Size-specific dose estimates of adult head, chest and abdominal multidetector computed tomography (MDCT) in a Tertiary Hospital in the Philippines

Mercedes Dizon, Marte, Alfredo II L., Laya, Bernard F., Pasia, Nelson V.

Objectives: This report evaluates and compares the size-specific dose estimates (SSDE) for head, chest and whole abdomen CT examinations of adult patients with internationally published values.

Methods: A cross sectional retrospective review using patients’ database who underwent multidetector computed tomography (MDCT)of the head, chest and whole abdomen at Saint Luke's Medical Center Global City (SLMC-GC) from January to December 2015 was undertaken. Patient’s age, sex, body weight, computed tomography dose index volume (CTDIvol) and dose length product (DLP) were gathered and size-specific dose estimates (SSDE) for each patient were determined. Frequency distribution was computed for each categorical variable while descriptive statistics such as mean and standard deviation were generated for all numerical variables including SSDE. To test if SSDE were different between patient profiles, Independent Samples t Test and Analysis of Variance (ANOVA) at 5% level of significance were used.

Results: Of the 1,474 patients aged 40 years old and above included in this study, data from 411 patients with recorded weights were used to determine the relationship of weight and SSDE. The highest SSDE values for plain CT procedures are14.13 ± 6.32 mGy,38.6 ± 5.4 mGy, 12.61 ± 5.87mGy, and 15.05 ± 6.43 mGy for abdomen, head, chest and stonogram respectively. The highest SSDE values for plain with contrast procedures are 38.00 ± 12.74 mGy,77.2 ± 16.9mGy, and 26.06 ± 15.61mGy for the abdomen, head, and chest. There are no significant differences in the SSDE of the lateral, anteroposterior and lateral + anteroposterior dimensions within the different weight ranges. There are however significant differences in the SSDE comparing plain and plain with contrast in all CT procedures. The SSDE values of the lateral, anteroposterior and lateral + anteroposterior dimensions of the plain head CT as well as the SSDE values of these dimensions for the plain with contrast examinations of the head are significantly different. This relationship is not shown in CT procedures of the abdomen, chest and stonogram.

Conclusion: SSDE data taken from Saint Luke's Medical Center Global City (SLMC-GC) are close to internationally published data. For the abdomen and head exams, our data is comparable with published data. However, for the unenhanced chest CT scan our data are lower while SSDE for stonogram are higher than published data. SSDE as a means of estimating patient dose is a more accurate way to communicate radiation exposure to the patient and care givers. It is also a more practical metric to incorporate in the radiologist's report.