Effect of tumor volume on the enhancement pattern of parathyroid adenoma on parathyroid four-dimensional CT

The purpose of this study is to assess the effect of tumor volume on the enhancement pattern of parathyroid adenoma (PTA) on four-dimensional computed tomography (4D-CT).

We analyzed the enhancement patterns of PTA on four-phase 4D-CT in 44 patients. Dependency of the changes of Hounsfield unit values (ΔHU) on the tumor volumes and clinical characteristics was evaluated using linear regression analyses. In addition, an unpaired t test was used to compare ΔHU of PTAs between PTA volume ≥1 cm(3) and <1 cm(3), thyroid gland, and lymph node.

PTA volume based on CT was the strongest factor on the ΔHUPre to Arterial and ΔHUArterial to Venous and ΔHUArterial to Delayed (R (2) = 0.34, 0.25, and 0.32, respectively, P < 0.001 for both). PTA ≥1 cm(3) had statistically significant greater enhancement between the unenhanced phase and the arterial phase than PTA <1 cm(3) (mean values ± standard deviations (SDs) of ΔHUPre to Arterial, 102.7 ± 33.7 and 57.5 ± 28.8, respectively, P < 0.001). PTA ≥1 cm(3) showed an early washout pattern on the venous phase, whereas PTA <1 cm(3) showed a progressive enhancement pattern on the venous phase (mean values ± SDs of ΔHUArterial to Venous, -13.2 ± 31.6 and 14.4 ± 32.7, respectively; P = 0.009).

The enhancement pattern of PTA on 4D-CT is variable with respect to PTA volume based on CT. Therefore, the enhancement pattern of PTA on 4D-CT requires careful interpretation concerning the tumor volume, especially in cases of PTA <1 cm(3).