Impact of the automatic tube current modulation (ATCM) system on virtual monoenergetic image quality for dual-source CT: A phantom study.

PURPOSE: To assess the impact of the automatic tube current modulation (ATCM) on virtual monoenergetic images (VMIs) quality in dual-source CT(DSCT). MATERIALS AND METHODS: Acquisitions were performed on DSCT using the Mercury phantom. The acquisition parameters for an abdomen-pelvic examination with single-energy CT(SECT) and dual-energy CT(DECT) imaging were used. Acquisitions were performed for each imaging mode using fixed mAs and ATCM. The mAs value was set to obtain a volume CT dose index of 11 mGy in fixed mAs acquisitions. This value was used as the reference mAs in ATCM acquisitions. The noise power spectrum and task-based transfer function at 40,50,60 and 70 keV levels were computed on VMIs and SECT images. The detectability index (d') was calculated for a lesion with an iodine concentration of 10 mg/mL. RESULTS: The noise magnitude on VMIs was higher with the ATCM system than with fixed mAs for all energy levels and section diameters of 21,26 and 31 cm. The noise texture and spatial resolution were similar between the fixed mAs and ATCM acquisitions for both imaging modes. The d' values were lower for all energy levels with ATCM than with fixed mAs acquisitions for 21 and 26 cm diameters by -39.82 ± 9.32%, similar at 31 cm diameter -4.13 ± 0.24% and higher at 36 cm diameter 10.40 ± 6.69%. It was higher on VMIs at all energy levels compared to SECT images. CONCLUSIONS: The ATCM system could be used with DECT imaging to optimize patient exposure without changing the noise texture and spatial resolution of VMIs compared to fixed mAs and SECT.

Coronary calcium scoring potential of large field-of-view spectral photon-counting CT: a phantom study.

OBJECTIVE: The aim of the current study was, first, to assess the coronary artery calcium (CAC) scoring potential of spectral photon-counting CT (SPCCT) in comparison with computed tomography (CT) for routine clinical protocols. Second, improved CAC detection and quantification at reduced slice thickness were assessed. METHODS: Raw data was acquired and reconstructed with several combinations of reduced slice thickness and increasing strengths of iterative reconstruction (IR) for both CT systems with routine clinical CAC protocols for CT. Two CAC-containing cylindrical inserts, consisting of CAC of different densities and sizes, were placed in an anthropomorphic phantom. A specific CAC was detectable when 3 or more connected voxels exceeded the CAC scoring threshold of 130 Hounsfield units (HU). For all reconstructions, total CAC detectability was compared between both CT systems. Significant differences in CAC quantification (Agatston and volume scores) were assessed with Mann-Whitney U tests. Furthermore, volume scores were compared with the known CAC physical. RESULTS: CAC scores for routine clinical protocols were comparable between SPCCT and CT. SPCCT showed 34% and 4% higher detectability of CAC for the small and large phantom, respectively. At reduced slice thickness, CAC detection increased by 142% and 169% for CT and SPCCT, respectively. In comparison with CT, volume scores from SPCCT were more comparable with the physical volume of the CAC. CONCLUSION: CAC scores using routine clinical protocols are comparable between conventional CT and SPCCT. The increased spatial resolution of SPCCT allows for increased detectability and more accurate CAC volume estimation. KEY POINTS: • Coronary artery calcium scores using routine clinical protocols are comparable between conventional CT and spectral photon-counting CT. • In comparison with conventional CT, increased coronary artery calcium detectability was shown for spectral photon-counting CT due to increased spatial resolution. • Volumes scores were more accurately determined with spectral photon-counting CT.

Performance of four dual-energy CT platforms for abdominal imaging: a task-based image quality assessment based on phantom data.

OBJECTIVES: To compare the spectral performance of dual-energy CT (DECT) platforms using task-based image quality assessment based on phantom data. MATERIALS AND METHODS: Two CT phantoms were scanned on four DECT platforms: fast kV-switching CT (KVSCT), split filter CT (SFCT), dual-source CT (DSCT), and dual-layer CT (DLCT). Acquisitions on each phantom were performed using classical parameters of abdomen-pelvic examination and a CTDIvol at 10 mGy. Noise power spectrum (NPS) and task-based transfer function (TTF) were evaluated from 40 to 140 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: The noise magnitude decreased from 40 to 70 keV for all DECT platforms, and the highest noise magnitude values were found for KVSCT and SFCT and the lowest for DSCT and DLCT. The average NPS spatial frequency shifted towards lower frequencies as the energy level increased for all DECT platforms, smoothing the image texture. TTF values decreased with the increase of keV deteriorating the spatial resolution. For both simulated lesions, higher detectability (d' value) was obtained at 40 keV for DLCT, DSCT, and SFCT but at 70 keV for KVSCT. The detectability of both simulated lesions was highest for DLCT and DSCT. CONCLUSION: Highest detectability was found for DLCT for the lowest energy levels. The task-based image quality assessment used for the first time for DECT acquisitions showed the benefit of using low keV for the detection of contrast-enhanced lesions. KEY POINTS: • Detectability of both simulated contrast-enhanced lesions was higher for dual-layer CT for the lowest energy levels. • The image noise increased and the image texture changed for the lowest energy levels. • The detectability of both simulated contrast-enhanced lesions was highest at 40 keV for all dual-energy CT platforms except for fast kV-switching platform.

Impact of iterative reconstructions on image quality and detectability of focal liver lesions in low-energy monochromatic images.

PURPOSE: To assess the impact of iterative reconstructions on image quality and detectability of focal liver lesions in low-energy monochromatic images from a Fast kV-Switching Dual Energy CT (KVSCT) platform. METHODS: Acquisitions on an image-quality phantom were performed using a KVSCT for three dose levels (CTDIvol:12.72/10.76/8.79 mGy). Raw data were reconstructed for five energy levels (40/50/60/70/80 keV) using Filtered Back Projection (FBP) and four levels of ASIR (ASIR30/ASIR50/ASIR70/ASIR100). Noise power spectrum (NPS) and task-based transfer function (TTF) were measured before computing a Detectability index (d') to model the detection task of liver metastasis (LM) and hepatocellular carcinoma (HCC) as function of keV. RESULTS: From 40 to 70 keV, noise-magnitude was reduced on average by -68% ± 1% with FBP; -61% ± 3% with ASIR50 and -52% ± 6% with ASIR100. The mean spatial frequency of the NPS decreased when the energy level decreased and the iterative level increased. TTF values at 50% decreased as the energy level increased and as the percentage of ASIR increased. The detectability of both lesions increased with increasing dose level and percentage of ASIR. For the LM, d' peaked at 70 keV for all reconstruction types, except for ASIR70 at 12.72 mGy and ASIR100, where d' peaked at 50 keV. For HCC, d' peaked at 60 keV for FBP and ASIR30 but peaked at 50 keV for ASIR50, ASIR70 and ASIR100. CONCLUSIONS: Using percentage of ASIR above 50% at low-energy monochromatic images could limit the increase of noise-magnitude, benefit from spatial resolution improvement and hence enhance detectability of subtle low contrast focal liver lesions such as HCC.

Impact of ultra-low dose CT acquisition on semi-automated RECIST tool in the evaluation of malignant focal liver lesions.

PURPOSE: To compare the evaluation of malignant focal liver lesions (FLLs) using a semi-automated RECIST tool with a standard and an ultra-low dose (ULD) computed tomography (CT) protocol. MATERIALS AND METHODS: Thirty-four patients with malignant FLLs underwent two abdominal-pelvic CT examinations one using a standard protocol and one using an ULD protocol. There were 23 men and 11 women with a mean age 64.3±14.4 (SD) years (range: 22-91 years). Dosimetric indicators were recorded, and effective dose was calculated for both examinations. Mean malignant FLL attenuation, image noise and contrast-to-noise-ratio (CNR) were compared. The largest malignant FLL per patient was evaluated using the semi-automated RECIST tool to determine longest axis length, longest orthogonal axis length, volume and World Health Organisation area. RESULTS: Dosimetric values were significantly reduced by -56% with ULD compared to standard protocol. No differences in mean malignant FLL attenuation values were found between the two protocols. Image noise was significantly increased for all locations (P<0.05) with ULD compared to standard protocol, and CNR was significantly reduced (P<0.05). On the 34 malignant FLLs analyzed, six semi-automated shapes non-concordant with radiologist's visual impression were highlighted with the software, including one FLL (1/34; 3%) with standard CT acquisition only, three FLLs (3/34; 9%) with ULD CT acquisition only and two FLLs (2/34; 6%) with both CT acquisitions. After manual editing, the concordance of the values of the studied criteria between both acquisitions was good and no significant difference was reported. CONCLUSION: Semi-automated RECIST tool demonstrates good performances using ULD CT protocol. It could be used in routine clinical practice with a ULD protocol for follow-up studies in patients with known malignant FLL.

Effect of tin filter-based spectral shaping CT on image quality and radiation dose for routine use on ultralow-dose CT protocols: A phantom study.

PURPOSE: The purpose of this study was to assess the impact of tin filter (TF) on X-ray beam quality, image quality and radiation dose and its suitability for routine use for chest and lumbar-spine/pelvis-hip ultralow-dose (ULD) CT examination protocols. MATERIALS AND METHODS: The X-ray beam quality was determined by measuring the half-value layer (HVL) and calculating the mean weighted energy for 100, 120, 150kVp (using standard filtration) and for 100 and 150kVp using TF (Sn100kVp and Sn150kVp, respectively). Acquisitions were performed on a phantom at four dose levels for each previously definedkVp. The mean attenuation (NCT), noise-power-spectrum (NPS) and task-based transfer function (TTF) were computed. The detectability index (d') was computed to model the detection of two lesions in spine and pelvic/hip examination and two for chest exploration. Image quality and detectability using a TF were assessed for two routinely used ULD protocols. RESULTS: The HVL and mean weighted energy increased using a TF for the same tube voltage. Using a TF for the same tube voltage changed NCT for bone and acrylic inserts, decreased the NPS peak without changing the NPS spatial frequency and increased the TTF values. The d' values were improved using a TF and with the dose increase. d' values of all modeled lesions were improved using Sn100kVp and Sn150kVp for the lumbar-spine/pelvis-hip and chest ULD protocols except for sclerotic bone lesion using Sn150kVp. CONCLUSION: The use of TF increases the X-ray beam quality and improves the image quality characteristics in phantom images, thus appearing as a promising tool for reducing dose and/or improving the image quality of ULD protocols.

CT dose optimization for the detection of pulmonary arteriovenous malformation (PAVM): A phantom study.

PURPOSE: To determine the lowest suitable dose level for the detection of pulmonary arteriovenous malformation (PAVM) using a task-based image quality assessment. MATERIAL AND METHODS: A phantom was scanned using the standard chest protocol (STD) and 4 other ultra-low dose protocols (ULD) using various kVp. Raw data were reconstructed using level 5 of the hybrid iterative reconstruction algorithm (iDose4) for the STD protocol, and level 6 of iDose4 and levels 1 to 3 of model-based iterative reconstruction (IMR) for the ULD protocols. Both quantitative criteria and qualitative analysis were used to compare protocols. Noise-power-spectrum and Task-based transfer function were computed using imQuest software. The detectability-index (d') was computed for the detection of PAVM. A subjective analysis was performed by 2 chest radiologists to validate the image-quality obtained on the anthropomorphic phantom for all protocols. RESULTS: Similar d' values were found for ULD-140 using iDose4 6 compared to STD protocol. Greater d' values were found for all ULD protocols using IMR compared to STD. Subjective image quality was rated as acceptable to excellent for ULD-140 and ULD-120 for all reconstruction types, for ULD-100 and ULD-80 using IMR2, and for ULD-100 using IMR1. Image smoothing was poor for IMR3 for ULD-100 and ULD-80. Finally, the ULD-80 protocol reconstructed with IMR2 was chosen for the detection of PAVM. With this protocol, the dose (CTDIvol of 0.3mGy) was reduced by 91% compared with the STD protocol. CONCLUSION: A dose level as low as 0.3mGy reconstructed with IMR2 provides an image quality suitable for the detection of PAVM.

Optimization of radiation dose for CT detection of lytic and sclerotic bone lesions: a phantom study.

OBJECTIVES: To determine the best compromise between low radiation dose and suitable image quality for the detection of lytic and sclerotic bone lesions of the lumbar spine and pelvis. METHODS: A phantom was scanned using the routine protocol (STD, 13 mGy) and six decreasing dose levels. Raw data were reconstructed using level 3 of iterative reconstruction (IR3) with 1-mm slice thickness for the STD protocol and highest IR levels with 3-mm slice thickness for the others. CTDIvol was used for radiation dose assessment. Quantitative criteria (noise power spectrum [NPS], task-based transfer function [TTF], and the detectability index [d']), as well as qualitative analysis, were used to compare protocols. NPS and TTF were computed using specific software (imQuest). d' was computed for two imaging tasks: lytic and sclerotic bone lesions. A subjective analysis was performed to validate the image quality obtained on the anthropomorphic phantom with the different dose values. RESULTS: Similar d' values were found for CTDIvol from 3 to 4 mGy with IR4 and from 1 to 2 mGy for IR5 compared with d' values using the STD protocol. Image quality was validated subjectively for IR4 but rejected for IR5 (image smoothing). Finally, for the same d', the dose was reduced by 74% compared with the STD protocol, with the CTDIvol being 3.4 mGy for the lumbar spine and for the pelvis. CONCLUSION: A dose level as low as 3.4 mGy, in association with high levels of IR, provides suitable image quality for the detection of lytic and sclerotic bone lesions of the lumbar spine and pelvis. KEY POINTS: • A CTDI volof 3.4 mGy, in association with high iterative reconstruction level, provides suitable image quality for the detection of lytic and sclerotic bone lesions, both at objective and subjective analysis. • Compared with the standard protocol, radiation dose can be reduced up to 74% for the lumbar spine and pelvis. • A task-based image quality assessment using  the detectability index represents an objective method for the assessment of image quality and bridges the gap between complex physical metrics and subjective image analysis.

CT iterative reconstruction algorithms: a task-based image quality assessment.

PURPOSE: To assess the dose performance in terms of image quality of filtered back projection (FBP) and two generations of iterative reconstruction (IR) algorithms developed by the most common CT vendors. MATERIALS AND METHODS: We used four CT systems equipped with a hybrid/statistical IR (H/SIR) and a full/partial/advanced model-based IR (MBIR) algorithms. Acquisitions were performed on an ACR phantom at five dose levels. Raw data were reconstructed using a standard soft tissue kernel for FBP and one iterative level of the two IR algorithm generations. The noise power spectrum (NPS) and the task-based transfer function (TTF) were computed. A detectability index (d') was computed to model the detection task of a large mass in the liver (large feature; 120 HU and 25-mm diameter) and a small calcification (small feature; 500 HU and 1.5-mm diameter). RESULTS: With H/SIR, the highest values of d' for both features were found for Siemens, then for Canon and the lowest values for Philips and GE. For the large feature, potential dose reductions with MBIR compared with H/SIR were - 35% for GE, - 62% for Philips, and - 13% for Siemens; for the small feature, corresponding reductions were - 45%, - 78%, and - 14%, respectively. With the Canon system, a potential dose reduction of - 32% was observed only for the small feature with MBIR compared with the H/SIR algorithm. For the large feature, the dose increased by 100%. CONCLUSION: This multivendor comparison of several versions of IR algorithms allowed to compare the different evolution within each vendor. The use of d' is highly adapted and robust for an optimization process. KEY POINTS: • The performance of four CT systems was evaluated by using imQuest software to assess noise characteristic, spatial resolution, and lesion detection. • Two task functions were defined to model the detection task of a large mass in the liver and a small calcification. • The advantage of task-based image quality assessment for radiologists is that it does not include only complicated metrics, but also clinically meaningful image quality.

Noise assessment across two generations of iterative reconstruction algorithms of three manufacturers using bone reconstruction kernel.

PURPOSE: To compare the noise-magnitude and noise-texture obtained using strong kernel across two generations of iterative reconstruction (IR) algorithms proposed by three manufacturers. MATERIALS AND METHODS: Five computed tomography (CT) systems equipped with two generations of IR algorithm (hybrid/statistical IR [H/SIR] or full/partial model-based IR [MBIR]) were compared. Acquisitions on Catphan 600 phantom were performed at 120kV and three dose levels (CTDIvol: 3, 7 and 12mGy). Raw data were reconstructed using standard "bone" kernel for filtered back projection and one iterative level of two generations of IR algorithms. Contrast-to-noise ratio (CNR) was computed using three regions of interest placed semi-automatically: two placed in the low-density polyethylene and Teflon inserts and another placed on the solid water. Noise power spectrum (NPS) was computed to assess the NPS-peak and noise-texture. RESULTS: CNR was significantly greater in MBIR compared to H/SIR algorithms for all CT systems (P<0.01). CNR were improved on average from H/SIR to MBIR of 36±14% [SD] (range: 24-57%) for GE-Healthcare, 109±19 [SD] % (range: 89-139%) for Philips Healthcare and 42±5 [SD] % (range: 36-47%) for Siemens Healthineers. The mean NPS peak decreased from H/SIR to MBIR by -41±6 [SD] % (range: -47--35%) for GE Healthcare, -79±3 [SD] % (range: -82--76%) for Philips Healthcare and -52±2 [SD] % (range: -54--51%) for Siemens Healthineers systems. NPS spatial frequencies were greater with MBIR than with H/SIR for Philips Healthcare (20 ± 2 [SD] %; range: 19-22%) and for Siemens Healthineers (9±5 [SD] %; range: 4-14%) but lower for GE Healthcare (-17±3 [SD] %; range: -14--20%). CONCLUSION: Using bone kernel with recent MBIR algorithms reduces the noise-magnitude for all CT systems assessed. Noise texture shifted towards high frequency for Siemens Healthineers and Philips Healthcare but the opposite for GE Healthcare.

Comparison of noise-magnitude and noise-texture across two generations of iterative reconstruction algorithms from three manufacturers.

PURPOSE: To compare the noise-magnitude and noise-texture across two generations of iterative reconstruction (IR) algorithms proposed by three manufacturers according to the dose level. MATERIALS AND METHODS: Five computed tomography (CT) systems equipped with two generations of IR algorithms (hybrid/statistical IR [H/SIR] or full/partial model-based IR [MBIR]) were compared. Acquisitions on Catphan 600 phantom were performed at 120kV and three dose levels (3-, 7- and 12-mGy). Raw data were reconstructed using standard "soft tissue" kernel for filtered back projection and one iterative level of two generations of IR algorithms. Contrast to-noise-ratio (CNR) was computed using three regions of interest: two of them placed in the low-density polyethylene (LDPE) and Teflon® inserts and another placed on the solid water. Noise power spectrum (NPS) was computed to assess the noise-magnitude (NPS peak) and noise-texture (NPS spatial frequency). RESULTS: CNR increased significantly in MBIR compared to H/SIR algorithms for General-Electric (GE) Healthcare (45%±12 [SD]) and Philips Healthcare systems (62%±11 [SD]) (P<0.001). Regarding Siemens Healthineers systems, CNR of MBIR was significantly lower than that of H/SIR (mean difference: -4%±5 [SD]) (P<0.001) for Teflon® insert but not for LDPE insert (mean difference: -4%±7 [SD]) (P=N.S.). NPS peaks were lower with MBIR than with H/SIR for GE Healthcare (-42%±8 [SD]) and Philips Healthcare (-75%±4 [SD]) systems, whereas it was greater with MBIR than with H/SIR for Siemens Healthineers (13%±11 [SD]) systems. NPS spatial frequencies were higher with MBIR than with H/SIR for Siemens (14%±10 [SD]) but lower for others (-17%±5 [SD] for GE Healthineers and -55%±3 [SD] for Philips Healthcare systems). CONCLUSION: This study demonstrates that recent MBIR algorithms, by comparison with the preceding generation, differ according to the main manufacturers with respect to noise-magnitude and noise-texture.

Influence of iterative reconstruction and dose levels on metallic artifact reduction: A phantom study within four CT systems.

PURPOSE: To compare metallic artifact reduction (MAR) algorithms proposed by four vendors according to the delivered dose and iterative level using a phantom study. METHODS: Four CT systems (Revolution GSI®, Ingenuity Elite®, Somatom Edge®, and Aquilion Prime®) equipped with MAR algorithms (Smart MAR®, O-MAR®, iMAR®, and SEMAR®) were compared. Acquisitions were performed with CIRS model 062M Phantom containing a titanium rod core insert using 120kV and two dose levels (3 and 7mGy). Images were reconstructed with and without MAR algorithms using standard "soft tissue" kernel for filtered back projection (FBP) and intermediary iterative level. Artifact propagation was assessed by counting the number of pixels containing a HU outside a defined threshold interval (>100HU and<-80 HU). Artifact correction was evaluated by computing the differences between images with and without MAR. RESULTS: Accuracy of NCT values increased significantly using MAR algorithms, IR, and high dose levels (P<0.001). Image noise reduced -31±15 (SD) % (range: -50%;-14%) with Smart-MAR®, -28±3 (SD) % (range -31%; -25%) with O-MAR®, -32±7 (SD) % (range: -40%; -24%) with iMARCN®, -52±8 (SD) % (range: -60%; -42%) with iMARTH® and -29±6 (SD) % (range: -37%; -23%) with SEMAR®. The number of pixels outside the threshold interval was also reduced using MAR algorithms. Each MAR algorithm corrected in distinct patterns, with satisfactory artifact correction for all MAR algorithms. CONCLUSION: This study demonstrates that artifact correction using MAR algorithms differs according to the main manufacturers, although corrections are satisfactory for all systems. Corrections also improved by using IR and increasing the dose level.

Patient dose reference levels in surgery: a multicenter study.

OBJECTIVE: To assess diagnostic reference levels (DRLs) in surgery for the most frequent procedures as required by the European Directive 2013/59/Euratom. METHODS: A survey was conducted in six centers. Eight orthopedic, urology and gastrointestinal surgical procedures were analyzed. Kerma area product (KAP) and fluoroscopy time (FT) were recorded for 50 patients (except for elbow: 30 patients) per procedure and per center from September 2016 to September 2017. DRLs were calculated as the 3rd quartiles of the distributions. For shoulder surgery, DRLs were defined according to the complexity of the procedure. For hand/wrist and foot/ankle surgery, DRLs were defined according to the technology (conventional C-arm vs. mini-C-arm). RESULTS: Results of 1870 procedures were retrieved. DRLs were calculated for the two dosimetric indicators and the eight procedures. DRLs were 2130 mGy.cm2 and 1.4 min for proximal femoral intramedullary nail, 1185 mGy.cm2 and 0.9 min for laparoscopic cholecystectomy and 2195 mGy.cm2 and 1.0 min for double-J (pigtail) ureteral catheter insertion. For shoulder surgery, KAP and FT were significantly higher (p < 0.05) for intramedullary procedures compared to extramedullary procedures. For hand/wrist and foot/ankle surgery, the KAPs were significantly higher (p < 0.05) with conventional C-arm compared to mini-C-arm, but FTs were not significantly different (p: not significant). CONCLUSION: This study reports DRLs in surgery based on a multicentric survey. KEY POINTS: • Delivered dose in surgery depends on procedure, practice and patient. • Diagnostic reference levels (DRLs) are proposed for eight surgical procedures. • DRLs are useful to benchmark practices and optimize protocols.

Correction to: Patient dose reference levels in surgery: a multicenter study.

The original version of this article, published on 01 August 2018, unfortunately contained two mistakes.

Decreased operator X-ray exposure by optimized fluoroscopy during radiofrequency ablation of common atrial flutter.

PURPOSE: To evaluate operator and patient irradiation during radiofrequency ablation (RFA) of common atrial flutter (AF) using three different fluoroscopy settings. MATERIAL AND METHOD: A total of 38 patients who underwent RFA of AF with three different fluoroscopy settings (low dose, standard dose and collimated field) were included. Twelve patients (11 men, 1 woman; mean age, 67±12 [SD]years) were included in the low dose group (3.75 frames per second), 13 patients (13 men; mean age, 66±8 [SD]years) were included in the standard dose group (7.5 frames per second) and 13 patients (13 men; mean age, 71±12 [SD]years) were included in the collimated field group (7.5 frames per second). Operator and patient exposure were compared between groups. RESULT: No differences in procedure time and radiation exposure were found between the three groups. In the low dose group, mean operator X-ray exposures of eye-lens (4.7±2.9 [SD]µSv/h; range: 0.9-10.5µSv/h), whole body (1.6±1.2 [SD]µSv/h; range 0.5-3.6µSv/h) and hand skin (11.1±10.8 [SD] µSv/h; range 2.4-35.4µSv/h) were significantly lower than those in the standard dose group (P<0.001). Significant patient dose reduction was found between low dose group (0.7±0.4 [SD]Gy/h; range: 0.3-0.9Gy/h) and standard (1.7±0.5 [SD]Gy/h; range: 0.8 to 3.9Gy/h) and collimated (1.8±0.5 [SD]Gy/h; range: 0.7-3.0Gy/h) groups (P<0.01). CONCLUSION: The use of a low dose setting (3.75 f/s) during fluoroscopy dramatically reduces operator's irradiation during RFA of AF by a mean of 90%.

Detection and characterization of focal liver lesions with ultra-low dose computed tomography in neoplastic patients.

PURPOSE: The purpose of this study was to evaluate and compare the diagnostic accuracy of ultra-low dose (ULD) computed tomography (CT) with that of standard dose (STD) CT in the detection and characterization of focal liver lesions in neoplastic patients. MATERIALS AND METHODS: A total of 177 neoplastic patients who underwent two abdominopelvic CT examinations (one with STD and one with ULD protocol) for suspected focal liver lesions were included. There were 103 men and 74 women with a mean age of 64.6±14.4 (SD) (range: 19-93 years). Raw data images were reconstructed with iterative reconstruction. Dose length product (DLP) and effective dose for both protocols were compared. Images were independently evaluated by two radiologists for image-quality, diagnostic quality, and confidence level. RESULTS: DLP for STD and ULD were respectively 215.4±92.0 (SD) mGy·cm (range: 76-599mGy·cm) and 90.7±37.2 (SD) mGy·cm (range: 32-254mGy·cm). Effective dose for STD and ULD CT were 3.2±1.4 (SD) mSv (range: 1.1-9.0mSv) and 1.4±0.6 (SD) mSv (range: 0.5 to 3.8mSv). A significant 58% dose reduction was found between the two protocols (P<0.05). Noise, signal-to-noise ratio and contrast-to-noise ratio were higher with the ULD protocol compared to the STD protocol. No differences in subjective image quality were found between the two protocols. STD CT revealed focal liver lesions in 80 patients and ULD CT in 70 patients (P<0.05). ULD protocol resulted in a sensitivity of 83.8% and a specificity of 96.9% for the diagnosis of focal liver lesions although it was not able to characterize them properly (Se 62.5%). CONCLUSION: STD CT helps detect and characterize focal liver lesions. ULD CT offers good performance to detect focal liver lesions but with lower performances for lesion characterization.

Assessment of patient's peak skin dose during abdominopelvic embolization using radiochromic (Gafchromic) films.

PURPOSE: To assess the value of the routine use of radiochromic films in abdominopelvic embolization procedures to improve patient follow-up. METHODS: A total of 55 patients who underwent transcatheter abdominopelvic embolization were prospectively included. Six types of procedures were evaluated including hepatic chemoembolization (HCE), gonadal veins embolization (GVE), uterine elective embolization (UEE), uterine urgent embolization (UUE), abdominal elective embolization (AEE), and abdominal urgent embolization (AUE). Dosimetric indicators (DIs) such as air-kerma (AK) and kerma-area-product (KAP) were collected and peak skin dose (PSD) was measured with radiochromic films. Correlations between PSD and DIs were searched for. RESULTS: The mean (±standard deviation [SD]) PSD for the various procedures were: 1033±502 mGy for HCE; 476±271 mGy for GVE; 460±171 mGy for UEE; 531±263 mGy for UUE; 708±896 mGy for AEE; 683±392 mGy for AUE. Strong correlations were observed between PSD and DIs (r=0.974 for AK and r=0.925 for KAP). PSD was>2Gy in one procedure and all procedures (7/132) procedures resulted in AK>2Gy, mostly for HCE and AEE. CONCLUSION: Dosimetry using radiochromic film is only appropriate for HCE, AEE and AUE, whereas dose-mapping systems present a more suitable solution for all embolizations including those with AK that occasionally exceed 2Gy.

Diagnostic performance of a low dose triple rule-out CT angiography using SAFIRE in emergency department.

OBJECTIVES: To compare the diagnostic performance of "triple rule out" CT angiography (TRO-CTA) at 100kVp using sinogram affirmed iterative reconstruction (SAFIRE) with TRO-CTA at 120kVp using filtered back projection (FBP) in patients with acute chest pain. METHODS: Consecutive non-prepared patients from a single radiological emergency department, referred for acute chest pain evaluation with TRO-CTA, were randomly assigned to two different TRO-CTA protocols. Fifty patients (66% men; mean age, 66.6±19.0 [SD] years [range: 24-97years]) had TRO-CTA at 120kVp with FBP and 97 patients (67% men; mean age, 62.8±17.9 [SD] years [range: 24-93years]) had TRO-CTA at 100kVp with SAFIRE. Two radiologists reviewed the TRO-CTA images for pathologic findings and degree of diagnostic confidence. Image noise, vessel attenuation value, signal-to-noise and contrast-to-noise ratios in five main thoracic arteries were measured for objective and subjective analysis. RESULTS: A total of 147 patients (98 men, 49 women; mean age, 64.7±18.4 [SD] [range, 24-97years) were included with good diagnostic confidence and equivalent pathological findings between the two TRO-CTA protocols. Objective and subjective analysis were identical between protocols and radiologists, except for vessel attenuation in the ascending aorta (P=0.02) and image noise in the pulmonary trunk (P=0.04). The effective radiation dose decreased significantly by 34% in the low dose TRO-CTA using SAFIRE protocol (5.7±2.7 vs 8.6±6.1mSv; P=4.7×10-6). CONCLUSIONS: Low dose TRO-CTA protocol using SAFIRE allows a high confidence diagnostic level with the benefit of a 34% radiation dose decrease compared with a standard TRO-CTA protocol using FBP.

Assessment of peak skin dose in interventional cardiology: A comparison between Gafchromic film and dosimetric software em.dose.

OBJECTIVE: To compare the use of a dose mapping software to Gafchromic film measurement for a simplified peak skin dose (PSD) estimation in interventional cardiology procedure. METHODS: The study was conducted on a total of 40 cardiac procedures (20 complex coronary angioplasty of chronic total occlusion (CTO) and 20 coronary angiography and coronary angioplasty (CA-PTCA)) conducted between January 2014 to December 2015. PSD measurement (PSDFilm) was obtained by placing XR-RV3 Gafchromic under the patient's back for each procedure. PSD (PSDem.dose) was computed with the software em.dose©. The calculation was performed on the dose metrics collected from the private dose report of each procedure. Two calculation methods (method A: fluoroscopic kerma equally spread on cine acquisition and B: fluoroscopic kerma is added to one air Kerma cine acquisition that contributes to the PSD) were used to calculate the fluoroscopic dose contribution as fluoroscopic data were not recorded in our interventional room. Statistical analyses were carried out to compare PSDFilm and PSDem.dose. RESULTS: The PSDFilm median (1st quartile; 3rd quartile) was 0.251(0.190;0.336)Gy for CA-PTCA and 1.453(0.767;2.011)Gy for CTO. For method-A, the PSDem.dose was 0.248(0.182;0.369)Gy for CA-PTCA and 1.601(0.892;2.178)Gy for CTO, and 0.267(0.223;0.446)Gy and 1.75 (0.912;2.584)Gy for method-B, respectively. For the two methods, the correlation between PSDFilm and PSDem.dose was strong. For all cardiology procedures investigated, the mean deviation between PSDFilm and PSDem.dose was 3.4±21.1% for method-A and 17.3%±23.9% for method-B. CONCLUSION: The dose mapping software is convenient to calculate peak skin dose in interventional cardiology.