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. 2018 Jun 15;8(1):50.
doi: 10.1186/s13550-018-0402-8.

The value of 99mTc-MAA SPECT/CT for lung shunt estimation in 90Y radioembolization: a phantom and patient study

Jonathan D Allred  1 , Jeremy Niedbala  2 , Justin K Mikell  3 , Dawn Owen  3 , Kirk A Frey  2 , Yuni K Dewaraja  4
Affiliations

The value of 99mTc-MAA SPECT/CT for lung shunt estimation in 90Y radioembolization: a phantom and patient study

Jonathan D Allred et al. EJNMMI Res. .

Abstract

Background: A major toxicity concern in radioembolization therapy of hepatic malignancies is radiation-induced pneumonitis and sclerosis due to hepatopulmonary shunting of 90Y microspheres. Currently, 99mTc macroaggregated albumin (99mTc-MAA) imaging is used to estimate the lung shunt fraction (LSF) prior to treatment. The aim of this study was to evaluate the accuracy/precision of LSF estimated from 99mTc planar and SPECT/CT phantom imaging, and within this context, to compare the corresponding LSF and lung-absorbed dose values from 99mTc-MAA patient studies. Additionally, LSFs from pre- and post-therapy imaging were compared.

Results: A liver/lung torso phantom filled with 99mTc to achieve three lung shunt values was scanned by planar and SPECT/CT imaging with repeat acquisitions to assess accuracy and precision. To facilitate processing of patient data, a workflow that relies on SPECT and CT-based auto-contouring to define liver and lung volumes for the LSF calculation was implemented. Planar imaging-based LSF estimates for 40 patients, obtained from their medical records, were retrospectively compared with SPECT/CT imaging-based calculations with attenuation and scatter correction. Additionally, in a subset of 20 patients, the pre-therapy estimates were compared with 90Y PET/CT-based measurements. In the phantom study, improved accuracy in LSF estimation was achieved using SPECT/CT with attenuation and scatter correction (within 13% of the true value) compared with planar imaging (up to 44% overestimation). The results in patients showed a similar trend with planar imaging significantly overestimating LSF compared to SPECT/CT. There was no correlation between lung shunt estimates and the delay between 99mTc-MAA administration and scanning, but off-target extra hepatic uptake tended to be more likely in patients with a longer delay. The mean lung absorbed dose predictions for the 28 patients who underwent therapy was 9.3 Gy (range 1.3-29.4) for planar imaging and 3.2 Gy (range 0.4-13.4) for SPECT/CT. For the patients with post-therapy imaging, the mean LSF from 90Y PET/CT was 1.0%, (range 0.3-2.8). This value was not significantly different from the mean LSF estimate from 99mTc-MAA SPECT/CT (mean 1.0%, range 0.4-1.6; p = 0.968), but was significantly lower than the mean LSF estimate based on planar imaging (mean 4.1%, range 1.2-15.0; p = 0.0002).

Conclusions: The improved accuracy demonstrated by the phantom study, agreement with 90Y PET/CT in patient studies, and the practicality of using auto-contouring for liver/lung definition suggests that 99mTc-MAA SPECT/CT with scatter and attenuation corrections should be used for lung shunt estimation prior to radioembolization.

Keywords: 90Y PET/CT; 99mTc-MAA SPECT/CT; Lung shunt; Transarterial radioembolization (TARE).

PubMed Disclaimer

Conflict of interest statement

Ethics approval and consent to participate

The study was approved by the University of Michigan Institutional Review Board, and all subjects signed an informed consent for 90Y PET/CT imaging and included consent to publish as part of an ongoing research study.

Consent for publication

All subjects signed an informed consent that included consent to publish data.

Competing interests

YKD is a consultant for MIM Software Inc., Beechwood, Ohio. The other authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
A coronal and transverse slice of a patient 99mTc-MAA SPECT/CT processed through the workflow for auto contouring and LSF calculation. The CT-threshold-based lung contour with and without the 2 cm exclusion region is shown as well as the SPECT threshold-based liver contour. The lung shunt (original) refers to the value calculated without the exclusion region
Fig. 2
Fig. 2
Phantom images corresponding to the different true lung shunt values 0, 3.6, and 6.9% showing a anterior/posterior views for planar imaging and b coronal and axial slices for SPECT/CT
Fig. 3
Fig. 3
a Posterior, anterior 99mTc-MAA planar images showing manually defined liver/lung regions for LSF calculation in the clinic. A coronal b 99mTc-MAA SPECT/CT slice and c 90Y PET/CT slice for the same patient processed through the workflow for LSF calculation
Fig. 4
Fig. 4
Correlation between planar and SPECT/CT derived lung shunt values for all patients (N = 40). Red symbols correspond to HCC patients, and black symbols correspond to patients with liver metastases
Fig. 5
Fig. 5
Correlation between planar and SPECT/CT derived lung absorbed dose values for patients who underwent therapy (N = 28). Red symbols correspond to HCC patients and black symbols correspond to patients with liver metastases
Fig. 6
Fig. 6
99mTc-MAA SPECT/CT images corresponding to a patient where the time between injection and imaging was 176 min demonstrating gastric mucosal and renal cortical extra-hepatic uptake
Fig. 7
Fig. 7
Comparison of pre-therapy 99mTc-MAA and post-therapy 90Y PET/CT-based lung shunt estimates (N = 20)
See this image and copyright information in PMC

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