Role of four-dimensional computer tomography (4D-CT) in non-localising and discordant first-line imaging in primary hyperparathyroidism

Abstract

Background: Accurate preoperative localisation of parathyroid adenoma is imperative for the success of minimally invasive parathyroidectomy (MIP).

Objective: Our study aimed to evaluate the role of four-dimensional computer tomography (4D-CT) scan as an imaging modality in patients with failed and discordant localisation reported in the first-line imaging modalities (ultrasonography and ^99mTc-MIBI-SPECT/CT).

Methods: This is a prospective cohort study performed at a university teaching centre from March 2013 to July 2021. All patients with primary hyperparathyroidism who had failed localisation by ultrasonography and ^99mTc-MIBI-SPECT/CT (SpCT), or discordance between them, had 4D-CT performed in this study.

Results: One hundred and two sporadic cases of pHPT with failed/discordant first-line imaging had 4D-CT imaging prior to parathyroidectomy. In 102 patients, 105 parathyroid adenomas were reported on histopathology. 4D-CT was able to localise 78% of them to the correct side and 64% to the correct quadrant in 102 patients, as compared with US (correct side 21%, correct quadrant 16%) and ^99mTc-MIBI-SPECT/CT (correct side 36%, correct quadrant 31%). 4D-CT had a sensitivity, precision, accuracy and F1 score for correct quadrant localisation as 79%, 81%, 66% and 80%; and for correct side localisation as 82%, 98%, 80% and 89%, respectively. 4D-CT was able to identify three ectopic adenomas (two in superior mediastinum and one in the oesophageal wall) which were not detected on US or SpCT.

Conclusion: 4D-CT was found to be sensitive and accurate in preoperative localising of the diseased parathyroid glands after failed/discordant US and SpCT. This led to more patients being offered MIP as the primary surgery and improved operative outcomes.

Keywords: Hyperparathyroidism; Four dimensional CT-scan; Parathyroid adenoma; Parathyroidectomy.

Figure 1

Distribution of the parathyroid adenomas according to the side and quadrant of primary hyperparathyroidism (pHPT) patients with failed/discordant imaging findings

Figure 2

(a)–(c) A 60-year-old woman with primary hyperparathyroidism having non-localising ultrasound and ^99mTc-MIBI SPECT-CT imaging. (a) 2mm 4-dimensional computer tomography (4D-CT) (axial plane images showing a hyperenhancing ovoid structure along the left posterior lateral wall of the cervical oesophagus, (b) sagittal 4D-CT images showing a 0.4cm TRANS×0.7cm AP with a length of 2cm parathyroid adenoma, (c) ^99mTc-MIBI SPECT-CT showing non-localising imaging. Red arrow – parathyroid adenoma.

Figure 3

(a)–(e) A 63-year-old man with primary hyperparathyroidism having non-localising ultrasound imaging with ^99mTc-MIBI SPECT-CT imaging and four-dimensional computer tomography (4D-CT) scan localising parathyroid adenoma in left inferior location. (a) 2mm 4-dimensional computer tomography axial plane images showing a subtle enhancing oblong structure measuring 1.1cm by 0.6cm by 1.4cm nodule in the soft tissues in the superior aspect of the sternal notch to the left of midline, (b) coronal image, (c) sagittal image, (d) virtual unenhanced multiplanar reconstruction (MPR) images, (e) ^99mTc-MIBI SPECT-CT showing left inferior parathyroid adenoma (red arrow – parathyroid adenoma).

Figure 4

Inter-modality agreement (in percentages) and Cohen’s kappa between ultrasound (US), ^99mTc-MIBI SPECT-CT (SpCT) and four-dimensional computer tomography (4D-CT) in localisation of parathyroid adenomas