CT Sets Research Articles

Assessment and management of interfraction variations of lumpectomy cavities in accelerated partial breast irradiation

Background: The purpose of this study is to quantitatively characterize interfraction variations of lumpectomy cavity (LC) in accelerated partial breast irradiation (APBI) and their dosimetric impacts, and to explore the use of an online adaptive replanning scheme to address these variations. Methods: A total of about 100 diagnostic-quality CT sets acquired using an in-room CT at each fraction during image-guided radiation therapy (IGRT) for ten randomly-selected patients treated with APBI in the supine position were analyzed. The LC, treated breast, lung and heart were delineated on each fraction CT. Organ volume change and deformation were quantified. For each fraction CT, three types of plans were created: adaptive, repositioning, and fully re-optimized plans. The plan qualities were compared. Results: Significant changes in LC shape and volume were observed during APBI. On average, the LC volume decreases by 23% from the planning CT. The average change in LC shape, as measured by the Dice’s coefficient, is 80%. For all patients, the adaptive plans were comparable to the re-optimization plans. For small and moderate LC changes (70%), the three types of plans were comparable, indicating that the current IGRT with the standard margins was sufficient to account for the interfraction variations. For cases with extreme LC change (30%), the adaptive plans offered improved target coverage and/or normal tissue sparing as compared with the repositioning plans. Conclusions: Significant variations in the LC between planning and treatment were found for APBI. The current practice of IGRT with standard planning target volume margins can account for these variations for most cases. Online adaptive replanning was needed for cases with extremely large changes in LC.

Particle swarm optimisation aided weighted averaging fusion strategy for CT and MRI medical images

Multimodal medical image fusion is a technique that combines two or more images into a single output image in order to enhance the accuracy of clinical diagnosis. In this paper, a non-subsampled contourlet transform (NSCT) image fusion framework that combines CT and MRI images is proposed. The proposed method decomposes the source images into low and high frequency bands using NSCT and the information across the bands are combined using weighted averaging fusion rule. The weights are optimised by particle swarm optimisation (PSO) with an objective function that jointly maximises the entropy and minimises root mean square error to give improved image quality, which makes different from existing fusion methods in NSCT domain. The performance of the proposed fusion framework is illustrated using five sets of CT and MRI images and various performance metrics indicate that the proposed method is highly efficient and suitable for medical application in better decision making.

Qualitative analysis of manual annotations of clinical text with SNOMED CT.

SNOMED CT provides about 300,000 codes with fine-grained concept definitions to support interoperability of health data. Coding clinical texts with medical terminologies it is not a trivial task and is prone to disagreements between coders. We conducted a qualitative analysis to identify sources of disagreements on an annotation experiment which used a subset of SNOMED CT with some restrictions. A corpus of 20 English clinical text fragments from diverse origins and languages was annotated independently by two domain medically trained annotators following a specific annotation guideline. By following this guideline, the annotators had to assign sets of SNOMED CT codes to noun phrases, together with concept and term coverage ratings. Then, the annotations were manually examined against a reference standard to determine sources of disagreements. Five categories were identified. In our results, the most frequent cause of inter-annotator disagreement was related to human issues. In several cases disagreements revealed gaps in the annotation guidelines and lack of training of annotators. The reminder issues can be influenced by some SNOMED CT features.

318. PET/CT image alignment: Methodology for assessment using a dedicated phantom

Purpose the alignment of transmission and emission images is a crucial requirement in nuclear medicine hybrid scanners (PET/CT and SPECT/CT). EANM and Italian (AIFM-AIMN) guidelines prescribe to perform the alignment test by using specific manufacturer phantoms combined with closed source analysis software packages supplied by the vendor. The purpose of this work was to propose a full independent tool for evaluating CT and PET images alignment by scanning a commercially available phantom. Methods PET/CT data were acquired on a Discovery-IQ PET/CT system (GE Healthcare, Milwaukee, USA) using a dedicated phantom (PET/CT Phantom, Data Spectrum Corporation). A Matlab code was written to perform image analysis. To evaluate translations, 5 coplanar spheres filled with 18F-FDG radioactive solution were considered through these steps: segmentation of the spheres using a region growing algorithm, calculation of the centre of mass for each sphere and comparison of its coordinates in PET and CT set of images. Rotations were assessed by considering the positioning of 3 aluminium rods filled with radioactive solution in PET and CT: the angles shown in figure were calculated in sagittal, coronal and axial views. A series of nominal translations (3–5–8–10 mm in the three spatial directions) and rotations (swivel, tilt and roll, 3.2° up to 6.8°) were simulated to validate the method. Download : Download high-res image (38KB) Download : Download full-size image Results the sensibility of the method turned out to be less than 1 mm for translations and between 1.0° and 1.7° for rotations. The reproducibility (coefficient of variation over 5 identical acquisitions) was less than 1% both for translations and for rotations. Linearity considered the detected translation/rotation as a function of the nominal one: the angular coefficient for the linear regression ranged from 0.87 (Y-axis translation) to 1.35 (tilt rotation). Conclusions the method proposed represents an alternative to the use of vendor specific phantoms and software analysis, providing a general validity across each type of scanner.

Location of arm draining lymph node in relation to breast cancer radiotherapy field and target volume

BackgroundLymphoedema of the arm following axillary surgery or radiotherapy remains a significant side effect affecting some women after breast cancer treatment. Axillary reverse mapping (ARM) is a technique used to identify the lymph node draining the arm (ARM node). Our study aim was to examine the location of the ARM nodes in relation to target volumes and treatment fields for breast cancer radiotherapy. Materials and methodsEighteen breast cancer patients underwent lymphoscintigraphy of contralateral arm (left 10, right 8) and SPECT CT scan on a research study. Patient position for the SPECT CT scan approximated the position used for radiotherapy. Using MIM software™, the ARM node for each subject was contoured on the SPECT CT and verified by a nuclear medicine physician. The CT component of the SPECT CT was then transferred to ECLIPSE™ radiotherapy planning software, and the contralateral breast and axilla were contoured on this CT scan according to the ESTRO contouring guideline. Two radiotherapy plans were generated for each subject using standard tangential IMRT technique at a dose of 50 Gy in 25 fractions, one treating contralateral breast alone, the other treating contralateral breast and contralateral axilla level 1–4. The ARM node was considered “within the radiotherapy field” if the mean dose received by the ARM node was more than 50% of the prescribed dose: i.e., 25 Gy. ResultsOne right-sided subject had 2 ARM nodes, all others had 1 ARM node. All ARM nodes (left 10, right 9) were located within level 1 of the axilla. For the subject with 2 ARM nodes, the node that received a higher dose was used for the analysis. The mean dose received by the ARM node in the whole breast radiotherapy plans ranged from 0.8 to 45.5 Gy, with a median of 10.9 Gy. The mean dose received by the ARM node in the whole breast and axilla plans ranged from 43.4 to 52.5 Gy, with a median of 49.3 Gy. In the whole breast radiotherapy plans, only 5 out of 18 ARM nodes were found to be “within radiotherapy field”, and only 2 ARM nodes received more than 40 Gy. In the breast and axilla plans, all 18 ARM nodes were “within radiotherapy field” and all received more than 40 Gy. To better visualise the locations of ARM nodes, all left sided ARM nodes were then mapped onto a CT set from one of the left-sided subjects, and all the right sided ARM nodes mapped onto one of the right-sided subjects, and digitally reconstructed radiograph (DRR) for radiotherapy fields were produced. ConclusionsOur study demonstrates that the vast majority of ARM nodes (72%) are outside the tangential whole breast radiotherapy fields. In our study, all the ARM nodes were within the axillary radiotherapy fields covering level 1–4 axillary volumes according to the ESTRO contouring guideline, and complete shielding of the humeral head according to the EORTC consensus did not lead to sparing of the ARM nodes. A prospective study is needed to examine the oncological safety of ARM node-sparing axillary radiotherapy and its potential to reduce the risk of arm lymphoedema.

Monte-Carlo Based Total-Body Irradiation Using Linac-Based Volumetric Modulated Arc Therapy

To assess the accuracy, feasibility, and reliability of a total-body irradiation (TBI) technique with linac-based volumetric modulated arc therapy (VMAT) in patients with acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL). From 2015-2017, 26 patients (15 men, 11 women) with AML or ALL underwent allogenic stem-cell transplantation following TBI with linac-based VMAT technique, which consisted of three isocenters and three overlapping arcs for head first CT sets. We added one or two more overlapping arcs, depending on the height of the patient for feet first CT sets. Patient age ranged from 6-63 years with a mean and median age of 20.5 and 17.5 years, respectively. TBI dose was prescribed to 90% of the clinical target volume receiving 12 Gy in six fractions, at two fractions per day. Mean lung and kidney doses were restricted less than 10 Gy, and maximum lens dose less than 6 Gy. Dose rate was variable, and mean dose rate was 250 MU/min. Calculation parameters were grid spacing 0.4 cm, minimum segment width 0.5 cm, maximum 180 control points per arc, fluence-smoothing medium, statistical uncertainty 1.0% per calculation, gantry increment of 30°, and calculate dose deposition to medium. Patients were immobilized in supine position using customized thermoplastic masks for head support and a vacuum cushion for body support on an adjustable combined immobilization board. Laser-based optical surface-guided devices were used for patient positioning and intra-fraction motion detection. Quality assurance (QA) comprised the verification of the radiation plans via dose-volume histograms (DVH) based 3D patient QA system. Average mean lung dose was 9.7 ± 0.2 Gy, mean kidney dose 9.6 ± 0.2 Gy, maximum lens dose 4.5 ± 0.4 Gy, mean planning treatment volume (PTV) dose 12.7 ± 0.1 Gy, and heterogenity index of PTV was 1.16 ± 0.02 in all patients. Overall acute toxicity was low with only grade 1 and 2 morbidity: patchy mucositis in 16 (62%), nausea not requiring antiemetics in 12 (46%), headache in 11 (42%), fatigue in 9 (35%), neck pain in 8 (31%), xerostomia in 7 (27%), loss of appetite in 6 (23%), and faint or dull erythema in 4 (15%) patients. Grade 3 and more acute radiation toxicity was not observed. All patients are stil alive. When comparing plan and DVH-based 3D patient QA results, average differences of 3.4% ± 1.3 in mean kidney doses, 1.0% ± 0.7 in mean lung doses, and 0.9% ± 0.4 in mean target doses were observed. Linac-based VMAT simplifies the process of TBI, and is accurate, feasible, and reliable. Partial cone-beam CT and optical surface-guided system assure patient positioning. Moreover, up to 6-mm longitudinal misalignment does not cause an average more than 3.5% mean lung dose enhancement. DVH-based 3D patient dose verification QA was possible with linac-based VMAT showing small differences between planned and delivered doses.

Radiomics Prediction of Radiation Treatment Outcomes in Oropharyngeal Cancer: A Clinical and Image Repository in Concert with the Cancer Imaging Archive (TCIA)

There is an unmet need for integrating quantitative imaging biomarkers into current risk stratification tools. To explore the correlation between radiomics features – alone or in combination with clinical prognosticators- and tumor outcome, we retrieved clinical meta-data and matched baseline contrast-enhanced computed tomography (CECT) scans from a single institution, institutional review board-approved cohort of 495 oropharyngeal cancer (OPC) patients. We opted to publicly share this large curated data set and subsequent radiomics analytical outcome via The Cancer Imaging Archive (TCIA) to serve as a resource for optimized standardization in the radiomics field. Diagnostic CECT images were acquired at our institution between 2005 and 2012 for 495 OPC patients (prior to any active intervention) in Digital Imaging and Communications in Medicine (DICOM) format . Expert radiation oncologists manually segmented primary and nodal disease gross volumes (GTVp & GTVn). Structure sets were named per the American Association of Physicists in Medicine (AAPM) TG-263 recommendations, then retrieved in DICOM RTSTRUCT format. Matched patient, disease, treatment and outcomes data were obtained. Radiomics analysis was performed using an open-source institutionally-developed software that runs on a computer algorithm. Protected health information (PHI) was removed from all DICOM elements in compliance with the DICOM standards committee P.S. 3.15 Annex E, Attribute Confidentiality Profile using the Radiological Society of North America clinical trial processor (RSNA CTP). TCIA’s curation process ensures the DICOM data is free of PHI and all linkages between CT and structure sets are correct. Following curation the data was archived in TCIA as a permanent open-access collection named “HNSCC”. Anonymized data for 495 OPC patients will be made publicly available from TCIA as downloadable DICOM files (N=**), clinical data, and processed outputs, i.e. tumor segmentations and extracted radiomics features. All data attributes can be cross-referenced via the same anonymized subject IDs. We prepared a data dictionary that specifies clinical data attributes, definitions and possible variables per North American Association of Central Cancer Registries (NAACCR) guidelines. Large-scale data curation-anonymization-transfer workflows, as well as advanced image registration algorithms and common ontology data dictionaries, are unmet needs for joint machine-learning/radiomics research projects. If these resources are paired with large, curated data sets, like those provided via open-access mega-data repositories, like TCIA, the potential benefits include identification of imaging-derived radiomics signatures associated with treatment outcomes and normal-tissue complications across various head and neck epidemiologic cohorts.

Investigating the cotton ring spun yarn structure using micro computerized tomography and digital image processing techniques

The micro-level structure of staple yarn and the fiber arrangement inside it has a decisive influence on its physical properties. This study aims to introduce a combined method based on micro computerized tomography (micro CT) and digital image processing techniques to probe the ring yarn structure in a non-invasive manner. Two micro CT systems at different CT settings were applied to achieve optimal quality CT images of cotton ring yarns. Three image processing algorithms were proposed to enhance and process the yarn CT images in order to extract yarn structural information. The proposed method was also applied on two yarn specimens, which varied significantly in terms of their tensile strength, to study differences in their underlying structures. The results showed that the longitudinal arrangement of fibers in terms of their migratory behavior had a decisive influence on the tensile properties of the yarn. The stronger yarn showed a higher value of the amplitude and intensity of fiber migration compared to the weaker yarn, suggesting that the protocol established in this study can effectively reveal fiber arrangements within a staple yarn structure in a non-invasive manner.

Efficacy and Radiation Exposure of Ultra-Low-Dose Chest CT at 100 kVp with Tin Filtration in CT-Guided Percutaneous Core Needle Biopsy for Small Pulmonary Lesions Using a Third-Generation Dual-Source CT Scanner

PurposeTo prospectively investigate efficacy and radiation dose of ultra-low-dose CT–guided percutaneous core needle biopsy (PCNB) at 100 kVp with tin filtration (100Sn kVp) for small pulmonary lesions. Materials and MethodsStudy enrolled and randomly assigned 210 patients to standard-dose CT (n = 70) or ultra-low-dose CT (n = 140; 1:2 randomization scheme) protocol. Standard-dose CT settings were reference 110 kVp and 50 mAs, and ultra-low-dose CT settings were fixed at 100Sn kVp and 70 mAs. All PCNBs in patients with small pulmonary lesions (< 3 cm) were performed on a third-generation dual-source CT scanner. Diagnostic performance, complication rate, image quality, and radiation dose were compared. ResultsSensitivity, specificity, and accuracy for diagnosis of malignancy were 95.7%, 100%, and 96.9% with standard-dose CT and 93.8%, 100%, and 95.4% with ultra-low-dose CT (P > .05). Complication rate showed no significant differences between protocols (P > .05). Mean volume CT dose index) and total dose-length product were significantly lower in ultra-low-dose CT compared with standard-dose CT (0.24 mGy vs 3.3 mGy ± 1.1 and 9.84 mGy-cm ± 0.70 vs 110.5 mGy-cm ± 45.1; P < .001). Effective dose for ultra-low-dose CT was significantly lower than that for standard-dose CT (0.14 mSv ± 0.02 vs 1.78 mSv ± 0.76; −92.1%; P < .001). Image quality of ultra-low-dose CT met the requirements of PCNB. ConclusionsUltra-low-dose CT-guided PCNB at 100Sn kVp spectral shaping significantly reduced radiation dose on a third-generation dual-source CT, while maintaining high diagnostic accuracy and safety for small pulmonary lesions.

Part II-adult skeletal age estimation using CT scans of cadavers: Revision of the pubic symphysis methods

Abstract Objective When present, the most commonly used element to estimate adult skeletal age at death is the pubic symphysis. In the second manuscript of this series, the Suchey–Brooks and Hartnett pubic symphysis methods are assessed to for their applicability to volume-rendered images (VRIs) generated from CT scans of cadavers to assess their applicability to VRIs. Materials and Methods CT scans of 420 cadavers from the Victorian Institute of Forensic Medicine were selected (age range 20 to 79 years). Siemens syngo.via software was used to view the DICOM images and create the VRIs. The Suchey–Brooks and Hartnett pubic symphysis methods were used to create a revised method to estimate age for VRIs. Results and Conclusion Several features described by Suchey–Brooks and Hartnett could be observed on the VRIs, including billows on the symphysis face in younger individuals, the ventral rampart, and the dorsal margin. However, distinguishing features such porosity and bone weight for the older phases could not always be assessed. A revised pubic symphysis method for use on VRIs was created using both morphological features and bone quality to assess age. The revised method is strongly correlated with age, and over 70% of the sample was placed in the correct age phase. The Suchey–Brooks method was more accurate for individuals under 40 years of age while the revised method was more accurate for individuals over 40 years of age, similar to the findings from other studies. This revised method should be tested on other populations using different CT settings and software.

Part III – Adult skeletal age estimation using CT scans of cadavers: Revision of the auricular surface methods

Abstract Objective The auricular surface of the ilium is often found preserved in both archaeological and forensic contexts. In the final manuscript of this three-part series, the features used by biological and forensic anthropologists to estimate adult skeletal age from the auricular surface are tested on volume-rendered images (VRIs) generated from CT scans of cadavers. Materials and methods CT scans of 420 cadavers from the Victorian Institute of Forensic Medicine were selected (age range 20–79 years). Siemens syngo.via software was used to view the DICOM images and create the VRIs. The Lovejoy et al. auricular surface method of age estimation was assessed for use on VRIs and a new method for VRIs was created. Results and conclusion Most of the features described by Lovejoy et al. could not be observed on the VRIs, and as previously established by Villa et al. (2013) [13], the Buckberry and Chamberlain method cannot be used on VRIs. Features such as transverse organization, surface texture, and microporosity are not visible on VRIs; however, features of the auricular surface and retroauricular area were seen to progress in a manner similar to that described by Lovejoy and colleagues, and a revised auricular surface method for use on VRIs was developed. The revised method is strongly correlated with age, and over 70% of the sample was placed within one standard deviation of the mean of the correct phase. This revised method should be tested on more populations using different CT settings and software.

P201] Metal artifact management in volumetric modulated arc therapy for head and neck treatment

Purpose CT-image artifacts caused by prosthetic materials, affect negatively the radiotherapy treatment planning by causing difficulties to delineate the target volumes (PTV) and by reducing the dose calculation accuracy. We investigated the clinical impact of use a new automatic tool, segment high density artifact (SHDA-tool), to delineate the high-z material in head and neck volumetric modulated arc therapy (VMAT). Methods We analyzed 50 VMAT plans for head and neck district on patients with nonremovable metal dental restoration (i.e. crowns, implants) generating artifacts, near and/or inside PTV. Dose distribution is calculated with Acuros-XB algorithm (Eclipse v.13.7, Varian Med.Sys) that needs to have defined the correlation between Houndsfield Unit and relative electron density for all patient CT-images voxels, also in high z-materials. For each patient we obtained two set of planning-CT: • Automatic-structure: voxels with unknown density ( > 3.00 g/cm3) are automatic drawn by SHDA-tool. We have assigned at this structure the Titanium Alloy density (4.42 g/cm3). No density are assigned in artifacts area in soft tissue regions (i.e. oral cavity mucosae); • Manual structure: prosthetic teeth and soft tissue regions with artifacts are manually contouring and assigned Titanium Alloy and muscle-skeletal (1.05 g/cm3) density respectively. At the end of optimization process, dose distributions were calculated on both CT set. For these we analyzed some clinical parameter from dose-volume histogram (DVH) of: PTV, mucosae, mucosae near implant interface, parotids and mandible. Results Automatic-structure volume is bigger than manual one for 81% (medium volume differences 6.7 cc (−0.5 ÷ 19.9 cc)). No significant differences were observed between dose distributions in PTV coverture and mean dose of PTV, parotids and mucosae. The maximum doses for oral mucosae and mucosae near implants have differences 2.5 Gy for 40% cases; while for PTV and mandible the differences are 2.0 Gy for 25% patients. In the other cases there are not significant differences. Conclusions The differences in dose distribution between the two methods, for each patient, are small and not clinically relevant. We decide to introduce the SHDA tool in our pianification instead of manual structures contouring. To improve the PTVs and OARs contouring we are evaluating the recently commercially algorithm for CT-image reconstruction.

P222] Assesing the dosimetric accuracy of TBI treatment with VMAT technique

Purpose Our propose was assesing the dosimetric accuracy and reliability of TBI treatment by using linac-based VMAT in 27 patients with acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL) and aplastic anemia (AA). Methods Patients underwent TBI radiotherapy treatment with a linac-based VMAT technique on the coach. The VMAT-TBI technique consisted of three isocentres and three overlapping arcs. If patients were taller than 120 cm, we added one or two more overlapping arcs for feet to gantry CT sets. We eliminated high dose junction region after fusion of two CT sets via bias dose properties of Monaco® 5.11 TPS (Elekta AB, Sweden). Each treatment plans were recalculated with 3 mm, 6 mm, 9 mm and 12 mm longitidudinal misallignment of second and third overlapping arcs. Also, the quality assurance comprised the verification of the irradiation plans via DVH based 3D patient QA system which was Dolphin® and Compass® (IBA Dosimetry, Germany). Results When we recalculated plan’s with longitidudinal misallignments, we obtained an average %2.0 ± 0,7, %2,9 ± 1,5, %6,5 ± 1,7 and %7,1 ± 1,8 higher mean lungs doses, %2,6 ± 1,6, %9,8 ± 3,9, %15,4 ± 4,4 and %23,0 ± 3,5 higher maximum lung doses and %3,7 ± 1,4, %11,8 ± 3,3, %20,4 ± 3,8 and %22,8 ± 4,1 higher point doses with each 3 mm, 6 mm, 9 mm and 12 mm longitidudinal misallignments. When we compared plan and DVH based 3D patient QA results, we determined an average difference %3,4 ± 1,3 mean kidneys doses, %0,8 ± 0,7 mean lungs doses and %0,9 ± 0,4 higher mean target doses. Conclusions Our results show that linac-based VMAT is reliable treatment for TBI. DVH based 3D patient QA dose verification is possible with linac-based VMAT and we determined high dosimetric accuracy for OARs and target between treatment plan and delivered dose.

Methods for Post Hoc Quantitative Computed Tomography Bone Density Calibration: Phantom-Only and Regression.

Quantitative computed tomography (qCT) relies on calibrated bone mineral density data. If a calibration phantom is absent from the CT scan, post hoc calibration becomes necessary. Scanning a calibration phantom after-the-fact and applying that calibration to uncalibrated scans has been used previously. Alternatively, the estimated density is known to vary with CT settings, suggesting that it may be possible to predict the calibration terms using CT settings. This study compares a novel CT setting regression method for post hoc calibration to standard and post hoc phantom-only calibrations. Five cadaveric upper limbs were scanned at 11 combinations of peak tube voltage and current (80-140 kV and 100-300 mA) with two calibration phantoms. Density calibrations were performed for the cadaver scans, and scans of the phantoms alone. Stepwise linear regression determined if the calibration equation terms were predictable using peak tube voltage and current. Peak tube voltage, but not current, was significantly correlated with regression calibration terms. Calibration equation slope was significantly related to the type of phantom (p < 0.001), calibration method (p = 0.026), and peak tube voltage (p < 0.001), but not current (p = 1.000). The calibration equation vertical intercept was significantly related to the type of phantom (p < 0.001), and peak tube voltage (p = 0.006), but not calibration method (p = 0.682), or current (p = 0.822). Accordingly, regression can correlate peak tube voltage with density calibration terms. Suggesting that, while standard qCT calibration is preferable, regression calibration may be an acceptable post hoc method when necessary.

Impact of clinical trial participation on survival in patients with castration-resistant prostate cancer: a multi-center analysis

BackgroundClinical trial (CT) participation may confer access to new, potentially active agents before their general availability. This study aimed to investigate the potential survival benefit of participation in investigational CTs of novel hormonal, chemotherapeutic, and radiopharmaceutical agents in patients with castration-resistant prostate cancer (CRPC).MethodsThis multi-center, retrospective analysis included 299 consecutive patients with newly diagnosed, non-metastatic or metastatic CRPC between September 2009 and March 2017. Of these, 65 (21.7%) patients participated in CTs pertaining to systemic treatment targeting CRPC and 234 (78.3%) patients received pre-established, standard systemic treatment outside of a CT setting. The survival advantage of CT participation regarding cancer-specific survival (CSS) was investigated.ResultsAn Eastern Cooperative Oncology Group performance status (ECOG PS) ≥2 at CRPC diagnosis was found in a lower proportion CT participants than in non-participants (4.6% vs. 14.9%; p = 0.033). During the median follow-up period of 16.0 months, CT participants exhibited significantly higher 2-year CSS survival rates (61.3% vs. 42.4%; p = 0.003) than did non-participants. Multivariate analysis identified prostate-specific antigen and alkaline phosphatase levels at CRPC onset, Gleason score ≥ 8, ECOG PS ≥2, less number of docetaxel cycles administered, and non-participation in CTs as independent predictors for a lower risk of CSS.ConclusionsPatients diagnosed with CRPC who participated in CTs exhibited longer CSS durations than non-participants who received pre-established, standard systemic therapy outside of a CT setting. Our findings imply that CT participation is associated with CSS, and that CT participation should be offered to patients with CRPC whenever indicated.

Effect of different CT scanners and settings on femoral failure loads calculated by finite element models.

ABSTRACTIn a multi‐center patient study, using different CT scanners, CT‐based finite element (FE) models are utilized to calculate failure loads of femora with metastases. Previous studies showed that using different CT scanners can result in different outcomes. This study aims to quantify the effects of (i) different CT scanners; (ii) different CT protocols with variations in slice thickness, field of view (FOV), and reconstruction kernel; and (iii) air between calibration phantom and patient, on Hounsfield Units (HU), bone mineral density (BMD), and FE failure load. Six cadaveric femora were scanned on four CT scanners. Scans were made with multiple CT protocols and with or without an air gap between the body model and calibration phantom. HU and calibrated BMD were determined in cortical and trabecular regions of interest. Non‐linear isotropic FE models were constructed to calculate failure load. Mean differences between CT scanners varied up to 7% in cortical HU, 6% in trabecular HU, 6% in cortical BMD, 12% in trabecular BMD, and 17% in failure load. Changes in slice thickness and FOV had little effect (≤4%), while reconstruction kernels had a larger effect on HU (16%), BMD (17%), and failure load (9%). Air between the body model and calibration phantom slightly decreased the HU, BMD, and failure loads (≤8%). In conclusion, this study showed that quantitative analysis of CT images acquired with different CT scanners, and particularly reconstruction kernels, can induce relatively large differences in HU, BMD, and failure loads. Additionally, if possible, air artifacts should be avoided. © 2018 Orthopaedic Research Society. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of the Orthopaedic Research Society. J Orthop Res 36:2288–2295, 2018.

Principal component reconstruction (PCR) for cine CBCT with motion learning from 2D fluoroscopy.

This work aims to generate cine CT images (i.e., 4D images with high-temporal resolution) based on a novel principal component reconstruction (PCR) technique with motion learning from 2D fluoroscopic training images. In the proposed PCR method, the matrix factorization is utilized as an explicit low-rank regularization of 4D images that are represented as a product of spatial principal components and temporal motion coefficients. The key hypothesis of PCR is that temporal coefficients from 4D images can be reasonably approximated by temporal coefficients learned from 2D fluoroscopic training projections. For this purpose, we can acquire fluoroscopic training projections for a few breathing periods at fixed gantry angles that are free from geometric distortion due to gantry rotation, that is, fluoroscopy-based motion learning. Such training projections can provide an effective characterization of the breathing motion. The temporal coefficients can be extracted from these training projections and used as priors for PCR, even though principal components from training projections are certainly not the same for these 4D images to be reconstructed. For this purpose, training data are synchronized with reconstruction data using identical real-time breathing position intervals for projection binning. In terms of image reconstruction, with a priori temporal coefficients, the data fidelity for PCR changes from nonlinear to linear, and consequently, the PCR method is robust and can be solved efficiently. PCR is formulated as a convex optimization problem with the sum of linear data fidelity with respect to spatial principal components and spatiotemporal total variation regularization imposed on 4D image phases. The solution algorithm of PCR is developed based on alternating direction method of multipliers. The implementation is fully parallelized on GPU with NVIDIA CUDA toolbox and each reconstruction takes about a few minutes. The proposed PCR method is validated and compared with a state-of-art method, that is, PICCS, using both simulation and experimental data with the on-board cone-beam CT setting. The results demonstrated the feasibility of PCR for cine CBCT and significantly improved reconstruction quality of PCR from PICCS for cine CBCT. With a priori estimated temporal motion coefficients using fluoroscopic training projections, the PCR method can accurately reconstruct spatial principal components, and then generate cine CT images as a product of temporal motion coefficients and spatial principal components.

Definitive External Beam Radiation Therapy With Stereotactic Body Radiation Therapy Boost for FIGO Stage IB-IIB Cancer of the Cervix: Minimum 4-Year Disease Control, Toxicity, and Quality of Life Outcomes from a Phase 2 Trial

SBRT for gynecologic cancers may offer practical advantages over brachytherapy at similar radiobiologic dosing. Dose-fractionation SBRT schedules may be selected to approximate those of HDR, and SBRT eliminates the needs of optimal applicator placement and sedation. Herein, we report health-related quality of life (HRQOL), toxicity, and disease control outcomes of a prospective, phase II trial of SBRT for primary cervical cancers. Eligible patients included those with (1) pathologically confirmed cervical squamous cell carcinoma or adenocarcinoma; (2) FIGO stage IB, IIA or IIB disease; (3) technical or medical contraindication to brachytherapy; and (4) primary GTV < 125 cc following induction therapy. Induction therapy consisted of external beam radiotherapy (EBRT) to a minimum dose of 45.0 Gy encompassing primary tumor and regional pelvic lymphatics. All patients received cisplatin-based chemotherapy concurrent to EBRT. SBRT boost treatment planning then followed, and GTV delineation was aided by co-registration of the boost planning CT set to a pre-EBRT FDG PET/CT scan and post-EBRT MRI. A boost dose of 40.0 Gy was prescribed to the primary tumor and delivered over a 10-day schedule of 5 fractions of 8.0 Gy each. Assessments included (1) disease response was determined pathologically by 3-month post-therapy biopsy and radiographically by biannual PET/CT imaging for 2 years; (2) acute and chronic toxicities were assessed using the National Cancer Institute's CTCAE v3 toxicity scales; and (3) quality-of-life was scored using FACT-G measurements. Thirty-five patients with FIGO stage IB - IIB cervical cancer have been treated since June 2007 and have been followed for a median of 66.0 months and a minimum of 48.0 months. Stage distribution was as follows: 4/35 FIGO stage IB1, 9/35 FIGO stage IB2, 3/35 FIGO stage IIA1, 3/35 FIGO stage IIA2 and 16/35 FIGO stage IIB. Post-SBRT biopsy at 3 months was negative for 32 of 35 patients, or 91.4%, for all patients. At 5 years, estimated local control by combined pathologic and radiographic (i.e., PET SUVmax < 2.5) criteria at the SBRT treatment site is 88.5 % for all patients. No NCI CTCAE grade 3 or greater urinary or bowel toxicities have been observed to date. Post-treatment FACT-G scores were statistically superior compared to pre-treatment assessments for the following studied domains: physical, emotional, and functional well-being. At a minimum follow-up of 4 years, SBRT offers an effective and well-tolerated boost modality for selected FIGO stage IB - IIB cervix cancer patients otherwise contraindicated for brachytherapy. To our knowledge, this prospective phase 2 study reports the largest cohort of cervical cancer cases treated with curative intent using boost SBRT.

Clinical adequacy assessment of autocontours for prostate IMRT with meaningful endpoints.

To determine if radiation treatment plans created based on autosegmented (AS) regions-of-interest (ROI)s are clinically equivalent to plans created based on manually segmented ROIs, where equivalence is evaluated using probabilistic dosimetric metrics and probabilistic biological endpoints for prostate IMRT. Manually drawn contours and autosegmented ROIs were created for 167 CT image sets acquired from 19 prostate patients. Autosegmentation was performed utilizing Pinnacle's Smart Probabilistic Image Contouring Engine. For each CT set, 78Gy/39 fraction 7-beam IMRT treatment plans with 1cm CTV-to-PTV margins were created for each of the three contour scenarios; PMD using manually delineated (MD) ROIs, PAS using autosegmented ROIs, and PAM using autosegmented organ-at-risks (OAR)s and the manually drawn target. For each plan, 1000 virtual treatment simulations with different systematic errors for each simulation and a different random error for each fraction were performed. The statistical probability of achieving dose-volume metrics (coverage probability (CP)), expectation values for normal tissue complication probability (NTCP), and tumor control probability (TCP) metrics for all possible cross-evaluation pairs of ROI types and planning scenarios were reported. In evaluation scenarios, the root mean square loss (RMSL) and maximum absolute loss (MAL) of coverage probability of dose-volume objectives, E[TCP], and E[NTCP] were compared with respect to the base plan created and evaluated with manually drawn contours. Femoral head dose objectives were satisfied in all situations, as well as the maximum dose objectives for all ROIs. Bladder metrics were within the clinical coverage tolerances except D35Gy for the autosegmented plan evaluated with the manual contours. Dosimetric indices for CTV and rectum could be highly compromised when the definition of the ROIs switched from manually delineated to autosegmented. Seventy-two percent of CT image sets satisfied the worst-case CP thresholds for all dosimetric objectives in all scenarios, the percentage dropped to 50% if biological indices were taken into account. Among evaluation scenarios, (MD,PAM ) bore the highest resemblance to (MD,PMD ) where 99% and 88% of cases metall CP thresholds for bladder and rectum, respectively. When including daily setup variations in prostate IMRT, the dose-volume metric CP, and biological indices of ROIs were approximately equivalent for the plans created based on manually drawn targets and autosegmented OARs in 88% of cases. The accuracy of autosegmented prostates and rectums are impediment to attain statistically equivalent plans created based on manually drawn ROIs.

Comparison of gastric-cancer radiotherapy performed with volumetric modulated arc therapy or single-field uniform-dose proton therapy

Background: Proton-beam therapy of large abdominal cancers has been questioned due to the large variations in tissue density in the abdomen. The aim of this study was to evaluate the importance of these variations for the dose distributions produced in adjuvant radiotherapy of gastric cancer (GC), implemented with photon-based volumetric modulated arc therapy (VMAT) or with proton-beam single-field uniform-dose (SFUD) method.Material and methods: Eight GC patients were included in this study. For each patient, a VMAT- and an SFUD-plan were created. The prescription dose was 45 Gy (IsoE) given in 25 fractions. The plans were prepared on the original CT studies and the doses were thereafter recalculated on two modified CT studies (one with extra water filling and the other with expanded abdominal air-cavity volumes).Results: Compared to the original VMAT plans, the SFUD plans resulted in reduced median values for the V18 of the left kidney (26%), the liver mean dose (14.8 Gy (IsoE)) and the maximum dose given to the spinal cord (26.6 Gy (IsoE)). However, the PTV coverage decreased when the SFUD plans were recalculated on CT sets with extra air- (86%) and water-filling (87%). The added water filling only led to minor dosimetric changes for the OARs, but the extra air caused significant increases of the median values of V18 for the right and left kidneys (10% and 12%, respectively) and of V10 for the liver (12%). The density changes influenced the dose distributions in the VMAT plans to a minor extent.Conclusions: SFUD was found to be superior to VMAT for the plans prepared on the original CT sets. However, SFUD was inferior to VMAT for the modified CT sets.