Multidetector Computed Tomography for the Assessment of Adnexal Mass: Is Unenhanced CT Scan Necessary?

OBJECTIVE: To compare the diagnostic performance and radiation dose between contrast-enhanced CT (ECT) alone, and combined unenhanced and contrast-enhanced CT (UE + ECT) for the assessment of adnexal mass. MATERIALS AND METHODS: This retrospective study was approved by the Institutional Review Board. A total of 146 consecutive patients (mean age, 41.1 years) who underwent preoperative unenhanced and contrast-enhanced multidetector CT of the pelvis and had adnexal masses found at surgery were included. Two readers independently evaluated the likelihood of adnexal malignancy on a 5-point scale on two different imaging datasets (ECT alone and UE + ECT). The area under the receiver operating characteristic curve (AUC) was used to evaluate diagnostic performance. Radiation dose to patients was calculated by the volume CT dose index (CTDI(vol)) and the dose length products (DLP) on each dataset. RESULTS: Of the total 178 adnexal masses, 133 masses were benign and 45 masses were malignant. For both readers, there is no significant difference of AUC values between ECT alone and UE + ECT for the detection of adnexal malignancy (reader 1, 0.93 vs. 0.95; reader 2, 0.92 vs. 0.91) (p > 0.05). The mean CTDI(vol) (12.6 ± 2.2 mGy) and DLP (641.2 ± 137.2 mGy) of ECT alone was significantly lower than the mean CTDI(vol) (21.5 ± 2.7 mGy) and DLP (923.6 ± 158.8 mGy) of UE + ECT (p < 0.0001). CONCLUSION: The use of unenhanced CT scan in addition to contrast-enhanced CT scan does not improve the detection of adnexal malignancy, but increases radiation exposure.