[en] Cervical cancer is a disease that requires considerable multidisciplinary coordination of care and labor in order to maximize tumor control and survival while minimizing treatment-related toxicity. As with external beam radiation therapy, the use of advanced imaging and 3-dimensional treatment planning has generated a paradigm shift in the delivery of brachytherapy for the treatment of cervical cancer. The use of image-based brachytherapy, most commonly with magnetic resonance imaging (MRI), requires additional attention and effort by the treating physician to prescribe dose to the proper volume and account for adjacent organs at risk. This represents a dramatic change from the classic Manchester approach of orthogonal radiographic images and prescribing dose to point A. We reviewed the history and currently evolving data and recommendations for the clinical use of image-based brachytherapy with an emphasis on MRI-based brachytherapy

[en] Purpose: A prospective feasibility study was conducted to investigate the utility of dual-energy (DE) imaging compared to conventional x-ray imaging for patients undergoing kV-based image guided radiation therapy (IGRT) for lung cancer. Methods and Materials: An institutional review board-approved feasibility study enrolled patients with lung cancer undergoing IGRT and was initiated in September 2011. During daily setup, 2 sequential respiration-gated x-ray images were obtained using an on-board imager. Imaging was composed of 1 standard x-ray image at 120 kVp (1 mAs) and a second image obtained at 60 kVp (4 mAs). Weighted logarithmic subtraction of the 2 images was performed offline to create a soft tissue-selective DE image. Conventional and DE images were evaluated by measuring relative contrast and contrast-to-noise ratios (CNR) and also by comparing spatial localization, using both approaches. Imaging dose was assessed using a calibrated ion chamber. Results: To date, 10 patients with stage IA to IIIA lung cancer were enrolled and 57 DE images were analyzed. DE subtraction resulted in complete suppression of overlying bone in all 57 DE images, with an average improvement in relative contrast of 4.7 ± 3.3 over that of 120 kVp x-ray images (P<.0002). The improvement in relative contrast with DE imaging was seen for both smaller (gross tumor volume [GTV] ≤5 cc) and larger tumors (GTV >5 cc), with average relative contrast improvement ratios of 3.4 ± 4.1 and 5.4 ± 3.6, respectively. Moreover, the GTV was reliably localized in 95% of the DE images versus 74% of the single energy (SE images, (P=.004). Mean skin dose per DE image set was 0.44 ± 0.03 mGy versus 0.43 ± 0.03 mGy, using conventional kV imaging parameters. Conclusions: Initial results of this feasibility study suggest that DE thoracic imaging may enhance tumor localization in lung cancer patients receiving kV-based IGRT without increasing imaging dose

[en] Purpose and Objectives: To quantify, through an observer study, the reduction in metal artifacts on cone beam computed tomographic (CBCT) images using a projection-interpolation algorithm, on images containing metal artifacts from dental fillings and implants in patients treated for head and neck (H&N) cancer. Methods and Materials: An interpolation-substitution algorithm was applied to H&N CBCT images containing metal artifacts from dental fillings and implants. Image quality with respect to metal artifacts was evaluated subjectively and objectively. First, 6 independent radiation oncologists were asked to rank randomly sorted blinded images (before and after metal artifact reduction) using a 5-point rating scale (1 = severe artifacts; 5 = no artifacts). Second, the standard deviation of different regions of interest (ROI) within each image was calculated and compared with the mean rating scores. Results: The interpolation-substitution technique successfully reduced metal artifacts in 70% of the cases. From a total of 60 images from 15 H&N cancer patients undergoing image guided radiation therapy, the mean rating score on the uncorrected images was 2.3 ± 1.1, versus 3.3 ± 1.0 for the corrected images. The mean difference in ranking score between uncorrected and corrected images was 1.0 (95% confidence interval: 0.9-1.2, P<.05). The standard deviation of each ROI significantly decreased after artifact reduction (P<.01). Moreover, a negative correlation between the mean rating score for each image and the standard deviation of the oral cavity and bilateral cheeks was observed. Conclusion: The interpolation-substitution algorithm is efficient and effective for reducing metal artifacts caused by dental fillings and implants on CBCT images, as demonstrated by the statistically significant increase in observer image quality ranking and by the decrease in ROI standard deviation between uncorrected and corrected images.

[en] Dual-energy (DE) imaging using planar imaging with an on-board imager (OBI) is being considered in radiotherapy. We describe here a custom phantom designed to optimize DE imaging parameters using the OBI of a commercial linear accelerator. The phantom was constructed of lung-, tissue- and bone-equivalent material slabs. Five simulated tumors located at two different depths were encased in the lung-equivalent materials. Two slabs with bone-equivalent material inserts were constructed to simulate ribs, which overlap the simulated tumors. DE bone suppression was performed using a weighted logarithmic subtraction based on an iterative method that minimized the contrast between simulated bone- and lung-equivalent materials. The phantom was subsequently used to evaluate different combinations of high-low kV x-ray pairs of images based on the signal-difference-to-noise ratio (SDNR) metric. The results show a strong correlation between tumor visibility and selected energy pairs, where higher energy separation leads to larger SDNR values. To evaluate the effect of image post-processing methods on tumor visibility, an anti-correlated noise reduction (ACNR) technique and adaptive kernel scatter correction method were applied to subsequent DE images. Application of the ACNR technique approximately doubled the SDNR values, hence increasing tumor visibility, while scatter correction had little effect on SDNR values. This phantom allows for quick image acquisition and optimization of imaging parameters and weighting factors. Optimized DE imaging increases soft tissue visibility and may allow for markerless motion tracking of lung tumors. (note)

[en] Purpose: A multi-institutional planning study was performed to evaluate the frequency that current guidelines established by Radiation Therapy Oncology Group (RTOG) protocols and other literature for lung stereotactic body radiotherapy (SBRT) treatments are followed. Methods: A total of 300 patients receiving lung SBRT treatments in four different institutions were retrospectively reviewed. The treatments were delivered using Linac based SBRT (160 patients) or image guided robotic radiosurgery (140). Most tumors were located peripherally (250/300). Median fractional doses and ranges were 18 Gy (8–20 Gy), 12 Gy (6–15 Gy), and 10 Gy (5–12 Gy) for three, four, and five fraction treatments, respectively. The following planning criteria derived from RTOG trials and the literature were used to evaluate the treatment plans: planning target volumes, PTV_V _1_0_0 ≥ 95% and PTV_V _9_5 ≥ 99%; conformality indices, CI_1_0_0_% < 1.2 and CI_5_0_% range of 2.9–5.9 dependent on PTV; total lung-ITV: V_2_0_G_y < 10%, V_1_2_._5_G_y < 15%, and V_5_G_y < 37%; contralateral lung V_5_G_y < 26%; and maximum doses for spinal cord, esophagus, trachea/bronchus, and heart and great vessels. Populations were grouped by number of fractions, and dosimetric criteria satisfaction rates (CSRs) were reported. Results: Five fraction regimens were the most common lung SBRT fractionation (46%). The median PTV was 27.2 cm"3 (range: 3.8–419.5 cm"3). For all plans: mean PTV_V _1_0_0 was 94.5% (±5.6%, planning CSR: 69.8%), mean PTV_V _9_5 was 98.1% (±4.1%, CSR: 69.5%), mean CI_1_0_0_% was 1.14 (±0.21, CSR: 79.1%, and 16.5% within minor deviation), and mean CI_5_0_% was 5.63 (±2.8, CSR: 33.0%, and 28.0% within minor deviation). When comparing plans based on location, peripherally located tumors displayed higher PTV_V _1_0_0 and PTV_V _9_5 CSR (71.5% and 71.9%, respectively) than centrally located tumors (61.2% and 57.1%, respectively). Overall, the planning criteria were met for all the critical structure such as lung, heart, spinal cord, esophagus, and trachea/bronchus for at least 85% of the patients. Conclusions: Among the various parameters that were used to evaluate the SBRT plans, the CI_1_0_0_% and CI_5_0_% were the most challenging criteria to meet. Although the CSRs of organs at risk were higher among all cases, their proximity to the PTV was a significant factor

No abstract available

[en] To investigate the survival endpoints in women with International Federation of Gynecology and Obstetrics (FIGO) stage II endometrial cancer who received adjuvant vaginal brachytherapy (VBT) alone using multi-institutional pooled data.

[en] Bladder-preserving curative radiation therapy (RT) has been established as an excellent treatment option for select patients with muscle-invasive bladder cancer (MIBC). However, some clinicians have concerns that good outcomes are only achievable at high-volume facilities (HVFs) and academic centers (ACs), questioning successful reproducibility of curative RT at smaller centers. This study sought to determine whether treatment at ACs or HVFs was associated with better overall survival (OS) than treatment at nonacademic centers or lower-volume facilities.

[en] 

Background

Five dose calculation algorithms commonly used in lung SBRT planning are evaluated for their dosimetric impact on planning target volume (PTV) and organ-at-risk (OAR) doses.

Methods and materials

Treatment plans for thirty lung SBRT patients were included in this multi-institutional planning study. Lung SBRT plans were initially generated using BrainLab Pencil Beam (PB) convolution algorithm to deliver 50 Gy in 5 fractions to PTV (PB_OP plans). Plans were recalculated using BrainLab Monte Carlo (MC) algorithm with the same beam parameters, field settings, and MUs (MC_NO plans) to investigate accuracy limits of PB plans. Next, these plans were re-optimized via MU scaling in MC algorithm while keeping original beam parameters and settings (MC_OP). Further, with these new MUs, all patient plans were recalculated with Pinnacle collapsed cone convolution superposition (CCC), Eclipse anisotropic analytic algorithm (AAA), and Eclipse Acuros XB (AXB) algorithms, and are referred to as AP_NO, AAA_NO, and AXB_NO plans, respectively. DVH of PTV and OARs were used to calculate dosimetric parameters for comparison with MC_OP plans. Patient plans were compared based on PTV size as well as the location in the lung: island targets, adjacent to the ribs/chest wall, or mixed.

Results

Lung SBRT plans using PB dose algorithm overestimated target doses by 10–20% of prescribed dose and these differences were highlighted mainly in the target periphery/dose-buildup region as seen in D_min and D₉₀. Compared with MC, both Pinnacle and AAA plans overestimated PTV dose in the penumbra region, whereas Acuros plans were in good agreement with MC plans. PTV dose differences ranged 3–5% among Pinnacle, AAA, and Acuros. In general, Acuros AXB performed well for adjacent and mixed targets near the ribs and chest wall, whereas Pinnacle CCC was favored for island targets. OAR D_max and lung V₂₀ were better reproduced in Pinnacle, whereas D_mean were comparable among all TPS.

Conclusion

Knowing the strengths and limitations of clinical treatment planning system allows more consistent and accurate dose comparison for patients enrolled in protocol studies.

[en] Purpose: To provide an update of the 2007 American brachytherapy survey on image-based brachytherapy, which showed that in the setting of treatment planning for gynecologic brachytherapy, although computed tomography (CT) was often used for treatment planning, most brachytherapists used point A for dose specification. Methods and Materials: A 45-question electronic survey on cervical cancer brachytherapy practice patterns was sent to all American Brachytherapy Society members and additional radiation oncologists and physicists based in the United States between January and September 2014. Responses from the 2007 survey and the present survey were compared using the χ"2 test. Results: There were 370 respondents. Of those, only respondents, not in training, who treat more than 1 cervical cancer patient per year and practice in the United States, were included in the analysis (219). For dose specification to the target (cervix and tumor), 95% always use CT, and 34% always use MRI. However, 46% use point A only for dose specification to the target. There was a lot of variation in parameters used for dose evaluation of target volume and normal tissues. Compared with the 2007 survey, use of MRI has increased from 2% to 34% (P<.0001) for dose specification to the target. Use of volume-based dose delineation to the target has increased from 14% to 52% (P<.0001). Conclusion: Although use of image-based brachytherapy has increased in the United States since the 2007 survey, there is room for further growth, particularly with the use of MRI. This increase may be in part due to educational initiatives. However, there is still significant heterogeneity in brachytherapy practice in the United States, and future efforts should be geared toward standardizing treatment.