Korean J Radiol.  2019 Sep;20(9):1358-1367. 10.3348/kjr.2018.0715.

Application of Vendor-Neutral Iterative Reconstruction Technique to Pediatric Abdominal Computed Tomography

• Lim WH
• Choi YH
• Park JE
• Cho YJ
• Lee S
• Cheon JE
• Kim WS
• Kim IO
• Kim JH

• KMID: 2455764
• DOI: http://doi.org/10.3348/kjr.2018.0715

Abstract

OBJECTIVE
To compare image qualities between vendor-neutral and vendor-specific hybrid iterative reconstruction (IR) techniques for abdominopelvic computed tomography (CT) in young patients.
MATERIALS AND METHODS
In phantom study, we used an anthropomorphic pediatric phantom, age-equivalent to 5-year-old, and reconstructed CT data using traditional filtered back projection (FBP), vendor-specific and vendor-neutral IR techniques (ClariCT; ClariPI) in various radiation doses. Noise, low-contrast detectability and subjective spatial resolution were compared between FBP, vendor-specific (i.e., iDose1 to 5; Philips Healthcare), and vendor-neutral (i.e., ClariCT1 to 5) IR techniques in phantom. In 43 patients (median, 14 years; age range 1-19 years), noise, contrast-to-noise ratio (CNR), and qualitative image quality scores of abdominopelvic CT were compared between FBP, iDose level 4 (iDose4), and ClariCT level 2 (ClariCT2), which showed most similar image quality to clinically used vendor-specific IR images (i.e., iDose4) in phantom study. Noise, CNR, and qualitative imaging scores were compared using one-way repeated measure analysis of variance.
RESULTS
In phantom study, ClariCT2 showed noise level similar to iDose4 (14.68-7.66 Hounsfield unit [HU] vs. 14.78-6.99 HU at CT dose index volume range of 0.8-3.8 mGy). Subjective low-contrast detectability and spatial resolution were similar between ClariCT2 and iDose4. In clinical study, ClariCT2 was equivalent to iDose4 for noise (14.26-17.33 vs. 16.01-18.90) and CNR (3.55-5.24 vs. 3.20-4.60) (p > 0.05). For qualitative imaging scores, the overall image quality ([reader 1, reader 2]; 2.74 vs. 2.07, 3.02 vs. 2.28) and noise (2.88 vs. 2.23, 2.93 vs. 2.33) of ClariCT2 were superior to those of FBP (p < 0.05), and not different from those of iDose4 (2.74 vs. 2.72, 3.02 vs. 2.98; 2.88 vs. 2.77, 2.93 vs. 2.86) (p > 0.05).
CONCLUSION
Vendor-neutral IR technique shows image quality similar to that of clinically used vendor-specific hybrid IR technique for abdominopelvic CT in young patients.

Keyword

Iterative reconstruction; Pediatric; Computed tomography; Abdomen; Vendor-neutral; Phantom

MeSH Terms

Abdomen
Child, Preschool
Clinical Study
Humans
Noise

Figure

• 

  Fig. 1 CT images of pediatric anthropomorphic phantom.Axial images obtained at level of upper abdomen with cylindrical (A) and line pair targets (B) inserted. Both images were obtained at CTDIvol level of 1.9 mGy and reconstructed using FBP. A. Window width: 200 and level: 50. B. Window width: 500 and level: 100. C. For quantitative noise measurements, four ROIs were drawn on each image: one ROI was located at center, and three were at peripheral portion of phantom. Wire located in spinal canal (arrow) was used for MTF measurement. CT = computed tomography, CTDIvol = volume CT dose index, FBP = filtered back projection, MTF = modulation transfer function, ROI = region of interest

• 

  Fig. 2 MTF and NPS according to reconstruction methods and strengths.A. MTF curves of FBP, iDose4, and ClariCT2 are shown. MTF10 measured at CTDIvol of 1.9 mGy was 5.93 lp/cm for FBP, 5.85 for iDose1 to iDose3, and 5.81 for iDose4 and iDose5. In case of ClariCT, MTF10 was 6.23, 6.23, 6.14, 6.14, and 6.19 lp/cm for ClariCT1 to ClariCT5, respectively. B. Results of NPS according to representative reconstruction methods are shown. Overall, heights of NPS curves of iDose4 and ClariCT2 are substantially lower than that of FBP, reflecting reduced noise levels. Curve shape in ClariCT2 is flatter than that of iDose4, indicating finer noise texture in ClariCT2 after denoise processing. iDose; Philips Healthcare, ClariCT; ClariPI. ClariCT2 = ClariCT level 2, HU = Hounsfield unit, iDose4 = iDose level 4, MTF10 = 10% MTF, NPS = noise power spectrum

• 

  Fig. 3 12-year-old male patient was taken CT scan because of fever.Abdominal CT scan revealed multifocal fungal abscess in liver (arrow on A) and spleen (not presented). A. FBP. B. iDose4. C. ClariCT2.

• 

  Fig. 4 12-year-old female patient visited emergency department with right lower quadrant abdominal pain.Patient was taken CT scan to rule out acute appendicitis, and CT scan revealed clear appendix (arrow on A). A. FBP. B. iDose4. C. ClariCT2.

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