CT Simulation Research Articles

Virtual cone-beam computed tomography simulator with human phantom library and its application to the elemental material decomposition

PurposeThe purpose of this study is to develop a virtual CBCT simulator with a head and neck (HN) human phantom library and to demonstrate the feasibility of elemental material decomposition (EMD) for quantitative CBCT imaging using this virtual simulator. MethodsThe library of 36 HN human phantoms were developed by extending the ICRP 110 adult phantoms based on human age, height, and weight statistics. To create the CBCT database for the library, a virtual CBCT simulator that simulated the direct and scattered X-ray on a flat panel detector using ray-tracing and deep-learning (DL) models was used. Gaussian distributed noise was also included on the flat panel detector, which was evaluated using a real CBCT system. The usefulness of the virtual CBCT system was demonstrated through the application of the developed DL-based EMD model for case involving virtual phantom and real patient. ResultsThe virtual simulator could generate various virtual CBCT images based on the human phantom library, and the prediction of the EMD could be successfully performed by preparing the CBCT database from the proposed virtual system, even for a real patient. The CBCT image degradation owing to the scattered X-ray and the statistical noise affected the prediction accuracy, although these effects were minimal. Furthermore, the elemental distribution using the real CBCT image was also predictable. ConclusionsThis study demonstrated the potential of using computer vision for medical data preparation and analysis, which could have important implications for improving patient outcomes, especially in adaptive radiation therapy.

Towards Personalization of Planning Target Volume Margins Fitted to the Abdominal Adiposity in Localized Prostate Cancer Patients Receiving Definitive or Adjuvant/Salvage Radiotherapy: Suggestive Data from an ExacTrac vs. CBCT Comparison.

This study aimed to assess whether the patient's abdominal adiposity affects the performance of the Exactrac imaging system compared to the cone beam computed tomography (CBCT)-based setup, which was used as the reference positioning for the image-guided radiotherapy (IGRT) delivery to patients with localized prostate cancer. The daily positionings of patients with localized prostate cancer undergoing definitive or adjuvant/salvage radiotherapy (RT) were analyzed. The abdominal fat areas and pelvic incidence angle were determined on the CT simulation for each patient. A couple of ExacTrac images and a CBCT were acquired daily to verify the patient setup. We recorded every daily set of the three residual translational errors detected on the CBCT after the ExacTrac-based setup. These sets were clustered within three different thresholds (0.1 mm, 0.2 mm, and 0.3 mm), for each of which the influence of adipose tissues on Exactrac accuracy was assessed as the percentage of sub-threshold displacements as the fat parameters varied. A full bladder and empty rectum preparation protocol was adopted as much as possible. From the assessment of 1,770 daily positionings in 55 patients (38 definitive RT, 17 adjuvant/salvage RT), a good agreement between ExacTrac and CBCT could be inferred, which was quite robust against slight variations in the bladder and rectal filling, and the presence or not of the prostate. The percentages of above-threshold corrections increased with increasing abdominal fat, which therefore seemed to reduce the ExacTrac accuracy. This might be influenced by any intrafraction prostate displacement, likely induced by abdominal respiratory movements, and are more pronounced among overweight men. Our results promote the CBCT use over ExacTrac for IGRT of overweight patients with localized prostate cancer, while calling for attention to the probable need for personalization of planning target volume margins depending on the patient's body habitus.

Inter-Breath-Hold Geometric and Dosimetric Variations in Organs at Risk during Pancreatic Stereotactic Body Radiotherapy: Implications for Adaptive Radiation Therapy.

Pancreatic cancer is the fourth leading cause of cancer-related death, with nearly 60,000 cases each year and less than a 10% 5-year overall survival rate. Radiation therapy (RT) is highly beneficial as a local-regional anticancer treatment. As anatomical variation is of great concern, motion management techniques, such as DIBH, are commonly used to minimize OARs toxicities; however, the variability between DIBHs has not been well studied. Here, we present an unprecedented systematic analysis of patients' anatomical reproducibility over multiple DIBH motion-management technique uses for pancreatic cancer RT. We used data from 20 patients; four DIBH scans were available for each patient to design 80 SBRT plans. Our results demonstrated that (i) there is considerable variation in OAR geometry and dose between same-subject DIBH scans; (ii) the RT plan designed for one scan may not be directly applicable to another scan; (iii) the RT treatment designed using a DIBH simulation CT results in different dosimetry in the DIBH treatment delivery; and (iv) this confirms the importance of adaptive radiation therapy (ART), such as MR-Linacs, for pancreatic RT delivery. The ART treatment delivery technique can account for anatomical variation between referenced and scheduled plans, and thus avoid toxicities of OARs because of anatomical variations between DIBH patient setups.

Prompt Pain Relief From Bone Metastases: The Virtual Simulation Program

Rapid pain relief for patients with bone metastases can be a challenge due to the lengthy and complex radiation therapy workflow. The purpose of this study was to evaluate the time (in days) between initial radiation oncology consultation and start of palliative radiation treatment after implementing an alternative virtual simulation palliative workflow. Patients meeting strict criteria were selected for virtual simulation, which included only those with painful bone metastases who were recommended palliative radiation therapy using standard anterior-posterior/posterior-anterior or opposed lateral fields. A recent (within 30 days) diagnostic computed tomography (CT) scan clearly visualizing the target volume was required for treatment planning. For comparison, a reference group of 40 consecutive patients with bone metastases who underwent in-person CT simulation before virtual simulation implementation was reviewed. Forty-five patients were treated for painful bone metastases as part of the virtual simulation program from May 2021 to October 2022. Regarding travel distance, 23 patients lived locally (<50 miles from the treatment center) and 22 patients were distant (≥50 miles from the treatment center). Average time from consultation to treatment for all patients undergoing virtual simulation was 3.7 days, compared with 7.5 days for patients undergoing in-person CT simulation (3.8 days sooner, on average; P ≤ .001). Before full implementation of the virtual simulation program, 5 eligible patients participated in a virtual simulation pilot from April 2021 to May 2021, in which each patient was contoured and planned on both a pre-existing diagnostic CT scan and a standard CT simulation scan. For virtual simulation-based plans, the average V90, V95, and V99 were 99.99%, 99.87%, and 96.70%. No significant planning target volume (PTV) coverage difference was found on subsequent in-person CT simulation scans. The virtual simulation program decreased the time from consultation to start of treatment by more than 50% for patients recommended palliative radiation therapy for painful bone metastases. This benefit was most significant for outpatients traveling ≥50 miles for treatment. Virtual simulation-based planning can be considered for patients anxious to proceed with radiation therapy quickly or in underserved settings with limited transportation options to regional treatment centers.

Improved compact representation method for Monte Carlo phase spaces

Phase space files used in particle Monte Carlo simulations can be large, and thereby awkward to distribute and slow to load into memory. To circumvent this, compact source models and phase space representations have been developed. In this study, the aim is to increase the versatility of a previously presented method, based on principal component analysis whitening, by evaluating several modifications to the method on simulated cone-beam computed tomography projection images. Scaling the phase space components before whitening was seen to give the largest improvement and allowed for accurate modelling of phase spaces with a shifted detector and/or a bowtie filter present, configurations where the original method struggled. The modified method reproduced results using the original phase space to within a few percent both in energy fluence on the detector and in simulated projection and scatter images of a patient pelvis, without obvious position-dependence of the errors. Hence, the modified method was deemed sufficiently accurate for most applications relying on cone-beam computed tomography simulations. The final aim is to use the more versatile method for a broader range of phase space-based applications such as linear accelerator beam simulations and room shielding calculations.

Palliative radiotherapy and the introduction of a Rapid Access Palliative Clinic in a national radiation oncology network

BackgroundPalliative radiotherapy (PRT) is commonly used to treat symptoms of advanced cancer. PRT has been associated with elevated 30-day mortality (30DM). A Rapid Access Palliative Clinic (RAPC) can streamline the treatment process for patients receiving treatment.AimsWe reviewed the PRT practices in a radiation oncology network in Ireland, and the implementation of a RAPC. Patient outcomes were assessed to inform future treatment decisions. MethodsA retrospective review of all patients who received PRT over 6 months in 2018 in St. Luke’s Radiation Oncology Network (SLRON) was undertaken. We assessed 30DM rates, demographics and referral to specialist palliative care (SPC) services. Subsequently, a retrospective analysis was conducted of a RAPC which ran for 6 months from 2019 to 2020. We assessed treatment data and mortality.ResultsOver 6 months, 645 patients commenced PRT in the SLRON. The 30DM for this cohort was 15.8% (n = 102), with most patients having lung primaries. Of the 30DM cohort, only 55% (n = 56) were referred to SPC services and only 26.4% (n = 27) had performance status recorded. Over 6 months, 40 patients attended 28 RAPCs. Of these, 88% (n = 35) received PRT. Single fraction therapy was utilised in 60% and 48% of patients underwent CT simulation and treatment on the same day. Ultimately, 75% of patients received SPC referral.ConclusionsReferral rates to SPC services and documentation of performance status were low in our 30DM retrospective review cohort. The RAPC facilitated quick treatment turnaround, fewer hospital visits and referral to SPC services.

Analysis of factors associated with operative difficulty in thoracoscopic esophageal cancer surgery in the left-decubitus position: a single-center retrospective study.

The degree of difficulty in the overall procedure and forceps handling encountered by surgeons is greatly influenced by the positional relationship of intrathoracic organs in minimally invasive esophagectomy. This study aimed to identify the anatomical factors associated with the difficulty of minimally invasive esophagectomy assessed by intraoperative injuries and postoperative outcomes. Minimally invasive esophagectomy in the left-decubitus position was performed in 258 patients. We defined α (mm) as the anteroposterior distance between the front of the vertebral body and aorta, β (mm) as the distance between the center of the vertebral body and center of the aorta, and γ (degree) as the angle formed at surgeon's right-hand port site by insertion of lines from the front of aorta and from the front of vertebrae in the computed tomography slice at the operator's right-hand forceps hole level. We retrospectively analyzed the correlations among clinico-anatomical factors, surgeon- or assistant-caused intraoperative organ injuries, and postoperative complications. Intraoperative injuries significantly correlated with shorter α (0.2 vs. 3.9), longer β (33.0 vs. 30.5), smaller γ (3.0 vs. 4.3), R1 resection (18.5% vs. 8.3%), and the presence of intrathoracic adhesion (46% vs. 26%) compared with the non-injured group. Division of the median values into two groups showed that shorter α and smaller γ were significantly associated with organ injury. Longer β was significantly associated with postoperative tachycardia onset, respiratory complications, and mediastinal recurrence. Furthermore, the occurrence of intraoperative injuries was significantly associated with the onset of postoperative pulmonary complications. Intrathoracic anatomical features greatly affected the procedural difficulty of minimally invasive esophagectomy, suggesting that preoperative computed tomography simulation and appropriate port settings may improve surgical outcomes.

Reappraisal of Treatment Volume Determination for Parametrial Boosting in Patients with Locally Advanced Cervical Cancer

Objective: In this study, we evaluated treatment volume determination for parametrial boosting in patients with locally advanced cervical cancer. Materials and Methods: Primary goal of this study has been to evaluate treatment volume determination for parametrial boosting based on CT only or fused CT-MRI in patients with locally advanced cervical cancer. We have carried out a comparative analysis of treatment volume determination by CT simulation images only or by integration of MRI. While we primarily focused on evaluation of incorporated multimodality imaging for treatment volüme determination, we also assessed critical organ contouring along with interobserver and intraobserver variations. Ground truth target volume has been utilized for comparative analysis, and it was determined by board certified radiation oncologists after detailed evaluation of all imaging and relevant data with thorough colleague peer review and consensus.

Investigation of fiber length distribution on crack resistance mechanism of basalt fiber asphalt mixture based on digital image processing technology

Basalt fiber has been widely used to enhance the crack resistance performance of asphalt mixtures. The length of the fiber is an essential parameter to affect the reinforcement effect. However, the research on fiber length distribution (FLD) on the anti-cracking mechanism of asphalt mixtures is still limited.This study aims to present an efficient methodology considering the FLD effect for investigating the crack resistance mechanism of basalt fiber asphalt mixture (BFAM). The X-ray computed tomography (CT) and discrete element (DE) simulation techniques are used to obtain morphological parameters of the BFAM correlated with the FLD (i.e. aggregate skeleton gap size parameters). Then, three indoor cracking tests of the BFAM at low and medium temperatures (i.e. trabecular bending test, IDEAL-CT test and SCB test) are conducted to investigate the relationship between crack resistance performance and morphological parameters. Influences of FLD on the fracture property indexes of the BFAM are discussed.Results indicate that the optimal FLD for the best anti-cracking performance of the BFAM with a specific dense-graded gradation can be found by using digital image processing technology. The morphological parameter of the longest axis of the aggregate skeleton gap is identified as the optimal FLD, which can significantly improve the fracture energy and fracture property indices of the BFAM compared with other FLDs. Under the same fiber content, the fracture energy enhancement of BFAM with different FLDs varies from 7.63% to 106.87%. As for the fracture property indices, the enhancement of the εB in trabecular bending test, CTindex in IDEAL-CT test, and FI in SCB test varies from 17.42% to 39.30%, 13.00% to 162.99%, and 7.46% to 77.61%, respectively. The results demonstrate that fiber length distribution indeed impacts the cracking resistance of the BFAM. The X-ray CT and DE simulation techniques are proved to be both highly efficient approaches for seeking the optimal FLD in the BFAM.

Integrating subvolume dose and myocardial perfusion imaging parameters to assess the impact of radiation therapy on heart function in breast cancer patients: A comparative analysis between left- and right-sided breast cancer.

This study aimed to utilize an innovative method of integrating the 20 subvolume dose of left ventricle and the Tl-201 single photon emission computed tomography (SPECT) with myocardial perfusion imaging (MPI) parameters in patients with left- and right-sided breast cancer after radiation therapy. Female patients with breast cancer underwent SPECT MPI before commencing radiotherapy and 12 months later were enrolled from January 2014 to December 2018. The images of CT simulation and SPECT MPI were integrated into the treatment planning system. The differences of doses and parameters of MPI in all cardiac subvolumes between left- and right-sided breast cancer patients were analyzed. Patients with left-sided breast cancer (n = 61) received a higher radiation dose to the heart, left ventricular, and its territories and subvolumes, compared to patients with right-sided breast cancer (n = 19). The 20-segment analysis also showed statistically significant disparities in the average radiation doses received by the two groups. In different coronary artery territories, the end-diastolic perfusion and end-systolic perfusion showed a decrease in both sides, with no significant differences. However, the wall motion and wall thickening showed a significant decline in subregions within the left- and right-sided coronary artery territories. This study demonstrates an innovative integrated method combining the left ventricular 20 regional doses with SPECT MPI which shows that left-sided breast cancer patients receive a higher subvolume dose than right-sided breast cancer patients. Further research is needed to confirm the potential impact on heart function after radiotherapy on both sides.

LMAP-13 THE IMPACT OF RADIATION TREATMENT DOSE TO THE TUMOR AND NORMAL TISSUES USING POST-OPERATIVE MRI VS. MR-SIMULATION FOR RADIOTHERAPY PLANNING OF HIGH-GRADE GLIOMA

Abstract BACKGROUND Radiotherapy (RT) targets are commonly defined on post-operative (post-op) MRI registered to CT simulation images. However, changes can occur between surgery and simulation due to tumor progression and post-operative healing. In this work, we evaluate the impact of treatment planning using MR images taken at the time of CT simulation (MR-sim) versus post-op MRI. METHODS We evaluated 30 patients with primary HGG who received post-op MRI followed by RT planned using an MR-sim. We retrospectively delineated the gross tumor volume (GTV), clinical target volume (CTV), and normal structures on the post-op MRI and generated an experimental RT plan for these volumes. The RT plans based on post-op and MR-sim images were compared to determine the volume of tumor tissue that would have been undertreated, and the amount of normal brain tissue that would have been exposed to radiation (overtreated) had the plan been based on the post-op imaging. RESULTS The mean length between post-op imaging and MR-sim was 26 days (range: 12-42). A mean of 7.3cc (range 0.36cc–25.23cc) and 32.4cc (0.35–140.14cc) of the GTV and CTV, respectively, were undertreated on the post-op MRI plan compared to the MR-sim plan. The plan based on post-op target volumes resulted in a mean decrease in prescription dose coverage of the MR-sim-based GTV and CTV of 15.8% (max 72%) and 11.7% (max 57%), respectively. A mean of 14.5cc (0.04cc–53.9cc) and 47.5cc (range 2.4–179.2) of non-target brain tissue as identified on the MR-sim were included in the post-op MRI-based GTV and CTV, respectively. On average, the optic chiasm and brainstem would have received 191cGy and 117cGy more dose than intended, respectively. CONCLUSIONS Our findings confirm the valuable impact of RT planning using MR-sim in HGG to optimize treatment targets and reduce the exposure of normal tissue to unnecessary toxicity.

Generative Synthesis of Defects in Industrial Computed Tomography Data

The need for data increases as more and more companies try to take their first steps with AI to improve their efficiency and processes. Addressing this problem, we propose a solution for synthetic generation of industrial CT data for further AI applications using a deep learning approach packaged in a process pipeline. Based on a few individual CT scans of components with internal defects, the pipeline is able to generate STLs of any component with a large variation of artificially generated defects inside. Using this data with CT simulation, for example, provides access to creating large databases to overcome data lag and enrich further AI applications.

Hybrid planning techniques for early-stage left-sided breast cancer: dose distribution analysis and estimation of projected secondary cancer-relative risk

Purpose The purpose of this study was to evaluate three techniques of irradiation of left-sided breast cancer patients, three-dimensional conformal radiotherapy (3D-CRT), hybrid Intensity-Modulated Radiotherapy (h-IMRT), and hybrid Volumetric-Modulated Arc Therapy (h-VMAT, h-ARC), in terms of dose distribution in the planning target volume (PTV) and organs at risk (OARs). The second aim was to estimate the projected relative risk of radiation-induced secondary cancers for hybrid techniques. Materials and methods Three treatment plans were prepared in 3D-CRT, h-IMRT, and h-VMAT techniques for each of the 40 patients, who underwent CT simulation in deep inspiration breath-hold (DIBH). For hybrid techniques, plans were created by combining 3D-CRT and dynamic fields with an 80%/20% dose ratio for 3D-CRT and IMRT or VMAT. Cumulative dose–volume histograms were used to compare dose distributions within the PTV and OARs (heart, left anterior descending coronary artery [LAD], left and right lung [LL, RL], right breast [RB]). Projected risk ratios for secondary cancers were estimated relative to 3D-CRT using the organ equivalent dose (OED) concept for the Schneider’s linear exponential, plateau, and full mechanistic dose–response model. Results All plans fulfilled the PTV criterium: V95%≥95%. Compared to 3D-CRT, both hybrid techniques showed significantly better target coverage (PTV: V95%>98%, p < 0.001), and the best conformality was achieved by h-ARC plans (CI: 1.18 ± 0.09, p < 0.001). Compared to 3D-CRT and h-ARC, h-IMRT increased the average sum of monitor units (MU) over 129.9% (p < 0.001). H-ARC increased the mean dose of contralateral organs and the LL V5Gy parameter (p < 0.001). Both hybrid techniques significantly reduced the D max of the heart by 5 Gy. Compared to h-IMRT, h-ARC increased secondary cancer projected relative risk ratios for LL, RL, and RB by 18, 152, and 81%, respectively. Conclusions The results confirmed that both hybrid techniques provide better target quality and OARs sparing than 3D-CRT. Hybrid VMAT delivers less MU compared to hybrid IMRT but may increase the risk of radiation-induced secondary malignancies.

Assessment of bladder filling during prostate cancer radiation therapy with ultrasound and cone-beam CT.

Prostate cancer patients undergoing external beam radiation therapy (EBRT) benefit from a full bladder to decrease bowel and bladder toxicity. Ultrasound may offer a proxy metric for evaluation, sparing CBCT dosing. Patients were prospectively enrolled pre-simulation from January 2017 to February 2018. Bladder volume was evaluated prior to RT using US daily and CBCT for three daily treatments and then weekly unless otherwise indicated. 29 patients completed median 40 days of RT, resulting in 478 CBCT and 1,099 US bladder volumes. 21 patients were treated to intact glands and 8 to the post-prostatectomy bed. Median patient age was 70 years. Bladder volume on CBCT and US positively correlated (r = 0.85), with average bladder volume for all patients of 162 mL versus 149 mL, respectively. Bladder volume during treatment was consistently lower than the volume at CT simulation (153 mL vs 194 mL, p<0.01) and progressively declined during treatment. Patients older than 70 years presented with lower average bladder volumes than those < 70 years (122 mL vs 208 mL, respectively, p<0.01). Patients with the highest agreement between CBCT and US (<10% variability) had higher average bladder volumes (192 mL vs 120 mL, p=0.01). US was found to be an accurate measure of bladder volume and may be used to monitor daily bladder volumes in patients being treated with radiation for prostate cancer.

Hemorrhagic Transformation Assessment Based on Dual Energy CT of Immediately and Twenty-Four Hours after Endovascular Thrombectomy for Acute Ischemic Stroke.

Dual-energy CT (DECT) shows good performance in differentiating hemorrhage from contrast staining (CS). However, no guidelines have standardized the post-endovascular thrombectomy (EVT) examination time. We evaluated the value of performing DECT immediately and 24 h post-EVT in the diagnosis and prediction of hemorrhagic transformation (HT). Two readers evaluated simulated conventional CT (sCCT) images compared with a second reading with DECT, establishing the diagnosis of HT immediately and 24 h post-EVT. Another reader's diagnosis 2-7 days post-EVT using non-contrast CT was identified as the final diagnostic criteria. DECT performed immediately and 24 h post-EVT changed 22.4% (52/232) and 12.5% (29/232) of sCCT-based HT diagnoses, respectively (χ2 = 10.7, p < 0.05). The sensitivity, negative predictive value (NPV), and accuracy of DECT performed immediately post-EVT for predicting the final diagnosis of HT were 33.6%, 58.9%, and 65.9%, respectively, whereas those for DECT performed 24 h post-EVT were 82.4%, 84.3%, and 90.9%, respectively (χ2 = 58.0, χ2 = 42.9, χ2 = 13.6; p < 0.05). The specificity and positive predictive value were both 100.0%. Delayed HT occurred in 50.0% (78/156) and 42.2% (19/45) of patients with CS diagnosed immediately and 24 h post-EVT, respectively. DECT performed immediately post-EVT changed a greater proportion of real-time HT diagnoses, whereas that performed 24 h post-EVT had higher sensitivity, NPV, and accuracy in predicting the final diagnosis of HT. A substantial proportion of patients with CS diagnosed at these two post-EVT timepoints subsequently developed delayed HT.

Organ sparing treatment for penile cancer using a 3D-printed high-dose-rate brachytherapy applicator

PURPOSEWe present a case study of the treatment of localized squamous cell carcinoma on the glans penis with a custom-fabricated high-dose-rate (HDR) brachytherapy applicator. METHODS AND MATERIALSA cylindrically shaped applicator was fabricated with eight embedded channels suitable for standard plastic brachytherapy catheters. An additional custom silicone bolus/sleeve was designed to be used with the 3D-printed applicator to provide an additional offset from the source to skin to reduce the surface dose and for patient comfort. RESULTSThe patient (recurrent cT1a penile cancer) underwent CT simulation, and the brachytherapy plan was created with a nominal prescription dose of 40 Gy in 10 fractions given bidaily to the surface, and 35 Gy at 5 mm depth. Dose coverage to the clinical target volume was 94% (D90). Most fractions were treated with only 5-10 min of setup time. Follow up visits up to 1 year showed no evidence of disease with no significant changes in urinary and sexual function and limited cosmetic detriment to the patient. CONCLUSIONSPatient-specific organ-sparing HDR plesiotherapy using 3D printing technology can provide reliable and reproducible patient setup and may be effective in achieving disease control for superficial penile cancer, although preserving patient quality of life.

Same-day versus delayed simulation imaging after placement of a perirectal hydrogel spacer for prostate radiotherapy.

Placement of a perirectal hydrogel spacer has been demonstrated to reduce the risk of rectal toxicity from prostate radiation. Practices vary regarding the timing of CT simulation after hydrogel placement, and the ideal schedule remains unknown. Thirty patients with localized prostate adenocarcinoma underwent transrectal ultrasound-guided placement of an iodinated SpaceOAR™ hydrogel prior to radiotherapy. Per evolving practice, 15 completed same-day simulation and 15 returned for simulation 1-2 weeks later. Hydrogel volume, perirectal distance, air-void volume, and rectal dosimetry per NRG GU005 were compared between CT simulation, 1st fraction Cone-Beam-CT (CBCT), and final CBCT. CT simulation occurred 8.8 ± 2.4 days after placement in the delayed group, with no significant difference in the interval between simulation and 1st fraction between groups (p = 0.165). Greater observed de-creases in hydrogel volume (0.57 cc vs. 0.04 cc, p = 0.0002), and perirectal distance at both mid-gland (1.32mm vs. 0.17mm) and tallest point (2.40mm vs. 0.04mm) were seen on 1st-fraction CBCT in the same-day group (p = 0.0039; p = 0.0002). Per dosimetry recalculated on 1st fraction CBCT, five (D3 cc and D50%) versus one (D50%) rectal dose parameters were exceeded in the same-day and delayed groups, respectively, and 10 versus one parameters had a relative increase of ≥ 20%. Due to the evolving anatomic changes in the days following hydrogel placement, same-day simulation scanning may introduce unintended variability in rectal dosimetry at the time of prostate radiotherapy.

Dosimetric comparison of rectal carcinoma radiation therapy using three dimensional conformal radiation therapy and intensity modulated radiation therapy: an analytical observational study

Rectal cancer is the second most common cancer in large intestine. Recently, preoperative chemoradiotherapy has been generally used in the management of locally advanced rectal cancer on the basis of several benefits proven by clinical studies, in the aspect of better locoregional tumor control, reduced toxicity of normal organs, and an increased chance of preserving the anal sphincter, when compared with postoperative chemoradiotherapy. In this observational study, conducted between January 2017 and December 2021, pursuant to the recommendations of the radiation therapy oncology group (RTOG), all patients underwent CT simulation, a bladder protocol and target contouring. 10 patients were treated with intensity modulated radiotherapy (IMRT) and 10 with three-dimensional conformal radiation therapy (3DCRT). Planned target volume (PTV) coverage, homogeneity index (HI), conformity index (CI), and doses to organs at risk (OAR) were compared. Our findings showed that 3DCRT and IMRT have statistically significant differences in PTV coverage and dosages to OAR (p&lt;0.001), proving that IMRT achieves improved target dose coverage and superior normal tissue avoidance (bladder and intestine) compared to 3DCRT.

Full Dose SBRT in Combination With Mediastinal Chemoradiation for Locally Advanced, Non-Small Cell Lung Cancer: A Practical Guide for Planning, Dosimetric Results From a Phase 2 Study, and a Treatment Planning Guide for the Phase 3 NRG Oncology LU-008 Trial

Stereotactic body radiation therapy (SBRT) has been utilized with high effectiveness in early stage NSCLC but has not been studied extensively in locally advanced NSCLC. We conducted a phase II study delivering SBRT to the primary tumor followed by conventionally fractionated chemoradiation to the involved lymph nodes for patients with node positive locally advanced NSCLC. This manuscript serves as both a guide to planning techniques utilized on this trial and the subsequent phase III study, NRG Oncology LU-008, and to report patient dosimetry and toxicity results. We initiated a phase II multi-center single arm study evaluating SBRT to the primary tumor (50-54 Gy in 3-5 fractions) followed by conventionally fractionated chemoradiation to 60 Gy in 2 Gy fractions with doublet chemotherapy to the involved lymph nodes for patients with stage III or unresectable stage II NSCLC. Patients eligible for adjuvant immunotherapy received up to 12 months of durvalumab. We report a detailed guide for the entire treatment process from CT simulation through treatment planning and delivery. The dosimetric outcomes from the 60 patients who completed therapy on study are reported both for target coverage and normal structure doses. We also report correlation between radiation related toxicities and dosimetric parameters. 60 patients were enrolled between 2017-2022. Planning techniques utilized were primarily VMAT for both SBRT to the primary tumor and conventionally fractionated radiation to the involved nodes, with a minority of cases utilizing dynamic conformal arcs technique or static DMLC IMRT. Grade 2 or higher pneumonitis was associated with lung dose V5Gy >70 % and grade 2 or higher pulmonary toxicity was associated with lung dose V10Gy>50%. Only 3 patients (5%) experienced grade 3 or higher pneumonitis. Grade 2 or higher esophagitis was associated with esophageal doses, including mean dose >20Gy, V60Gy >7%, and D1cc >55Gy. Only one patient (1.7%) experienced grade 3 esophagitis. SBRT to the primary tumor followed by conventionally fractionated chemoradiation to the involved lymph nodes is feasible with planning techniques as described. Radiation related toxicity on this phase II study was low. This manuscript serves as a guideline for the recently activated NRG Oncology LU-008 phase III trial evaluating this experimental regimen.

Pelvic insufficiency fractures after intensity modulated radiation therapy combined with chemotherapy for cervix carcinoma: Incidence and impact of bone mineral density

Background and PurposeThe aim of this study was to evaluate the incidence and predictive factors of Pelvic Insufficiency Fractures (PIFs) occurring after Intensity Modulated Radiation Therapy (IMRT) combined with chemotherapy for locally advanced cervical cancer (CC).Material and methodsMedical records of patients receiving radio-chemotherapy with IMRT between 2010 and 2020 for advanced CC were reviewed. PIFs were detected during follow-up on pelvic Magnetic Resonance Imaging (MRI) or Computed Tomography (CT). The cumulative incidence rate of PIFs and its confidence interval were calculated at 2 and 5 years of follow-up. Pre-therapeutic Bone Mineral Density (BMD) (g/cm3) was evaluated on CT simulation for sacrum and the fourth lumbar (L4) vertebrae. Sacrum dosimetric parameters (V30Gy, V40Gy, D50%, Dmean) were analyzed.Results136 patients were included. The median follow-up was 4.4 years. Median dose of D50% and V40Gy sacrum were 35.2 Gy (20.6–46.4) and 32.2% (7.2–73.4) respectively. The 2-year and 5-year cumulative incidence rates were 15.7% (95% CI: 9.88–22.71) and 22% (95% CI: 14.58–30.45) respectively. Median time interval between RT completion and PIFs’ detection was 11.5 months (IQR: 7.4–22.3). Univariate analysis showed that older age (p < 0.01), postmenopausal status at baseline (p < 0.01), and lower sacral and spinal BMD at baseline (respectively p < 0.001 and p < 0.01) were significantly associated to all sites of PIFs, and lower sacral BMD with sacral fractures (p < 0.001).ConclusionPost-IMRT PIFs were detected in 18.4% of patients with locally advanced CC. Individual predisposing factors as older age, postmenopausal status, decreased bone density on the CT simulation were mainly predictive.