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. 2024 Feb 29;19(2):e0271711.
doi: 10.1371/journal.pone.0271711. eCollection 2024.

PET/CT and SPECT/CT imaging of 90Y hepatic radioembolization at therapeutic and diagnostic activity levels: Anthropomorphic phantom study

Anna Budzyńska  1   2 , Agata Kubik  1 , Krzysztof Kacperski  1   3 , Patrycja Pastusiak  1 , Michał Kuć  4 , Piotr Piasecki  5 , Marcin Konior  6 , Michał Gryziński  4 , Mirosław Dziuk  1   2 , Edward Iller  6
Affiliations

PET/CT and SPECT/CT imaging of 90Y hepatic radioembolization at therapeutic and diagnostic activity levels: Anthropomorphic phantom study

Anna Budzyńska et al. PLoS One. .

Abstract

Purpose: Prior to 90Y radioembolization procedure, a pretherapy simulation using 99mTc-MAA is performed. Alternatively, a small dosage of 90Y microspheres could be used. We aimed to assess the accuracy of lung shunt fraction (LSF) estimation in both high activity 90Y posttreatment and pretreatment scans with isotope activity of ~100 MBq, using different imaging techniques. Additionally, we assessed the feasibility of visualising hot and cold hepatic tumours in PET/CT and Bremsstrahlung SPECT/CT images.

Materials and methods: Anthropomorphic phantom including liver (with two spherical tumours) and lung inserts was filled with 90Y chloride to simulate an LSF of 9.8%. The total initial activity in the liver was 1451 MBq, including 19.4 MBq in the hot sphere. Nine measurement sessions including PET/CT, SPECT/CT, and planar images were acquired at activities in the whole phantom ranging from 1618 MBq down to 43 MBq. The visibility of the tumours was appraised based on independent observers' scores. Quantitatively, contrast-to-noise ratio (CNR) was calculated for both spheres in all images.

Results: LSF estimation. For high activity in the phantom, PET reconstructions slightly underestimated the LSF; absolute difference was <1.5pp (percent point). For activity <100 MBq, the LSF was overestimated. Both SPECT and planar scintigraphy overestimated the LSF for all activities. Lesion visibility. For SPECT/CT, the cold tumour proved too small to be discernible (CNR <0.5) regardless of the 90Y activity in the liver, while hot sphere was visible for activity >200 MBq (CNR>4). For PET/CT, the cold tumour was only visible with the highest 90Y activity (CNR>4), whereas the hot one was seen for activity >100 MBq (CNR>5).

Conclusions: PET/CT may accurately estimate the LSF in a 90Y posttreatment procedure. However, at low activities of about 100 MBq it seems to provide unreliable estimations. PET imaging provided better visualisation of both hot and cold tumours.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. 3D MIP PET (top row) and SPECT (bottom row) images of the anthropomorphic phantom for scans performed at high (left) and low (right) activity levels of 90Y.
Fig 2
Fig 2. Geometric mean images composed from the anterior and posterior planar images for acquisitions with a total phantom activity of 1582 and 126 MBq.
Fig 3
Fig 3. LSF estimated from PET and SPECT imaging for a true LSF of (9.8±0.6)% (A) and LSFsimulated, i.e. 0% (B) as a function of total 90Y activity in the anthropomorphic phantom.
For both plots, the highlighted areas are shown in magnification on the right side of the figure. For PET, LSFs computed both with and without the natural background correction are presented. For SPECT modality, the results are shown for acquisitions with different energy window settings: W1, W2, and W3.
Fig 4
Fig 4. LSF estimated from planar images acquired using energy windows of W1 and W2 for a true LSF of (9.8±0.6)% as a function of total 90Y activity in the anthropomorphic phantom.
The results are presented for calculations both with and without background correction.
Fig 5
Fig 5. Coronal (top row) and axial (bottom row) views of the PET (A) and SPECT (B) images of the anthropomorphic phantom for scans performed at high and low activity levels of 90Y (middle and right column).
Left column presents corresponding CT slices. Yellow arrows indicate the location of the extrahepatic deposition while the red and blue ones—the locations of the hot and cold hepatic tumours, respectively.
Fig 6
Fig 6. CNR values calculated for the hot lesion in the liver in SPECT/CT imaging for all of the analysed energy window settings.
The solid lines represent the border values depending on the Rose criterion (middle line at 3 and supporting ones at 2.5 and 3.5).
Fig 7
Fig 7. CNR values calculated for the cold lesion in the liver in SPECT/CT for all of the analysed energy window settings.
The solid lines represent the border values depending on the Rose criterion (middle line at 3 and supporting ones at 2.5 and 3.5).
Fig 8
Fig 8. CNR values calculated for the cold and hot lesions in the liver in PET/CT imaging.
The solid lines represent the border values depending on the Rose criterion (middle line at 3 and supporting ones at 2.5 and 3.5).
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Grants and funding

KK and PP received no specific funding for this work. All of the remaining authors were funded by project OPUS-13 no 2017/25/B/ST7/01745 funded by National Science Centre of Poland (https://www.ncn.gov.pl). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.