Reduction of contrast medium volume in abdominal aorta CTA: multiphasic injection technique versus a test bolus volume

The use of dual and triple rule-out computerized tomography angiography by using diagnostic low-dose contrast material and radiation in acute chest pain

BACKGROUND

Triple rule-out computed tomography angiography (CTA) provides imaging of the coronary arteries, pulmonary arteries, and thoracic aorta filled with contrast material (CM) to exclude or diagnose the pathologies of these three systems. Although dual rule-out adapted to exclude aortic and pulmonary pathologies. Iodinated CM may result in contrast-induced nephropathy, which lengthens hospital stay.

PURPOSE

To compare image quality of dual/triple rule-out CTA by reducing the radiation dose by using relatively high mAs with less contrast material and low kilovoltage without affecting the diagnostic value.

METHODS

We acquired standard dual/triple rule-out CTA 120 kilovoltage peak (kVp) with 95 mL contrast material. The low-dose group acquired 80 Kvp with total 60 contrast material. There were 91 patients in the standard-dose group and 88 patients in the low-dose group.

RESULTS

Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated separately. There was no significant difference in CNR values between the two groups in the aorta and pulmonary and coronary arteries; however, a significant difference was found in SNR values. In subjective image quality evaluation, no significant difference was found between the standard- and low-dose patients. The radiation dose was reduced by 63.80% and the contrast material by 31.5% in the low-dose group in comparison to the standard dose.

CONCLUSION

Our study showed that dual/triple rule-out CTA can be performed with low-dose radiation and low-volume contrast material. Low-dose CTA may be preferred in emergencies situations that patients with borderline renal function tests or the risk group.

Exploring Intra-arterial Contrast Administration for Intraoperative Imaging Using a Swine Model

Intraoperative computed tomography (CT) imaging with endovascular delivery of intra-arterial (IA) contrast could potentially provide higher attenuation with lower contrast volumes than intravenous (IV) administration. We aimed to compare IA and IV contrast use for organ-specific CT abdominal imaging. Five anesthetized swine had external jugular and brachial artery access with ascending aortic pigtail placement. An IV protocol was 100 mL at 5 mL/sec over 20 sec vs 50 mL of IA contrast at 5 mL/sec over 10 sec. Region-of-interest markers were applied to anatomical regions to measure attenuation (HU) over time. IA and IV contrast protocols achieved adequate aortic opacification (IA, 455 ± 289 vs IV, 450 ± 114 HU). The IA contrast aortic attenuation curve reached peak attenuation compared with IV contrast (IA, 8 vs 23 sec; P < .001). Time to peak attenuation was similar between IA and IV contrast in the portal vein (IA, 38 vs IV, 42 sec, P = .25). IA administration achieved a superior contrast-to-noise ratio (CNR) in less time compared with IV (R2 = .94; P < .001). IA contrast achieved adequate opacification with less bolus broadening and a superior CNR compared with IV contrast while using a smaller contrast volume for directed organ-directed imaging.

Feasibility of utilizing ultra-low-dose contrast medium for pancreatic artery depiction using the combination of advanced virtual monoenergetic imaging and high-concentration contrast medium: an intra-patient study

Objectives

The least amount of contrast medium (CM) should be used under the premise of adequate diagnosis. The purpose of this study is to evaluate the feasibility of utilizing ultra-low-dose (224 mgI/kg) CM for pancreatic artery depiction using the combination of advanced virtual monoenergetic imaging (VMI+) and high-concentration (400 mgI/mL) CM.

Materials and methods

41 patients who underwent both normal dose CM (ND-CM, 320 mgI/kg) and low dose CM (LD-CM, 224 mgI/kg) thoracoabdominal enhanced CT for tumor follow-up were prospectively included. The VMI+ at the energy level of 40-kev for LD-CM images was reconstructed. CT attenuation, signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs) of the abdominal artery, celiac artery, and superior mesenteric artery (SMA) and qualitative scores of pancreatic arteries depiction were recorded and compared among the three groups (ND-CM, LD-CM, and VMI+ LD-CM images). ANOVA and Friedman tests were used for statistical analysis.

Results

All quantitative and qualitative parameters on LD-CM images were lower than that on ND-CM images (all p < 0.01). There were no significant differences of all arteries’ qualitative scores between ND-CM and VMI+ LD-CM images (all p > 0.05). VMI+ LD-CM images had the highest mean CT and CNR values of all arteries (all p < 0.0001). The CM volume was 52.6 ± 9.4 mL for the ND-CM group and 37.0 ± 6.7 mL for the LD-CM group.

Conclusion

Ultra-low-dose CM (224 mgI/kg) was feasible for depicting pancreatic arteries. Inferior angiographic image quality could be successfully compensated by VMI+ and high-concentration CM.

Contrast Volume for Preoperative CT Angiography of the Aorta Based on Patient Heart Rate and Body Surface Area: A Pilot Study

Purpose:

To evaluate contrast agent dose reduction using an algorithm based on heart rate and body surface area.

Methods:

A prospective study with 55 patients undergoing aortic CT was performed. Contrast agent dose, enhancement and image quality between three study groups were compared. Group 1: a fixed, standard dose of 120 ml, group 2: contrast agent dose calculated based on heart rate and body surface area, group 3: additional dilution of 50% of the calculated dose based on heart rate and body surface area.

Results:

The mean contrast agent dose in group 2 was reduced by 15% (P < 0.01) with unchanged high visual scoring in comparison to group 1. In group 3, contrast agent dose reduction was 60% (P < 0.01); average image quality dropped 19% (P < 0.01) compared to group 1, but was still sufficient, except for two patients.

Conclusions:

Contrast agent dose was significantly reduced without compromising diagnostic efficacy using the proposed algorithm.

High-quality low-dose cardiovascular computed tomography (CCT) in pediatric patients using a 64-slice scanner

Background Cardiovascular computed tomography (CCT) technology is rapidly advancing allowing to perform good quality examinations with a radiation dose as low as 1.2 mSv. However, latest generation scanners are not available in all centers. Purpose To estimate radiation dose and image quality in pediatric CCT using a standard 64-slice scanner. Material and Methods A total of 100 patients aged 6.9 ± 5.4 years (mean ± standard deviation) who underwent a 64-slice CCT scan using 80, 100, or 120 kVp, were retrospectively evaluated. Radiation effective dose was calculated on the basis of the dose length product. Two independent readers assessed the image quality through signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and a qualitative score (3 = very good, 2 = good, 1 = poor). Non-parametric tests were used. Results Fifty-five exams were not electrocardiographically (ECG) triggered, 20 had a prospective ECG triggering, and 25 had retrospective ECG triggering. The median effective dose was 1.3 mSv (interquartile range [IQR] = 0.8-2.7 mSv). Median SNR was 30.6 (IQR = 23.4-33.6) at 120 kVp, 29.4 (IQR = 23.7-34.8) at 100 kVp, and 24.7 (IQR = 19.4-34.3) at 80 kVp. Median CNR was 21.0 (IQR = 14.8-24.4), 19.1 (IQR = 15.6-23.9), and 25.3 (IQR = 19.4-33.4), respectively. Image quality was very good, good, and poor in 56, 39, and 5 patients, respectively. No significant differences were found among voltage groups for SNR ( P = 0.486), CNR ( P = 0.336), and subjective image quality ( P = 0.296). The inter-observer reproducibility was almost perfect (κ = 0.880). Conclusion High-quality pediatric CCT can be performed using a 64-slice scanner, with a radiation effective dose close to 2 mSv in about 50% of the cases.

Unenhanced MRI as an Alternative to 99mTc-Labeled Dimercaptosuccinic Acid Scintigraphy in the Detection of Pediatric Renal Scarring

OBJECTIVE

The purpose of this study was to determine whether unenhanced MRI without sedation is a feasible substitute for dimercaptosuccinic acid (DMSA) scintigraphy in the detection of renal scars in pediatric patients.

SUBJECTS AND METHODS

Patients scheduled for ^99mTc-labeled DMSA scintigraphy for assessment of possible renal scars were recruited to undergo unenhanced MRI (free-breathing fat-suppressed T2-weighted single-shot turbo spin-echo and T1-weighted gradient-echo imaging, 13 minutes' total imaging time). Scintigraphic and MRI studies were evaluated by two independent blinded specialty-based radiologists. For each imaging examination, readers identified scars in upper, middle, and lower kidney zones and rated their diagnostic confidence and the quality of each study. The scintigraphic readers' consensus score opinion for the presence of scars was considered the reference standard.

RESULTS

DMSA scintigraphy showed scarring in 19 of the 78 (24.4%) evaluated zones and MRI in 18 of the 78 (23.1%). The two MRI readers found mean sensitivities of 94.7% and 89.5%, identical specificities of 100%, and diagnostic accuracies of 98.7% and 97.4%. Interobserver agreement was 98.7% for MRI and 92.3% for DMSA scintigraphy. The MRI readers were significantly more confident in determining the absence rather than the presence of scars (p = 0.02). MRI readers were more likely to rate study quality as excellent (84.6%) than were the scintigraphic readers (57.7%) (p = 0.024).

CONCLUSION

Unenhanced MRI has excellent sensitivity, specificity, diagnostic accuracy, and interobserver agreement for detecting renal scars in older children who do not need sedation. It may serve as a substitute modality, especially when DMSA is not available.

Computerized tomography angiography by direct intra-aortic low volume contrast injection in patients being evaluated for EVAR

Background Computerized tomography angiography is an important tool for endovascular repair of abdominal aortic aneurysm planning. This study aimed to evaluate the utility of computerized tomography angiography using direct intra-aortic injection of low volume of iodinated contrast in patients being considered for endovascular repair of abdominal aortic aneurysm. Design A 5F high-flow angiographic catheter was positioned in the mid-thoracic aorta through femoral percutaneous access. Computerized tomography angiography was performed with image acquisition starting simultaneously with power injection of 10 mL of iopamidol 76% diluted with normal saline to 50 mL, at 6 mL/s through the angiographic catheter. Aortic enhancement was assessed with a circular region-of-interest within the aorta. Values ≥150 HU were considered adequate. Results Nine patients with abdominal aortic aneurysm and chronic renal dysfunction underwent computerized tomography angiography with intra-arterial contrast injection for endovascular repair of abdominal aortic aneurysm planning. Mean age 78.8 ± 5.0 years, mean baseline creatinine 1.8 ± 0.4 mg/dL and mean glomerular filtration rate 36.8 ± 4.2 mL/min. Adequate computerized tomography angiography aortic enhancement was obtained in all cases (mean intra-aortic density: 300.4 ± 72.8 HU). The total contrast volume used for the computerized tomography angiography and the endovascular repair of abdominal aortic aneurysm combined was 30.0 ± 21.4 mL. Seventy-five percent of the patients received ≤30 mL of contrast. No significant renal function deterioration occurred (creatinine clearance pre- and post-procedure 36.8 ± 4.2 mL/min versus 38.6 ± 6.1 mL/min, p = 0.32). Successful endovascular repair of abdominal aortic aneurysm was achieved in eight patients. One patient underwent open treatment based on computerized tomography angiography information. No endoleak or aneurysm growth occurred (median follow-up: 121 days (range 36-1242)). Conclusion Direct intra-aortic injection of low volume of iodinated contrast provides adequate and reproducible pattern of aortic enhancement on computerized tomography angiography. The computerized tomography angiography so acquired can be used for endovascular repair of abdominal aortic aneurysm limiting the total volume of iodinated contrast required.

Feasibility of a low concentration test bolus in CT angiography

AIM

To investigate the feasibility of using a low-concentration test bolus in abdominal aorta computed tomography (CT) angiography (CTA).

MATERIALS AND METHODS

In 10 patients referred for CTA of the abdominal aorta with a body mass index (BMI) ≤28 kg/m², a standard test bolus of 10 ml contrast medium (CM; 350 mg iodine/ml) was compared with a low-concentration test bolus (5 ml CM; 350 mg iodine/ml; 1:1 diluted with saline) in terms of time to peak enhancement (tPE) and peak enhancement (PE).

RESULTS

No significant differences were found between the standard and low-concentration test bolus in terms of tPE and PE.

CONCLUSIONS

A low-concentration test bolus (5 ml, 1:1 diluted with saline) is feasible in patients with a BMI ≤28 kg/m².

A non-invasive cardiac output measurement as an alternative to the test bolus technique during CT angiography

AIM

To investigate the association between a non-invasive cardiac output (CO) measurement and the scan delay, as derived from a test bolus injection protocol. The secondary objective was to determine which factors affect the relationship between the CO and scan delay.

MATERIALS AND METHODS

Fifty-five patients referred for a contrast-enhanced (thorax-)abdomen CT examination were included in this feasibility study. A test bolus examination was performed prior to the abdominal CT. During the test bolus injection, the CO of the patient was measured using a non-invasive finger-cuff measurement. Associations were analysed using linear regression analyses. Age, gender, height, weight, and blood pressure were included as potential confounders.

RESULTS

Linear regression analysis showed a negative and significant association between CO and delay. The regression formula was as follows: scan delay (seconds) = 26.8-1.6 CO (l/min), with a 95% CI between -2.3 and -1.0 (p<0.001). Weight appeared to be a confounder in this relation, and gender and blood pressure were effect modifiers. There was no interaction between scan delay and age, height and weight.

CONCLUSIONS

There is a negative and significant association between the non-invasive CO measurement and the CT scan delay; however, to validate these findings a larger cohort study is needed to investigate whether the non-invasively determined scan delay is as accurate as the use of a test bolus.

Dual Energy CT Angiography of Peripheral Arterial Disease: Feasibility of Using Lower Contrast Medium Volume

OBJECTIVE

One of the main drawbacks associated with Dual Energy Computed Tomography Angiography (DECTA) is the risk of developing contrast medium-induced nephropathy (CIN). The aim of the present study was firstly, to design an optimal CT imaging protocol by determining the feasibility of using a reduced contrast medium volume in peripheral arterial DECTA, and secondly, to compare the results with those obtained from using routine contrast medium volume.

METHODS

Thirty four patients underwent DECTA for the diagnosis of peripheral arterial disease. They were randomly divided into two groups: Group 1 (routine contrast volume group) with n = 17, injection rate 4-5 ml/s, and 1.5 ml/kg of contrast medium, and Group 2 ((low contrast volume group), with n = 17, injection rate 4-5ml/s, and contrast medium volume 0.75 ml/kg. A fast kilovoltage-switching 64-slice CT scanner in the dual-energy mode was employed for the study. A total of 6 datasets of monochromatic images at 50, 55, 60, 65, 70 and 75 keV levels were reconstructed with adaptive statistical iterative reconstruction (ASIR) at 50%. A 4-point scale was the tool for qualitative analysis of results. The two groups were compared and assessed quantitatively for image quality on the basis of signal-to-noise ratio (SNR) and contrast-to-noise-ratio (CNR). Radiation and contrast medium doses were also compared.

RESULTS

The overall mean CT attenuation and mean noise for all lower extremity body parts was significantly lower for the low volume contrast group (p<0.001), and varied significantly between groups (p = 0.001), body parts (p<0.001) and keVs (p<0.001). The interaction between group body parts was significant with CT attenuation and CNR (p = 0.002 and 0.003 respectively), and marginally significant with SNR (p = 0.047), with minimal changes noticed between the two groups. Group 2 (low contrast volume group) displayed the lowest image noise between 65 and 70 keV, recorded the highest SNR and CNR at 65 keV, and produced significantly lower results with respect to contrast medium volume and duration of contrast injection (p<0.001). The effect of radiation dose was not statistically significant between the two groups.

CONCLUSIONS

DECTA images created at 65 keV and 50% ASIR with low contrast medium volume protocol, yielded results that were comparable to routine contrast medium volume, with acceptable diagnostic images produced during the evaluation of peripheral arteries.

Feasibility of low contrast media volume in CT angiography of the aorta

Objectives

Using smaller volumes of contrast media (CM) in CT angiography (CTA) is desirable in terms of cost reduction and prevention of contrast-induced nephropathy (CIN). The purpose was to evaluate the feasibility of low CM volume in CTA of the aorta.

Methods

77 patients referred for CTA of the aorta were scanned using a standard MDCT protocol at 100 kV. A bolus of 50 ml CM (Iopromide 300 mg Iodine/ml) at a flow rate of 6 ml/s was applied (Iodine delivery rate IDR = 1.8 g/s; Iodine load 15 g) followed by a saline bolus of 40 ml at the same flow rate. Scan delay was determined by the test bolus method. Subjective image quality was assessed and contrast enhancement was measured at 10 anatomical levels of the aorta.

Results

Diagnostic quality images were obtained for all patients, reaching a mean overall contrast enhancement of 324 ± 28 HU. Mean attenuation was 350 ± 60 HU at the thoracic aorta and 315 ± 83 HU at the abdominal aorta.

Conclusions

A straightforward low volume CM protocol proved to be technically feasible and led to CTA examinations reaching diagnostic image quality of the aorta at 100 kV. Based on these findings, the use of a relatively small CM bolus can be incorporated into routine clinical imaging.