Comparison of image quality in pediatric head computed tomography reconstructed using blended iterative reconstruction versus filtered back projection

Pediatric head computed tomography with advanced modeled iterative reconstruction: focus on image quality and reduction of radiation dose

BACKGROUND

Iterative reconstruction has become the standard method for reconstructing computed tomography (CT) scans and needs to be verified for adaptation.

OBJECTIVE

To assess the image quality after adapting advanced modeled iterative reconstruction (ADMIRE) for pediatric head CT.

MATERIALS AND METHODS

We included image sets with filtered back projection reconstruction (the cFBP group, n=105) and both filtered back projection and ADMIRE reconstruction (the lower-dose group, n=109) after dose reduction. All five strength levels of ADMIRE and filtered back projection were adapted for the lower-dose group and compared with the cFBP group. Quantitative parameters including noise, signal-to-noise ratio and contrast-to-noise ratio and qualitative parameters including noise, white matter and gray matter differentiation of the supra- and infratentorial levels, sharpness, artifact, and diagnostic accuracy were also evaluated and compared with interobserver agreement.

RESULTS

There was a mean dose reduction of 30.6% in CT dose index volume, 32.1% in dose length product, and 32.1% in effective dose after tube current reduction. There was gradual reduction of noise in air, cerebrospinal fluid and white matter with strength levels of ADMIRE from 1 to 5 (P<0.001). Signal-to-noise ratio and contrast-to-noise ratio in all age groups increased among strength levels of ADMIRE, in sequence from 1 to 5, with statistical significance (P<0.001). Gradual reduction of qualitative parameters was noted among strength levels of ADMIRE in sequence from 1 to 5 (P<0.001).

CONCLUSION

Use of ADMIRE for pediatric head CT can reduce radiation dose without degrading image quality.

Comparison of Iterative Model Reconstruction versus Filtered Back-Projection in Pediatric Emergency Head CT: Dose, Image Quality, and Image-Reconstruction Times

BACKGROUND AND PURPOSE

Noncontrast CT of the head is the initial imaging test for traumatic brain injury, stroke, or suspected nonaccidental trauma. Low-dose head CT protocols using filtered back-projection are susceptible to increased noise and decreased image quality. Iterative reconstruction noise suppression allows the use of lower-dose techniques with maintained image quality. We review our experience with children undergoing emergency head CT examinations reconstructed using knowledge-based iterative model reconstruction versus standard filtered back-projection, comparing reconstruction times, radiation dose, and objective and subjective image quality.

MATERIALS AND METHODS

This was a retrospective study comparing 173 children scanned using standard age-based noncontrast head CT protocols reconstructed with filtered back-projection with 190 children scanned using low-dose protocols reconstructed with iterative model reconstruction. ROIs placed on the frontal white matter and thalamus yielded signal-to-noise and contrast-to-noise ratios. Volume CT dose index and study reconstruction times were recorded. Random subgroups of patients were selected for subjective image-quality review.

RESULTS

The volume CT dose index was significantly reduced in studies reconstructed with iterative model reconstruction compared with filtered back-projection, (mean, 24.4 ± 3.1 mGy versus 31.1 ± 6.0 mGy, P < .001), while the SNR and contrast-to-noise ratios improved 2-fold (P < .001). Radiologists graded iterative model reconstruction images as superior to filtered back-projection images for gray-white matter differentiation and anatomic detail (P < .001). The average reconstruction time of the filtered back-projection studies was 101 seconds, and with iterative model reconstruction, it was 147 seconds (P < .001), without a practical effect on work flow.

CONCLUSIONS

In children referred for emergency noncontrast head CT, optimized low-dose protocols with iterative model reconstruction allowed us to significantly reduce the relative dose, on average, 22% compared with filtered back-projection, with significantly improved objective and subjective image quality.

Comparing Fourth Generation Statistical Iterative Reconstruction Technique to Standard Filtered Back Projection in Pediatric Head Computed Tomography Examinations

OBJECTIVE

Although advanced statistical iterative reconstruction (IR) techniques are valued in pediatric computed tomography (CT) imaging, there is little published data on how these techniques affect image quality and radiation dose in the pediatric population. This is particularly true in the context of pediatric head CT examinations. This study analyzed the differences in image quality and several standard metrics of radiation dose on multidetector pediatric head CT examinations performed using standard filtered back projection (FBP) with reconstructions using iDose, a fourth-generation statistical iterative reconstruction technique.

MATERIALS AND METHODS

Using a retrospective review of 282 pediatric head CT examinations, we compared how iDose fared against FBP for effects on several standard metrics of radiation dose and qualitative and quantitative assessment of image quality.

RESULTS

Our assessment revealed that examinations obtained using low-dose protocols reconstructed using iDose, when compared with standard-dose examinations reconstructed using FBP, resulted in significant radiation dose reduction while performing equally or better in quantitative image quality parameters. For most qualitative image quality parameters, the iDose group demonstrated equal performance to standard filtered back technique with a few notable exceptions. In the parameter of image sharpness in the 1.5 to 7 year olds, iDose fared better than FBP. However, FBP outperformed iDose in the qualitative parameters of decreased image graininess/noise in patients older than 13 years, improved image sharpness in patients aged between 7 and 13 years, and improved visibility of small parts for those aged 7 to 13 years.

CONCLUSIONS

We conclude that iDose is effective at allowing significant radiation dose reduction while maintaining or, rarely, even improving quantitative image quality compared with FBP in the setting of pediatric head CT examinations. However, for certain qualitative image quality parameters in older-aged children, the use of iDose resulted in a poorer performance compared with FBP.

Optimization of hybrid iterative reconstruction level and evaluation of image quality and radiation dose for pediatric cardiac computed tomography angiography

BACKGROUND

Hybrid iterative reconstruction can reduce image noise and produce better image quality compared with filtered back-projection (FBP), but few reports describe optimization of the iteration level.

OBJECTIVE

We optimized the iteration level of iDose⁴ and evaluated image quality for pediatric cardiac CT angiography.

MATERIALS AND METHODS

Children (n = 160) with congenital heart disease were enrolled and divided into full-dose (n = 84) and half-dose (n = 76) groups. Four series were reconstructed using FBP, and iDose⁴ levels 2, 4 and 6; we evaluated subjective quality of the series using a 5-grade scale and compared the series using a Kruskal-Wallis H test. For FBP and iDose⁴-optimal images, we compared contrast-to-noise ratios (CNR) and size-specific dose estimates (SSDE) using a Student's t-test. We also compared diagnostic-accuracy of each group using a Kruskal-Wallis H test.

RESULTS

Mean scores for iDose⁴ level 4 were the best in both dose groups (all P < 0.05). CNR was improved in both groups with iDose⁴ level 4 as compared with FBP. Mean decrease in SSDE was 53% in the half-dose group. Diagnostic accuracy for the four datasets were in the range 92.6-96.2% (no statistical difference).

CONCLUSION

iDose⁴ level 4 was optimal for both the full- and half-dose groups. Protocols with iDose⁴ level 4 allowed 53% reduction in SSDE without significantly affecting image quality and diagnostic accuracy.

Dose reduction in paediatric cranial CT via iterative reconstruction: a clinical study in 78 patients

AIM

To assess how adaptive statistical iterative reconstruction (ASIR) contributes to dose reduction and affects image quality of non-contrast cranial computed tomography (cCT) in children.

MATERIALS AND METHODS

Non-contrast cranial CT acquired in 78 paediatric patients (age 0-12 years) were evaluated. The images were acquired and processed using four different protocols: Group A (control): 120 kV, filtered back projection (FBP), n=18; Group B: 100 kV, FBP, n=22; Group C: 100 kV, scan and reconstruction performed with 20% ASIR, n=20; Group D1: 100 kV, scan and reconstruction performed with 30% ASIR, n=18; Group D2: raw data from Group D1 reconstructed using a blending of 40% ASIR and 60% FBP, n=18. The effective dose was calculated and the image quality was assessed quantitatively and qualitatively.

RESULTS

Compared to Group A, Groups C and D1/D2 showed a significant reduction of the dose-length product (DLP) by 34.4% and 64.4%, respectively. All experimental groups also showed significantly reduced qualitative levels of noise, contrast, and overall diagnosability. Diagnosis-related confidence grading showed Group C to be adequate for everyday clinical practice. Quantitative measures of Groups B and C were comparable to Group A with only few parameters compromised. Quantitative scores in Groups D1 and D2 were mainly lower compared to Group A, with Group D2 performing better than Group D1. Group D2 was considered adequate for follow-up imaging of severe acute events such as bleeding or hydrocephalus.

DISCUSSION

The use of ASIR combined with low tube voltage may reduce radiation significantly while maintaining adequate image quality in non-contrast paediatric cCT.

Hybrid and model-based iterative reconstruction techniques for pediatric CT

OBJECTIVE. Radiation exposure from CT examinations should be reduced to a minimum in children. Iterative reconstruction (IR) is a method to reduce image noise that can be used to improve CT image quality, thereby allowing radiation dose reduction. This article reviews the use of hybrid and model-based IRs in pediatric CT and discusses the possibilities, advantages, and disadvantages of IR in pediatric CT and the importance of radiation dose reduction for CT of children. CONCLUSION. IR is a promising and potentially highly valuable technique that can be used to substantially reduce the amount of radiation in pediatric imaging. Future research should determine the maximum achievable radiation dose reduction in pediatric CT that is possible without a loss of diagnostic image quality.