PCD-CT enables contrast media reduction in abdominal imaging compared to an individualized kV-adapted contrast media injection protocol on EID-CT.

OBJECTIVES: This study aims to demonstrate reduced iodine contrast media (CM) in routine abdominal CT scans in portal venous phase (PVP) using a photon-counting detector CT (PCD-CT) compared to total body weight (TBW) and kV-adapted CM injection protocols on a state-of-the-art energy-integrating detector CT (EID-CT) while maintaining sufficient image quality (IQ). MATERIALS AND METHODS: Consecutive contrast-enhanced abdominal PVP CT scans from an EID-CT (Nov 2022-March 2024) and a PCD-CT (Sep 2023-Dec 2023) were compared. CM parameters (total iodine load (TIL), iodine delivery rate (IDR) and dosing factor (DF)) were reported. An individualized acquisition and CM injection protocol based on TBW and kV was applied for the EID-CT and a TBW adapted CM injection protocol was used for the PCD-CT. Objective IQ was evaluated with mean attenuation (Hounsfield Units, HU), signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR)). Subjective IQ was assessed via a 5-point Likert scale by 2 expert readers based on diagnostic confidence. RESULTS: Based on 91 EID-CT scans and 102 PCD-CT scans a TIL reduction of 20.1 % was observed for PCD-CT. PCD-CT demonstrated significantly higher SNR (9.9 ± 1.7 vs. 9.1 ± 1.8, p < 0.001) and CNR (5.1 ± 1.7 vs. 4.3 ± 1.3, p < 0.001) compared to EID-CT. Subjective IQ assessment showed that all scans had sufficient diagnostic IQ. CONCLUSIONS: PCD-CT allows for CM reduction while providing higher SNR and CNR compared to EID-CT, using clinical individualized scan and CM injection protocols.

Individually Body Weight-Adapted Contrast Media Application in Computed Tomography Imaging of the Liver at 90 kVp.

OBJECTIVES: The aim of the present study was to evaluate the attenuation and image quality (IQ) of a body weight-adapted contrast media (CM) protocol compared with a fixed injection protocol in computed tomography (CT) of the liver at 90 kV. MATERIALS AND METHODS: One hundred ninety-nine consecutive patients referred for abdominal CT imaging in portal venous phase were included. Group 1 (n = 100) received a fixed CM dose with a total iodine load (TIL) of 33 g I at a flow rate of 3.5 mL/s, resulting in an iodine delivery rate (IDR) of 1.05 g I/s. Group 2 (n = 99) received a body weight-adapted CM protocol with a dosing factor of 0.4 g I/kg with a subsequent TIL adapted to the patients' weight. Injection time of 30 seconds was kept identical for all patients. Therefore, flow rate and IDR changed with different body weight. Patients were divided into 3 weight categories; 70 kg or less, 71 to 85 kg, and 86 kg or greater. Attenuation (HU) in 3 segments of the liver, signal-to-noise ratio, and contrast-to-noise ratio were used to evaluate objective IQ. Subjective IQ was assessed by a 5-point Likert scale. Differences between groups were statistically analyzed (P < 0.05 was considered statistically significant). RESULTS: No significant differences in baseline characteristics were found between groups. The CM volume and TIL differed significantly between groups (P < 0.01), with mean values in group 1 of 110 mL and 33 g I, and in group 2 of 104.1 ± 21.2 mL and 31.2 ± 6.3 g I, respectively. Flow rate and IDR were not significantly different between groups (P > 0.05). Body weight-adapted protocoling led to more homogeneous enhancement of the liver parenchyma compared with a fixed protocol with a mean enhancement per weight category in group 2 of 126.5 ± 15.8, 128.2 ± 15.3, and 122.7 ± 21.2 HU compared with that in group 1 of 139.9 ± 21.4, 124.6 ± 24.8, and 116.2 ± 17.8 HU, respectively. CONCLUSIONS: Body weight-adapted CM injection protocols result in more homogeneous enhancement of the liver parenchyma at 90 kV in comparison to a fixed CM volume with comparable objective and subjective IQ, whereas overall CM volume can be safely reduced in more than half of patients.

Computed Tomography Pulmonary Angiography during Pregnancy: Radiation Dose of Commonly Used Protocols and the Effect of Scan Length Optimization.

OBJECTIVE: To evaluate the radiation dose for pregnant women and fetuses undergoing commonly used computed tomography of the pulmonary arteries (CTPA) scan protocols and subsequently evaluate the simulated effect of an optimized scan length. MATERIALS AND METHODS: A total of 120 CTPA datasets were acquired using four distinctive scan protocols, with 30 patients per protocol. These datasets were mapped to Cristy phantoms in order to simulate pregnancy and to assess the effect of an effective radiation dose (in mSv) in the first, second, or third trimester of pregnancy, including a simulation of fetal dose in second and third trimesters. The investigated scan protocols involved a 64-slice helical scan at 120 kVp, a high-pitch dual source acquisition at 100 kVp, a dual-energy acquisition at 80/140 kVp, and an automated-kV-selection, high pitch helical scan at a reference kV of 100 kVref. The effective dose for women and fetuses was simulated before and after scan length adaptation. The original images were interpreted before and after scan length adaptations to evaluate potentially missed diagnoses. RESULTS: Large inter-scanner and inter-protocol variations were found; application of the latest technology decreased the dose for non-pregnant women by 69% (7.0-2.2 mSv). Individual scan length optimization proved safe and effective, decreasing the fetal dose by 76-83%. Nineteen (16%) cases of pulmonary embolism were diagnosed and, after scan length optimization, none were missed. CONCLUSION: Careful CTPA scan protocol selection and additional optimization of scan length may result in significant radiation dose reduction for a pregnant patient and her fetus, whilst maintaining diagnostic confidence.

Personalization of injection protocols to the individual patient's blood volume and automated tube voltage selection (ATVS) in coronary CTA.

PURPOSE: The aim was to assess personalised contrast media (CM) protocols-based on patient's blood volume (BV) and automated tube voltage selection (ATVS)-in coronary computed tomography angiography (CCTA). METHODS: A total of 114 consecutive patients received an ECG-triggered or ECG-gated helical scan on a 3rd-generation dual-source CT with 70-120kV (ATVS) and 330mAsqual.ref. CM was adapted to BV, scan time (s) and kV. Image quality (IQ) was assessed in a 17-segment coronary model using attenuation values (HU), contrast-to-noise (CNR), signal-to-noise ratio (SNR) (objective IQ) and a Likert scale (subjective IQ: 1 = poor/2 = sufficient/3 = good/4 = excellent). ig. RESULTS: Patient distribution was: n = 60 for 70kV, n = 37 80kV and n = 17 90kV. Mean BV was 5.4±0.6L for men and 4.1±0.6L for women. Mean CM volume (300 mg I/mL) and flow rate were: 30.9±6.4mL and 3.3±0.5mL/s (70kV); 40.8±7.1mL and 4.5±0.6mL/s (80kV); 53.6±8.6mL and 5.7±0.6mL/s (90kV). Overall mean HU was >300HU in 98.2% (112/114) of patients. Overall mean attenuation was below 300HU in two scans (70kV) due to late scan timing. Of 1.661 segments, 95.4% was assessable. Mean CNR was 14±4(70kV), 13±3(80kV) and 14±4(90kV); mean SNR was 10±2(both 70kV+80kV) and 9±2(90kV). Objective IQ was comparable between kV settings, protocols and sex. Subjective IQ was diagnostic in all scans and excellent-sufficient in 95.4% of segments. CONCLUSIONS: Personalisation of CCTA CM injection protocols to BV and ATVS is a promising technique to tailor CM administration to the individual patient, while maintaining diagnostic IQ.

Aortic root evaluation prior to transcatheter aortic valve implantation-Correlation of manual and semi-automatic measurements.

BACKGROUND: Pre-procedural TAVI planning requires highly sophisticated and time-consuming manual measurements performed by experienced readers. Semi-automatic software may assist with partial automation of assessment of multiple parameters. The aim of this study was to evaluate differences between manual and semi-automatic measurements in terms of agreement and time. METHODS: One hundred and twenty TAVI candidates referred for the retrospectively ECG-gated CTA (2nd and 3rd generation dual source CT) were evaluated. Fully manual and semi-automatic measurements of fourteen aortic root parameters were assessed in the 20% phase of the R-R interval. Reading time was compared using paired samples t-test. Inter-software agreement was calculated using the Intraclass correlation coefficient (ICC) in a 2-way mixed effects model. Differences between manual and semi-automatic measurements were evaluated using Bland-Altman analysis. RESULTS: The time needed for evaluation using semi-automatic assessment (3 min 24 s ± 1 min 7 s) was significantly lower (p<0.001) compared to a fully manual approach (6 min 31 sec ± 1 min 1 sec). Excellent inter-software agreement was found (ICC = 0.93 ± 0.0; range:0.90-0.95). The same prosthesis size from manual and semi-automatic measurements was selected in 92% of cases, when sizing was based on annular area. Prosthesis sizing based on annular short diameter and perimeter agreed in 99% and 96% cases, respectively. CONCLUSION: Use of semi-automatic software in pre-TAVI evaluation results in comparable results in respect of measurements and selected valve prosthesis size, while necessary reading time is significantly lower.

Do CTA measurements of annular diameter, perimeter and area result in different TAVI prosthesis sizes?

Incorrect prosthesis size has direct impact on patient outcome after transcatheter aortic valve implantation (TAVI) procedure. Currently, annular diameter, area or perimeter may be used for prosthesis size selection. The aim was to evaluate whether the use different annular dimensions would result in the selection of different prosthesis sizes, when assessed in the same TAVI-candidate during the same phase of a cardiac cycle. Fifty consecutive TAVI-candidates underwent retrospectively ECG-gated computed tomography angiography (CTA). Aortic root dimensions were assessed in the 20% phase of the R-R interval. Annular short diameter, perimeter and area were used to select the prosthesis size, based on the industry recommendations for a self-expandable (Medtronic CoreValve; MCV) and balloon-expandable (Edwards Sapien XT Valve; ESV) valve. Complete agreement on selected prosthesis size amongst all three annular dimensions was observed in 62% (31/50; ESV) and 30% (15/50; MCV). Short aortic annulus measurement resulted in a smaller prosthesis size in 20% (10/50; ESV) and in 60% of cases (30/50; MCV) compared to the size suggested by both annular perimeter and area. In 18% (9/50; ESV) and 10% of cases (5/50; MCV) a larger prosthesis would have been selected based on annular perimeter compared to annular diameter and area. Prosthesis size derived from area was always in agreement with at least one other parameter in all cases. Aortic annulus area appears to be the most robust parameter for TAVI-prosthesis size selection, regardless of the specific prosthesis size. Short aortic annulus diameter may underestimate the prosthesis size, while use of annular perimeter may lead to size overestimation in some cases.

CT Angiography in the Lower Extremity Peripheral Artery Disease Feasibility of an Ultra-Low Volume Contrast Media Protocol.

PURPOSE: The ALARA principle is not only relevant for effective dose (ED) reduction, but also applicable for contrast media (CM) management. Therefore, the aim was to evaluate the feasibility of an ultra-low CM protocol in the assessment of peripheral artery disease (PAD). MATERIALS AND METHODS: Fifty PAD patients were scanned on third-generation dual-source computed tomography, from diaphragm to the forefoot, as follows: tube voltage: 70 kV, reference effective tube current: 90 mAs, collimation: 192 × 2 × 0.6 mm, with individualized acquisition timing. The protocol ED (mSv) was quantified with dedicated software. CM protocol consisted of 15 ml test bolus and 30 ml main bolus (300 mgI/ml) injected at 5 ml/s, followed by a 40 ml saline chaser at the same flow rate. Aorto-popliteal bolus transit time was used to calculate the overall acquisition time and delay. Objective (hounsfield units-HU; contrast-to-noise ratio-CNR) and subjective image quality (four-point Likert score) were assessed at different anatomical regions from the aorta down to the forefoot. RESULTS: Mean attenuation values were exceeding 250 HU from aorta down to the anterior tibial artery with CNR < 13. However, decline in attenuation was observed in more distal region with mean values of 165 and 199 HU, in left and right dorsalis pedis artery, respectively. Mode subjective image quality from the level of aorta down to the popliteal segment was excellent; below the knee mode score was good. The mean ED per protocol was 1.1 ± 0.5 mSv. CONCLUSION: Use of an ultra-low CM volume protocol at 70 kV is feasible in the evaluation of PAD, resulting in good to excellent image quality with mean ED of 1.1 ± 0.5 mSv. LEVEL OF EVIDENCE: Level 3, Local non-random sample.

The role of standard non-ECG gated chest CT in cardiac assessment: design and rationale of the Cardiac Pathologies in standard chest CT (CaPaCT) study.

Modern high-performance computed tomography (CT) scanners with improved scan acquisition times now allow for routine assessment of cardiac pathologies on chest CTs, which can result in numerous incidental cardiac findings. The CaPaCT study, an observer blinded, single-centre study, aims to assess the visibility, management and possible clinical impact of incidental cardiac pathologies that are now becoming visible on standard chest CTs. A total of 217 consecutive patients referred for a chest CT on a high-performance third-generation dual-source CT scanner will be included. Tube voltage settings will be chosen via automated kV selection. Dedicated cardiac reconstructions will be added to the standard post-processing: 0.6-mm slice thickness, 0.4-mm increment and Bv36 kernel (iterative reconstruction/strength 3). Primary endpoints will be the presence and extent of coronary artery disease (CAD) assessed via a 17-segment model. These data will be collected and analysed by two experienced, blinded cardiac radiologists. Furthermore, information on aortic and mitral valve morphology/calcification and pericardial abnormalities will be collected. The CAD Reporting and Data System classification will subsequently be used to assess the management and possible clinical burden of any incidentally detected CAD. Additionally, objective and subjective image quality (attenuation, contrast-to-noise, signal-to-noise and 5-point Likert scale) of the obtained cardiac reconstructions will be assessed.

Contrast agent concentration optimization in CTA using low tube voltage and dual-energy CT in multiple vendors: a phantom study.

We investigated the feasibility and extent to which iodine concentration can be reduced in computed tomography angiography imaging of the aorta and coronary arteries using low tube voltage and virtual monochromatic imaging of 3 major dual-energy CT (DECT) vendors. A circulation phantom was imaged with dual source CT (DSCT), gemstone spectral imaging (GSI) and dual-layer spectral detector CT (SDCT). For each scanner, a reference scan was acquired at 120 kVp using routine iodine concentration (300 mg I/ml). Subsequently, scans were acquired at lowest possible tube potential (70, 80, 80 kVp, respectively), and DECT-mode (80/150Sn, 80/140 and 120 kVp, respectively) in arterial phase after administration of iodine (300, 240, 180, 120, 60, 30 mg I/ml). Objective image quality was evaluated using attenuation, CNR and dose corrected CNR (DCCNR) measured in the aorta and left main coronary artery. Average DCCNR at reference was 227.0, 39.7 and 60.2 for DSCT, GSI and SDCT. Maximum iodine concentration reduction without loss of DCCNR was feasible down to 180 mg I/ml (40% reduced) for DSCT (DCCNR 467.1) and GSI (DCCNR 46.1) using conventional CT low kVp, and 120 mg I/ml (60% reduced) for SDCT (DCCNR 171.5) using DECT mode. Low kVp scanning and DECT allows for 40-60% iodine reduction without loss in image quality compared to reference. Optimal scan protocol and to which extent varies per vendor. Further patient studies are needed to extend and translate our findings to clinical practice.

Implementation of Size-Dependent Local Diagnostic Reference Levels for CT Angiography.

OBJECTIVE: Diagnostic reference levels (DRLs) are established for standard-sized patients; however, patient dose in CT depends on patient size. The purpose of this study was to introduce a method for setting size-dependent local diagnostic reference levels (LDRLs) and to evaluate these LDRLs in comparison with size-independent LDRLs and with respect to image quality. MATERIALS AND METHODS: One hundred eighty-four aortic CT angiography (CTA) examinations performed on either a second-generation or third-generation dual-source CT scanner were included; we refer to the second-generation dual-source CT scanner as "CT1" and the third-generation dual-source CT scanner as "CT2." The volume CT dose index (CTDIvol) and patient diameter (i.e., the water-equivalent diameter) were retrieved by dose-monitoring software. Size-dependent DRLs based on a linear regression of the CTDIvol versus patient size were set by scanner type. Size-independent DRLs were set by the 5th and 95th percentiles of the CTDIvol values. Objective image quality was assessed using the signal-to-noise ratio (SNR), and subjective image quality was assessed using a 4-point Likert scale. RESULTS: The CTDIvol depended on patient size and scanner type (R2 = 0.72 and 0.78, respectively; slope = 0.05 and 0.02 mGy/mm; p < 0.001). Of the outliers identified by size-independent DRLs, 30% (CT1) and 67% (CT2) were adequately dosed when considering patient size. Alternatively, 30% (CT1) and 70% (CT2) of the outliers found with size-dependent DRLs were not identified using size-independent DRLs. A negative correlation was found between SNR and CTDIvol (R2 = 0.36 for CT1 and 0.45 for CT2). However, all outliers had a subjective image quality score of sufficient or better. CONCLUSION: We introduce a method for setting size-dependent LDRLs in CTA. Size-dependent LDRLs are relevant for assessing the appropriateness of the radiation dose for an individual patient on a specific CT scanner.

Optimizing Pulmonary Embolism Computed Tomography in the Age of Individualized Medicine: A Prospective Clinical Study.

PURPOSE: The aim of the study was to simultaneously optimize contrast media (CM) injection and scan parameters for the individual patient during computed tomography pulmonary angiography (CTPA). METHODS: In this study (NCT02611115), 235 consecutive patients suspected of having pulmonary embolism were prospectively enrolled. Automated kV selection software on a third-generation multidetector computed tomography adapted tube voltage to the individual patient, based on scout scans. The contrast injection protocol was adapted to both patient body weight and kV-setting selection via a predefined formula, based on previous research. Injection data were collected from a contrast media and radiation dose monitoring software. Attenuation was measured in Hounsfield units (HU) in the pulmonary trunk (PT); attenuation values 200 HU or greater were considered diagnostic. Subjective image quality was assessed by using a 4-point Likert scale at the level of the PT, lobar, segmental, and subsegmental arteries. Results between groups were reported as mean ± SD. RESULTS: Two hundred twenty-two patients (94%) were scanned at a kV setting below 100 kV: n = 108 for 70 kV, n = 82 for 80 kV, and n = 32 for 90 kV. Mean CM bolus volume (in milliliters) and total iodine load (in grams of iodine) for 70 to 90 kV were as follows: 24 ± 3 mL and 7 ± 1 g I, 29 ± 4 mL and 9 ± 2 g I, and 38 ± 4 mL and 11 ± 1 g I, respectively. Mean flow rates (in milliliters per second) and iodine delivery rates (in grams of iodine per second) were 3.0 ± 0.4 mL/s and 0.9 ± 0.1 g I/s (70 kV), 3.6 ± 0.4 mL/s and 1.0 ± 0.1 g I/s (80 kV), and 4.7 ± 0.5 mL/s and 1.3 ± 0.1 g I/s (90 kV). Mean radiation doses were 1.3 ± 0.3 mSv at 70 kV, 1.7 ± 0.4 mSv at 80 kV, and 2.2 ± 0.6 mSv at 90 kV. Mean vascular attenuation in the PT for each kV group was as follows: 397 ± 101 HU for 70 kV, 398 ± 96 HU for 80 kV, and 378 ± 100 HU for 90 kV, P = 0.59. Forty-six patients (21%) showed pulmonary embolism on the CTPA. One scan (90 kV) showed nondiagnostic segmental pulmonary arteries, and 5% of subsegmental arteries were of nondiagnostic image quality. All other segments were considered diagnostic-excellent subjective image quality. CONCLUSIONS: Simultaneously optimizing both CM injections and kV settings to the individual patient in CTPA results in diagnostic attenuation with on average 24 to 38 mL of CM volume and a low radiation dose for most patients. This individualized protocol may help overcome attenuation-variation problems between patients and kV settings in CTPA.

Patient Comfort During Contrast Media Injection in Coronary Computed Tomographic Angiography Using Varying Contrast Media Concentrations and Flow Rates: Results From the EICAR Trial.

PURPOSE: Pain sensation and extravasation are potential drawbacks of contrast media (CM) injection during computed tomographic angiography. The purpose was to evaluate safety and patient comfort of higher flow rates in different CM protocols during coronary computed tomographic angiography. METHODS: Two hundred consecutive patients of a double-blind randomized controlled trial (NCT02462044) were analyzed. Patients were randomized to receive 94 mL of prewarmed iopromide 240 mg I/mL at 8.3 mL/s (group I), 75 mL of 300 mg I/mL at 6.7 mL/s (group II), or 61 mL of 370 mg I/mL at 5.4 mL/s (group III), respectively. Iodine delivery rate (2.0 g I/s) and total iodine load (22.5 g I) were kept identical. Outcome was defined as intravascular enhancement, patient comfort during injection, and injection safety, expressed as the occurrence of extravasation. Patients completed a questionnaire for comfort, pain, and stress during CM injection. Comfort was graded using a 5-point scale, 1 representing "very bad" and 5 "very well." Pain was graded using a 10-point scale, 0 representing "no pain" and 10 "severe pain." Stress was graded using a 5-point scale, 1 representing "no stress" and 5 "unsustainable stress." RESULTS: Mean enhancement levels within the coronary arteries were as follows: 437 ± 104 Hounsfield units (HU) (group I), 448 ± 111 HU (group II), and 447 ± 106 HU (group III), with P ≥ 0.18. Extravasation occurred in none of the patients. Median (interquartile range) for comfort, pain, and stress was, respectively, 4 (4-5), 0 (0-0), and 1 (1-2), with P ≥ 0.68. CONCLUSIONS: High flow rates of prewarmed CM were safely injected without discomfort, pain, or stress. Therefore, the use of high flow rates should not be considered a drawback for CM administration in clinical practice.

Individualized CT Angiography Protocols for the Evaluation of the Aorta: A Feasibility Study.

PURPOSE: Ionizing radiation and iodinated contrast media are potential drawbacks to repetitive follow-up CT angiography in current practice. The aim of the present study was to optimize radiation dose and contrast agent volume by using individualized CT angiography protocols. MATERIALS AND METHODS: Eighty consecutive patients referred for CT angiography of the whole aorta were prospectively evaluated. Patients were divided into groups of patients with a body mass index (BMI) < 28 kg/m(2) (group 1; n = 50) and those with a BMI ≥ 28 kg/m(2) (group 2; n = 30). A control group consisted of 50 consecutive patients who were retrospectively evaluated. CT angiography parameters on a second-generation dual-source scanner were 128 × 0.6-mm collimation, pitch of 0.9, rotation time of 0.33 seconds, tube voltages of 80/100/120 kVp (group 1/group 2/control), reference tube current of 400 mA, and image reconstruction at 1-mm/0.8-mm slice thickness (kernels, B30f [control] and I30f/strength 3 [groups 1/2]). The control group received 120 mL of contrast agent (300 mgI/mL) at 4.8 mL/s; groups 1 and 2 received 44 mL and 53 mL at 3.3 mL/s and 4 mL/s, respectively. Effective dose was evaluated for each patient. Image quality was determined by qualitative image analysis at the levels of the thoracic, abdominal, and pelvic aorta as nondiagnostic, diagnostic, good, or excellent, and quantitative image analysis was performed, including attenuation values and contrast-to-noise ratio (CNR). RESULTS: Mean effective radiation dose values for CT angiography of the aorta were 3.7 mSv ± 0.7 in group 1, 6.7 mSv ± 1.4 in group 2, and 8.7 mSv ± 1.9 in the control group (P < .001). Mean attenuation values and CNR levels were 334 HU ± 66 and 16 ± 8, respectively, in group 1, 277 HU ± 56 and 14 ± 5 in group 2, and 305 HU ± 77 and 11 ± 4 in the control group. CONCLUSIONS: Iterative reconstruction algorithms resulted in 23%-57% less radiation in combination with 55%-63% less contrast agent volume compared with standard CT protocols.