Feasibility study of iterative model reconstruction combined with low tube voltage, low iodine load, and low iodine delivery rate in craniocervical CT angiography

Low-dose three-dimensional CT angiography for the evaluation of posterolateral protrusion of the vertebral artery over the posterior arch of the atlas: a quantitative anatomical comparison study of the rotational and neutral positions

AIM

To investigate the changes in relevant anatomical parameters of posterolateral protrusion of the vertebral artery (VA) between head-neck rotational and neutral positions using low-dose three-dimensional computed tomography angiography (3D-CTA).

MATERIALS AND METHODS

Low-dose 3D-CTA images obtained for various craniocervical diseases in 36 non-dominant VA side patients with neutral, left and right head-neck rotational positions were evaluated. The relevant parameters from superior and inferior views, including external diameter (ED), internal diameter (ID), transverse diameter (TD), heights and diameters of posterolateral protrusion of the VA over the posterior arch of the atlas in the neutral and rotational positions, were recorded and compared.

RESULTS

There was no significant differences in the rotational angle (left/right: 31.23 ± 6.60/29.94 ± 6.09°, p>0.05). There were no significant differences in heights and diameters of bilateral VA between rotational and neutral positions (all p>0.05). The contralateral ID, ED, and TD of the rotational positions were significantly shorter than those of the neutral position (all p<0.05), while there were no significant differences in the three ipsilateral diameters (all p>0.05).

CONCLUSIONS

Posterolateral protrusion of the VA is not uncommon in the population, and surgeons should be aware of its presence, especially the increased possibility of injury to the VA caused by head-neck rotation, during the operation; thus, preoperative evaluation by low-dose 3D-CTA should be considered.

Comparison of two different GSI scanning protocols in head and neck CT angiography: Image quality and radiation dose

OBJECTIVES

To compare image quality and radiation dose of computed tomography angiography (CTA) of the head and neck in patients using two Gemstone Spectral Imaging (GSI) scanning protocols.

METHODS

A total of 100 patients who underwent head-neck CTA were divided into two groups (A and B) according to the scanning protocols, with 50 patients in each group. The patients in group A underwent GSI scanning protocol 1 (GSI profile: head and neck CTA), while those in group B underwent GSI scanning protocol 2 (GSI profile: chest 80 mm). All images were reconstructed using 40% and 70% pre- and post-adaptive level statistical iterative reconstruction V (pre-ASiR-V and post-ASiR-V) algorithms, respectively. The CT dose index (CTDIvol) and dose-length (DLP) product were recorded and the mean value was calculated and converted to the effective dose. CT values, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of all images were calculated. Additionally, subjective image evaluation was conducted by two independent radiologists using a five-point scoring method. All data were statistically analyzed.

RESULTS

There were no significant differences in the CT values, SNR, CNR, and subjective score between groups A and B (p > 0.05); however, the mean effective dose (1.2±0.1 mSv) in group B was 45.5% lower than that in group A (2.2±0.2 mSv) (p < 0.05).

CONCLUSIONS

GSI scanning protocol 2 could more effectively reduce the radiation dose in head-neck CT angiography while maintaining image quality compared to GSI scanning protocol 1.

Impact of 80 kVp with iterative reconstruction algorithm and low-dose contrast medium on the image quality of craniocervical CT angiography

PURPOSE

To assess the image quality of 80-kVp craniocervical CT angiography (CCCTA) protocol combined with adaptive statistical iterative reconstruction-V (ASIR-V) and low-dose contrast medium (CM).

METHODS

A total of 119 patients were randomly divided into three groups. For group A, 120-kVp protocol was followed with 60 ml CM and filtered back projection; for group B, 80-kVp protocol with 60 ml CM and ASIR-V; and for group C, 80-kVp protocol with 45 ml CM and ASIR-V. Both subjective and objective image quality and radiation doses were evaluated.

RESULTS

Arterial attenuation, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the head, neck, and shoulder regions were significantly higher in groups B and C compared with group A. Group C yielded significantly better subjective image quality than that observed in groups A and B (both p < .05). As compared with group A, effective radiation dose and the iodine load of group C were reduced by 51.4% and 25%, respectively.

CONCLUSIONS

The CCCTA protocol with 80 kVp, ASIR-V, and 45 ml of CM injected at 3 ml/s significantly reduced the radiation dose, iodine load, and iodine delivery rate while providing better subjective and objective image quality, including higher arterial enhancement and a higher SNR and CNR compared with the 120-kVp protocol.

Evaluation of Intracranial Vascular Status in Patients with Acute Ischemic Stroke by Time Maximum Intensity Projection CT Angiography: A Preliminary Study

RATIONALE AND OBJECTIVES

To describe the application of time maximum intensity projection CTA (t-MIP CTA) in acute ischemic stroke and compare t-MIP CTA and single-phase CTA (sCTA) in assessing collateral circulation and predicting prognosis.

MATERIALS AND METHODS

Twenty-nine acute ischemic stroke patients who underwent one-stop CT angiography (CTA)-CT perfusion scan were reviewed retrospectively. sCTA and t-MIP CTA were developed by CT perfusion scanning data. Image quality and collateral circulation were compared between the sCTA and t-MIP CTA groups. CT attenuation values, image noise, signal to noise , contrast to noise, and subjective image quality were obtained and compared between these two groups. The correlations of clinical prognosis and infarct volume with collateral status on t-MIP CTA and sCTA were analyzed, separately. Receiver operating characteristic curve was used to reveal the sensitivity and specificity of t-MIP CTA and sCTA in predicting outcome.

RESULTS

All images exhibited good quality for diagnosis. In objective evaluation, the noise level of t-MIP CTA was significantly lower than that of sCTA (p < 0.001). Vascular attenuation (signal to noise and contrast to noise) of t-MIP were higher than those of sCTA (all, p < 0.001). The collateral status on t-MIP CTA and sCTA were both negatively correlated with modified Rankin Scale scores (t-MIP CTA, r = -0.709, p < 0.001; sCTA, r = -0.551, p = 0.024) and the final infarction volume (t-MIP CTA, r = -0.716, p = 0.001; sCTA, r = -0.629, p = 0.003). t-MIP CTA was better for predicting prognosis (AUC, 0.956; sensitivity, 0.917; specificity, 0.941; p < 0.001) than sCTA (AUC, 0.824; sensitivity, 0.500; specificity, 0.941; p = 0.003).

CONCLUSION

In comparison with sCTA, t-MIP images showed higher image quality of intracranial vascularity and MIP could reveal vascular occlusion and evaluate collateral circulation more accurately. It was speculated that t-MIP could predict the prognosis more precisely.

Ultra-low-dose multiphase CT angiography derived from CT perfusion data in patients with middle cerebral artery stenosis

PURPOSE

Computed tomography (CT) perfusion (CTP) source images contain both brain perfusion and cerebrovascular information, and may allow a dynamic assessment of collaterals. The purpose of the study was to compare the image quality and the collaterals identified on multiphase CT angiography (CTA) derived from CTP datasets (hereafter called CTPA) reconstructed with iterative model reconstruction (IMR) algorithm in patients with middle cerebral artery (MCA) steno-occlusion with those of routine CTA.

METHODS

Consecutive patients with a unilateral MCA steno-occlusion underwent non-contrast CT (NCCT), CTP, and CTA. CTPA images were reconstructed from CTP datasets. The vascular attenuation, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of routine CTA and CTPA were measured and analyzed by Student's t test. Subjective image quality and collaterals were scored and compared using the Wilcoxon signed-rank test.

RESULTS

Fifty-eight patients (mean age 61.7 years, 78% males, median National Institutes of Health Stroke Scale score = 12) were included. The effective radiation dose of CTP was 1.28 mSv. The vascular attenuation, SNR, CNR, and the image quality of CTPA were considerably higher than that of CTA (all, p < 0.001). Collaterals were rated higher on CTPA compared with CTA (1.79 ± 0.64 vs. 1.22 ± 0.84, p < 0.001). Fifty-three percent of patients with poor collaterals assessed on single-phase CTA had good collaterals on CTPA.

CONCLUSION

CTPA derived from CTP datasets reconstructed with IMR algorithm offers image quality comparable to routine CTA and provides time-resolved evaluation of collaterals in patients with MCA ischemic disease.

Assessment of radiation dose and iodine load reduction in head-neck CT angiography using two scan protocols with wide-detector

OBJECTIVE

To compare image quality, radiation dose, and iodine intake of head-neck CT angiography (CTA) acquired by wide-detector with the gemstone spectral imaging (GSI) combination with low iodine intake or routine scan protocol.

METHODS

Three hundred patients who had head-neck CTA were enrolled and divided into three groups according to their BMI values: group A (18.5 kg/m2 ≦ BMI <24.9 kg/m2), group B (24.9 kg/m2 ≦ BMI <29.9 kg/m2) and group C (29.9 kg/m2 ≦ BMI ≦ 34.9 kg/m2) with 100 patients in each group. Patients in each group were randomly divided into two subgroups (n = 50) namely, A1, A2, B1, B2, C1 and C2. The patients in subgroups A1, B1 and C1 underwent GSI with low iodine intake (270 mgI/ml, 50 ml) and combined with the ASiR-V algorithm. Other patients underwent three dimensional (3D) smart mA modulation with routine iodine intake (350 mgI/ml, 60 ml). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of all images were calculated after angiography. Images were then subjectively assessed using a 5-point scale. CT dose index of volume and dose-length product (DLP) was converted to the effective dose (ED) and then compared.

RESULTS

The mean CT values, SNR, CNR and subjective image quality in subgroups A2, B2 and C2 are significantly lower than in subgroups A1, B1, and C1 (P < 0.01), respectively. The ED values in subgroup A1, B1, and C1 are 55.18%, 61.89%, and 69.64% lower than those in A2, B2, and C2, respectively (P < 0.01). The total iodine intakes in subgroups A1, B1, and C1 are 35.72% lower than those in subgroups A2, B2, and C2.

CONCLUSIONS

The gemstone spectral imaging with monochromatic images at 53-57 keV combined with ASiR-V algorithm allows significant reduction in iodine load and radiation dose in head-neck CT angiography than those yielded in routine scan protocol. It also enhances signal intensity of head-neck CTA and maintains image quality.

Comparative analysis of radiation dose and image quality between organ dose modulation and 3D smart mA modulation during head-neck CT angiography

OBJECTIVE

To assess the difference in absorbed organ dose and image quality for head-neck CT angiography using organ dose modulation compared with 3D smart mA modulation in different body mass indices (BMIs) using an adaptive statistical iterative reconstruction (ASiR-V) algorithm.

METHODS

Three hundred patients underwent head-neck CTA were equally divided into three groups: A (18.5 kg/m2≦BMI < 24.9 kg/m2), B (24.9 kg/m2≦BMI < 29.9 kg/m2) and C (29.9 kg/m2≦BMI≦34.9 kg/m2). The groups were randomly subdivided into two subgroups (n = 50): A1-A2, B1-B2 and C1-C2. The patients in subgroups A1, B1 and C1 underwent organ dose modulation with the ASiR-V algorithm, while other patients underwent 3D smart mA modulation. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of all head-neck CT angiography images were calculated. Images were then subjectively evaluated. Mean values of several indices including dose-length product (DLP) were computed. The DLP was converted to the effective dose (ED). SNR, CNR and ED in groups A, B, and C were compared in statistical data analysis.

RESULTS

SNR, CNR, and subjective image scores show no statistical differences in three groups (P  >  0.05). However, there is significant difference of ED values (P  <  0.05) . For example, in subgroup A1 mean ED values are 15.30% and 23.66% lower than those in subgroup A2 at thyroid gland and eye lens, respectively. Similar patterns also exist in groups B (B1 vs. B2) and C (C1 vs. C2).

CONCLUSIONS

Using organ dose modulation and applying the ASiR-V algorithm can more effectively reduce the radiation dose in head-neck CT angiography than using 3D smart mA modulation, while maintaining image quality. Thus, using organ-based dose modulation has the additional benefit of reducing dose to the thyroid gland and eye lens.