Radiotherapy is a common and effective treatment for certain breast cancers. One potential drawback from this therapy is the development of varying degrees of erythema that typically occur after the treatment has been completed. Currently there are no tools to quantify radiation-induced skin changes during and after radiation and the standardized scoring systems remain subjective. Developing these tools would not only allow clinicians to objectively assess patients, but could potentially inform them as to which patients are likely to develop more severe side effects. Spatial Frequency Domain Imaging (SFDI) is a non-invasive, non-contact imaging technique capable of quantitatively mapping tissue absorption and scattering properties that can be converted into tissue oxygen saturation, total hemoglobin concentration and reduced scattering coefficients. Here we present a study of 13 breast cancer patients that have been prescribed radiation therapy and imaged using SFDI before, during, and after radiation treatment over the course of several weeks. A preliminary analysis of the data shows increases in total hemoglobin concentration as high as 75% in the treated breast tissue compared to highs of 10% in control regions at the end of the radiation treatments. Additionally, changes in the reduced scattering coefficient as high as 25% in the treated breast tissue can be seen a week before the treatment is complete and hyperpigmentation is visible. The aim of this study is to characterize radiation induced changes in skin using SFDI in order to provide clinicians with a technology that can inform radiation protocols (such as dose, frequency and duration) thereby minimizing unnecessary skin toxicity while maximizing treatment efficacy.

Extensive work has been done on the characteristics, dosimetry, and efficacy of flattening filter free (FFF) beams in radiosurgery. However, no study has addressed the dosimetric impact of FFF beam energy selection on treatment plan quality. This study aims to present a systematic dosimetric comparison of plan quality between 10 FFF vs 6 FFF beams in intracranial stereotactic radiosurgery (SRS) treatments using volumetric modulated arc therapy (VMAT). The dosimetric evaluation is based on radiation therapy oncology group (RTOG) dose conformity (CIRTOG) and gradient (GIRTOG) indices, and irradiated normal brain tissue volume. Thirty-five VMAT-based intracranial SRS treatments to multiple brain metastases using a 2.5 mm multileaf collimator (MLC) and 10 MV FFF beam were replanned with a 6 MV FFF and same MLC. The replans incorporated the same arc arrangement, planning target volume (PTV) and organs at risk structures, PTV coverage and prescription isodose normalization. The 6 MV FFF had a sharper dose fall-off compared to the 10 MV FFF (GIRTOG-10 FFF = 4.70, GIRTOG-6 FFF = 4.56; p < 0.05) and comparable conformity index (CIRTOG-10 FFF = 1.11, CIRTOG-6 FFF = 1.10; p = 0.9). On average, the irradiated normal brain tissue volume was 11% lower with 6 MV FFF compared to 10 MV FFF (p < 0.05). However, this difference was diminished for large target volumes and increased number of targets treated. The main dosimetric improvement of a 6 MV FFF over a 10 MV FFF beam is the sharper dose fall-off which directly correlates with less normal brain tissue volume irradiation.

106 Background: By virtue of their disease acuity and symptom burden, inpatients are good candidates for radiation therapy but may also be at risk of not benefitting from treatment due to premature treatment discontinuation or early demise. The current study describes the inpatient radiation therapy experience at an academic medical center. Methods: Patients receiving palliative radiotherapy in the hospital at any point in their care form the study population. Dose prescriptions were determined on an individual basis by the faculty radiation oncologist. Brachytherapy, IORT, and radiosurgery cases were excluded. Descriptive data was aggregated for analysis. Results: 315 courses given to 275 inpatients between January 2013 and September 2017 form this analysis. Mean age was 56.5 yrs. 96% began as inpatients. The top hospitalization indications were pain (32%), neurological symptoms (9%), and dyspnea (7%). The top treatment indications were spinal metastases (34%), brain metastases (21%), and non-spine bone metastases (12%). The estimated median survival of the entire group was 8.9 wks (range <1 – 189). Ten courses were given during the terminal hospitalization. The overall rate of treatment non-completion was 18%. Non-completion and survival figures for the most common indications provided. Spine treatments in which shorter courses predominated had a non-completion rate (12%) that was lower than for the overall group. The rate of treatment non-completion was particularly high for brain metastases (28%). Conclusions: Hospitalized patients receiving palliative radiation therapy carry a poor prognosis. Their significant symptom burden and limited life expectancies place them at risk for treatment non completion. While short courses developed for spine irradiation are associated with lower non-completion rates, longer courses seen as appropriate for brain irradiation are associated with particularly high non-completion rates.[Table: see text]

In September 2013, ASTRO drew attention to the choice of fractionation for bone metastases as part of the national Choosing Wisely campaign: "Don't routinely use extended schemes (>10 fractions) for palliation of bone metastases." This study seeks to determine whether the campaign and subsequent increased residency education on palliative care can have a durable effect on utilization patterns. The five faculty radiation oncologists prescribed dose fractionation schemes determined on an individual basis and without a standing policy. Following the debut of Choosing Wisely, the faculty and residents held lectures and journal clubs to discuss the campaign's recommendations. Palliative care topics were then regularly scheduled in subsequent years. Data from the treatment courses such as sites, doses, # fractions, dates of treatment, prescribing faculty, basic demographic data, and inpatient vs. outpatient status were abstracted from the department’s practice management system. SBRT cases were excluded. Utilization of single (1), short (2-5), standard (6-10), and long (>10) courses were recorded from the two years preceding through four years after the September 2013 Choosing Wisely campaign. Greater attention was given to incorporating palliative care into the residency lecture series following Choosing Wisely. Utilization rates were calculated in year long blocks. Between September 2011 and December 2017, 369 courses were given to 219 pts. Eighty (21.6%) of courses were given to inpatients. The most common diagnoses were lung (24.5%), breast (19%), and prostate (11.7%). The most common sites treated were spine (57%), pelvis (8.2%), and hip (7.1%). The utilization of shorter (2-5 fx) and especially single fx (SFX) courses increased from the pre-Choosing Wisely baseline of 23.9% (2-5), 4.3% (SFX) to 42.7, 39.7, 61, 67.3, and 48.1% for short course (2-5 fx) and 24, 38.1, 18.2, 23.6, and 41% for SFX at 1, 2, 3, 4, and 4+ yrs after the campaign (see table). The effect was particularly marked for inpatient use of SFX where the pre-campaign baseline of 0% rose to 23.1, 27.8, 56.3, 53.3, and 42.9% at 1, 2, 3, 4, and 4+ yrs after the campaign.Abstract TU_15_3040; Table 1No. Fx2011-2012 (%)2012-2013 (%)2013-2014 (%)2014-2015 (%)2015-2016 (%)2016-2017 (%)2017 (3 mo) (%)> 1014.34.35.36.32.61.806 - 1053.667.42844.418.27.311.12 – 528.623.942.739.76167.348.113.64.32438.118.223.640.7Mean8.68.757.55.64.54.1Median910510555courses26467563775527 Open table in a new tab ASTRO's campaign along with attention to training in palliative radiation oncology can have a durable effect on utilization patterns even after 4 years. The effect is particularly marked for inpatients receiving palliative radiation therapy. Specialty societies and professional organizations can influence practice patterns at the level of individual physicians through strategic campaigns designed to foster discussion reinforced by residency education.

The present study aims at quantitatively characterizing, monitoring, and potentially predicting skin toxicity induced by radiation for the treatment of breast cancer using an experimental imaging device, Spatial Frequency Domain Imaging (SFDI).

Radiotherapy is a critical component in the treatment of breast cancer. During radiation therapy (RT), patients develop varying degrees of erythema with some developing dry or moist desquamation. Additionally, patients can develop permanent discoloration of the skin and thickening of underlying breast tissue. Quantifying radiation-induced skin changes during and after radiation is challenging, since standardized scoring systems (RTOG Radiation Morbidity Scoring Scheme and CTCAE v.4) are subjective. Development of a non-invasive technique to reproducibly and objectively measure acute and late radiation-induced skin changes is needed. Spatial frequency domain imaging (SFDI) is a non-invasive and rapid functional imaging technique. It uses spatially-structured light at 8 different wavelengths (470 - 850 nm) to quantitatively map superficial tissue absorption and scattering in a wide-field, noncontact imaging geometry. Tissue oxygen saturation, oxyhemoglobin, deoxyhemoglobin, and melanin content can be calculated from the SFDI absorption data. Ten female patients undergoing RT for breast cancer were given written informed consent and enrolled in an IRB-approved, prospective pilot trial for SFDI of skin changes during and after RT. Dose to the whole breast was 50 Gy, followed by 10 Gy electron boost to the lumpectomy cavity or chest wall scar. Patients were measured before initiation of RT, weekly during their RT, 2 weeks after RT, and every 3 months using SFDI. Photographs were taken at the time of SFDI measurement to document cosmesis. The contralateral, untreated breast was also measured and used as an internal control. Melanin content steadily increased in the treated breast and correlated with hyperpigmentation noted by the physician. The onset of melanin increase is observable as early as 10 Gy. Throughout the treatment course, total hemoglobin steadily increased and correlated with area of erythema. There was a sudden reduction in tissue oxygen saturation after 40 Gy, suggesting radiation-induced damage of the microvasculature. Tissue oxygen saturation and oxyhemoglobin returned to baseline 2 weeks after completion of radiation. Melanin concentration peaked at the end of radiation, but was persistently elevated even after 3 months on followup examination. Our preliminary data from ten patients have validated the feasibility and reproducibility of SFDI to measure spatial and temporal changes in the skin during and after breast RT. We plan to recruit more females of different skin types and backgrounds, to identify different patterns of melanin and hemoglobin changes in radiated breast tissue. In the future, SFDI can be used to measure efficacy of different creams used to reduce acute and late effects of radiation-induced dermatitis and hyperpigmentation, and potentially predict patient’s skin response to breast RT from pre-treatment SFDI measurements.

The reported incidence of uterine perforation in tandem & ovoid brachytherapy ranges from 2 to 10%. Perforation not only potentially increases short term infection risk but treating a tandem in extrauterine or in a false myometrial passage may increase the risk of late rectal or sigmoid complications. When identified at the time of simulation, the brachytherapy may be cancelled, the apparatus removed, and antibiotics started with a subsequent low risk of infection. However, with modern HDR plan optimization, another option may be to treat before device removal if satisfactory dosimetry is achievable since the patient has already accrued the risks of a perforation. Between 2009-2016, 407 tandem & ovoid and 3 tandem & interstitial procedures were performed in 103 patients with cervical cancer. Procedures where the tandem perforated the uterus or created a false passage were identified from the simulation CT scans. HR-CTVs were retrospectively contoured in order to compare V100, D100, D90, rectal Dmax, and sigmoid Dmax doses between insertions with or without perforations and for patients with tandem false passages. Uterine perforations were identified in 12 insertions (2.9%) of which 9 (in 6 pts) were treated before removal. Tandem myometrial false passages without perforation were identified in 20 insertions (5%) in 4 pts all of whom were treated. Median follow up for all patients was 18 months (5 – 69). No acute complications and only 2 late GI toxicities occurred (1, Gr 2 and 1, Gr 3, both from false passage cases). At last follow up, there was 1 pt (10%) with local failure, 1 pt (10%) dead of metastases, 1 (10%) alive with metastases, and 7 (70%) alive without disease. For the 6 patients who had insertions with (9) and without (13) perforations, dosimetry for perforation vs. non-perforation insertions was: V100 74.5% (54 – 97) vs. 86.7% (66 – 100), D100 2.9 Gy (1.8 – 3.4) vs. 3.9 Gy (2.7 – 6.1), D90 4.7 Gy (3.1 – 6.1) vs. 6.2 Gy (3.8 – 9.6), rectal Dmax 3.7 Gy (1.6 – 6.6) vs. 3.8 Gy (2.4 – 5.1), and sigmoid Dmax 9.5 Gy (5 – 14) vs. 9.3 Gy (5.1 – 22). There were no statistically significant differences between the V100, D100, D90, rectal, and sigmoid doses between the insertions with and without perforations. For the false passage insertions (20 in 4 patients): V100 84.4% (66 – 99), D100 3.4 Gy (2.2 – 5.4), D90 5.6 Gy (3.8 – 8.8), rectum Dmax 3.7 Gy (2.1 – 4), and sigmoid Dmax 7.2 Gy (5.4 – 10). Routine abandonment of malpositioned tandem and ovoid brachytherapy insertions may not be necessary. Acute toxicity following uterine perforation is low. Moreover, in selected cases, optimized dosimetry may make possible comparable target volume coverage and normal tissue sparing despite perforating or malpositioned tandems.

We thank the authors of the letter for their interest in our work. [1] Yu S. Lawrenson L. Wei R. et al. The dosimetric impact of image guided radiation therapy by intratumoral fiducial markers. Pract Radiat Oncol. 2016; 6: 276-283 Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar They make an interesting suggestion. The intention of the clinical prescription is to deliver to the planning target volume (PTV) the clinically required dose. This approach guarantees that the clinical target volume, which is inherently difficult to define accurately, [2] Kim L. Wang C. Khan A. et al. Clinical target volume: The third front. Int J Radiat Oncol Biol Phys. 2016; 95: 800-801 Abstract Full Text Full Text PDF PubMed Scopus (6) Google Scholar receives the prescribed dose as required for appropriate clinical management throughout treatment. Regarding: “The dosimetric impact of image guided radiation therapy by intratumoral fiducial markers”Practical Radiation OncologyVol. 7Issue 1PreviewI read with interest the original report, “The dosimetric impact of image guided radiation therapy by intratumoral fiducial markers,” by Yu et al.1 For a cohort of pancreatic patients treated with image-guided radiation therapy (IGRT), the authors compared dosimetric coverage of the treated plan, which used intratumoral fiducial alignment, with coverage that would have been achieved had bone-anatomy alignment been used for treatments. Treatment plans were based on planning target volumes (PTVs), which were generated by expanding the internal target volumes (ITVs) by 5 mm in all directions. Full-Text PDF

While radiation therapy has been shown to increase local control and overall survival for breast cancer, cardiac toxicity remains a concern. Morbidity and mortality have been shown to increase proportionally to the mean heart dose. Deep inspiration breath hold (DIBH) can reduce heart dose compared to free-breathing (FB) delivery by increasing the distance from the heart to the chest wall, especially in left-sided breast cancer. DIBH requires monitoring of patients' respiratory motion. We report our experience with DIBH in left breast and chest-wall irradiation using 3D optical surface tracking. Thirty patients were treated using DIBH with a surface tracking system that provides a real time 3D surface image of the patient. This image is registered with the patient's body contour to facilitate setup and provide real time position offsets. Treatment plans were created on FB and DIBH images to compare doses to the heart and lungs. The distance between the heart and chest wall was measured at the 7th thoracic vertebra at 11 cm anterior to the spinal canal. Unpaired t-test was used to compare means and mean differences in heart and lung doses between plans. Correlation coefficients were derived for anatomic variances, such as heart and chest wall separation as well as heart and lung volumes. A comparison of DIBH and FB plans showed a decrease in mean and maximum heart doses in all patients. Individual patients’ mean heart doses decreased by an average of 1.12 Gy, and the average mean heart dose for DIBH plans was significantly lower than for FB plans (1.02 vs 2.12 Gy; P<0.0001). When lumpectomy and mastectomy patients were separated, this statistical significance was maintained in each group (P<0.0001 and P = 0.0233, respectively). Maximum heart dose decreased by an average of 11.88 Gy and was significantly lower in DIBH plans versus FB plans (28.33 vs 43.7 Gy; P = 0.0001). The average difference in heart to chest-wall separation between DIBH and FB images was 2.41 cm. This difference correlated positively with mean (R = 0.24) and maximum (R = 0.51) heart doses. While a trend towards improved left lung V20 was noted (14.04 vs 15.78%; P = 0.057), a significant difference was noted only for intact breast patients treated with opposed tangents alone (12.25 vs 15.06 Gy; P = 0.0257) versus plans with additional regional nodal radiation fields. Heart volume did not correlate with any measurements. However, DIBH left lung volume and the measured increase in volume on inspiration inversely correlated with maximum heart dose (R = 0.39) and left lung V20 (R = 0.32). DIBH with 3D surface tracking can significantly benefit patients with left sided disease by limiting the mean and maximum heart dose. In addition, DIBH showed a trend in improving lung V20 in intact breast patients treated with tangents alone. DIBH appears to be a viable option to reduce heart dose for left sided breast cancer patients and thus potentially reduce long-term complications without prolonging treatment delivery.

Purpose: To investigate the relationship between abdominal chemoradiation (CRT) for locally advanced cancers and bone mineral density (BMD) reduction in the vertebral spine.Materials and methods: Data from 272 patients who underwent abdominal radiation therapy from January 1997 to May 2015 were retrospectively reviewed. Forty-two patients received computed tomography (CT) scans of the abdomen prior to initiation and at least twice after radiation therapy. Bone attenuation (in Hounsfield unit) (HU) measurements were collected for each vertebral level from T7 to L5 using sagittal CT images. Radiation point dose was obtained at each mid-vertebral body from the radiation treatment plan. Percent change in bone attenuation (Delta%HU) between baseline and post-radiation therapy were computed for each vertebral body. The Delta%HU was-compared against radiation dose using Pearson's linear correlation.Results: Abdominal radiotherapy caused significant reduction in vertebral BMD as measured by HU. Patients who received only chemotherapy did not show changes in their BMD in this study. The Delta%HU was significantly correlated with the radiation point dose to the vertebral body (R = -0.472, P < 0.001) within 4-8 months following RT. The same relationship persisted in subsequent follow up scans 9 months following RT (R = -0.578, P < 0.001). Based on the result of linear regression, 5 Gy, 15 Gy, 25 Gy, 35 Gy, and 45 Gy caused 21.7%, 31.1%, 40.5%, 49.9%, and 59.3% decrease in HU following RT, respectively. Our generalized linear model showed that pre-RT HU had a positive effect (beta = 0.830) on determining post-RT HU, while number of months post RT (beta = -0.213) and radiation point dose (beta = -1.475) had a negative effect. A comparison of the predicted versus actual HU showed significant correlation (R = 0.883, P < 0.001) with the slope of the best linear fit = 0.81. Our model's predicted HU were within 20 HU of the actual value in 53% of cases, 70% of the predictions were within +/- 30 HU, 81% were within +/- 40 HU, and 90% were within +/- 50 HU of the actual post-RT HU. Four of 42 patients were found to have vertebral body compression fractures in the field of radiation.Conclusions: Patients who receive abdominal chemoradiation develop significant BMD loss in the thoracic and lumbar vertebrae. Treatment-related BMD loss may contribute to the development of vertebral compression fractures. A predictive model for post-CRT BMD changes may inform bone protective strategies in patients planned for abdominal CRT. (C) 2016 Elsevier Ireland Ltd. All rights reserved.

Does the use of quality assurance peer review chart rounds help in attaining ACGME competencies in radiation oncology residents and other staff members. Surveys were conducted to assess perceived improvement in competences amongst staff members and resident trainees within an academic radiation department from February 2011 to October 2012. Participants were residents, staff physician, therapists, nurses, dosimetrists and physicists, each completed one questionnaire per week at the end of each round. Rounds consisted of a one hour meeting of the entire radiation treatment team; whereby, patient’s progress and radiation dosing/plan/contours were reviewed collectively. Perceived level of ACGME competence and overall effectiveness of the rounds were measured using a 23-item survey on a 5-point Likert scale. Quantitative descriptive analysis was used to describe the pattern of responses. One-way multivariate analysis of variance (MANOVA) was used to examine differences between resident trainees and staff physicians. A total of 50 interdisciplinary chart rounds were conducted within the study period, with 176 survey responses generated from all staff members. Number of responses from each role was as follows: residents: n=17, staff physician: n=68, physicist: n=67, therapist: n=3, nurse: n=7; overall, staff members perceived positive effects on ACGME competencies through interdisciplinary chart rounds, with means ranging from 4.23 to 4.35 (‘agree’ to ‘strongly agree’). Multivariate analysis of variance showed a significant difference in residents’ ratings when compared with other staff members (P<.05). Post-hoc analysis revealed significantly higher value perceived by residents in two ACGME competencies: Medical knowledge and practice-based learning. During the study period, there were 116 counts whereby staff agreed or strongly agreed that rounds had changed their respective practices. Rounds also seemed to be positive learning opportunity across a variety of dosimetric learning objectives (mean range across objectives: 4.20-4.33). This study finds that quality assurance peer review chart rounds promote attaining professional competence in ACGME competencies in radiation oncology. Rounds were generally well-received by most staff members and should be considered in all radiation oncology programs.

PURPOSE:Pancreatic fiducials have proven superior over other isocenter localization surrogates, including anatomical landmarks and intratumoral or adjacent stents. The more clinically relevant dosimetric impact of image guided radiation therapy (IGRT) using intratumoral fiducial markers versus bony anatomy has not yet been described and is therefore the focus of the current study. METHODS AND MATERIALS:Using daily orthogonal kV or cone beam computed tomography (CBCT) images and positional and dosimetric data were analyzed for 12 consecutive patients treated with fiducial based IGRT and volumetric modulated arc therapy to the intact pancreas. The shifts from fiducial to bone (ΔFid-Bone) required to realign the daily fiducial-matched pretreatment images (kV, CBCTs) to the planning computed tomography (CT) using bony anatomic landmarks were recorded. The isocenter was then shifted by (ΔFid-Bone) for 5 evenly spaced treatments, and the dosimetric impact of ΔFid-Bone was calculated for planning target volume coverage (PTV50.4 and PTV47.9) and organs at risk (liver, kidney, and stomach/duodenum). RESULTS:The ΔFid-Bone were greatest in the superoinferior direction (ΔFid-Bone anteroposterior, 2.7 ± 3.0; left-right, 2.8 ± 2.8; superoinferior, 6.3 ± 7.9 mm; mean ± standard deviation; P = .03). PTV50.4 coverage was reduced by 13% (fiducial plan 95 ± 2.0 vs bone plan 82 ± 12%; P = .005; range, 5%-52%; >5% loss in all; and >10% loss in 42% of patients), and to a lesser degree for PTV47.9 (difference, -8%; range, 1%-30%; fiducial plan 100 ± 0.3% vs bone plan 92 ± 7.6%; P = .003; with reductions of >5% in 66% and >10% in 33% of patients). The dosimetric impact of ΔFid-Bone on the organs at risk was not significant. Positional shifts for kV- and CBCT-based realignments were nearly identical. CONCLUSION:Compared with matching by fiducial markers, IGRT matched by bony anatomy substantially reduces the PTV50.4 and PTV47.9 coverage, supporting the use of intratumoral pancreatic markers for improved targeting in IGRT for pancreatic cancer.

Recent development of 3-dimensional conformal radiation therapies provides a concentrated radiation dose to the tumor. To achieve this goal, a complex design of multiple narrow beamlets is used to shape the radiation exposure to conform to the shape of the tumor. Imaging findings after novel radiation therapy techniques differ from those of conventional radiation therapy. This article discusses changes in the liver parenchyma and tumor after conformal radiation therapy focusing on magnetic resonance imaging.

Purpose: The aim of this study is to quantify dosimetric effects resulting from variation in pancreatic tumor position assessed by bony anatomy and implanted fiducial markers Methods: Twelve pancreatic cancer patients were retrospectively analyzed for this study. All patients received modulated arc therapy (VMAT) treatment using fiducial-based Image Guided Radiation Therapy (IGRT) to the intact pancreas. Using daily orthogonal kV and/or Cone beam CT images, the shift needed to co-register the daily pre-treatment images to reference CT from fiducial to bone (Fid-Bone) were recorded as Left-Right (LR), Anterior-Posterior (AP) and Superior-Inferior (SI). The original VMAT plan iso-center was shifted based on KV bone matching positions at 5 evenly spaced fractions. Dose coverage of the planning target volumes (PTVs) (V100%), mean dose to liver, kidney and stomach/duodenum were assessed in the modified plans. Results: A total of 306 fractions were analyzed. The absolute fiducial-bone positional shifts were greatest in the SI direction, (AP = 2.7 ± 3.0, LR = 2.8 ± 2.8, and SI 6.3 ± 7.9 mm, mean ± SD). The V100% was significantly reduced by 13.5%, (Fid-Bone = 95.3 ± 2.0 vs. 82.3 ± 11.8%, p=0.02). This varied widely among patients (Fid-Bone V100% Range = 2–60%), where 33% of patients had a reduction in V100% of more than 10%. The impact on OARs was greatest to the liver (Fid-Bone= 14.6 vs. 16.1 Gy, 10%), and stomach, (Fid-Bone = 23.9 vx. 25.5 Gy, 7%), however was not statistically significant (p=0.10 both). Conclusion: Compared to matching by fiducial markers, matching by bony anatomy would have substantially reduced the PTV coverage by 13.5%. This reinforces the importance of online position verification based on fiducial markers. Hence, implantation of fiducial markers is strongly recommended for pancreatic cancer patients undergoing intensity modulated radiation therapy treatments.

Recent development of 3-dimensional conformal radiation therapies provides a concentrated radiation dose to the tumor. To achieve this goal, a complex design of multiple narrow beamlets is used to shape the radiation exposure to conform to the shape of the tumor. Imaging findings after novel radiation therapy techniques differ from those of conventional radiation therapy. This article discusses changes in the liver parenchyma and tumor after conformal radiation therapy focusing on magnetic resonance imaging.

Purpose:Flattening Filter Free (FFF) beams offer the potential for higher dose rates, short treatment time, and lower out of field dose. Therefore, the aim of this study was to investigate the dosimetric effects and out of field dose of Volumetric Modulated Arc Therapy (VMAT) plans using FFF vs Flattening Filtering (FF) beams for partial brain irradiation.Methods:Ten brain patients treated with a 6FF beam from a Truebeam STX were analyzed retrospectively for this study. These plans (46Gy at 2 Gy per fraction) were re‐optimized for 6FFF beams using the same dose constraints as the original plans. PTV coverage, PTV Dmax, total MUs, and mean dose to organs‐at‐risk (OAR) were evaluated. In addition, the out‐of‐field dose for 6FF and 6FFF plans for one patient was measured on an anthropomorphic phantom. TLDs were placed inside (central axis) and outside (surface) the phantom at distances ranging from 0.5 cm to 17 cm from the field edge. Paired T‐test was used for statistical analysis.Results:PTV coverage and PTV Dmax were comparable for the FF and FFF plans with 95.9% versus 95.6% and 111.2% versus 111.9%, respectively. Mean dose to the OARs were 3.7% less for FFF than FF plans (p<0.0001). Total MUs were, on average, 12.5% greater for FFF than FF plans with 481±55 MU (FFF) versus 429±50 MU (FF), p=0.0003. On average, the measured out of field dose was 24% less for FFF compared to FF, p<0.0001. A similar beam‐on time was observed for the FFF and FF treatment.Conclusion:It is beneficial to use 6FFF beams for regular fractionated brain VMAT treatments. VMAT treatment plans using FFF beams can achieve comparable PTV coverage but with more OAR sparing. The out of field dose is significant less with mean reduction of 24%.

Significant anatomic and volumetric changes during the course of fractionated radiation therapy warrant performing adaptive radiation therapy (ART). "Dose of the day" verification of delivered 3D dose distribution during each fraction has been suggested in literature for accurate dose accumulation during ART. Cone beam CT (CBCT) images have been used routinely for patient positioning throughout the treatment course. However, use of CBCT for dose calculation is still investigational. The purpose of this study is to explore the feasibility of using CBCT images for treatment planning. A CT quality assurance phantom was used to compare the dosimetric and geometric accuracy between conventional CT and on board CBCT. CBCT images were obtained both in full fan and half fan modes. Hounsfield units (HU) profiles at different density areas were evaluated. An AP-PA plan with two planning target volumes (PTVs) at heterogonous regions of the phantom was applied to both CT and CBCT phantom images. Isodose distributions and dose-volume-histograms (DVH's) were compared. Patient studies included two brain patients, and one head and neck (H&N) patient. Brain and H&N sites were employed in this study because superior rigid image co-registration can be accomplished. Volumetric Modulated Arc Therapy (VMAT) plans generated on the patients' treatment planning CT was applied to CBCT images obtained during the first treatment, and DVH's were calculated. For the phantom study, HU ranges from -1000 to +1000. The HU difference between CT and CBCT is within 100 (maximum 96 HU for Teflon CBCT images in full fan mode). The impact of these differences on the calculated dose distributions was clinically insignificant. Without HU correction, the dosimetric parameters are nearly identical for the PTVs. In both phantom and patient studies, target DVH's based on CBCT images were in excellent agreement with those based on planning CT images. Minimum, maximum and mean doses agreed within 0-2.8% with those calculated on planning CT images. A slightly larger discrepancy is observed in the patient studies compared to that seen in the phantom study, (0-1% vs 0.3-2.8%). CBCT images can be used to accurately predict dosimetric results, without any HU correction. It is feasible to use CBCT to evaluate the actual dose delivered at each fraction. The dosimetric consequences resulting from tumor response and patient geometry changes could be monitored. An additional planning CT may be needed to perform VMAT re-planning in order to accurately delineate tumor and organs. CBCT has the potential to become a very useful tool for on-line ART.

Purpose: Cone beam CT (CBCT) images have been used routinely for patient positioning throughout the treatment course. However, use of CBCT for dose calculation is still investigational. The purpose of this study is to assess the utility of CBCT images for Volumetric Modulated Arc Therapy (VMAT) plan dose calculation. Methods: A CATPHAN 504 phantom (The Phantom Laboratory, Salem, NY) was used to compare the dosimetric and geometric accuracy between conventional CT and CBCT (in both full and half fan modes). Hounsfield units (HU) profiles at different density areas were evaluated. A C shape target that surrounds a central avoidance structure was created and a VMAT plan was generated on the CT images and copied to the CBCT phantom images. Patient studies included three brain patients, and one head and neck (H' N) patient. VMAT plans generated on the patients treatment planning CT was applied to CBCT images obtained during the first treatment. Isodose distributions and dosevolume‐ histograms (DVHs) were compared. Results: For the phantom study, the HU difference between CT and CBCT is within 100 (maximum 96 HU for Teflon CBCT images in full fan mode). The impact of these differences on the calculated dose distributions was clinically insignificant. In both phantom and patient studies, target DVHs based on CBCT images were in excellent agreement with those based on planning CT images. Mean, Median, near minimum (D98%), and near maximum (D2%) doses agreed within 0‐2.5%. A slightly larger discrepancy is observed in the patient studies compared to that seen in the phantom study, (0‐1% vs. 0 – 2.5%). Conclusion: CBCT images can be used to accurately predict dosimetric results, without any HU correction. It is feasible to use CBCT to evaluate the actual dose delivered at each fraction. The dosimetric consequences resulting from tumor response and patient geometry changes could be monitored.