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. 2021 Apr 7;21(1):64.
doi: 10.1186/s12880-021-00597-1.

Detection of parathyroid adenomas with multiphase 4DCT: towards a true four-dimensional technique

Steven Raeymaeckers  1 , Yannick De Brucker  2 , Tim Vanderhasselt  2 , Nico Buls  2   3 , Johan De Mey  2   4
Affiliations

Detection of parathyroid adenomas with multiphase 4DCT: towards a true four-dimensional technique

Steven Raeymaeckers et al. BMC Med Imaging. .

Abstract

Background: Four-dimensional computed tomography (4DCT) is a commonly performed examination in the management of primary hyperparathyroidism, combining three-dimensional imaging with enhancement over time as the fourth dimension. We propose a novel technique consisting of 16 different contrast phases instead of three or four different phases. The main aim of this study was to ascertain whether this protocol allows the detection of parathyroid adenomas within dose limits. Our secondary aim was to examine the enhancement of parathyroid lesions over time.

Methods: For this prospective study, we included 15 patients with primary hyperparathyroidism and a positive ultrasound prior to surgery. We performed 4DCT with 16 different phases: an unenhanced phase followed by 11 consecutive arterial phases and 4 venous phases. Continuous axial scanning centered on the thyroid was performed over a fixed 8 cm or 16 cm coverage volume after the start of contrast administration.

Results: In all patients, an enlarged parathyroid lesion was demonstrated, and the mean lesion size was 13.6 mm. The mean peak arterial enhancement for parathyroid lesions was 384 Hounsfield units (HU) compared to 333 HU for the normal thyroid. No significant difference could be found. The time to peak (TTP) was significantly earlier for parathyroid adenomas than for normal thyroid tissue: 30.8 s versus 32.3 s (p value 0.008). The mean slope of increase (MSI) of the enhancement curve was significantly steeper than that of normal thyroid tissue: 29.8% versus 22.2% (p value 0.012). The mean dose length product was 890.7 mGy cm with a calculated effective dose of 6.7 mSv.

Conclusion: Our 4DCT protocol may allow better visualization of the pattern of enhancement of parathyroid lesions, as enhancement over time curves can be drawn. In this way, wash-in and wash-out of contrast in suspected lesions can be readily demonstrated. Motion artifacts are less problematic as multiple phases are available. Exposure to our proposed 4DCT technique is comparable to that for classic helical 4DCT. Careful selection of parameters (lowering kV and SNR) can help to further reduce the dose.

Keywords: 4DCT; CT dose reduction; Endocrine disorders; Hyperparathyroidism; Parathyroid.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Schematic overview of the different phases in our 4DCT protocol
Fig. 2
Fig. 2
Axial images at the level of the thyroid at different time intervals. Scans at 0–20–22–24–26–28–30–32–34–36–38–40 s after administration of contrast, left to right from the top. Suspected parathyroid adenoma posterior from the left thyroid lobe in close relation to the common carotid artery (arrows). Note the lower enhancement on NECT (red arrow), higher enhancement compared with the thyroid in the arterial phase (white arrow) and the wash-out of contrast in the early venous phase (yellow arrow)
Fig. 3
Fig. 3
Enhancement (Y-axis) over time (X-axis) curve. The curve for the suspected parathyroid (yellow) is steeper than the curve for the thyroid (green), and the peaks for the artery (red) and vein (blue) are higher in comparison. An artifact due to motion is observed at 34 s with suboptimal HU measurement of the small parathyroid lesion. The graph also demonstrates venous wash-out of the suspected parathyroid (50–70 s). Additionally, note the lack of prominent difference in enhancement between the adenoma and the thyroid at 25 s after administration of contrast. The purple curve indicates slow continuous enhancement of a lymph node
See this image and copyright information in PMC

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