E2926. Low-Tube-Voltage Contrast-Enhanced Pediatric CT: Impact on Image Quality and Radiation Dose
  1. Sebastian Gallo-Bernal; Harvard Medical School; Massachusetts General Hospital
  2. Valeria Pena-Trujillo; Harvard Medical School; Massachusetts General Hospital
  3. Sjirk Westra; Harvard Medical School; Massachusetts General Hospital
  4. Pallavi Sagar; Harvard Medical School; Massachusetts General Hospital
  5. Kalra Mannudeep; Harvard Medical School; Massachusetts General Hospital
  6. Michael S. Gee; Harvard Medical School; Massachusetts General Hospital
To determine the feasibility of low-tube-voltage contrast-enhanced CT imaging of the abdomen and evaluate image quality compared with standard-voltage techniques.

Materials and Methods:
In this retrospective study, we searched the electronic health records of a large pediatric academic center between 2017 and 2021 to identify all monoenergetic, contrast enhanced abdominopelvic CTs performed on patients age 1-12 years. Technical parameters including CTDIvol, DLP, tube voltage, and amperage were extracted from the PACS. Cases were classified based on tube current (70 -120 kV), and scans performed at <100kV were considered low kV. Images were evaluated individually for different parameters by 2 experienced radiologists with subspecialty training (pediatric and abdominal), using a 5-point scale. We obtained mean CT attenuation values (Hounsfield units) and standard deviations (SD) for the aorta, liver, spleen, abdominal fat, urinary bladder, and bilateral paraspinal muscles by manually placing circular ROIs. Size-specific dose estimates (SSDE) were calculated following AAPM recommendations. Achievable doses (AD) and diagnostic reference levels (DRL) were defined as the median and 75th percentile of the distribution of the SSDE data, respectively. Categorical variables were compared using X2-test and ordinal variables using Wilcoxon rank test. Interobserver agreements were assessed using k statistics. Analyses were performed in R v4.0.5

A total of 541 cases were analyzed (mean age 6.81 ± 3.1; 242 [44.7%] female). 33 cases (6.1%) were performed at 70 kV, 236 (43.6%) at 80 kV, 51 (9.4%) at 90 kV, 175 (32.3%) at 100 kV, and 46 (8.5%) at 120 kV. Overall, the SSDE AD and DLR were inferior for all age categories compared to the national averages (0 to <1 yrs: 3.33/5.3 vs 4.2/5.3; 1 to <5 yrs: 3.820/5.88 vs. 4.6/5.9; 5 to <10 yrs: 5.45/7.2 vs 5.8/8.0; 10 to <15 yrs: 6.54/8.31 vs 8.9/11). Low kV scans yielded significantly (p < 0.05) lower SSDE AD and DLR for all age categories when compared to the standard (1 to <5 yrs: 3.12/4.76 vs 6.1/6.72; 5 to <10 yrs: 4/5.57 vs 6.65/8.45; 10 to <15 yrs: 4.74/6.18 vs 7.37/9.16). Attenuation values were significantly (p < 0.05) higher in the liver, spleen, aorta, and paraspinal muscles. SDs were higher (p < 0.05) for low kV scans in the aorta, abdominal fat, and bladder. Subjectively, standard scans were considered to have superior overall image quality (5 vs 4; k: 0.7) and image noise (4 vs 3; k: 0.64). No differences were found in the diagnostic confidence of tumors, infectious processes, or anatomic abnormalities. Due to insufficient image quality, additional imaging was required in 10% of the 70 kV scans.

Low kV scanning for pediatric contrast-enhanced CTs results in significantly lower radiation while maintaining satisfactory image quality and improving iodine contrast enhancement of highly vascularized structures. However, caution is granted as excessively low radiation may cause nondiagnostic image quality and the need for additional studies.