First Results of a New Deep Learning Reconstruction Algorithm on Image Quality and Liver Metastasis Conspicuity for Abdominal Low-Dose CT.

The study's aim was to assess the impact of a deep learning image reconstruction algorithm (Precise Image; DLR) on image quality and liver metastasis conspicuity compared with an iterative reconstruction algorithm (IR). This retrospective study included all consecutive patients with at least one liver metastasis having been diagnosed between December 2021 and February 2022. Images were reconstructed using level 4 of the IR algorithm (i4) and the Standard/Smooth/Smoother levels of the DLR algorithm. Mean attenuation and standard deviation were measured by placing the ROIs in the fat, muscle, healthy liver, and liver tumor. Two radiologists assessed the image noise and image smoothing, overall image quality, and lesion conspicuity using Likert scales. The study included 30 patients (mean age 70.4 ± 9.8 years, 17 men). The mean CTDIvol was 6.3 ± 2.1 mGy, and the mean dose-length product 314.7 ± 105.7 mGy.cm. Compared with i4, the HU values were similar in the DLR algorithm at all levels for all tissues studied. For each tissue, the image noise significantly decreased with DLR compared with i4 (p < 0.01) and significantly decreased from Standard to Smooth (-26 ± 10%; p < 0.01) and from Smooth to Smoother (-37 ± 8%; p < 0.01). The subjective image assessment confirmed that the image noise significantly decreased between i4 and DLR (p < 0.01) and from the Standard to Smoother levels (p < 0.01), but the opposite occurred for the image smoothing. The highest scores for overall image quality and conspicuity were found for the Smooth and Smoother levels.

Task-Based Image Quality Assessment Comparing Classical and Iterative Cone Beam CT Images on Halcyon®.

BACKGROUND: Despite the development of iterative reconstruction (IR) in diagnostic imaging, CBCT are generally reconstructed with filtered back projection (FBP) in radiotherapy. Varian medical systems, recently released with their latest Halcyon® V2.0 accelerator, a new IR algorithm for CBCT reconstruction. PURPOSE: To assess the image quality of radiotherapy CBCT images reconstructed with FBP and an IR algorithm. METHODS: Three CBCT acquisition modes (head, thorax and pelvis large) available on a Halcyon® were assessed. Five acquisitions were performed for all modes on an image quality phantom and reconstructed with FBP and IR. Task-based image quality assessment was performed with noise power spectrum (NPS), task-based transfer function (TTF) and detectability index (d'). To illustrate the image quality obtained with both reconstruction types, CBCT acquisitions were made on 6 patients. RESULTS: The noise magnitude and the spatial frequency of the NPS peak was lower with IR than with FBP for all modes. For all low and high-contrast inserts, the values for TTF at 50% were higher with IR than with FBP. For all inserts and all modes, the contrast values were similar with FBP and IR. For all low and high-contrast simulated lesions, d' values were higher with IR than with FBP for all modes. These results were also found on the 6 patients where the images were less noisy but smoother with IR-CBCT. CONCLUSIONS: Using the IR algorithm for CBCT images in radiotherapy improve image quality and thus could increase the accuracy of online registration and limit positioning errors during processing.

Improved image quality and dose reduction in abdominal CT with deep-learning reconstruction algorithm: a phantom study.

OBJECTIVES: To assess the impact of a new artificial intelligence deep-learning reconstruction (Precise Image; AI-DLR) algorithm on image quality against a hybrid iterative reconstruction (IR) algorithm in abdominal CT for different clinical indications. METHODS: Acquisitions on phantoms were performed at 5 dose levels (CTDIvol: 13/11/9/6/1.8 mGy). Raw data were reconstructed using level 4 of iDose4 (i4) and 3 levels of AI-DLR (Smoother/Smooth/Standard). Noise power spectrum (NPS), task-based transfer function (TTF) and detectability index (d') were computed: d' modelled detection of a liver metastasis (LM) and hepatocellular carcinoma at portal (HCCp) and arterial (HCCa) phases. Image quality was subjectively assessed on an anthropomorphic phantom by 2 radiologists. RESULTS: From Standard to Smoother levels, noise magnitude and average NPS spatial frequency decreased and the detectability (d') of all simulated lesions increased. For both inserts, TTF values were similar for all three AI-DLR levels from 13 to 6 mGy but decreased from Standard to Smoother levels at 1.8 mGy. Compared to the i4 used in clinical practice, d' values were higher using the Smoother and Smooth levels and close for the Standard level. For all dose levels, except at 1.8 mGy, radiologists considered images satisfactory for clinical use for the 3 levels of AI-DLR, but rated images too smooth using the Smoother level. CONCLUSION: Use of the Smooth and Smoother levels of AI-DLR reduces the image noise and improves the detectability of lesions and spatial resolution for standard and low-dose levels. Using the Smooth level is apparently the best compromise between the lowest dose level and adequate image quality. KEY POINTS: • Evaluation of the impact of a new artificial intelligence deep-learning reconstruction (AI-DLR) on image quality and dose compared to a hybrid iterative reconstruction (IR) algorithm. • The Smooth and Smoother levels of AI-DLR reduced the image noise and improved the detectability of lesions and spatial resolution for standard and low-dose levels. • The Smooth level seems the best compromise between the lowest dose level and adequate image quality.

Early results of ultra-low-dose CT-scan for extremity traumas in emergency room.

Background: Ultra-low dose computed tomography (ULD-CT) was shown to be a good alternative to digital radiographs in various locations. This study aimed to assess the diagnostic sensitivity and specificity of ULD-CT versus digital radiographs in patients consulting for extremity traumas in emergency room. Methods: Digital radiography and ULD-CT scan were performed in patients consulting at the emergency department (February-August 2018) for extremity traumas. Fracture detection was evaluated retrospectively by two blinded independent radiologists. Sensitivity and specificity were evaluated using best value comparator (BVC) and a Bayesian latent class model (LCM) approaches and clinical follow-up. Image quality, quality diagnostic and diagnostic confidence level were evaluated (Likert scale). The effective dose received was calculated. Results: Seventy-six consecutive patients (41 men, mean age: 35.2±13.2 years), with 31 wrists/hands and 45 ankles/feet traumas were managed by emergency physicians. According to clinical data, radiography had 3 false positive and 10 false negative examinations, and ULD-CT, 2 of each. Radiography and ULD-CT specificities were similar; sensitivities were lower for radiography, with BVC and Bayesian. With Bayesian, ULD-CT and radiography sensitivities were 90% (95% CI: 87-93%) and 76% (95% CI: 71-81%, P<0.0001) and specificities 96% (95% CI: 93-98%) and 93% (95% CI: 87-97%, P=0.84). The inter-observer agreement was higher for ULD-CT for all subjective indexes. The effective dose for ULD-CT and radiography was 0.84±0.14 and 0.58±0.27 µSv (P=0.002) for hand/wrist, and 1.50±0.32 and 1.44±0.78 µSv (P=NS) for foot/ankle. Conclusions: With an effective dose level close to radiography, ULD-CT showed better detection of extremities fractures in the emergency room and may allow treatment adaptation. Further studies need to be performed to assess impact of such examination in everyday practice. Trial Registration: ClinicalTrials.gov Identifier: NCT04832490.

Microwave Ablation of Liver, Kidney and Lung Lesions: One-Month Response and Manufacturer's Charts' Reliability in Clinical Practice.

Microwave ablation systems allow for performing tumoral destruction in oncology. The objective of this study was to assess the early response and reliability of the microwave ablation zone size at one month for liver, kidney and lung lesions, as compared to the manufacturer's charts. Patients who underwent microwave ablation with the EmprintTM ablation system for liver, kidney and lung lesions between June 2016 and June 2018 were retrospectively reviewed. Local response and ablation zone size (major, L, and minor, l, axes) were evaluated on the one-month follow-up imaging. Results were compared to the manufacturers' charts using the Bland-Altman analysis. Fifty-five patients (mean age 68 ± 11 years; 95 lesions) were included. The one-month complete response was 94%. Liver ablations showed a good agreement with subtle, smaller ablation zones (L: -2 ± 5.7 mm; l: -5.2 ± 5.6 mm). Kidney ablations showed a moderate agreement with larger ablations for L (L: 8.69 ± 7.94 mm; l: 0.36 ± 4.77 mm). Lung ablations showed a moderate agreement, with smaller ablations for l (L: -5.45 ± 4.5 mm; l: -9.32 ± 4.72 mm). With 94% of early complete responses, the system showed reliable ablations for liver lesions, but larger ablations for kidney lesions, and smaller for lung lesions.

A national dose analysis of guided tumor destruction: influence of sex, age, localization and destruction technique used.

Background: Percutaneous destructions of tumor lesions by ablation (microwave, radiofrequency or cryoablation) under computed tomography (CT) guidance allow high efficiency with minimally-invasive techniques, and acute needle placement and follow-up during procedure. This study investigated the impact of patient and technique parameters on the dose delivered during these procedures under CT guidance. Methods: Data were extracted from a previous nationwide retrospective study. Patients who underwent percutaneous destruction of bone lesions, abdominal and lung tumors were included. Univariate and multivariate linear regression of the dose length product (DLP) log were performed, according to patient's gender, age, lesion location, destruction technique, adjusted to the participating center. Results: A total of 822 patients (556 men), of mean age 62±14 years, were included: 150 patients had bone lesions, 463 abdominal and 209 thoracic tumors. The mean DLP was 991.6±979.0 mGy·cm for patients with bone lesions, 2,130.7±2,051.8 mGy∙cm for abdominal tumors and 825.2±545.4 mGy·cm for lung tumors. In multivariate analysis, the age was significantly associated with higher DLP for bone (P=0.0082) but not for abdominal and thoracic lesions; the DLP was significantly higher in men for abdominal tumors (P<0.0001) while sex had no impact on the dose for bone and thoracic lesions. The dose depended on the lesion location only for bone (P<0.0001) percutaneous destructions. The technique was not correlated to DLP for all lesions. Conclusions: Patient and tumor characteristics such as sex, age and lesion location impacted on the dose delivered during percutaneous destructions of bone, abdominal and thoracic lesions, but not the destruction technique used. Further studies are needed to propose sharper reference dose levels.

Comparison of virtual monoenergetic imaging between a rapid kilovoltage switching dual-energy computed tomography with deep-learning and four dual-energy CTs with iterative reconstruction.

BACKGROUND: To assess the spectral performance of rapid kV switching dual-energy CT (KVSCT-Canon) equipped with a Deep-Learning spectral reconstruction algorithm on virtual-monoenergetic images at low-energy levels and to compare its performances with four other dual-energy CT (DECT) platforms equipped with iterative reconstruction algorithms. METHODS: Two CT phantoms were scanned on five DECT platforms: KVSCT-Canon, fast kV-switching CT (KVSCT-GE), split filter CT, dual-source CT (DSCT), and dual-layer CT (DLCT). The classical parameters of abdomen-pelvic examinations were used for all phantom acquisitions, and a CTDIvol close to 10 mGy. For KVSCT-Canon, virtual-monoenergetic images were reconstructed with a clinical slice thickness of 0.5 and 1.5 mm to be close to other platforms. Noise power spectrum (NPS) and task-based transfer function (TTF) were evaluated from 40 to 80 keV of virtual-monoenergetic images. A detectability index (d') was computed to model the detection task of two contrast-enhanced lesions as function of keV. RESULTS: For KVSCT-Canon, the noise magnitude and average NPS spatial frequency (fav) decreased from 40 to 70 keV and increased thereafter. Similar noise magnitude outcomes were found for KVSCT-GE but the opposite for fav. For the other DECT platforms, the noise magnitude decreased as the keV increased. For split filter CT, DSCT and DLCT, the fav values increased from 40 to 80 keV. For all DECT platforms, TTF at 50% (f50) decreased as the keV increased, decreasing spatial resolution. For KVSCT-Canon, d' values peaked at 60 and 70 keV for both simulated lesions and from 50 to 70 keV for KVSCT-GE. d' decreased between 40 and 70 keV for DSCT, DLCT and split filter CT. For KVSCT-Canon, the increase in slice thickness decreases noise magnitude, fav and f50 and increases d' values. The highest d' values were found for DLCT at 40 and 50 keV and for KVSCT-Canon at 1.5 mm for other keV. CONCLUSIONS: For KVSCT-Canon, the detectability of contrast-enhanced lesions was highest at 60 keV. The highest d' values were found for DLCT at 40 and 50 keV and for KVSCT-Canon at 1.5 mm for other keV.

Effect of a new deep learning image reconstruction algorithm for abdominal computed tomography imaging on image quality and dose reduction compared with two iterative reconstruction algorithms: a phantom study.

BACKGROUND: New reconstruction algorithms based on deep learning have been developed to correct the image texture changes related to the use of iterative reconstruction algorithms. The purpose of this study was to evaluate the impact of a new deep learning image reconstruction [Advanced intelligent Clear-IQ Engine (AiCE)] algorithm on image-quality and dose reduction compared to a hybrid iterative reconstruction (AIDR 3D) algorithm and a model-based iterative reconstruction (FIRST) algorithm. METHODS: Acquisitions were carried out using the ACR 464 phantom (and its body ring) at six dose levels (volume computed tomography dose index 15/10/7.5/5/2.5/1 mGy). Raw data were reconstructed using three levels (Mild/Standard/Strong) of AIDR 3D, of FIRST and AiCE. Noise-power-spectrum (NPS) and task-based transfer function (TTF) were computed. Detectability index was computed to model the detection of a small calcification (1.5-mm diameter and 500 HU) and a large mass in the liver (25-mm diameter and 120 HU). RESULTS: NPS peaks were lower with AiCE than with AIDR 3D (-41%±6% for all levels) or FIRST (-15%±6% for Strong level and -41%±11% for both other levels). The average NPS spatial frequency was lower with AICE than AIDR 3D (-9%±2% using Mild and -3%±2% using Strong) but higher than FIRST for Standard (6%±3%) and Strong (25%±3%) levels. For acrylic insert, values of TTF at 50 percent were higher with AICE than AIDR 3D and FIRST, except for Mild level (-6%±6% and -13%±3%, respectively). For bone insert, values of TTF at 50 percent were higher with AICE than AIDR 3D but lower than FIRST (-19%±14%). For both simulated lesions, detectability index values were higher with AICE than AIDR 3D and FIRST (except for Strong level and for the small feature; -21%±14%). Using the Standard level, dose could be reduced by -79% for the small calcification and -57% for the large mass using AICE compared to AIDR 3D. CONCLUSIONS: The new deep learning image reconstruction algorithm AiCE generates an image-quality with less noise and/or less smudged/smooth images and a higher detectability than the AIDR 3D or FIRST algorithms. The outcomes of our phantom study suggest a good potential of dose reduction using AiCE but it should be confirmed clinically in patients.

Comparison of acquisition and iterative reconstruction parameters in abdominal computed tomography-guided procedures: a phantom study.

BACKGROUND: Many computed tomography (CT) navigation systems have been developed to help radiologists improve the accuracy and safety of the procedure. We evaluated the accuracy of one CT computer-assisted guided procedure with different reduction dose protocols. METHODS: A total of 128 punctures were randomly made by two operators on two different anthropomorphic phantoms. The tube voltage was fixed to 100 kVp. Tube currents (mAs) were defined to obtain 4 dose levels: 180 mAs (D1.00), 90 mAs (D0.50), 45 mAs (D0.25) and 15 mAs (D0.10) with respective volume CT dose index (CTDIvol) of 7.02, 3.52, 1.75 and 0.59 mGy. The raw data were reconstructed using level 2 of advanced model-based iterative reconstruction (ADMIRE) (A2) for D1.00, A3 for D0.50, A4 for D0.25 and A5 for D0.10. Two 12-mm targets per phantom were selected. The mean Euclidean distance (EuD) between the tip of the needle and the isocenter of the target was measured for each puncture. The different measures were compared by paired Student's t-tests. RESULTS: The mean EuD was 7.0±3.1 mm for the 128 punctures performed. Regardless of which phantom was considered, no significant difference in accuracy occurred between the 4 dose levels, which were 7.1±3.5 mm for D1.00; 7.1±3.1 mm for D0.50; 7.2±3.0 mm for D0.25 and 6.6±2.6 mm for D0.10. CONCLUSIONS: Abdominal CT-guided procedures, using computer-assisted navigation and iterative reconstruction algorithms, allow precise punctures on anthropomorphic phantoms with a dose reduction of -92% compared to a standard protocol.

Ultra-low-dose chest CT performance for the detection of viral pneumonia patterns during the COVID-19 outbreak period: a monocentric experience.

BACKGROUND: Ultra low dose chest computed tomography (CT) acquisitions have been used for selected emergency room patients with acute dyspnea or minor thoracic trauma. The purpose of this study was to evaluate the diagnostic performance of ultra-low-dose (ULD) chest CT for detecting viral pneumonia patterns compared to standard (STD) dose chest CT. METHODS: All consecutive adult patients with two non-enhanced chest CT acquisitions, one STD and one ULD, for suspicion of viral pneumonia between March 5th and April 2nd 2020 were included. CT results were divided into two groups: non-viral pneumonia CT or compatible with viral pneumonia CT based on viral pneumonia CT patterns: ground-glass opacity (GGO), consolidation, crazy paving, air bronchogram signs and fibrous stripes. The diagnostic performance of ULD CT for suspicion of viral pneumonia was evaluated. For CTs compatible with viral pneumonia, CT pattern detection on ULD CT was assessed and STD CT was used as a reference. RESULTS: The study included 380 patients with 97 CTs (25.5%) compatible with viral pneumonia. The mean effective doses (EDs) were 1.66 (1.29; 2.18) mSv for STD and 0.20 (0.18; 0.22) mSv for ULD CT (P<0.001). The sensitivity and specificity of ULD CT for viral pneumonia detection were 98.9% and 99.0%, respectively. GGO, consolidation and fibrous stripes were equally visible in STD and ULD in 100% (n=97), 36% (n=35) and 23% (n=22) of compatible viral pneumonia-CT patients, respectively. Air bronchogram sign detection was equivalent, concerning 23% (n=22) of patients in STD and 22% (n=21) in ULD. Crazy paving was visible in 24% (n=23) of patients in STD and only 8% (n=8) in ULD (P=0.003). CONCLUSIONS: In comparison to STD dose chest CT, ULD chest CT, with a mean reduction dose of 88.0%, has comparable diagnostic performance for detecting viral pneumonia on CT.

Impact of four kVp combinations available in a dual-source CT on the spectral performance of abdominal imaging: A task-based image quality assessment on phantom data.

PURPOSE: To compare the spectral performance of four combinations of kVp available in a third generation dual-source CT (DSCT) on abdominal imaging. METHODS: An image-quality phantom was scanned with a DSCT using four kVp pairs (tube "A" voltage/tube "B" voltage): 100/Sn150 kVp, 90/Sn150 kVp, 80/Sn150 kVp, and 70/Sn150 kVp, classic parameters and dose level for abdomen examination (CTDIvol : 11 mGy). The noise power spectrum (NPS) and the task-based transfer function (TTF) of two inserts were computed on virtual monochromatic images (VMIs) at 40/50/60/70 keV and for mixed, low-, and high-kVp images. Detectability index (d') was computed on VMIs and mixed images to model the detection task of liver metastasis (LM) and hepatocellular carcinoma (HCC). Iodine quantification accuracy was assessed using the Root Mean Square Deviation (RMSDiodine ) and the iodine bias (IB). RESULTS: Noise magnitude decreased by -55%± 0% between 40 and 70 keV for all kVp pairs. Compared to 70/Sn150 kVp, noise magnitude was increased by 9% ± 0% with 80/Sn150 kVp, by 16% ± 1% with 90/Sn150 kVp and by 24%± 1% with 100/Sn150 kVp. The average NPS spatial frequency (fav ) shifted toward higher frequencies as energy level increased for all kVp pairs. Lowest fav values were found for 70/Sn150 kVp and highest for 100/Sn150 kVp. The value of TTF at 50% (f50 ) shifted toward lower frequencies with increasing energy level. The highest f50  values occurred for 100/Sn150 kVp and the lowest for 80/Sn150 kVp. For both lesions, d' was highest for 70/Sn150 kVp and lowest for 100/Sn150 kVp. Compared to 70/Sn150 kVp, d' decreased by -6% ± 3% with 80/Sn150 kVp, by -11% ± 2% with 90/Sn150 kVp and by -13%± 2% with 100/Sn150 kVp. For all acquisitions, the RSMDiodine and IB were the lowest for 100/Sn150 kVp (0.29 ± 0.10 mg/ml and 0.88 ± 0.30 mg/ml, respectively) and increased when the tube "A" voltage decreased (2.34 ± 0.29 mg/ml for 70/Sn150 kVp and 7.42 ± 0.51 mg/ml respectively). CONCLUSION: 70/Sn150 kVp presented the lowest image noise and highest detectability in VMIs of two small focal liver lesions. 100/Sn150 kVp presented the lowest image noise on mixed images and highest accuracy of iodine quantification in iodine images.

A retrospective comparison of organ dose and effective dose in percutaneous vertebroplasty performed under CT guidance or using a fixed C-arm with a flat-panel detector.

PURPOSE: To compare the organ-dose and effective-dose (E) delivered to the patient during percutaneous vertebroplasty (PVP) of one thoracic or lumbar vertebra performed under CT guidance or using a fixed C-arm. METHODS: Consecutive adult patients undergoing PVP of one vertebra under CT-guidance, with optimized protocol and training of physicians, or using a fixed C-arm were retrospectively included from January 2016 to June 2017. Organ-doses were computed on 16 organs using CT Expo 2.4 software for the CT procedures and PCXMC 2.0 for the fixed C-arm procedures. E was also computed with both software. Dosimetric values per anatomic locations for all procedures were compared using the paired Mann-Whitney-Wilcoxon test. RESULTS: In total, 73 patients were analysed (27 men and 46 women, mean age 78 ± 10 years) among whom 35 (48%) underwent PVP under CT guidance and 38 (52%) PVP using a fixed C-arm. The median E was 11.31 [6.54; 15.82] mSv for all PVPs performed under CT guidance and 5.58 [3.33; 8.71] mSv for fixed C-arm and the differences was significant (p<0.001). For lumbar PVP, the organ doses of stomach, liver and colon were significantly higher with CT-scan than with the fixed C-arm: 97% (p=0.02); 21% (p=0.099) and 375% (p=0.002), respectively. For thoracic PVP, the lung organ dose was significantly higher with CT-scan than with the fixed C-arm (127%; p<0.001) and the oesophagus organ doses were not significantly different (p = 0.626). CONCLUSION: This study showed that the E and the organ dose on directly exposed organs were both higher for PVP performed under CT-guidance than with the fixed C-arm.

Early Results of Unilateral Prostatic Artery Embolization as a Focal Therapy in Patients with Prostate Cancer under Active Surveillance: Cancer Prostate Embolisation, a Pilot Study.

PURPOSE: To evaluate the feasibility of prostatic artery embolization in patients with low-risk prostate cancer (PC) under active surveillance (AS). METHODS: This monocentric prospective pilot study, running from June 2018 to June 2019, included 10 patients with low-risk PC under AS, median age 72 years (range, 62-77 years), with a unilateral focal lesion visible on magnetic resonance (MR) imaging, with Prostate Imaging Reporting and Data System v2 score ≥3/5 confirmed by multiparametric MR imaging-targeted biopsy and Gleason score 6. The patients underwent unilateral prostatic artery embolization with 300-500 µm Embospheres in the affected prostatic lobe. The primary endpoint was technical feasibility (prostate and no off-target ischemia in the imaging). The secondary endpoints included safety, negative biopsies/MR imaging response/functional outcomes at 6 months, and oncologic efficacy at 1 year. RESULTS: Embolization was successfully achieved in all patients; prostate ischemia was confirmed on multiparametric MR imaging, and no off-target ischemia was reported. No major complications were reported. Four patients (40%) presented with both negative targeted and systematic biopsies at 6 months. No lesions were seen on the MR imaging in 30% of patients. The mean International Prostate Symptom Score and International Index of Erectile Function score were 7 and 19 and 5 and 20 at baseline and 6 months, respectively, with no significant difference. Nine patients (90%) were still under AS at 1 year. One patient (10%) had PC progression outside the target lesion and was switched over to curative radiotherapy. CONCLUSIONS: Prostatic artery embolization is feasible and appears safe for prostate cancer patients under AS, with no impact on erectile function or continence status. These results justify the pursuit of further studies.

National dose reference levels in computed tomography-guided interventional procedures-a proposal.

OBJECTIVES: To establish national reference levels (RLs) in interventional procedures under CT guidance as required by the 2013/59/Euratom European Directive. METHODS: Seventeen categories of interventional procedures in thoracic, abdominopelvic, and osteoarticular specialties (percutaneous infiltration, vertebroplasty, biopsy, drainage, tumor destruction) were analyzed. Total dose length product (DLP), number of helical acquisitions (NH), and total DLP for helical, sequential, or fluoroscopic acquisitions were recorded for 10 to 20 patients per procedure at each center. RLs were calculated as the 3rd quartiles of the distributions and target values for optimization process (TVOs) as the median. RLs and TVOs were compared with previously published studies. RESULTS: Results on 5001 procedures from 49 centers confirmed the great variability in patient dose for the same category of procedures. RLs were proposed for the DLPs and NHs in the seventeen categories. RLs in terms of DLP and NH were 375 mGy.cm and 2 NH for spinal or peri-spinal infiltration, 1630 mGy.cm and 3 NH for vertebroplasty, 845 mGy.cm and 4 NH for biopsy, 1950 mGy.cm and 8 NH for destruction of tumors, and 1090 mGy.cm and 5 NH for drainage. DLP and NH increased with the complexity of procedures. CONCLUSIONS: This study was the first nationwide multicentric survey to propose RLs for interventional procedures under CT guidance. Heterogeneity of practice in centers were found with different levels of patient doses for the same procedure. The proposed RLs will allow imaging departments to benchmark their practice with others and optimize their protocols. KEY POINTS: • National reference levels are proposed for 17 categories of interventional procedures under CT guidance. • Reference levels are useful for benchmarking practices and optimizing protocols. • Reference levels are proposed for dose length product and the number of helical acquisitions.

Experimental evaluation of a radiation dose management system-integrated 3D skin dose map by comparison with XR-RV3 Gafchromic® films.

OBJECTIVE: To assess the interactive Skin Dose Map® tool (SDMTool) integrated to the radiation dose management system (RDMS) DoseWatch® with Gafchromic® films for implementation in routine practice. METHODS: A retrospective dose estimation software SDMTool was used to calculate Peak Skin Dose (PSD) and display the patient skin dose distribution. PSD was calculated with a triangle mesh of 0.055 cm2 resolution on ICRP 110 male anthropomorphic phantom and with a square ROI of 1 cm2 on flat phantom. The tool uses Radiation Dose Structured Reports (RDSR) data to model exposure events and calculate the PSD per event. The PSD and the skin dose distribution estimated with SDMTool were evaluated in comparison with Gafchromic® films positioned under the PMMA phantom (20 cm) for 13 configurations. Measurements were performed on a Philips system. Statistical analysis were carried out to compare PSDFilm and PSDSDM. RESULTS: Average differences between PSDFilm and PSDSDM were 6% ±â€¯6% (range from -3% to 22%) for flat phantom and 5% ±â€¯7% (range from -3% to 25%) for ICRP phantom. Concordance was good between the measured PSDFilm and the estimated PSDSDM with Lin's coefficient estimation and 95% Confidence Interval of 0.979 [0.875; 0.984] for flat phantom and 0.977 [0.877; 0.985] for ICRP phantom. Dose map representations are concordant for 11 of the 13 tests on PMMA phantom. Disparities arose from the limitations of the RSDR format: table displacement during fluoroscopy events and the use of wedge filter. CONCLUSION: The results found in this experimental evaluation show that the SDMTool is a suitable alternative to Gafchromic® film to calculate PSD.

Radiation Exposure During Transarterial Chemoembolization: Angio-CT Versus Cone-Beam CT.

INTRODUCTION: Cone-beam computed tomography (CBCT) has been developed to improve reliability of many interventional radiology (IR) procedures performed with Angio system, such as transarterial chemoembolization (TACE). Angio-CT has emerged as a new imaging technology that combines a CT scanner with an Angio system in the same IR suite. The purpose of our study was to compare Angio system with CBCT capability and Angio-CT in terms of patient radiation exposure during TACE procedures. MATERIALS AND METHODS: Consecutive TACE procedures performed between January 2016 and September 2017 with the two imaging modalities (Artis Zeego defining the CBCT group and Infinix-i 4D-CT defining the Angio-CT group) were reviewed. TACE and patient's characteristics and patient radiation exposure parameters were collected. Dose-area products (DAP) and dose-length products (DLP) were converted into effective doses (ED) using conversion factors. Accuracy of tumor targeting and response was retrospectively assessed. RESULTS: A total of 114 TACE procedures in 96 patients were included with 57 procedures in each group. The total ED in the Angio-CT group was 2.5 times lower than that in the CBCT group (median 15.4 vs. 39.2 mSv, p < 0.001). Both 2D ED and 3D ED were lower in the Angio-CT group than in the CBCT group (5.1 vs. 20 mSv, p < 0.001, and 7.4 vs. 17.9 mSv, p < 0.001, respectively). There was no significant difference neither in terms of classes of tumor targeting (p = 0.509) nor in terms of classes of tumor response (p = 0.070) between both groups. CONCLUSION: Angio-CT provides significant decrease in patient effective dose during TACE procedures compared to Angio system with CBCT.

Assessment of combined use of ArcCheck® detector and portal dosimetry for delivery quality assurance of head and neck and prostate volumetric-modulated arc therapy.

PURPOSE: To assess the efficiency of combined use of ArcCheck® detector (AC) and portal dosimetry (PDIP) for delivery quality assurance of head and neck and prostate volumetric-modulated arc therapy. MATERIALS AND METHODS: Measurement processes were studied with the Gamma index method according to three analysis protocols. The detection sensitivity to technical errors of each individual or combined measurement processes was studied by inserting collimator, dose and MLC opening error into five head and neck and five prostate initial treatment plans. A total of 220 plans were created and 660 analyses were conducted by comparing measurements to error free planned dose matrix. RESULTS: For head and neck localization, collimator errors could be detected from 2° for AC and 3° for PDIP. Dose and MLC errors could be detected from 2% and 0.5 mm for AC and PDIP. Depending on the analysis protocol, the detection sensitivity of total simulated errors ranged from 54% to 88% for AC vs 40% to 74% for PDIP and 58% to 92% for the combined process. For the prostate localization, collimator errors could be detected from 4° for AC while they could not be detected by PDIP. Dose and MLC errors could be detected from 3% and 0.5 mm for AC and PDIP. The detection sensitivity of total simulated errors ranged from 30% to 56% for AC vs 16% to 38% for PDIP and 30% to 58% for combined process. CONCLUSION: The combined use of the two measurement processes did not statistically improve the detectability of technical errors compared to use of single process.

Surgeon's and patient's radiation exposure during percutaneous thoraco-lumbar pedicle screw fixation: A prospective multicenter study of 100 cases.

HYPOTHESIS: Percutaneous pedicle screw fixations (PPSF) are increasingly used in spine surgery, minimizing morbidity through less muscle breakdown but at the cost of intraoperative fluoroscopic guidance that generates high radiation exposure. Few studies have been conducted to measure them accurately. MATERIAL AND METHODS: The objective of our study is to quantify, during a PPSF carried out in different experimented centers respecting current radiation protection recommendations, this irradiation at the level of the surgeon and the patient. We have prospectively included 100 FPVP procedures for which we have collected radiation doses from the main operator. For each procedure, the doses of whole-body radiation, lens and extremities were measured. RESULTS: Our results show a mean whole body, extremity and lens exposure dose per procedure reaching 1.7±2.8µSv, 204.7±260.9µSv and 30.5±25.9µSv, respectively. According to these values, the exposure of the surgeon's extremities and lens will exceed the annual limit allowed by the International Commission on Radiological Protection (ICRP) after 2440 and 4840 procedures respectively. CONCLUSION: Recent European guidelines will reduce the maximum annual exposure dose from 150 to 20mSv. The number of surgical procedures to not reach the eye threshold, according to our results, should not exceed 645 procedures per year. Pending the democratization of neuronavigation systems, the use of conventional fluoroscopy exposes the eyes in the first place. Therefore they must be protected by leaded glasses. LEVEL OF PROOF: IV, case series.

Interventional spine procedures under CT guidance: How to reduce patient radiation dose without compromising the successful outcome of the procedure?

This technical note proposes a method to reduce radiation dose for spine interventions under CT guidance without compromising the successful outcome of the procedure. Two consecutive periods of 14months before and after optimization were investigated with 162 and 440 patients, respectively. By optimizing the acquisition parameters (decreased kV and mAs) and appropriately adjusting the reconstruction (kernels, slice thickness, etc) and visualization parameters, image quality was maintained suitable to perform the procedure. By reducing both kV and mAs, dose was reduced by 72% on fluoroscopy mode (i-fluoro) and sequential mode (i-sequence). Moreover, dose was reduced by 58% on helical mode (i-spiral). Depending on the radiologist, the fluoroscopy time was decreased by between 37% and 56%. Acquisitions with i-sequence were less irradiating than the i-fluoro or the i-spiral modes. Radiation doses were reduced by 65% for infiltrations, 51% for vertebral expansions, and 56% for bone biopsies. Median (1st quartile; 3rd quartile) effective dose were 2.1 (1.3; 3.5)mSv, 10.8 (6.7; 18.3)mSv for and 3.0 (2.4; 4.3)mSv, respectively. Radiologists reported "satisfactory" image quality. During interventional spine procedures under CT scan, reducing kV and mAs associated with the use of i-sequence substantially reduces patient dose.

Value of ultra-low-dose chest CT with iterative reconstruction for selected emergency room patients with acute dyspnea.

OBJECTIVE: To compare the diagnostic confidence between low-dose computed-tomography (LDCT) and ultra-low-dose CT (ULDCT) of the chest on a single source CT system (SSCT) for patients with acute dyspnoea. MATERIALS AND METHODS: One hundred thirty-three consecutive dyspnoeic patients referred from the emergency room (ER) were selected to undergo two sequential non-enhanced chest CT acquisitions: LDCT first acquisition (100kVp and 60mAs), followed by ULDCT (100kVp±20 and 10mAs). Images were reconstructed with sinogram affirmed reconstruction (SAFIRE). Objective and subjective image quality assessments were made. Two radiologists evaluated subjective image quality and the level of diagnostic confidence as certain or uncertain. RESULTS: The mean effective doses (ED) were 1.164±0.403 and 0.182±0.028mSv for LDCT and ULDCT, respectively. Objective image quality improved significantly on lung images of ULDCT compared with LDCT (p<0.05). Subjective image quality was rated excellent/good in 90% of patients with BMI=25kg/m(2) for ULDCT. The level of diagnostic confidence was "certain" in all cases for both radiologists with excellent inter-observer agreement (k=1). CONCLUSION: Chest ULDCT with SAFIRE on a SSCT allows a high level diagnostic confidence for the evaluation of selected acute dyspnoeic patients.