Target Volume Definition In Radiotherapy Research Articles

Investigation of uncertainty in internal target volume definition for lung stereotactic body radiotherapy

This study evaluated the validity of internal target volumes (ITVs) defined by three- (3DCT) and four-dimensional computed tomography (4DCT), and subsequently compared them with actual movements during treatment. Five patients with upper lobe lung tumors were treated with stereotactic body radiotherapy (SBRT) at 48 Gy in four fractions. Planning 3DCT images were acquired with peak-exhale and peak-inhale breath-holds, and 4DCT images were acquired in the cine mode under free breathing. Cine images were acquired using an electronic portal imaging device during irradiation. Tumor coverage was evaluated based on the manner in which the peak-to-peak breathing amplitude on the planning CT covered the range of tumor motion (± 3 SD) during irradiation in the left–right, anteroposterior, and cranio-caudal (CC) directions. The mean tumor coverage of the 4DCT-based ITV was better than that of the 3DCT-based ITV in the CC direction. The internal margin should be considered when setting the irradiation field for 4DCT. The proposed 4DCT-based ITV can be used as an efficient approach in free-breathing SBRT for upper-lobe tumors of the lung because its coverage is superior to that of 3DCT.

68Ga-DOTATATE PET in Restaging and Response to Therapy in Neuroblastoma: A Case Series and a Mini Review.

68Ga-DOTATATE PET/CT is widely used for the evaluation of neuroendocrine tumors. Some reports exist on its use in the management of neuroblastoma. Building on the prior reports as well as our previous experience in using this technique for initial staging, we propose to describe its practical benefits in restaging and response to therapy. We describe different aspects including supply logistics, preparation, spatial resolution, and other practical applications. Methods: We reviewed the medical records for 8 patients who were evaluated with 68Ga-DOTATATE PET/CT at our institution over 2 y. A note was made of the patient and disease characteristics and the indication for PET imaging, and the results were retrospectively analyzed for feasibility, logistics, radiation exposure, and utility in answering the clinical question. Results: Eight children (5 girls and 3 boys; age range, 4-60 mo; median age, 30 mo) diagnosed with neuroblastoma were imaged with 68Ga-DOTATATE PET/CT and 5 with 123I-metaiodobenzylguanidine (123I-MIBG) SPECT/CT over 2 y. Three 68Ga-DOTATATE PET scans were done for staging, 10 for response evaluation, and 2 for restaging. 68Ga-DOTATATE PET accurately identified neuroblastoma lesions suspected or seen on anatomic imaging. It has been shown to be more specific and more sensitive than 123I-MIBG and at times also MRI. It had better spatial and contrast resolution than 123I-MIBG. 68Ga-DOTATATE PET was better than 123I-MIBG SPECT/CT, CT, and MRI in the detection of early progression and viable tumor delineation for response assessment, as well as in target volume definition for external-beam radiotherapy and proton-beam radiotherapy. 68Ga-DOTATATE PET was also better at assessing bony and bone marrow disease changes with time. Conclusion: 68Ga-DOTATATE PET/CT offers added value and a superior edge to other imaging modalities in restaging and response assessment in neuroblastoma patients. Further multicenter evaluations in larger cohorts are needed.

Building an Institutional-Consensus Artificial Intelligence Model for Prostate Bed Auto-Segmentation through Incremental Learning

<h3>Purpose/Objective(s)</h3> Clinical target volume (CTV) definition for post-operative prostate bed radiotherapy is subject to large intra- and inter-observer variations for radiation oncologists, despite various publications of group consensus guidelines. The aim is to study the utility of artificial intelligence (AI) transferred incremental learning for building institutional group Intelligence-based models for post-operative prostate bed CTV and organs-at-risk (OARs) delineation. <h3>Materials/Methods</h3> One hundred and ten prostate bed patients were retrospectively collected and randomly divided into training (n=60) and testing (n=50) groups. Each dataset included physician-approved prostate bed CTV and five OARs (bladder, rectum, left/right femoral head, and penile bulb). The training group dataset was used to build two customized AI models (OAR and CTV) from the existing vendor-provided models. Quantitative and qualitative evaluations were performed for AI-generated contours on the 50 testing datasets in comparison with the corresponding manual ones. The qualitative evaluation was conducted amongst six expert radiation oncologists (RO) tasked to score at four levels (precision, acceptable, minor revision, and manual redraw) and indicated clinical preference given two sets of contours blindly (AI vs. manual). Scoring subjectivity was studied in cross-comparison amongst six ROs. Physician editing times was studied among all six ROs for five patients that had the CTV scored as <i>minor corrections</i> by physician consensus. <h3>Results</h3> Physicians chose the AI-generated OAR and CTV over the manual ones 34% and 32% of the time (range: 2%-54% and 12%-60%). The AI- generated and manual OARs were scored precise or acceptable 90% and 98% of cases (median values), respectively. The AI-generated CTVs were scored equal to or better than the corresponding manual delineation 53% of the time (ranges: 22% to 88% for the six experts). The average physician editing time from the AI-generated CTV was 3m 10s ± 36s. The time required to train the custom models were 27h 20m ± 8m. <h3>Conclusion</h3> Blinded scoring with benchmarking to the manual contours eliminates personal subjectivity. Contour comparison metrics and physician scoring demonstrated comparable results between AI-generated and manual OAR contours. Although almost half of the AI-generated CTVs required physician edit, the editing time is considered moderate. The custom-trained AI models using the transferred learning can facilitate OAR and target contouring efficiency and consistency for prostate bed patients.

Is there any additional benefit of 68Ga-PSMA PET on radiotherapy target volume definition in patients with glioblastoma?

To investigate the contribution of 68Gallium (68Ga)-PSMA (prostate-specific membrane antigen) positron emission tomography (PET) in defining radiotherapy (RT) target volume for glioblastoma and to compare the target volumes defined by Magnetic Resonance Imaging (MRI). RT planning Computed Tomography (CT) images were fused separately with pre-operative MRI and PET/MRI images of 10 glioblastoma patients, retrospectively. The contrast-enhanced area in T1 weighted MRI was contoured as gross tumor volume (GTV) and clinical target volume (CTV1) was obtained by including the cavity and T2/FLAIR hyperintense areas after giving a margin of 2 cm to the GTV. 68Ga-PSMA uptake area was contoured as biological tumor volume (BTV) and CTV2 was obtained with a margin of 2 cm to BTV. Planning target volumes (PTVs) were created with the 3 mm added to the CTVs. Conformity index (CI), dice similarity coefficient (DSC) and overlap volume (OV) were calculated by obtaining the intersection and union volumes. Volumetric comparison, similarity and overlap analyzes were performed statistically by Wilcoxon signed rank and One sample t-test. The median GTV was 21,96 cc (1,04 - 82,04) and BTV was 25,58 cc (2,43 - 99,47). BTV was on average 47% larger than GTV which was statistically significant (p = 0.03). For GTV-BTV, CTV1-CTV2 and PTV1-PTV2; mean values of CI were 0,56, 0,76 and 0,76; DSC were 0,70, 0,86 and 0,86; OV were 0,88, 0,94 and 0,94, respectively. There was no significant difference on size and spatial similarity between CTV1 and CTV2, PTV1 and PTV2. Altough BTV was larger than GTV, this significance was lost while we gave the same CTV margin including the peripheral edema. It seems that it may help to improve defining non-enhancing tumor part and also recurrent tumor volume. Recent studies have focused on the role of 68Ga-PSMA PET in imaging of glial tumors. It has been observed that 68Ga-PSMA PET can clearly define the tumor borders and it can be beneficial in target volume delineation, especially in reirradiation of recurrent tumors.

Radiotherapy Target Volume Definition in Newly Diagnosed High-Grade Glioma Using 18F-FET PET Imaging and Multiparametric MRI: An Inter Observer Agreement Study.

Background: The aim of this prospective monocentric study was to assess the inter-observer agreement for tumor volume delineations by multiparametric MRI and 18-F-FET-PET/CT in newly diagnosed, untreated high-grade glioma (HGG) patients. Methods: Thirty patients HGG underwent O-(2-[18F]-fluoroethyl)-l-tyrosine(18F-FET) positron emission tomography (PET), and multiparametric MRI with computation of rCBV map and K2 map. Three nuclear physicians and three radiologists with different levels of experience delineated the 18-F-FET-PET/CT and 6 MRI sequences, respectively. Spatial similarity (Dice and Jaccard: DSC and JSC) and overlap (Overlap: OV) coefficients were calculated between the readers for each sequence. Results: DSC, JSC, and OV were high for 18F-FET PET/CT, T1-GD, and T2-FLAIR (>0.67). The Spearman correlation coefficient between readers was ≥0.6 for these sequences. Cross-comparison of similarity and overlap parameters showed significant differences for DSC and JSC between 18F-FET PET/CT and T2-FLAIR and for JSC between 18F-FET PET/CT and T1-GD with higher values for 18F-FET PET/CT. No significant difference was found between T1-GD and T2-FLAIR. rCBV, K2, b1000, and ADC showed correlation coefficients between readers <0.6. Conclusion: The interobserver agreements for tumor volume delineations were high for 18-F-FET-PET/CT, T1-GD, and T2-FLAIR. The DWI (b1000, ADC), rCBV, and K2-based sequences, as performed, did not seem sufficiently reproducible to be used in daily practice.

Patterns of nodal spread in stage III NSCLC: importance of EBUS-TBNA and 18F-FDG PET/CT for radiotherapy target volume definition

PurposeThe aim of this study was to compare the pattern of intra-patient spread of lymph-node (LN)-metastases within the mediastinum as assessed by 18F-FDG PET/CT and systematic endobronchial ultrasound-guided transbronchial-needle aspiration (EBUS-TBNA) for precise target volume definition in stage III NSCLC.MethodsThis is a single-center study based on our preceding investigation, including all consecutive patients with initial diagnosis of stage IIIA-C NSCLC, receiving concurrent radiochemotherapy (12/2011–06/2018). Inclusion criteria were curative treatment intent, 18F-FDG PET/CT and EBUS-TBNA prior to start of treatment. The lymphatic drainage was classified into echelon-1 (ipsilateral hilum), echelon-2 (ipsilateral LN-stations 4 and 7) and echelon-3 (rest of the mediastinum, contralateral hilum). The pattern of spread was classified according to all permutations of echelon-1, echelon-2, and echelon-3 EBUS-TBNA findings.ResultsIn total, 180 patients were enrolled. Various patterns of LN-spread could be identified. Skip lesions with an involved echelon distal from an uninvolved one were detected in less than 10% of patients by both EBUS-TBNA and PET. The pattern with largest asymmetry was detected in cases with EBUS-TBNA- or PET-positivity at all three echelons (p < 0.0001, exact symmetry test). In a multivariable logistic model for EBUS-positivity at echelon-3, prognostic factors were PET-positivity at echelon-3 (Hazard ratio (HR) = 12.1; 95%-CI: 3.2–46.5), EBUS-TBNA positivity at echelon-2 (HR = 6.7; 95%-CI: 1.31–31.2) and left-sided tumor location (HR = 4.0; 95%-CI: 1.24–13.2). There were significantly less combined ipsilateral upper (LN-stations 2 and 4) and lower (LN-station 7) mediastinal involvements (16.8% of patients) with EBUS-TBNA than with PET (38.9%, p < 0.0001, exact symmetry test). EBUS-TBNA detected a lobe specific heterogeneity between the odds ratios of LN-positivity in the upper versus lower mediastinum (p = 0.0021, Breslow-Day test), while PET did not (p = 0.19).ConclusionFrequent patterns of LN-metastatic spread could be defined by EBUS-TBNA and PET and discrepancies in the pattern were seen between both methods. EBUS-TBNA showed more lobe and tumor laterality specific patterns of LN-metastases than PET and skipped lymph node stations were rare. These systematic relations offer the opportunity to further refine multi-parameter risk of LN-involvement models for target volume delineation based on pattern of spread by EBUS-TBNA and PET.

Radiotherapy for Glioma

Gliomas are infiltrative tumors that are difficult to cure by surgery alone. Postoperative radiotherapy or chemoradiotherapy is the treatment option for patients with high-grade gliomas. However, most pathological types of glioma other than glioblastoma do not have enough evidence, especially concerning the dose-fractionation scheme and clinical target volume definition for radiotherapy. This study presents standard methods of radiotherapy for each pathological type of glioma and recent radiotherapy technologies including their significance and treatment results.

Improving deformable image registration with point metric and masking technique for postoperative breast cancer radiotherapy.

Deformable image registration (DIR) is increasingly used for target volume definition in radiotherapy. However, this method is challenging for postoperative breast cancer patients due to the large deformations and non-correspondence caused by tumor resection and clip insertion. In this study, an improved B-splines based DIR method was developed to address this issue for higher registration accuracy. The conventional B-splines based DIR method was improved with the introduction of point metric and masking technique. The point metric minimizes the distance between 2 point sets with known correspondence for regularization of intensity-based B-splines registration. The masking technique reduces the influence of non-corresponding regions in breast computed tomography (CT) images. Two sets of CT images before and after breast surgery were used for image registration. One set was the diagnostic CT image acquired before surgery, and another set was the planning CT image acquired after surgery for breast cancer radiotherapy. A total of 26 sets of CT images from 13 patients were collected retrospectively for the test. The improved DIR method's registration accuracy was evaluated by target registration error (TRE), the Jacobian determinant, and visual assessment. For soft tissue, the difference in the median TRE between the improved DIR method and the conventional DIR method was statistically significant (2.27 vs. 5.88, P<0.05). The Jacobian determinant of the deformation field was positive for all patients. For visual assessment, the improved DIR method with point metric achieved better matching for soft tissue. The improved DIR method's registration accuracy was higher than the conventional DIR method based on the preliminary results. With point metric and masking technique, the influence of large deformations and non-correspondence on registration between pre- and post-operative CT images can be effectively reduced. Therefore, this method provides a feasible way for target volume definition in postoperative breast cancer radiotherapy treatment planning.

Evaluation of irregular breathing effects on internal target volume definition for lung cancer radiotherapy.

Irregular breathing may compromise the treated volume for free-breathing lung cancer patients during radiotherapy. We try to find a measure based on a breathing amplitude surrogate that can be used to select the patients who need further investigation of tumor motion to ensure that the internal target volume (ITV) provides reliant coverage of the tumor. Fourteen patients were scanned with four-dimensional computed tomography (4DCT) during free-breathing. The breathing motion was detected by a pneumatic bellows device used as a breathing amplitude surrogate. In addition to the 4DCT, a breath-hold (BH) scan and three cine CT imaging sessions were acquired. The cine images were taken at randomized intervals at a rate of 12 per minute for 8 minutes to allow tumor motion determination during a typical hypo-fractionated treatment scenario. A clinical target volume (CTV) was segmented in the BH CT and propagated over all cine images and 4DCT bins. The center-of-volume of the translated CTV (CTVCOV ) in the ten 4DCT bins were interconnected to define the 4DCT determined tumor trajectory (4DCT-TT). The volume of CTV inside ITV for all cine CTs was calculated and reported at the 10th percentile (VCTV10% ). The deviations between CTVCOV in the cine CTs and the 4DCT-TT were calculated and reported at its 90th percentile (d90% ). The standard deviation of the bellows amplitude peaks (SDP) and the ratio between large and normal inspirations, κrel , were tested as surrogates for VCTV10% and d90% . The values of d90% ranged from 0.6 to 5.2mm with a mean of 2.2mm. The values of VCTV10% ranged from 59-93% with a mean of 78 %. The SDP had a moderate correlation (r=0.87) to d90% . Less correlation was seen between SDP and VCTV10% (r=0.77), κrel and d90% (r=0.75) and finally κrel and VCTV10% (r=0.75). The ITV coverage had a large variation for some patients. SDP seems to be a feasible surrogate measure to select patients that needs further tumor motion determination.

The Distribution of Pelvic Nodal Metastases in Prostate Cancer Reveals Potential to Advance and Personalize Pelvic Radiotherapy.

BackgroundTraditional clinical target volume (CTV) definition for pelvic radiotherapy in prostate cancer consists of large volumes being treated with homogeneous doses without fully utilizing information on the probability of microscopic involvement to guide target volume design and prescription dose distribution.MethodsWe analyzed patterns of nodal involvement in 75 patients that received RT for pelvic and paraaortic lymph node metastases (LNs) from prostate cancer in regard to the new NRG-CTV recommendation. Non-rigid registration-based LN mapping and weighted three-dimensional kernel density estimation were used to visualize the average probability distribution for nodal metastases. As independent approach, the mean relative proportion of LNs observed for each level was determined manually and NRG and non-NRG levels were evaluated for frequency of involvement. Computer-automated distance measurements were used to compare LN distances in individual patients to the spatial proximity of nodal metastases at a cohort level.Results34.7% of patients had pelvic LNs outside NRG-consensus, of which perirectal was most common (25.3% of all patients) followed by left common iliac nodes near the left psoas major (6.7%). A substantial portion of patients (13.3%) had nodes at the posterior edge of the NRG obturator level. Observer-independent mapping consistently visualized high-probability hotspots outside NRG-consensus in the perirectal and left common iliac regions. Affected nodes in individual patients occurred in highly significantly closer proximity than at cohort-level (mean distance, 6.6 cm vs. 8.7 cm, p < 0.001).ConclusionsBased on this analysis, the common iliac level should extend to the left psoas major and obturator levels should extend posteriorly 5 mm beyond the obturator internus. Incomplete coverage by the NRG-consensus was mostly because of perirectal involvement. We introduce three-dimensional kernel density estimation after non-rigid registration-based mapping for the analysis of recurrence data in radiotherapy. This technique provides an estimate of the underlying probability distribution of nodal involvement and may help in addressing institution- or subgroup-specific differences. Nodal metastases in individual patients occurred in highly significantly closer proximity than at a cohort-level, which supports that personalized target volumes could be reduced in size compared to a “one-size-fits-all” approach and is an important basis for further investigation into individualized field designs.

Radiation dosimetric influence by different target volume definition in Cyberknife lung cancer and abdomen stereotactic body radiotherapy

ABSTRACT Purpose: The dosimetric characteristics between four-dimensional with end-expiration and end-inspiration CT dose distributions of Cyberknifeare to be evaluated. Methods: A set of four dimensional (4D) CT images and two sets of CT scans,includingend-inspiration and end-expiration breath-hold, were obtained from 15 CyberKnife treated patients. Three internal target volumes (ITVs) were created from the three sequence images. Allpatients were treated using ITV-based strategy with an additional ITV-to-PTV margin of 3 mm. Results: In all of the 15 patients, the PTVfuse consistently has the smallest volumes compared to other PTV’s. The nCI and coveragesof the plans were based on PTVfuse, which provided statistically significant differences for PTV4DE and PTV4DI. Additionally, the dose of normal tissue showed no statistical differences in the three type of plans (plan PTV4DE VS PTV4DI, p = 0.76), (plan PTV4DE VSPTVfuse, p = 0.23) and (plan PTV4DI VSPTVfuse, p = 0.16). Conclusion: The fusion of breath-hold sequences is beneficial to provide excellent target coverage than the end-inspiration or end-expiration with 4D-CT approach for target definition. Furthermore, the fusion of the end-expiration and end-inspiration CT scans may be used as an alternative to 4D CT in the absence of multi-modality images.

18F-FDG PET/CT for Target Volume Contouring in Lung Cancer Radiotherapy.

In 2005, Nestle et al. ([1][1]) published their seminal paper comparing different methods to delineate radiotherapy target volume from 18F-FDG PET in non–small cell lung cancer (NSCLC). They compared 4 different methods for primary delineation of gross-tumor target volume: a visual method, 2 fixed

Target Volume Definition for Radiotherapy of Staple Line Recurrences of Non-Small Cell Lung Cancer

Target Volume Definition for Radiotherapy of Staple Line Recurrences of Non-Small Cell Lung Cancer

Radiotherapy target volume definition in newly diagnosed high grade glioma using 18F-FET PET imaging and multiparametric perfusion MRI: A prospective study (IMAGG)

PurposeThe aim of this study was to prospectively investigate tumor volume delineation by amino acid PET and multiparametric perfusion magnetic resonance imaging (MRI) in patients with newly diagnosed, untreated high grade glioma (HGG). Materials and methodsThirty patients with histologically confirmed HGG underwent O-(2-[18F]-fluoroethyl)-l-tyrosine (18F-FET) positron emission tomography (PET), conventional Magnetic Resonance Imaging (MRI) as contrast-enhanced (CE) and fluid-attenuated inversion recovery (FLAIR) and multiparametric MRI as relative cerebral blood volume (rCBV) and permeability estimation map (K2). Areas of MRI volumes were semi-automatically segmented. The percentage overlap volumes, Dice and Jaccard spatial similarity coefficients (OV, DSC, JSC) were calculated. ResultsThe 18F-FET tumor volume was significantly larger than the CE volume (median 43.5 mL (2.5–124.9) vs. 23.8 mL (1.4–80.3), p = 0.005). The OV between 18F-FET uptake and CE volume was low (median OV 0.59 (0.10–1)), as well as spatial similarity (median DSC 0.52 (0.07–0.78); median JSC 0.35 (0.03–0.64)). Twenty-five patients demonstrated both rCBV and CE on MRI: The median rCBV tumor volume was significantly smaller than the median CE volume (p < 0.001). The OV was high (median 0.83 (0.54–1)), but the spatial similarity was low (median DSC 0.45 (0.04–0.83); median JSC 0.29 (0.07–0.71)). Twenty-eight patients demonstrated both K2 and CE on MRI. The median K2 tumor volume was not significantly larger than the median CE volume. The OV was high (median OV 0.90 (0.61–1)), and the spatial similarity was moderate (median DSC 0.75 (0.01–0.83); median JSC 0.60 (0.11–0.89)). ConclusionWe demonstrated that multiparametric perfusion MRI volumes (rCBV, K2) were highly correlated with CE T1 gadolinium volumes whereas 18F-FET PET provided complementary information, suggesting that the metabolically active tumor volume in patients with newly diagnosed untreated HGG is critically underestimated by contrast enhanced MRI. 18F-FET PET imaging may help to improve target volume delineation accuracy for radiotherapy planning.

Advances in cancer imaging require renewed radiotherapy dose and target volume concepts

Advances in diagnostic imaging create opportunities for improved therapeutic targeting of cancer but conceptual thinking about radiotherapy target volume definition and dose-prescription is not keeping up. In this opinion paper we discuss how modern imaging can contribute to new concepts for radiotherapy dose-prescription and target volume definition illustrated by the example of head and neck cancer. These new insights have the potential to significantly reduce radiation associated toxicity and may have important impact on the combination of radiotherapy with systemic cancer therapies.

PO-0774: Role of Magnetic Resonance Imaging in radiotherapy target volume definition in Oesophageal Cancer

PO-0774: Role of Magnetic Resonance Imaging in radiotherapy target volume definition in Oesophageal Cancer

Magnetic resonance imaging in radiotherapy treatment target volumes definition for brain tumours: a systematic review and meta-analysis

AbstractPurposeThe aim of this study is to establish clinical evidence regarding the use of magnetic resonance imaging (MRI) in target volume definition for radiotherapy treatment planning of brain tumours.MethodsPrimary studies were systematically retrieved from six electronic databases and other sources. Studies included were only those that quantitatively compared computed tomography (CT) and MRI in target volume definition for radiotherapy of brain tumours. Study characteristics and quality were assessed and the data were extracted from eligible studies. Effect estimates for each study was computed as mean percentage difference based on individual patient data where available. The included studies were then combined in meta-analysis using Review Manager (RevMan) software version 5.0.ResultFive studies with a total number of 72 patients were included in this review. The quality of the studies was rated strong. The percentages mean differences of the studies were 7·47, 11·36, 30·70, 41·69 and −24·6% using CT as the baseline. The result of statistical analysis showed small-to-moderate heterogeneity; τ2=36·8; χ2=6·23; df=4 (p=0·18); I2=36%. The overall effect estimate was −1·85 [95% confidence interval (CI); −7·24, 10·94], Z=0·40 (p=0·069&gt;0·5).ConclusionBrain tumour volumes measured using MRI-based method for radiotherapy treatment planning were larger compared with CT defined volumes but the difference lacks statistical significance.

Short interactive workshops reduce variability in contouring treatment volumes for spine stereotactic body radiation therapy: Experience with the ESTRO FALCON programme and EduCase™ training tool

We report the results of 4, 2-h contouring workshops on target volume definition for spinal stereotactic radiotherapy. They combined traditional teaching methods with a web-based contouring/contour-analysis platform and led to a significant reduction in delineation variability. Short, interactive workshops can reduce interobserver variability in spine SBRT target volume delineation.

Clinical Target Volume Definition in Preoperative Radiotherapy of Rectal Carcinoma: a Systematic Review

Preoperative radiotherapy (RT) or chemoradiation represents a standard option in neoadjuvant treatment of rectal cancer (RC). The aim of this analysis is to present a systematic review of clinical target volume (CTV) definition in preoperative RT of RC. A systematic review of published literature was performed. Studies providing clear indications for CTV definition in preoperative RT of RC were eligible. Only studies published as full text were considered. The search was restricted to English, German, and French languages. The CTV delineation, based on the different guidelines, was drawn on selected slices of a CT scan and the CTV definition based on different guidelines was reported in a table to facilitate the comparison. A total of six publications containing indications for CTV delineation fulfilled the selection criteria and were included in our review. The studies showed a large variability in available indications between CTV contouring guidelines of RC, partly arising from differences in methods used to propose the single guidelines: expert opinion, systematic review, computer-generated consensus, and 3D modeling of recurrence sites. In our systematic analysis, the available indications for CTV definition in preoperative RT of RC were reviewed. A large variation in target volume delineation was observed.

Application of gated FDG PET/CT in target volume definition for radiotherapy in esophageal cancer

Application of gated FDG PET/CT in target volume definition for radiotherapy in esophageal cancer