (SD) with respect to the median delineation were calculated. RESULTS: Using a Preop-CT reduced the mean COMd of the boost-CTV from 1.1cm to 1.0 cm (p<0.001). No effect was seen on the CI, but the boost-CTV volume reduced from 42 cc to 36 cc (p=0.005), implying a reduction of interobserver variation. We saw no significant change in the SD. CONCLUSION: Use of a Preop-CT in BCT results in a modest but statistically significant reduction in interobserver variation of the boost-CTV delineations and in a significant reduction in the boost-CTV volume.

Is contrast enhancement required to visualize a known breast tumor in a pre-operative CT scan?

BACKGROUND AND PURPOSE: A pre-operative CT scan with contrast enhancement (CE) has recently been proposed to improve tumorbed delineation in breast conserving therapy. However, it is not clear whether CE is required for visualization of a known breast tumor. The main aims of this study were to compare the sensitivity of a CE-CT scan with a native CT scan (i.e. without CE) and to identify characteristics predictive for the requirement of CE. PATIENTS AND METHODS: Both a CE-CT and a native CT were made in 58 breast cancer patients (age 37-75 yr), prior to breast conserving surgery. Visibility of the tumor on CT was scored by three observers (clearly visible/doubtful/not visible). Age, tumor size, palpable tumor yes/no, histology, and visibility on mammography were analyzed with respect to the visibility of the tumor on the native CT. RESULTS: The sensitivity for tumor detection was better for CE-CT (95%) than for native CT (83%) (p<0.001). Only mammographic visibility scores appeared to be significantly correlated with the visibility of the tumor on the native CT (p=0.013). CONCLUSION: In most patients CE is not required to visualize a known breast tumor. Mammographic visibility is a good parameter to decide on the use of CE.

Customized computed tomography-based boost volumes in breast-conserving therapy: use of three-dimensional histologic information for clinical target volume margins.

PURPOSE: To determine the difference in size between computed tomography (CT)-based irradiated boost volumes and simulator-based irradiated volumes in patients treated with breast-conserving therapy and to analyze whether the use of anisotropic three-dimensional clinical target volume (CTV) margins using the histologically determined free resection margins allows for a significant reduction of the CT-based boost volumes. PATIENTS AND METHODS: The CT data from 49 patients were used to delineate a planning target volume (PTV) with isotropic CTV margins and to delineate a PTV(sim) that mimicked the PTV as delineated in the era of conventional simulation. For 17 patients, a PTV with anisotropic CTV margins was defined by applying customized three-dimensional CTV margins, according to the free excision margins in six directions. Boost treatment plans consisted of conformal portals for the CT-based PTVs and rectangular fields for the PTV(sim). RESULTS: The irradiated volume (volume receiving > or =95% of the prescribed dose [V(95)]) for the PTV with isotropic CTV margins was 1.6 times greater than that for the PTV(sim): 228 cm(3) vs. 147 cm(3) (p < .001). For the 17 patients with a PTV with anisotropic CTV margins, the V(95) was similar to the V(95) for the PTV(sim) (190 cm(3) vs. 162 cm(3); p = NS). The main determinant for the irradiated volume was the size of the excision cavity (p < .001), which was mainly related to the interval between surgery and the planning CT scan (p = .029). CONCLUSION: CT-based PTVs with isotropic margins for the CTV yield much greater irradiated volumes than fluoroscopically based PTVs. Applying individualized anisotropic CTV margins allowed for a significant reduction of the irradiated boost volume.