Target Volume Definition Research Articles

Deep learning derived tumor infiltration maps for personalized target definition in Glioblastoma radiotherapy

PurposeGlioblastoma is routinely treated by concomitant radiochemotherapy. Current target definition guidelines use anatomic MRI (magnetic resonance imaging) scans, taking into account contrast enhancement and the rather unspecific hyperintensity on the fluid-attenuated inversion recovery (FLAIR) sequence. Methods and materialsWe applied deep learning based free water correction of diffusion tensor imaging (DTI) scans to estimate the infiltrative gross tumor volume (iGTV) inside of the FLAIR hyperintense region. We analyzed the resulting iGTVs and their impact on target volume definition in a retrospective cohort of 33 GBM patients. ResultsiGTVs were significantly smaller compared to standard pre- and post-operative gross tumor volume (GTV) definitions. Two novel infiltrative tumor GTVs (nGTVPRE-OP and nGTVPOST-OP) defined as the conjunction volume of the standard GTV and the iGTV showed only a moderate increase in size compared to standard GTV definitions. On postoperative scans, the iGTV was predominantly covered by the two clinical target volume (CTV) concepts CTVEORTC and CTVROTG1. A novel infiltrative tumor CTV (nCTV) [nGTVPOST-OP + 2 cm margin] was significantly smaller compared to CTVROTG1 but larger than CTVEORTC. The overlap volume and conformity index demonstrated a distinct spatial configuration of the nCTV. Tumor recurrences overlapped with the iGTV in all but one patients and were completely covered by the nCTV in all patients. After reducing the margin to 1 cm recurrences coverage was at least in-field in all patients. ConclusionTo conclude, free water corrected DTI scans may help to define infiltrative tumor areas of GBM that could ultimately be used to individualize RT treatment planning in terms of dose sparing or dose escalation.

Clinical relevance of metal artefact reduction in computed tomography (iMAR) in the pelvic and head and neck region: Multi‐institutional contouring study of gross tumour volumes and organs at risk on clinical cases

Artefacts caused by dental implants and hip replacements may impede target volume definition and dose calculation accuracy. The iterative metal artefact reduction (iMAR) algorithm can provide a solution for this problem. The present study compares delineation of gross tumour volumes (GTVs) and organs at risk (OARs) in the pelvic and the head and neck (H & N) regions using computed tomography (CT) with and without iMAR, and thus the practical applicability of iMAR for routine clinical use. The native planning CT and CT-iMAR data of two typical clinical cases with image-distorting artefacts were used for multi-institutional contouring and analysis using the Dice similarity coefficient (DSC). GTV/OAR contours were compared with an intraobserver approach and compared to predefined reference structures. Mean volume for GTVprostate in the intraobserver approach decreased from 87±44cm3 (native CT) to 75±22cm3 (CT-iMAR) (P=0.168). Compared to the reference, DSC values for GTVP rostate increased from 0.68±0.15 to 0.78±0.07 (CT vs. iMAR) (P<0.05). In the H & N region, the reference for GTVT ongue (34cm3 ) was underestimated on both data sets. No significant improvement in DSC values (0.83±0.06 (native CT) versus 0.86±0.06 (CT-iMAR)) was observed. The use of iMAR improves the anatomical delineation at the transition of prostate and bladder in cases of bilateral hip replacement. In the H & N region, anatomical residual structures and experience were apparently sufficient for precise contouring.

MRI-based interstitial brachytherapy for vaginal tumors: A multi-institutional study on practice patterns, contouring, and consensus definitions of target volumes

PurposeInterstitial brachytherapy (ISBT) can be effective for vaginal tumors due to its ability to deliver conformal treatment with 3D planning. As there is no consensus for 3D vaginal brachytherapy (BT) contouring, the goals of this study are to evaluate the variability in practices and contouring, and to develop consensus concepts on target definitions. MethodsA survey/contouring study was conducted with 16 radiation oncologists from 10 Canadian academic centers. The study included three vaginal ISBT cases. Participants were provided staging, prebrachytherapy (pre-BT), and BT MRIs. Participants responded to a questionnaire and contoured on the provided images. Agreement between contours was analyzed. A meeting was held to develop consensus definitions of targets. ResultsMedian ISBT experience was 3.5 years. All 16 participants regularly contour with MRI, whereas three also plan on MRI. For the three cases, there was variation into how CTVHR and CTVIR was defined. Kappa statistics showed higher agreement with bulky tumors (mean 0.59) as compared with small residual tumors (mean 0.29). For all cases, kappa was highest in pre-BT GTVres as compared with BT GTVres (mean 0.58, 0.46). Consensus concepts to define targets were developed. ConclusionsVariations exist in how ISBT targets are defined for vaginal tumors. Highest contouring variability was seen with small residual at BT. Contouring is more consistent on pre-BT MRI as compared with BT MRI suggesting a needle distortion effect. Consensus CTVHR and CTVIR definitions have been developed and further work is warranted to establish international standards.

Advantages of using reduced-volume intensity modulated radiation therapy for the treatment of nasopharyngeal carcinoma: a retrospective paired study

BackgroundThe definition of clinical target volume (CTV) in intensity modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC) has not been addressed. We performed this study to assess the feasibility and efficacy of using IMRT with reduced-volume CTV for the treatment of nasopharyngeal carcinoma.MethodsWe retrospectively reviewed 293 non-metastatic NPC patients treated with IMRT from 2002 to 2013. A total of 180 matched cases finally included with 90 received conventional-volume IMRT (CV-IMRT) and 90 received reduced-volume IMRT (RV-IMRT). Kaplan-Meier method and log-rank tests were used to compare NPC-specific survival. Multivariate analyses using the Cox proportional hazards model were conducted to detect independent predictors.ResultsWith a median follow-up of 70 months, the 3-year overall survival, progression-free survival, distant metastasis-free survival, local recurrence-free survival, regional recurrence-free survival, locoregional recurrence-free survival rates were 88.9, 84.4, 92.2, 91.1, 98.9, 91.1% for the CV-IMRT arm and 92.2, 85.6, 90.0, 93.3, 98.9, 93.3% for the RV-IMRT arm, respectively. None significant survival difference was observed. Additionally, RV-IMRT was associated with reduced risk of late xerostomia (P = 0.039) and hearing loss (P = 0.008), compared versus CV-IMRT.ConclusionsThe use of RV-IMRT for the treatment of NPC led to comparable survival condition and truly reduced toxicity reactions compared versus CV-IMRT.

Quality of reporting on thoracic radiotherapy technique in prospective lung cancer trials: A systematic review.

Background:The aim of this study is to assess the quality of reporting of thoracic (T) RT technique for curative intent treatment in prospective lung cancer trials.Methods:We searched MEDLINE for eligible trials published from 1996 to 2016. We assessed the included trials’ reports on whether they reported the RT dose prescription method; RT dose-planning procedures; algorithm for tissue inhomogeneity dose corrections; organs at risk dose constraints; target volume definition, simulation and/or motion management procedures; treatment verification procedures; total RT dose; fractionation schedule; conduct of quality assurance as well as presence or absence of deviations in RT treatment planning and delivery adequately. We performed univariable and multivariable logistic regression to determine the factors that may influence the quality of reporting.Results:We found 85 eligible trial reports. Target volume definition, total RT dose, and fractionation schedules were reported adequately in more than 90% of the included trials. Algorithm for tissue inhomogeneity dose corrections, simulation and verification procedures, presence or absence of deviations in RT treatment planning and delivery were reported adequately in less than 20% of the included trials. Twenty-three trials (27%) reported 7 criteria or more adequately. Both univariable and multivariable logistic regression showed that trials with RT focused research question were more likely to have adequate quality in reporting (judged as adequate reporting in 7 criteria or more) than trials with non-RT focused question (odds ratio 4.11, 95% confidence interval 1.10 to 15.43, P value = .04).Conclusion:There is significant variability in the quality of reporting on thoracic radiotherapy treatment in prospective lung cancer trials. Future research should focus on developing consensus guidelines to standardize the reporting of radiotherapy technique in clinical trials.

Enhancing value of quality assurance rounds in improving radiotherapy management: a retrospective analysis from King Hussein Cancer Center in Jordan.

PurposeThe quality assurance (QA) chart rounds are multidisciplinary meetings to review radiation therapy (RT) treatment plans. This study focus on describing the changes in RT management based on QA round reviews in a single institution.Materials and MethodsAfter 9 full years of implementation, a retrospective review of all patients whose charts passed through departmental QA chart rounds from 2007 to 2015. The reviewed cases were presented for RT plan review; subcategorized based on decision in QA rounds into: approved, minor modifications or major modifications. Major modification defined as any substantial change which required patient re-simulation orre-planning prior to commencement of RT. Minor modification included treatment plan changes which didn’t necessarily require RT re-planning. ResultsOverall 7,149 RT treatment plans for different anatomical sites were reviewed at QA rounds. From these treatment plans, 6,654 (93%) were approved, 144 (2%) required minor modifications, while 351 (5%) required major modifications. Major modification included changes in: selected RT dose (96/351, 27%), target volume definition (127/351, 36%), organs-at-risk contouring (10/351, 3%), dose volume objectives/constraints criteria (90/351, 26%), and intent of treatment (28/351, 8%). The RT plans which required major modification according to the tumor subtype were as follows: head and neck (104/904, 12%), thoracic (12/199, 6%), gastrointestinal (33/687,5%), skin (5/106, 5%), genitourinary (16/359, 4%), breast (104/2387, 4%), central nervous system (36/846, 4%), sarcoma (11/277, 4%), pediatric (7/251, 3%), lymphoma (10/423, 2%), gynecological tumors (2/359, 1%), and others (11/351, 3%).ConclusionMulti-disciplinary standardized QA chart rounds provide a comprehensive and an influential method on RT plans and/ or treatment decisions.

Target volume and motion position evaluation of four-dimensional cone-beam CT: comparison with 4D-CT using dynamic thorax phantom

Purpose: This study evaluated the target volume (TV) definition and motion position accuracies of 4D cone-beam computed tomography (CBCT) through comparison with 4D-CT, using a dynamic thorax phantom. Methods: A dynamic thorax phantom was used to acquire 4D images with respiration motion. Targets with 20-mm diameters, motion periods of 3, 4, and 6 s, and 1D and 3D motion patterns corresponding to sin and cos6 curves were used. The TV definition was contoured on all 10 phase images via threshold segmentation on all 4D datasets. The TV union was defined as the internal target volume (ITV). The TV and ITV were compared to the theoretical TVR and ITVR. For motion position evaluation, the TV centroid positions were measured and the root mean square errors (RMSEs) of these measured positions calculated relative to the phantom setup positions. In addition, the breathing patterns of patients with lung tumor were evaluated. Results: The maximum differences in TV and ITV for 4D-CT were 0.66 cm3 and −14.03% for a cos6 motion pattern with a 3-s period, respectively. In contrast, the maximum average differences in TV and ITV for 4D-CBCT were 0.43 cm3 and −6.48%, respectively, for all motion patterns and periods. The 4D-CT and 4D-CBCT RMSEs were within 2.5 mm for most motion patterns. For patient breathing patterns, the average differences in TV, ITV, and positions between 4D-CT and 4D-CBCT were 0.18 cm3, 0.23 cm3, and 1.1 mm, respectively. Conclusions: Although 4D-CT and 4D-CBCT have differences in image acquisition and voxel size, the TV and motion position accuracies for 4D-CBCT are consistent with those of 4D-CT.

Positron emission tomography with computed tomography imaging (PET/CT) for the radiotherapy planning definition of the biological target volume: PART 2.

Positron Emission Tomography with Computed Tomography (PET/CT) has been proven to be useful in the definition of Radiotherapy (RT) target volume. In this regard, the present expert review summarizes existing data for pancreas, prostate, gynecological and rectum/anal cancer. A comprehensive search of published original article was made, based on SCOPUS and PubMed database, selecting the paper that evaluated the role of PET/CT in the definition of RT volume. FDG-PET has an important and promising role for pancreatic cancer. Choline PET/CT could be useful for identifying high-risk volumes for prostate cancer; while PSMA PET/CT is still under evaluation. FDG PET/CT in gynecological cancers has been shown to impact external-beam RT planning. The role of FDG-PET for Gross Tumor volume identification is crucial, representing a useful and powerful tool for anal and rectal cancer. Taken together, molecular and functional imaging approaches offer a major step to individualize radiotherapeutic approach.

Time course of pain response and toxicity after whole-nerve-encompassing LINAC-based stereotactic radiosurgery for trigeminal neuralgia-aprospective observational study.

To prospectively evaluate the time course of pain response and toxicity after linear accelerator-based whole-nerve-encompassing radiosurgery (LINAC-SRS) using auniform treatment schedule for dosing and target volume definition in patients with refractory trigeminal neuralgia. From December 2012 to December 2016, 21patients were treated using astandardized protocol. Patients received LINAC-SRS with 70 Gy to the cisternal portion while aiming for the 90% isodose to fully envelope the nerve in one cross-sectional plane. Data on pain, analgesics, and toxicity were gathered prospectively. Four time intervals (1-6, 6-12, 12-18, and 18-24months) were defined and compared to baseline and each other. The median follow-up from radiotherapy was 16months. Freedom from pain was achieved at least once in 90.5, 81.0, and 85.7% of patients for everyday pain, rest pain, and pain peaks, respectively. At 1-6months, pain was significantly reduced in everyday routine (mean VAS, 2.0/10 vs. 5.8/10; P = 0.004), at rest (1.5/10 vs. 4.0/10; P = 0.002), and for pain peaks (2.9/10 vs. 10/10; P < 0.001), as was the number of analgesics (mean 1.5 vs. 2.9; P < 0.001). No significant increase in pain or analgesics was observed for subsequent time intervals. At last follow-up, reduction in pain compared to baseline for everyday routine (2.1/10 vs. 5.8/10; P = 0.010) and for pain peaks (3.3/10 vs. 10/10; P < 0.001) was significant, whereas it was not for rest pain (1.8/10 vs. 3.9/10; P = 0.073). Most toxicities were related to trigeminal nerve impairment, with 42.9% reporting new-onset hypoesthesia at last follow-up. This study provides prospective data after whole nerve encompassing LINAC-SRS for trigeminal neuralgia. No significant pain relapse was observed.

Abstract ES4-3: Techniques and technical considerations

Abstract Purpose: Partial breast irradiation (PBI) treats the lumpectomy cavity and a margin of adjacent breast tissue allowing for a reduction in treatment volume, duration and potentially toxicity. Body: Multiple PBI techniques are available. Interstitial brachytherapy (IB) represents the oldest PBI technique; mature data from randomized trials are available with 5-10 year follow-up and demonstrate comparable local control and toxicity profiles. Technically, multiple target volume definitions are currently utilized. Applicator based brachytherapy has evolved from single-lumen applicators, increasing the degrees of freedom for treatment planning. Prospective, non-randomized 5 year data are available with applicator based brachytherapy, demonstrating low rates of recurrence, comparable rates of toxicity, and high rates of excellent/good cosmetic outcomes. The treatment volume for applicator based brachytherapy is 1 cm surrounding the device, with adjustments for the skin and chest wall. External beam radiation therapy includes 3D-CRT, IMRT and proton based techniques. Data from 3D-CRT studies have suggested higher toxicities and inferior cosmetic outcomes. However, randomized studies evaluating IMRT PBI have not, demonstrating comparable or improved toxicity and cosmetic outcomes. Intraoperative radiation therapy (IORT) is unique as two randomized trials have evaluated IORT and found higher rates of local recurrence as compared to WBI. Low-energy IORT delivers 25-30% of prescription at 1 cm, different from other PBI techniques while electron IORT allows for modulation of energy/depth. Currently, ASTRO PBI guidelines do not recommend low-energy IORT off protocol and electron IORT only for suitable risk patients, while ABS guidelines do not recommend IORT off trial. Finally, newer PBI techniques include non-invasive image-guided breast brachytherapy and permanent seed implants. As with all PBI techniques, use of guidelines for the application of PBI is encouraged for patient selection and the application of well-established dosimetric criteria for target coverage and normal tissue tolerances. Partial Breast TechniquesTechniqueRandomized TrialsDose/Target VolumesDurationInterstitial BrachytherapyNational Institute of Oncology (Hungary);GEC-ESTRO;NSABP B-39/RTOG 041336.4 Gy/7 fx BID;32 Gy/8 fx BID, 30.3 Gy/7 fx BID, 50 Gy PDR; 34 Gy/10 fx BID15-20 mm expansion (limit skin, chest wall);20 mm minimum (sum of pathologic margin + radiation margin) CTV; Cavity + 15 mm (5 mm from skin, posterior breast)4-5 treatment days;4-5 treatment days; 5 treatment daysApplicator Based BrachytherapyNSABP B-39/RTOG 041334 Gy/10 fx BID10 mm from surface/device (5 mm from skin and posterior breast)5 treatment days3D-CRTNSABP B-39/RTOG 0413; RAPID38.5 Gy/10 fx BID; 38.5 Gy/10 fx BID15 mm CTV (5 mm from skin and posterior breast), 10 mm PTV, PTV-EVAL (5 mm from skin, posterior breast); 10 mm CTV inside breast, 10 mm PTV5 treatment days; 5 treatment daysIMRTUniversity of Florence; IMPORT LOW30 Gy/5 fx QOD; 40 Gy/15 fx10 mm CTV (3 mm from skin), 10 mm PTV ( 4 mm into lung, 3 mm from skin); 15 mm CTV (5 mm from skin, pec fascia)/10 mm PTV (5 mm from skin)5 treatment days over 2 weeks; 3 weeks (15 treatments) Conclusions: Partial breast irradiation represents a standard of care strategy for appropriately selected patients. Citation Format: Vicini F. Techniques and technical considerations [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr ES4-3.

Radiation therapy planning using MRI-CT fusion in dogs and cats with brain tumors.

Volume definition is a delicate step within the radiation treatment planning process and the precision of defining the volumes to irradiate is important for the success of the radiation treatment. Traditionally, radiation plans are created using computed tomography (CT) studies. Due to its different mechanism of action, magnetic resonance imaging (MRI) is more sensitive for detection of brain lesions. Therefore, using fused images of both imaging modalities should result in a more precise definition of the volumes to irradiate. The feasibility to fuse CT and MRI studies performed at different institutions was tested to subsequently analyse the influence of the fused images on target volume definition. Fourteen dogs and four cats with brain lesions having MR- and CT-imaging were included. Contrast-enhanced radiotherapy planning CT scans were fused to T1-weighted post-contrast and T2-weighted MRI scans. The gross tumor volume (GTV), the clinical tumor volume (CTV) and the planning target volume (PTV) were delineated on CT- and MRI studies. CT and MRI volumes were compared with regard to volumetric and spatial differences. The mean GTV was larger on MRI than on CT (2.15 vs.1.54 cm3). Also the mean CTV was larger on MRI than on CT (5.34 vs. 4.38 cm3). Consequently, the mean PTV was larger on MRI than on CT (14.20 vs. 10.82 cm3) as well. None of the differences in defined volumes were significant. Fusion images were accepted showing mean errors of 1.32 mm (mean error) and 1.73 mm (maximal error). CT-MRI fusion was feasible especially when defined, reliable, and consistent anatomic landmarks were used as registration points. Volumetric differences between CT and MRI were insignificant. In general, GTV and CTV were easier identified on MRI.

A step towards international prospective trials in carbon ion radiotherapy: investigation of factors influencing dose distribution in the facilities in operation based on a case of skull base chordoma

BackgroundCarbon ion radiotherapy (CIRT) has been delivered to more than 20,000 patients worldwide. International trials have been recommended in order to emphasize the actual benefits. The ULICE program (Union of Light Ion Centers in Europe) addressed the need for harmonization of CIRT practices. A comparative knowledge of the sources and magnitudes of uncertainties altering dose distribution and clinical effects during the whole CIRT procedure is required in that aim.MethodsAs part of ULICE WP2 task group, we sent a centrally reviewed questionnaire exploring candidate sources of uncertainties in dose deposition to the ten CIRT facilities in operation by February 2017. We aimed to explore native beam characterization, immobilization, anatomic data acquisition, target volumes and organs at risks delineation, treatment planning, dose delivery, quality assurance prior and during treatment. The responders had to consider the clinical case of a clival chordoma eligible for postoperative CIRT according to their clinical practice. With the results, our task group discussed ways to harmonize CIRT practices.ResultsWe received 5 surveys from facilities that have treated 77% of the patients worldwide per November 2017. We pointed out the singularity of the facilities and beam delivery systems, a divergent definition of target volumes, the multiplicity of TPS and equieffective dose calculation approximations.ConclusionMultiple uncertainties affect equieffective dose definition, deposition and calculation in CIRT. Although it is not possible to harmonize all the steps of the CIRT planning between the centers, our working group proposed counter-measures addressing the improvable limitations.

Positron emission tomography with computed tomography imaging (PET/CT) for the radiotherapy planning definition of the biological target volume: PART 1.

Functional and molecular imaging, including positron emission tomography with computed tomography imaging (PET/CT) is increasing for radiotherapy (RT) definition of the target volume. This expert review summarizes existing data of functional imaging modalities and RT management, in terms of target volume delineation, for the following anatomical districts: brain (for primary and secondary tumors), head/neck and lung. A collection of available published data was made, by PubMed a search. Only original articles were carefully and critically revised. For primary and secondary brain tumors, amino acid PET radiotracers could be useful to identify microscopic residual areas and to differ between recurrence and treatment-related alterations in case of re-irradiation. As for head and neck neoplasms may benefit from precise PET/CT-based target delineation, due to the major capability to identify high-risk RT areas. In primary and secondary lung cancer, PET/CT could be useful both to delimit a tumor and collapsed lungs and as a predictive parameter of treatment response. Taken together, molecular and functional imaging approaches offer a major step to individualize radiotherapeutic care going forward. Nevertheless, several uncertainties remain on the standard method to properly assess the target volume definition including PET information for primary and secondary brain tumors.

Three-Fraction Accelerated Partial Breast Irradiation (APBI) Delivered With Brachytherapy Applicators Is Feasible and Safe: First Results From the TRIUMPH-T Trial

Shorter courses of accelerated partial-breast irradiation delivered as single-fraction intraoperative therapy are now offered as an alternative to 4 to 6weeks of whole-breast irradiation after lumpectomy. However, this approach has potential shortcomings in patient selection and target volume definition and in dosimetric, radiobiological, and logistical issues. We designed a prospective, phase 2, multi-institution clinical trial to study 2- or 3-day accelerated partial breast irradiation delivered with brachytherapy applicators. This trial treats select breast cancers after breast-conserving surgery with brachytherapy applicators that deliver 22.5Gy in 3 fractions of 7.5Gy. The planning treatment volume was 1 to 1.5cm beyond the surgical cavity. Eligible women were aged ≥45years with unicentric invasive or in situ tumors ≤3.0cm with positive estrogen or progesterone receptors and no metastasis to axillary nodes that have been excised with negative margins. Strict dosimetric parameters were required to be met before acceptance into the trial. A group of 200 patients was prospectively enrolled and followed for a minimum of 6months. Two- or 3-day brachytherapy was associated with low acute or subacute toxicity, 97.25% excellent or good cosmetic outcomes, and excellent local control in select breast cancers. Ultrashort breast brachytherapy is dosimetrically feasible and can be delivered with excellent short-term tolerance and low toxicity.

244. Target volume definition with MRI and 68 Ga-DOTATOC-PET/CT for patients with meningiomas

PurposeTo investigate the impact of 68 Ga-DOTATOC PET/CT in addition to MRI and CT for retrospectively assessing the GTV delineation of meningiomas of the skull base in patients treated with particle therapy. MethodsSixteen patients underwent 68 Ga-DOTATOC PET/CT for diagnosis followed by constract-enhanced (CE) MRI and CT for treatment planning with particle therapy.GTV was defined on the CE-MRI fused to the simulation CT (CTsim) integrating information from the PET/CT. Three methods to delineate the PET volume were evaluated:manual (PETman), semiautomatic (42% threshold of SUVmax, PETSUV42%) and automatic adaptive thresholding method incorporating PET reconstruction parameters (PETauto) (iTA, TA). PETman volumes were delineated by the same nuclear medicine physician, while PETSUV42% and PETauto volumes were determined by medical physicists.The PET/CT, CE-RMI and CTsim were co-registered with a deformable image registration algorithm using the MIM Software.The overlapping region of MRI and PETman resulted in GTVcommon. ResultsThe lesions had a median SUVmax of 12.1 ± 6.8 (range:3.2–32.6).Overall, the GTV-MRI was larger than GTV-PETman in 7 patients (43.8%), smaller in 6 (37.5%) and almost the same in 3 (18.8%).The median value of the different volumes were:GTV-MRI = 14.3 ± 37.2 cc, GTV-PETman=14.4±47.0cc, GTVcommon=12.2±33.6cc,GTV-PETSUV42%=8.3±18.3cc, GTV-PETauto=11.3±26.2cc. GTV-PETSUV42% were always smaller than GTV-PETman(Δ=-51.0±32.7%) and GTV-PETauto(Δ=-21.5±12.7%) being variations in tumor heterogeneity not accounted for. Largest differences were observed for lesions showing high SD of SUV. The median difference between GTV-PETman and GTV-PETauto was 39.6 ± 29.5%. Conclusions68 Ga-DOTATOC-PET/CT seems to improve the target volume delineation in skull base meningiomas, often leading to a reduction of GTV compared with MRI. The automatic adaptive thresholding delineation method may provide robust and reliable tool to help physician in segmenting PET images, reducing inter- and intra-observer variability.

Recommendation for the definition of postoperative radiotherapy target volume based on a pooled analysis of patterns of failure after radical surgery among patients with thoracic esophageal squamous cell carcinoma

BackgroundElective use of radiation therapy to treat regionally involved lymph nodes (LNs) after radical surgery for esophageal squamous cell carcinoma (ESCC) is controversial. We studied metastasis patterns through a pooled analysis of published results to guide post-operative radiotherapy (PORT) target designation.MethodsWe searched the MEDLINE database for literature published from May 1977 to March 2018, and found 14 relevant original studies that included 2738 patients with thoracic ESCC. We calculated probabilities of recurrence and metastasis in local (including anastomoses and tumor bed), LNs and distal areas.ResultsRecurrence rates were 1.88% for local, 13.18% for distal, and 22.16% for LNs. Within LNs, recurrence rates were cervical/supraclavicular: 37.69%, upper mediastinal: 44.30%, middle mediastinal: 21.81%, lower mediastinal: 2.57%, abdominal paraaortic: 25% and upper abdominal: 9.56%. Whereas cervical/supraclavicular and upper mediastinal LNs had the highest recurrence rates, abdominal LNs also had high recurrence rates in patients with lower thoracic ESCC.ConclusionsPORT volume should include the cervical/supraclavicular and upper mediastinal LNs for all thoracic ESCC, and abdominal paraaortic LNs for lower thoracic ESCC. Anastomoses and tumor beds should not be included in the PORT volume if they are not adjacent to the PORT-LN regions. Upper abdominal LNs might not necessarily be included in the PORT volume for thoracic ESCC.

An atlas for clinical target volume definition, including elective nodal irradiation in definitive radiotherapy of biliary cancer

Radiotherapy (RT) is a treatment option for advanced biliary tract cancer (BTC), often combined with sequential and/or concurrent chemotherapy. The use of modern RT techniques requires accurate clinical target volume (CTV) definition and delineation. However, guidelines for CTV delineation in BTC are lacking. Therefore, the aim of this study was to propose a computer tomography (CT) atlas for CTV definition of BTC. We previously proposed guidelines to define the nodal CTV (CTV-N) in BTC. In this study, based on a literature analysis, we defined the margins to be added to the gross tumor volume (GTV; subclinical and microscopic disease) to define the primary tumor CTV (CTV-T). An abdominal contrast enhanced planning CT scan was performed on three different patients with unresectable intrahepatic cholangiocarcinoma (CC), extrahepatic CC and gallbladder cancer. The GTV and anatomical reference structures were outlined on CT images. Then, based on our guidelines, the CTV-T and CTV-N were delineated and merged to define the final CTV in the three patients. An atlas, showing the defined CTV, was generated from the reference CT images to illustrate the CTV for intra-hepatic CC, extra-hepatic CC and gallbladder cancer. This atlas can be used as an aid for CTV definition in patients with BTC treated with modern RT techniques.

Integrating a low-field open MR scanner with a static proton research beam line: proof of concept

On-line image guidance using magnetic resonance (MR) imaging is expected to improve the targeting accuracy of proton therapy. However, to date no combined system exists. In this study, for the first time a low-field open MR scanner was integrated with a static proton research beam line to test the feasibility of simultaneous irradiation and imaging. The field-of-view of the MR scanner was aligned with the beam by taking into account the Lorentz force induced beam deflection. Various imaging sequences for extremities were performed on a healthy volunteer and on a patient with a soft-tissue sarcoma of the upper arm, both with the proton beam line switched off. T1-weighted spin echo images of a tissue-mimicking phantom were acquired without beam, with energised beam line magnets and during proton irradiation. Beam profiles were acquired for the MR scanner’s static magnetic field alone and in combination with the dynamic gradient fields during the acquisition of different imaging sequences. It was shown that MR imaging is feasible in the electromagnetically contaminated environment of a proton therapy facility. The observed quality of the anatomical MR images was rated to be sufficient for target volume definition and positioning. The tissue-mimicking phantom showed no visible beam-induced image degradation. The beam profiles depicted no influence due to the dynamic gradient fields of the imaging sequences. This study proves that simultaneous irradiation and in-beam MR imaging is technically feasible with a low-field MR scanner integrated with a static proton research beam line.

Cavity volume changes after surgery of a brain metastasis—consequences for stereotactic radiation therapy

For alarge or symptomatic brain metastasis, resection and adjuvant radiotherapy are recommended. Hypofractionated stereotactic radiotherapy (HFSRT) is increasingly applied in patients with alimited number of lesions. Exact target volume definition is critical given the small safety margins. Whilst technical advances have minimized inaccuracy due to patient positioning and radiation targeting, little is known about changes in target volume. This study sought to evaluate potential changes in the resection cavity of abrain metastasis. In all, 57patients treated with HFSRT after surgical resection of one brain metastasis between 2008 and 2015 in our institution were included in this study. Gross tumor volume (GTV) of the initial metastasis and the volume of the resection cavity in the post-operative, planning, and follow-up MRIs were measured and compared. The mean cavity size decreased after surgery with the greatest change of -23.4% (±41.5%) occurring between post-operative MRI and planning MRI (p < 0.01). During this time period, the cavity volume decreased, remained stable, and increased in 79.1, 3.5, and 17.4%, respectively. Afurther decrease of -20.7% (±58.1%) was perceived between planning MRI and first follow-up (p < 0.01). No significant difference in pattern of change could be observed depending on the volume of initial GTV, size of the post-operative resection cavity, initial or post-resection FLAIR (fluid-attenuated inversion recovery) hyper-intensity, postsurgical ischemia, or primary tumor. The resection cavities of patients with post-operative ischemia were significantly larger than resection cavities of patients without ischemia. The resection cavity seems to be very dynamic after surgery. Hence, it remains necessary to use very recent scans for treatment planning.

Internal Mammary Lymph Nodes Involvement in Patients with Breast Cancer: Anatomical Characteristics and Implication for Target Definition

Internal mammary nodes (IMN) as one of the regional lymph nodes (RLN) in breast cancer, its importance to be included in regional nodes irradiation (RNI) has been assessed by important prospective trials. Optimal definition of target volume is critical in balancing target coverage and toxicity to normal tissues. The imaging and anatomical information for IMN metastasis are less described than other RLN in breast cancer. The current study aims to collect and analyze the imaging information of IMN involvement so as to provide information for optimize IMN delineation. Patients with IMN involvement were identified from single-center breast cancer database with imaging data. The image information including thoracic CT, breast MRI, and PET/CT. Anatomical characteristics from axial imaging including distribution of involved ribs, distance from the internal mammary vessels (IMV) were collected for each metastatic nodes. IMNs greater than 5 mm in short axis was defined as metastasis in this study. A total of 53 breast cancer patients with a total number of 63 metastatic IMN met the criteria for INM involvement were identified and located in this study. In 27 patients (50.9%), more than one intercostal spaces were involved, of which the second rib space was the most involved (26/27). The number of metastatic nodes in the 1st, 2nd, 3rd and 4th intercostal space were 26 (41.3%), 43 (68.3%), 21 (33.3%) and 4(6.3%) respectively. The maximal radial distance from center of metastatic nodes to the IMV in each patient were measured. The percentage of including IMN with a 4mm, 5mm, 6mm and 7mm medial/lateral distance to the IMV were 56.6% (30/53), 75.5% (40/53), 90.6% (48/53) and 96.2% (51/53) respectively. While in maximal dorsal/ventral distance, all extension of the IMN nodes were in dorsal direction, the percentage of including IMN with a 4mm, 5mm, 6mm and 7mm depth to the IMV were 85%(45/53), 90.6% (48/53), 94.3%(50/53) and 98.1%(52/53) respectively, one case had enlarged mass invading the fourth rib, in which the identification was difficult. In total, 28 of 53 patients had no documentation of IMN disease on imaging report regardless of the visible IMN mass on thoracic CT. The most common description was parasternal mass (50%, 14/28), chest-wall mass (7.1%, 2/28) and no description at all (32.1%, 9/28). All these 12 patients had thoracic CT as the only image evaluation. In 12 patients combined with breast MRI and one patient combined with PET/CT, none had miss diagnosis of IMN disease. In most of the patients indicated for IMN irradiation in the adjuvant setting, clinical target volume of IMN can be delineated with a 6mm medial/lateral distance and a 5mm depth to the IMV on the same axial CT image. This optimization in delineation might facilitate the balance of target coverage and normal tissue constraints. Multimodal image information may help to improve the sensitivity of diagnosis in IMN metastasis.