Coronary artery calcium scoring assessment in ultra-low-dose chest computed tomography.

OBJECTIVES: To investigate the effect of non-electrocardiogram (ECG) -triggered ultra-low-dose CT (ULD-CT) with different reconstruction protocols on coronary artery calcium (CAC) scoring assessment, compared with ECG-triggered CAC CT (CAC-CT). METHODS: This prospective study included 115 patients who underwent CAC-CT and ULD-CT scans under the same topogram images. CAC-CT adopted a prospective ECG-triggered sequential acquisition with a tube potential of 120 kV, and the reconstruction protocol was standard Qr36 + slice 3 mm (CACQr-3mm group). ULD-CT adopted a non-ECG-triggered high-pitch acquisition with a tube potential of Sn100 kV, and four groups of images (named ULDQr-3mm, ULDSa-3mm, ULDQr-1.5mm, and ULDSa-1.5mm) were reconstructed using different reconstruction algorithms (standard Qr36, kV-independent Sa36) and slice thicknesses (3 mm, 1.5 mm). The accuracy of CAC detection by ULD-CT was calculated. The agreement of the CAC score between ULD-CT and CAC-CT scans was assessed using intraclass correlation coefficients (ICC) and Bland-Altman plot, and the agreement of risk categorization was assessed using weighted kappa. RESULTS: The sensitivity and specificity of the ULDSa-1.5mm group for detecting positive CAC were 100% and 97.4%, respectively (k = 0.980). The CAC score for the ULDSa-3mm and ULDSa-1.5mm groups demonstrated excellent agreement with the CACQr-3mm group (ICC = 0.992, 0.990, respectively), with a mean difference of -12.3 and - 12.4. The agreement of risk categorization based on absolute and percentile CAC score between the ULDSa-1.5mm and CACQr-3mm groups was excellent (weighted k = 0.954, 0.983, respectively), and risk reclassification rates were low (3.5%, 2.8%, respectively). The effective dose was reduced by approximately 77.2% for the ULD-CT compared to the CAC-CT (0.18 mSv vs. 0.79 mSv, p < 0.001). CONCLUSION: Reconstruction with a 1.5-mm slice thickness and kV-independent iterative algorithmic protocol in ULD-CT yielded excellent agreement in CAC score quantification and risk categorization compared with ECG-triggered CAC-CT.

Optimization of uniformity in coronary artery enhancement using a bolus tracking technique with a dual region of interest in coronary computed tomographic angiography.

BACKGROUND: Consistent coronary artery enhancement is essential to achieve accurate and reproducible quantification of coronary plaque composition. PURPOSE: To optimize coronary artery uniformity of enhancement using a bolus tracking technique with a dual region of interest (ROI) in coronary computed tomography angiography (CCTA) on a 320-detector CT scanner. MATERIAL AND METHODS: This prospective study recruited 100 consecutive patients who underwent CCTA and were randomly divided into two groups, namely, a manual trigger group (n = 50), in which a manual fast start technique was used to start the diagnostic scan with the visual evaluation of attenuation in the left atrium and left ventricle, and an automatic trigger group (n = 50), in which a bolus tracking technique was used to automatically start the breath-holding command and diagnostic scan with two ROIs placed in the right and left ventricles. Coronary artery image quality was assessed using quantitative and qualitative scores. The enhancement uniformity was characterized by attenuation variability of the ascending aorta (AAO) and coronary arteries. RESULTS: No statistically significant differences in the image quality of the coronary arteries were observed between the two groups (all P > 0.05). The coefficients of variation (COVs) of arterial attenuation in the automatic trigger group were significantly smaller than in the manual trigger group (AAO: 9.89% vs. 17.93%; LMA: 10.35% vs. 18.98%; LAD proximal: 12.09% vs. 20.84%; LCX proximal: 11.85% vs. 20.95%; RCA proximal: 12.13% vs. 20.84%; all P < 0.05). CONCLUSION: The automatic trigger technique accompanied with dual ROI provides consistent coronary artery enhancement and optimizes coronary artery enhancement uniformity in CCTA on a 320-detector CT scanner.

Size-Specific Dose Estimates of Radiation Based on Body Weight and Body Mass Index for Chest and Abdomen-Pelvic CTs.

BACKGROUND: To correlate body weight, body mass index (BMI), and water-equivalent diameter (d w) and to assess size-specific dose estimates (SSDEs) based on body weight and BMI for chest and abdomen-pelvic CT examinations. METHODS: An in-house program was used to calculate d w, size-dependent conversion factor (f), and SSDE for 1178 consecutive patients undergoing chest and abdomen-pelvic CT examinations. Associations among body weight, BMI, and d w were determined, and linear equations were generated using linear regression analysis of the first 50% of the patient population. SSDEs (SSDEweight and SSDEBMI) were calculated based on body weight and BMI as d w surrogates on the second 50% of the patient population. Mean root-mean-square errors of SSDEweight and SSDEBMI were computed with SSDE from the axial images as reference values. RESULTS: Both body weight and BMI correlated strongly with d w for the chest (r = 0.85, 0.87, all p < 0.001) and abdomen-pelvis (r = 0.85, 0.86, all p < 0.001). Mean values of SSDEweight and SSDEBMI based on the linear equations for body weight, BMI, and d w were in close agreement with SSDE from the axial images, with overall mean root-mean-square errors of 0.62 mGy (6.10%) and 0.57 mGy (5.65%), for chest, and 0.76 mGy (5.61%) and 0.71 mGy (5.22%), for abdomen-pelvis, respectively. CONCLUSIONS: Both body weight and BMI, serving as d w surrogates, can be used to calculate SSDEs in the chest and abdomen-pelvis CT examinations, providing values comparable to SSDEs from the axial images, with an overall mean root-mean-square error of less than 0.76 mGy or 6.10%.

Size-Specific Dose Estimates Based on Water-Equivalent Diameter and Effective Diameter in Computed Tomography Coronary Angiography.

BACKGROUND To determine the difference in size-specific dose estimates (SSDEs), separately based on effective diameter (deff) and water equivalent diameter (dw) of the central slice of the scan range in computed tomography coronary angiography (CTCA). MATERIAL AND METHODS There were 134 patients who underwent CTCA examination, were electronically retrieved. SSDEs (SSDEdeff and SSDEdw) were calculated using 2 approaches: deff and dw. The median SSDEs and mean absolute relative difference of SSDEs were calculated. Linear regression model was used to assess the absolute relative difference of SSDEs based on the ratio of deff to dw. RESULTS The median values of SSDEdeff and SSDEdw were 18.26 mGy and 20.56 mGy, respectively (P<0.01). The former was about 10.08% smaller than the latter. The mean absolute relative difference of SSDEs was 10.48%, ranging from 0.33% to 24.16%. A considerably positive correlation was found between the absolute relative difference of SSDEs and the ratio of deff to dw (R²=0.9561, r=0.979, P<0.01). CONCLUSIONS The value of SSDEdeff was smaller by an average of about 10.08% than SSDEdw in CTCA, and the absolute relative difference increased linearly with the ratio of effective diameter to water equivalent diameter.

Simultaneous changes of magnetic resonance diffusion-weighted imaging and pathological microstructure in locally advanced cervical cancer caused by neoadjuvant chemotherapy.

PURPOSE: To investigate the changes to diffusion-weighted imaging (DWI) correlated with histopathology after neoadjuvant chemotherapy (NACT) in patients with locally advanced cervical cancer (LACC). MATERIALS AND METHODS: Thirty-three patients with LACC were examined with 3T magnetic resonance imaging (MRI) with DWI and apparent diffusion coefficient (ADC) maps. MRIs were performed for each patient at three timepoints: before the first NACT, 2 weeks after the first NACT, and 2 weeks after the second NACT. Uterine cervical specimens were collected at the same timepoints. Specimens were stained for tumor cell density, proliferating cell nuclear antigen (PCNA), and aquaporin 1 (AQP1). Treatment responses were classified as the effective group (complete and partial response) and the ineffective group (stable and progressive disease). RESULTS: The ADC value of the effective group after the first chemotherapy was higher than that before chemotherapy (P = 0.002), and expressions of three pathological indicators (tumor cell density, PCNA, and AQP1) significantly decreased after the first NACT compared with those prechemotherapy (P < 0.001). Changes of PCNA expression were negatively correlated with changes of ADC values after the first NACT in the effective group (r = -0.56, P = 0.03). Changes of cellular density were negatively correlated with changes of ADC values from the time of prechemotherapy to after the second NACT in the effective group (r = -0.51, P = 0.04). CONCLUSION: The ADC change after successful chemotherapy is closely related with cellular characteristics preceding size reduction. ADC may be used as an early imaging biomarker of NACT response in LACC.

Basic T1 Perfusion magnetic resonance imaging evaluation of the therapeutic effect of neoadjuvant chemotherapy in locally advanced cervical cancer.

OBJECTIVE: The objective of this study was to evaluate the dynamic changes of blood perfusion coinciding with tumor regression after neoadjuvant chemotherapy (NACT) in locally advanced cervical cancer (LACC). METHODS: Thirty patients with LACC received conventional 3.0-T magnetic resonance imaging and perfusion-weighted imaging scans at 3 different times (before NACT, 2 weeks after the first NACT, and 2 weeks after the second NACT). Characteristics of time-intensity diagrams and patterns of blood perfusion maps according to the parameter of area under the curve (AUC) were observed. Eight perfusion parameters were compared among 3 time points at 2 different chemotherapy-sensitive groups by the software of Basic T1 Perfusion. RESULTS: The effective chemotherapy rate was 73.3% (22/30). The characteristic of time-intensity diagrams in cervical cancer was a rapid onset with plateau. There were 3 patterns of AUC perfusion maps. The common perfusion map was rich blood supply type in the effective chemotherapy group and peripheral blood supply type in the ineffective chemotherapy group. Four parameter values (relative enhancement, maximum enhancement, wash-in rate, and AUC) were significantly reduced 2 weeks after the second NACT than those before the therapy (P = 0.000; P = 0.009; P = 0.011; and P = 0.000) in the effective chemotherapy group, especially the value of relative enhancement 2 weeks after the first NACT, was obviously decreased compared to that before the therapy (P = 0.042). The value of time to peak 2 weeks after the second NACT was significantly longer than that before the therapy in the effective chemotherapy group (P = 0.001). There were no obvious changes of blood perfusion parameters among the 3 different times in the ineffective chemotherapy group. CONCLUSIONS: Tumor blood perfusion has obviously decreased after effective NACT in the treatment of LACC.

The value of diffusion-weighted magnetic resonance imaging in assessing the response of locally advanced cervical cancer to neoadjuvant chemotherapy.

OBJECTIVE: The objective of this study was to investigate whether magnetic resonance diffusion-weighted imaging (DWI) of locally advanced cervical cancer (LACC) both in the sagittal and axial planes could be used to assess the response of LACC to neoadjuvant chemotherapy (NACT). METHODS: Thirty women with LACC received conventional magnetic resonance imaging and DWI at 3 different times (before NACT, 2 weeks after the first NACT, and 2 weeks after the second NACT). Treatment response was determined according to the change in tumor size 2 weeks after the second NACT, and they were classified as the effective group and the ineffective group. The apparent diffusion coefficients (ADCs) were compared between 2 imaging planes, and dynamic changes in ADCs were observed in different chemotherapy-sensitive groups and imaging planes. One-way analysis of variance was calculated between those ADC parameters and tumor response. RESULTS: The effective chemotherapy rate was 76.67%. Apparent diffusion coefficient values of the axial plane at 3 different times were 0.88 (SD, 0.08) × 10⁻³ mm²/s, 0.96 (SD, 0.10) × 10⁻³ mm²/s, and 1.19 (SD, 0.11) × 10⁻³ mm²/s, respectively. Meanwhile, ADC values of the sagittal planes were 0.89 (SD, 0.09) × 10⁻³ mm²/s, 0.97 (SD, 0.12) × 10⁻³ mm²/s, and 1.19 (SD, 0.12) × 10⁻³ mm²/s at 3 different stages. There were no statistical differences between the ADC values of the 2 planes at 3 different times (P = 0.927, P = 0.863, P = 0.946). Apparent diffusion coefficients 2 weeks after the first NACT were significantly increased compared with those before chemotherapy both in the axial and sagittal planes (P = 0.003, P = 0.012). In the ineffective group, ADCs 2 weeks after the first NACT were not statistically higher than those before chemotherapy (axial planes, P = 0.694; sagittal planes, P = 0.900). After 2 weeks of the first NACT, ADCs in both planes were obviously increased in the effective group than those in the ineffective group (P = 0.043, P = 0.022). CONCLUSIONS: The axial and sagittal DWI may detect the changes in LACC after therapy. Apparent diffusion coefficient values measured both in the 2 planes may be used to evaluate the response of LACC to NACT.