Comparison of the cardiothoracic ratio between postmortem and antemortem computed tomography.

As postmortem imaging has gained prominence as a supplement to traditional autopsy, it is important to understand the normal postmortem changes to enable the accurate evaluation of postmortem imaging. No studies have evaluated the postmortem changes in cardiothoracic ratio (CTR) compared with antemortem images in the same subjects. We studied 147 consecutive subjects who underwent antemortem and postmortem CT, and autopsy. Postmortem CT was performed <23h after death and was followed by autopsy. The subjects were divided into three groups: normal heart, old myocardial infarction, and CPR-treated hearts. CTR was compared between antemortem and postmortem CT using paired t tests, which revealed that the CTR was greater on postmortem CT than on antemortem CT in all groups (mean CTR: 0.53±0.06vs. 0.50±0.06, respectively; P<0.01). Sex, age, time elapsed since death, and the causes of death were examined as potential confounding factors for the postmortem changes in CTR, but no significant associations were found. Receiver-operating characteristic (ROC) curves were used to determine CTR values for cardiomegaly, which was defined according to the autopsy weight of the heart. The area under the ROC curve was 0.71 (95% confidence interval 0.63-0.79). The CTR threshold of 0.54 identified cardiomegaly with the greatest accuracy, compared with the general threshold of 0.50. In conclusion, the CT-determined CTR increases after death, irrespective of the heart's condition. We should be cautious of overdiagnosis of cardiomegaly on postmortem CT, and new criteria for interpreting cardiomegaly on postmortem CTR are needed.

Subjective and objective evaluation of 10-30% dose reduced coronary artery phantom scans reconstructed with Forward projected model-based Iterative Reconstruction SoluTion (FIRST).

The data presented in this articles are related to the research article entitled "The feasibility of Forward-projected model-based Iterative Reconstruction SoluTion (FIRST) for coronary 320-row computed tomography angiography: a pilot study" (E. Maeda, N. Tomizawa, S. Kanno, K. Yasaka, T. Kubo, K. Ino, R. Torigoe, K. Ohtomo, 2016) [1]. This article describes subjective and objective evaluations of 2 mm-4 mm coronary artery phantom scanned with 100% dose and reconstructed with hybrid iterative reconstruction, and 90%, 80% and 70% dose reconstructed with full iterative reconstruction.

The feasibility of Forward-projected model-based Iterative Reconstruction SoluTion (FIRST) for coronary 320-row computed tomography angiography: A pilot study.

BACKGROUND: We aimed to assess and compare the influence of Forward projected model-based Iterative Reconstruction SoluTion (FIRST), a recently introduced full iterative reconstruction method, on radiation doses and image quality with that of Adaptive Iterative Dose Reduction (AIDR) 3D for 320-row cardiac computed tomography (CT). METHODS: A total of 184 patients subjected to single-beat reconstruction cardiac CT were retrospectively included. The first 89 patients received standard radiation doses; their data were reconstructed using AIDR 3D, whereas the last 95 patients received in average 20% reduction in tube current; their data were reconstructed using FIRST. Subjective image quality (blooming, image sharpness, image noise, and overall subjective image quality) were graded using 3-, 5-, 4-, and 4-point scales (0-2, 1-5, 1-4, and 1-4), respectively; for all items, the highest score indicated excellent image quality. Image noise and signal-to-noise ratios at proximal segments were analyzed as objective measures of image quality. RESULTS: FIRST reconstruction allowed 28% dose reduction compared with AIDR 3D (1.88 vs. 2.61 mSv, p = 0.012) and yielded better subjective image quality in terms of blooming, image sharpness, image noise, and overall image quality (1.10 vs. 1.01, p = 0.0007; 3.02 vs. 2.74, p < 0.0001; 3.61 vs. 3.17, p < 0.0001; and 3.30 vs. 2.98, p < 0.0001, respectively). Although no significant difference was observed in image noise, the signal-to-noise ratio was significantly higher with FIRST (18.4 vs. 16.6, p = 0.0066). CONCLUSIONS: FIRST allowed 28% dose reduction while improving image quality.

Diagnostic Phase of Calcium Scoring Scan Applied as the Center of Acquisition Window of Coronary Computed Tomography Angiography Improves Image Quality in Minimal Acquisition Window Scan (Target CTA Mode) Using the Second Generation 320-Row CT.

OBJECTIVE: To compare the image quality of coronary computed tomography angiography (CCTA) acquired under two conditions: 75% fixed as the acquisition window center (Group 75%) and the diagnostic phase for calcium scoring scan as the center (CS; Group CS). METHODS: 320-row cardiac CT with a minimal acquisition window (scanned using "Target CTA" mode) was performed on 81 patients. In Group 75% (n = 40), CS was obtained and reconstructed at 75% and the center of the CCTA acquisition window was set at 75%. In Group CS (n = 41), CS was obtained at 75% and the diagnostic phase showing minimal artifacts was applied as the center of the CCTA acquisition window. Image quality was evaluated using a four-point scale (4-excellent) and the mean scores were compared between groups. RESULTS: The CCTA scan diagnostic phase occurred significantly earlier in CS (75.7 ± 3.2% vs. 73.6 ± 4.5% for Groups 75% and CS, resp., p = 0.013). The mean Group CS image quality score (3.58 ± 0.63) was also higher than that for Group 75% (3.19 ± 0.66, p < 0.0001). CONCLUSIONS: The image quality of CCTA in Target CTA mode was significantly better when the center of acquisition window is adjusted using CS.

Comparison of volume and attenuation of the spleen between postmortem and antemortem computed tomography.

OBJECTIVES: The purpose of this study is to compare the postmortem changes in computed tomography (CT) findings between normal spleen, splenic infarct, and splenic tumor infiltration. METHODS: The institutional review board approved this study, and informed consent was obtained from the next of kin. We studied 63 consecutive subjects who underwent antemortem CT, postmortem CT, and autopsy between February 2012 and December 2013. Postmortem CT was performed within 1678 min after death and was followed by pathological studies. The subjects were divided into three groups based on the pathological findings: normal, splenic infarct, and splenic tumor infiltration. The volume and attenuation of the spleen were compared between antemortem and postmortem CT using paired t tests. Gender, age, time elapsed since death, and the causes of death were examined as potential confounding factors of the postmortem changes in volume and attenuation. RESULTS: In all groups, the spleen decreased in volume and attenuation increased on postmortem CT compared with antemortem CT. The postmortem changes in spleen volume and attenuation were not significantly associated with sex, age, time elapsed since death, or causes of death. CONCLUSIONS: Spleen volume decreased and attenuation increased on postmortem CT compared with antemortem CT in subjects with a normal spleen, splenic infarct, or splenic tumor infiltration. These results should caution us against underestimating the significance of splenomegaly on postmortem CT, misinterpreting reduced splenic volume as the presence of hypovolemic or distributive shock in the subject while alive, and confusing postmortem splenic hyperattenuation with diseases characterized by this finding.

Optimized heart rate for 320-row cardiac CT can be feasibly predicted from prescan parameters.

To evaluate the degree of heart rate (HR) changes at rest (HRrest), during breath hold (HRtest), and during cardiac CT examinations (HRscan) in a large group of patients , and to derive and asses the feasibility of a predictive formula for HRscan. HRrest, HRtest, and HRscan were retrospectively compared in a total of 563 consecutive patients who underwent 320-row cardiac CT. Multiple regression analysis was performed to derive predictive formulae for HRscan in the entire study population and, in each group of patients with decreased (Dec) or increased (Inc) HR during breath hold. The predictive formula was evaluated as accurate when less than 5 % of the actual HRscan exceeded the predicted HRscan by ±5 beats per minute (bpm). The average values of the HRtest (65.3 ± 12.0 bpm) and HRscan (63.7 ± 11.9 bpm) significantly decreased from those of the HRrest (68.4 ± 11.9 bpm) (p < 0.0001). The predictive formula (HRscan = 3.601 + 0.113HRrest + 0.8HRtest) was determined to be accurate only in Group Dec. The HRtest significantly decreased from the HRrest, and the HRscan significantly decreased from the HRtest. An accurate predictive formula for HRscan could be built only for Group Dec.

Minimizing the acquisition phase in coronary CT angiography using the second generation 320-row CT.

PURPOSE: We aimed to compare the radiation dose and image quality of a minimal phase window centered at 77 % compared with a wide phase window in coronary CT angiography using the second-generation 320-row CT. MATERIALS AND METHODS: Eighty patients with heart rate ≤75 bpm were retrospectively included. The first 40 patients underwent scanning with a wide phase window (65-85 %), while the last 40 patients underwent scanning with a minimal phase window centered at 77 %. Subjective image quality was graded using a 4-point scale (4 = excellent). Image noise and contrast-to-noise ratio at the proximal segments were also analyzed. The mean effective dose was derived from the dose length product multiplied by a chest conversion coefficient (κ = 0.014 mSv mGy(-1) cm(-1)). RESULTS: Minimal phase window scanning centered at 77 % reduced the radiation dose by 30 % compared with wide phase window scanning (1.7 vs 2.4 mSv, p = 0.0009). The subjective image quality showed no significant difference (3.75 vs 3.76, p = 0.77). No significant difference was observed in the image noise, CT number, and contrast-to-noise ratio. CONCLUSIONS: Radiation dose could be reduced while maintaining image quality by use of a minimal phase window centered at 77 % compared with a wide phase window in coronary CT angiography using the second generation 320-row CT.