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.</p

Geometric mean images composed from the anterior and posterior planar images for acquisitions with a total phantom activity of 1582 and 126 MBq.

Geometric mean images composed from the anterior and posterior planar images for acquisitions with a total phantom activity of 1582 and 126 MBq.</p

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).</p

PET, SPECT and planar data for LSF calculations.

PurposePrior 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 methodsAnthropomorphic 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.ResultsLSF estimation. For high activity in the phantom, PET reconstructions slightly underestimated the LSF; absolute difference was Lesion visibility. For SPECT/CT, the cold tumour proved too small to be discernible (CNR 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).ConclusionsPET/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.</div

CNR calculation methods.

PurposePrior 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 methodsAnthropomorphic 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.ResultsLSF estimation. For high activity in the phantom, PET reconstructions slightly underestimated the LSF; absolute difference was Lesion visibility. For SPECT/CT, the cold tumour proved too small to be discernible (CNR 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).ConclusionsPET/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.</div

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.

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.</p

LSF estimated from PET and SPECT imaging for a true LSF of (9.8±0.6)% (A) and LSF_simulated, 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.</p

Characteristics of radionuclides: Yttrium-90 (⁹⁰Y) and metastable technetium-99 (^99mTc) [1–7].

Characteristics of radionuclides: Yttrium-90 (90Y) and metastable technetium-99 (99mTc) [1–7].</p

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).</p

Energy window settings for SPECT and planar acquisition.

Energy window settings for SPECT and planar acquisition.</p