Body CT examinations in oncologic patients: the impact of subspecialty radiology on radiation exposure in the clinical practice. A quality care study.

PURPOSES: The primary objective of this retrospective study was to assess whether the CT dose delivered to oncologic patients was different in a subspecialty radiology department, compared to a general radiology department. The secondary explorative objective was to assess whether the objective image quality of CT examinations was different in the two settings. MATERIALS AND METHODS: Chest and abdomen CT scans performed for oncologic indications were selected from a general radiology department and a subspecialty radiology department. By using a radiation dose management platform, we extracted and compared CT dose index (CTDIvol) and dose length product (DLP) both for each phase and for the entire CT exams. For objective image quality evaluation, we calculated the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) at the level of the liver and of the aorta. A P-value < 0.05 was considered significant. RESULTS: A total of 7098 CT examinations were included. CTDIvol was evaluated in 12,804 phases; DLP in 10,713 phases and in 6714 examinations. The CTDIvol and DLP overall were significantly lower in the subspecialty radiology department compared to the general radiology department CTDI median (IQR) 5.19 (3.91-7.00) and 5.51 (4.17-7.72), DLP median and IQR of 490.0 (342.4-710.6) and 503.4 (359.9-728.8), p < 0.001 and p = 0.01, respectively. The objective image quality showed no significant difference in the general and subspecialty radiology departments, with median and IQR of 4.03 (2.82-5.51) and 3.84 (3.09-4.94) for SNRLiv (p = 0.58); 4.81 (2.70-7.62) and 4.34 (3.05-6.25) for SNRAo (p = 0.30); 0.83 (0.20-1.89) and 1.00 (0.35-1.57) for CNRLiv (p = 0.99); 2.23 (0.09-3.83) and 1.01 (0.15-2.84) for CNRAo (p = 0.24) with SNRLiv (p = 0.58), SNRAo (p = 0.30), CNRLiv (p = 0.99) and CNRAo (p = 0.24). CONCLUSION: In a subspecialty radiology department, CT protocols are optimized compared to a general radiology department leading to lower doses to oncologic patients without significant objective image quality degradation.

Image quality and radiation dose in spinal surgery: a comparison of three imaging systems in phantom.

Purpose: Using optimal settings for x-ray scans is crucial for obtaining three-dimensional images of high quality while keeping the patient dose low. Our work compares dose and image quality (IQ) of three intraoperative imaging systems [O-arm cone-beam computed tomography (CBCT), ClarifEye C-arm CBCT, and Airo computed tomography] used for spinal surgery. Approach: Patients of 70, 90, and 110 kg were simulated with an anthropomorphic phantom by adding tissue-equivalent material. Titanium inserts were placed in the phantom spine for reproducing metal artifacts in the images. Organ dose was measured with thermo-luminescent dosimeters for effective dose (E) calculation. Subjective IQ was assessed by ranking the images acquired with the manufacturer-defined imaging protocols. Objective IQ was assessed with a customized Catphan phantom. Results: The ClarifEye protocols resulted in the lowest E ranging from 1.4 to 5.1 mSv according to phantom size and protocol. The highest E was measured for the high-definition protocol of O-arm (E 2.2 to 9 mSv) providing the best subjective IQ for imaging of the spine without titanium inserts. For the images with metal, the best IQ was obtained with ClarifEye. Airo (E 5.5 to 8.4 mSv) was ranked with the lowest IQ for images without metal while the rank improved for images with metal. Airo images had better uniformity, noise, and contrast sensitivity compared with CBCTs but worse high-contrast resolution. The values of these parameters were comparable between the CBCT systems. Conclusions: Both CBCT systems provided better IQ compared with Airo for navigation of lumbar spinal surgery for the original phantom. Metal artifacts particularly affect O-arm images decreasing the subjective IQ. The high spatial resolution of CBCT systems resulted in a relevant parameter for the visibility of anatomical features important for spine navigation. Low dose protocols were enough to obtain a clinically acceptable contrast-to-noise ratio in the bones.

Plan quality and consistency in spine radiosurgery treatment planning: comparison between automatic treatment planning with Elements Spine SRS and manual inverse planning with Varian Eclipse.

Spine radiosurgery treatment planning can be a challenging task since a high radiation dose is delivered to target volumes close to the spinal cord, therefore a steep dose gradient is required. Plan quality is greatly influenced by the planner skills, so automatic treatment planning has been proposed to overcome this issue and assure high-quality plans. The Brainlab Elements Spine SRS treatment planning system is specially designed for spine radiosurgery treatments. It is an automatic treatment planning system that works through predefined protocols, with minimal planner interaction required. In this work, we evaluated the plan quality and consistency among the planners within the same institution when using the Elements Spine SRS compared to manual inverse planning with the Varian Eclipse system. Six planners produced a plan for 3 sample target volumes representing different spine metastases in the thoracic region using both treatment planning systems. Dose prescription was 16 Gy in a single fraction, at more than 80% of the target volume. The most important organ at risk was the spinal canal. The dose constraint was V10 Gy < 0.35 cm3. High dose spillage outside the target volume, the homogeneity index, the Paddick conformity index and the number of monitor units were also evaluated. The mean dose to the target volumes in the Elements Spine SRS plans were consistently higher by 0.8 Gy to 1.5 Gy and the maximum dose to the target volumes were consistently higher by 1.8 Gy to 3.1 Gy. Spinal cord sparing was comparable to the Eclipse plans. However, the number of monitor units was greatly reduced, up to 2270 monitor units less. No difference was found in plan quality variability among the planners.

Diagnostic yield, safety, and advantages of ultra-low dose chest CT compared to chest radiography in early stage suspected SARS-CoV-2 pneumonia: A retrospective observational study.

ABSTRACT: To determine the role of ultra-low dose chest computed tomography (uld CT) compared to chest radiographs in patients with laboratory-confirmed early stage SARS-CoV-2 pneumonia.Chest radiographs and uld CT of 12 consecutive suspected SARS-CoV-2 patients performed up to 48 hours from hospital admission were reviewed by 2 radiologists. Dosimetry and descriptive statistics of both modalities were analyzed.On uld CT, parenchymal abnormalities compatible with SARS-CoV-2 pneumonia were detected in 10/12 (83%) patients whereas on chest X-ray in, respectively, 8/12 (66%) and 5/12 (41%) patients for reader 1 and 2. The average increment of diagnostic performance of uld CT compared to chest X-ray was 29%. The average effective dose was, respectively, of 0.219 and 0.073 mSv.Uld CT detects substantially more lung injuries in symptomatic patients with suspected early stage SARS-CoV-2 pneumonia compared to chest radiographs, with a significantly better inter-reader agreement, at the cost of a slightly higher equivalent radiation dose.

Effective dose and image quality for intraoperative imaging with a cone-beam CT and a mobile multi-slice CT in spinal surgery: A phantom study.

PURPOSE: To compare the effective dose (ED) and image quality (IQ) of O-arm cone-beam CT (Medtronic, Minneapolis, MN, USA) and Airo multi-slice CT (Brainlab AG, Munich, Germany) for intraoperative-CT (i-CT) in spinal surgery. METHODS: The manufacturer-defined protocols available in the O-arm and Airo systems for three-dimensional lumbar spine imaging were compared. Organ dose was measured both with thermo-luminescent dosimeters and GafChromic films in the Alderson RadiationTherapy anthropomorphic phantom. A subjective analysis was performed by neurosurgeons to compare the clinical IQ of the anthropomorphic phantom images acquired with the different i-CT systems and imaging protocols. Image uniformity, noise, contrast-to-noise-ratio (CNR), and spatial resolution were additionally assessed with the Catphan 504 phantom. RESULTS: O-arm i-CT caused 56% larger ED than Airo due to the high definition (HD) imaging protocol. The noise was larger for O-arm images leading to a lower CNR than that measured for Airo. Moreover, scattering and beam hardening effects were observed in the O-arm images. Better spatial resolution was measured for the O-arm system (9 lp/cm) than for Airo (4 lp/cm). For all the investigated protocols, O-arm was found to be better for identifying anatomical features important for accurate pedicle screw positioning. CONCLUSIONS: According to phantom measurements, the HD protocol of O-arm offered better clinical IQ than Airo but larger ED. The larger noise of O-arm images did not compromise the clinical IQ while the superior spatial resolution of this system allowed a better visibility of anatomical features important for pedicle screw positioning in the lumbar region.

Patient-based low dose cone beam CT acquisition settings for prostate image-guided radiotherapy treatments on a Varian TrueBeam linear accelerator.

OBJECTIVE: To evaluate the performance of low dose cone beam CT (CBCT) acquisition protocols for image-guided radiotherapy of prostate cancer. METHODS: CBCT images of patients undergoing prostate cancer radiotherapy were acquired with the settings currently used in our department and two low dose settings at 50% and 63% lower exposure. Four experienced radiation oncologists and two radiation therapy technologists graded the images on five image quality characteristics. The scores were analysed through Visual Grading Regression, using the acquisition settings and the patient size as covariates. RESULTS: The low dose acquisition settings have no impact on the image quality for patients with body profile length at hip level below 100 cm. CONCLUSIONS: A reduction of about 60% of the dose is feasible for patients with size below 100 cm. The visibility of low contrast features can be compromised if using the low dose acquisition settings for patients with hip size above 100 cm. ADVANCES IN KNOWLEDGE: Low dose CBCT acquisition protocols for the pelvis, based on subjective evaluation of patient images.

Radiological exposure of patients undergoing transcatheter aortic valve implantation in contemporary practice.

BACKGROUND: Radiological exposure associated with transcatheter aortic valve implantation (TAVI) is unknown and might impact on broadening indications to lower risk patients. Radiological exposure of TAVI patients and its predictors are herein reported. METHODS: Radiological exposure derived from exams/procedures performed within 30 days preceding/following TAVI were acquired and converted into effective-dose. Total effective-dose was defined as the sum of each single dose derived from diagnostic/therapeutic sources. Univariable and multivariable analyses were performed to recognize correlates of exposure. RESULTS: Seventy-five patients aged 82.6 ±â€Š6.0 years with a median Euroscore II 3.6 [IQR 1.93-6.65] were analysed. Median total effective-dose was 41.39 mSv [IQR 27.93-60.88], with TAVI accounting for 47% of it. Age (coefficient -0.031, 95% CI -0.060 to -0.002; P = 0.031) and previous history of cerebrovascular accidents (CVA; coefficient -0.545; 95% CI -1.039 to -0.010; P = 0.046) resulted as inversely correlated to total effective-dose (log-transformed), whereas left ventricular ejection fraction (LVEF) less than 50% (coefficient 0.430, 95% CI 0.031-0.828; P = 0.035) was directly associated. CONCLUSION: Multiple radiological sources are responsible for the observed exposure, with TAVI being the prominent source. Age is inversely related to the radiological exposure.

A simple method for low-contrast detectability, image quality and dose optimisation with CT iterative reconstruction algorithms and model observers.

BACKGROUND: The aim of this work was to evaluate detection of low-contrast objects and image quality in computed tomography (CT) phantom images acquired at different tube loadings (i.e. mAs) and reconstructed with different algorithms, in order to find appropriate settings to reduce the dose to the patient without any image detriment. METHODS: Images of supraslice low-contrast objects of a CT phantom were acquired using different mAs values. Images were reconstructed using filtered back projection (FBP), hybrid and iterative model-based methods. Image quality parameters were evaluated in terms of modulation transfer function; noise, and uniformity using two software resources. For the definition of low-contrast detectability, studies based on both human (i.e. four-alternative forced-choice test) and model observers were performed across the various images. RESULTS: Compared to FBP, image quality parameters were improved by using iterative reconstruction (IR) algorithms. In particular, IR model-based methods provided a 60% noise reduction and a 70% dose reduction, preserving image quality and low-contrast detectability for human radiological evaluation. According to the model observer, the diameters of the minimum detectable detail were around 2 mm (up to 100 mAs). Below 100 mAs, the model observer was unable to provide a result. CONCLUSION: IR methods improve CT protocol quality, providing a potential dose reduction while maintaining a good image detectability. Model observer can in principle be useful to assist human performance in CT low-contrast detection tasks and in dose optimisation.

Initial experience of ArcCHECK and 3DVH software for RapidArc treatment plan verification.

The purpose of this study was to perform delivery quality assurance with ArcCHECK and 3DVH system (Sun Nuclear, FL) and to evaluate the suitability of this system for volumetric-modulated arc therapy (VMAT) (RapidArc [RA]) verification. This software calculates the delivered dose distributions in patients by perturbing the calculated dose using errors detected in fluence or planar dose measurements. The device is tested to correlate the gamma passing rate (%GP) and the composite dose predicted by 3DVH software. A total of 28 patients with prostate cancer who were treated with RA were analyzed. RA treatments were delivered to a diode array phantom (ArcCHECK), which was used to create a planned dose perturbation (PDP) file. The 3DVH analysis used the dose differences derived from comparing the measured dose with the treatment planning system (TPS)-calculated doses to perturb the initial TPS-calculated dose. The 3DVH then overlays the resultant dose on the patient's structures using the resultant "PDP" beams. Measured dose distributions were compared with the calculated ones using the gamma index (GI) method by applying the global (Van Dyk) normalization and acceptance criteria, i.e., 3%/3mm. Paired differences tests were used to estimate statistical significance of the differences between the composite dose calculated using 3DVH and %GP. Also, statistical correlation by means of logistic regression analysis has been analyzed. Dose-volume histogram (DVH) analysis for patient plans revealed small differences between treatment plan calculations and 3DVH results for organ at risk (OAR), whereas planning target volume (PTV) of the measured plan was systematically higher than that predicted by the TPS. The t-test results between the planned and the estimated DVH values showed that mean values were incomparable (p < 0.05). The quality assurance (QA) gamma analysis 3%/3mm showed that in all cases there were only weak-to-moderate correlations (Pearson r: 0.12 to 0.74). Moreover, clinically relevant differences increased with increasing QA passing rate, indicating that some of the largest dose differences occurred in the cases of high QA passing rates, which may be called "false negatives." The clinical importance of any disagreement between the measured and the calculated dose is often difficult to interpret; however, beam errors (either in delivery or in TPS calculation) can affect the effectiveness of the patient dose. Further research is needed to determinate the role of a PDP-type algorithm to accurately estimate patient dose effect.

Development and optimization of a beam shaper device for a mobile dedicated IOERT accelerator.

PURPOSE: The aim of this study was to design and build a prototype beam shaper to be used on a dedicated mobile accelerator that protects organs at risk within the radiation field and conforms the beam to the target geometry during intraoperative electron radiotherapy (IOERT). A dosimetric characterization of the beam shaper device was performed based on Monte Carlo (MC) simulations, as well as experimental data, at different energies, field sizes, and source to skin distances. METHODS: A mobile light intraoperative accelerator (LIAC(®), Sordina, Italy) was used. The design of the beam shaper prototype was based on MC simulations (BEAMnrc∕OMEGA and DOSXYZnrc code) for a selection of materials and thicknesses, as well as for dosimetric characterization. Percentage depth dose (PDD) and profile measurements were performed using a p-type silicon diode and a commercial water phantom, while output factors were measured using a PinPoint ion chamber in a PMMA phantom. Planar doses in planes of interest were carried out using radiochromic films (Gafchromic(TM) EBT and EBT2) in PMMA and in a Solid Water(®) phantom. Several experimental set-ups were investigated with the beam shaper device fixed on the top of the phantom, varying both the short side of the rectangular field and the air gap between the device and the phantom surface, simulating the clinical situation. The output factors (OFs) were determined using different geometrical set-ups and energies. RESULTS: The beam shaper prototype consists of four blades sliding alongside each other and mounted on a special support at the end of the 10 cm diameter PMMA circular applicator. Each blade is made of an upper layer of 2.6 cm of Teflon(®) and a lower layer of 8 mm of stainless steel. All rectangles inscribed in a 5 cm diameter can be achieved in addition to any "squircle-shaped" field. When one side of the rectangular field is held constant and the second side is reduced, both R(50) and R(max) move towards the phantom surface. Comparing the PDDs obtained with the 5 cm circular applicator and with a 4.4 × 4.4 cm(2) square field (that is the equivalent square of the 5 cm circular field) obtained with the beam shaper, a different behavior was observed in the region extending from the surface to a depth of 50% of the maximum dose. Isodoses measured for rectangular fields used for clinical cases (i.e., 4 × 9 cm(2) 8 MeV) are shown, with different air gaps. For each energy investigated, the normalized OFs slowly increase, when the length of the side decreases down to about 4 cm, and then rapidly decreases for smaller field widths. MC simulation showed an excellent agreement with experimental data (<2%). CONCLUSIONS: The beam shaper device is able to provide square∕rectangular∕squircle fields with adequate dose homogeneity for mobile dedicated accelerators, thus allowing conformal treatment with IOERT. Monte Carlo simulation can be a very useful tool to simulate any clinical set up and can be used to create a data set to calculate MUs, thereby increasing the accuracy of the delivered dose during IOERT procedures.

SNPs in DNA repair or oxidative stress genes and late subcutaneous fibrosis in patients following single shot partial breast irradiation.

BACKGROUND: The aim of this study was to evaluate the potential association between single nucleotide polymorphisms related response to radiotherapy injury, such as genes related to DNA repair or enzymes involved in anti-oxidative activities. The paper aims to identify marker genes able to predict an increased risk of late toxicity studying our group of patients who underwent a Single Shot 3D-CRT PBI (SSPBI) after BCS (breast conserving surgery). METHODS: A total of 57 breast cancer patients who underwent SSPBI were genotyped for SNPs (single nucleotide polymorphisms) in XRCC1, XRCC3, GST and RAD51 by Pyrosequencing technology. Univariate analysis (ORs and 95% CI) was performed to correlate SNPs with the risk of developing ≥ G2 fibrosis or fat necrosis. RESULTS: A higher significant risk of developing ≥ G2 fibrosis or fat necrosis in patients with: polymorphic variant GSTP1 (Ile105Val) (OR = 2.9; 95%CI, 0.88-10.14, p = 0.047). CONCLUSIONS: The presence of some SNPs involved in DNA repair or response to oxidative stress seem to be able to predict late toxicity. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01316328.