Four-dimensional computed tomography as first-line imaging in primary hyperparathyroidism, a retrospective comparison to conventional imaging in a predominantly single adenoma population

Background: To determine the use of four-dimensional CT as first-line imaging compared to the traditional combination of ultrasound and [^99mTc]Tc-Sestamibi SPECT. Materials and methods: Retrospective review of preoperative imaging in patients with primary hyperparathyroidism, who underwent parathyroidectomy between 2012 and 2021. In one group, the combination ultrasound and [^99mTc]Tc-Sestamibi SPECT was used as first-line imaging (n = 54), in the other group four-dimensional CT was the first-line imaging modality (n = 51). Sensitivity and positive predictive value were calculated on patient, lateralisation and localisation level. The need for additional imaging was also assessed for both groups. Results: Four-dimensional CT had a significantly higher sensitivity compared to the combination of ultrasound/[^99mTc]Tc-Sestamibi SPECT on patient and localisation level (70.6% vs. 51.9%, p = 0.049 and 60.8% vs. 35.2%, p = 0.009 respectively). Sensitivity for lateralisation also appeared higher, but did not reach significance (62.7% vs. 44.4%, p = 0.060). Positive predictive value was not significantly higher for four-dimensional CT compared to ultrasound and [^99mTc]Tc-Sestamibi SPECT (88.9% vs. 85.7% for lateralisation and 86.1% vs. 67.9% for localisation respectively). Additional imaging was required in 14 patients with four-dimensional CT as first-line imaging (27.4%) consisting of 2 ultrasound/[^99mTc]Tc-Sestamibi SPECT and 13 [¹⁸F]fluorocholine PET/CT, compared to 24 patients with ultrasound/[^99mTc]Tc-Sestamibi SPECT as first-line imaging (44.4%), requiring 22 four-dimensional CT and 9 [¹⁸F]fluorocholine PET/CT. Conclusions: Four-dimensional CT as the sole first-line parathyroid imaging modality had higher sensitivity than the combination of ultrasound and [^99mTc]Tc-Sestamibi SPECT, therefore requiring fewer additional procedures. Although the most costly, [¹⁸F]fluorocholine PET/CT was the most effective technique to localise parathyroid adenoma in case all other imaging was negative.