ABSTRACT
INTRODUCTION: The purpose of this study was to evaluate the radiation dose and image quality of computed tomography urograms (CTU) using tin-filtration compared to conventional CTU (without tin-filtration) examinations in patients with suspected urolithiasis. METHODS: Group 1 consisted of 100 patients who were examined using the tin-filtered CTU protocols (Sn100kVp or Sn150kVp); Group 2 consisted of 100 patients who were examined using the same protocols but without tin-filtration (GE-NI41 or GE-NI43). The scanning protocol was based on the patients' body weight (<80â¯kg and ≥80â¯kg). The effective doses of all scans were compared between the two groups. Subjective image quality was evaluated by two blinded radiologists. The objective image quality was assessed for noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and figure-of-merit (FOM) using the CTU scans acquired from both the tin-filtered and non-tin-filtered protocols. RESULTS: Tin-filtration resulted in the reduction of effective radiation dose ranging between 72% to 88% for the ≥80â¯kg and <80â¯kg patient groups respectively. For both groups, tin-filtration resulted in no significant differences in SNR and a significant increase in FOM. For the <80â¯kg group, tin-filtration resulted in significantly noisier images but with no significant difference in CNR. For the ≥80â¯kg group, tin-filtration resulted in significantly higher CNR. There was no significant difference in subjective image quality when assessed by the radiologists in terms of diagnostic confidence for urolithiasis. CONCLUSION: Tin-filtration significantly reduces patient dose while maintaining diagnostic image quality of CTUs for patients with suspected urolithiasis.
Subject(s)
Radiation-Protective Agents/therapeutic use , Tin/therapeutic use , Tomography, X-Ray Computed/methods , Urolithiasis/diagnostic imaging , Female , Humans , Male , Middle Aged , Observer Variation , Radiation Dosage , Radiation Protection/methods , Radiographic Image Interpretation, Computer-Assisted/methods , Radiologists , Signal-To-Noise Ratio , Tomography, X-Ray Computed/standards , Urography/methods , Urography/standardsABSTRACT
OBJECTIVES: To compare the image quality between fine focal spot size (FFSS) and standard focal spot size (SFSS) in computed tomography of the abdomen and pelvis (CTAP) METHODS: This retrospective review included all consecutive adult patients undergoing contrast-enhanced CTAP between June and September 2014. Two blinded radiologists assessed the margin clarity of the abdominal viscera and the detected lesions using a five-point grading scale. Cohen's kappa test was used to examine the inter-observer reliability between the two reviewers for organ margin clarity. Mann-Whitney U testing was utilised to assess the statistical difference of the organ and lesion margin clarity. RESULTS: 100 consecutive CTAPs were recruited. 52 CTAPs were examined with SFSS of 1.1 × 1.2 mm and 48 CTAPs were examined with FFSS of 0.6 × 0.7 mm. Results showed that there was substantial agreement for organ margin clarity (mean κ = 0.759, p < 0.001) among the reviewers. FFSS produces images with clearer organ margins (U = 76194.0, p < 0.001, r = 0.523) and clearer lesion margins (U = 239, p = 0.052, r = 0.269). CONCLUSION: FFSS CTAP improves image quality in terms of better organ and lesion margin clarity. Fine focus CT scanning is a novel technique that may be applied in routine CTAP imaging. KEY POINTS: ⢠Fine focal spot improves organ margin clarity. ⢠Fine focal spot improves lesion margin clarity. ⢠Fine focal spot can be used in routine CT abdominal imaging.
