Lung shunt fraction calculations before Y-90 transarterial radioembolization: Comparison of accuracy and clinical significance of planar scintigraphy and SPECT/CT - 04/01/23

Doi : 10.1016/j.diii.2022.12.002

Shamar Young ^a,^⁎, Siobhan Flanagan ^b, Donna D'Souza ^b, Soorya Todatry ^b, Ranjan Ragulojan ^b, Tina Sanghvi ^c, Jafar Golzarian ^b
^a Department of Medical Imaging, Division of Interventional Radiology, University of Arizona, Tucson, AZ 85724, USA
^b Department of Radiology, Division of Interventional Radiology, University of Minnesota, Minneapolis, MN 55455, USA
^c Department of Radiology, Arizona Veterans Administration Hospital, Minneapolis, MN 55417, USA

^⁎Corresponding author: shamar@arizona.edu

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Highlights

•	Lung shunt fraction is better estimated using single-photon emission computerized tomography (SPECT) computed tomography (CT) than using planar scintigraphy.
•	A significant percentage of patients with lung shunt fraction ≥ 7.5% at planar scintigraphy would benefit of SPECT/CT in terms of avoiding dose reduction or treatment cancelation.
•	For various subgroups of yttrium-90 treatments, such as hemiliver and selective deliveries or treatment of hepatocellular carcinoma or metastatic disease, planar scintigraphy results in significantly greater overestimation of the realized lung shunt fraction compared to SPECT/CT.

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Abstract

Purpose

To determine the accuracy and clinical significance of planar scintigraphy lung shunt fraction (PLSF) and single-photon emission computerized tomography (SPECT) computed tomography (CT) lung shunt fraction (SLSF) before Y-90 transarterial radioembolization.

Materials and methods

Seventy patients (46 men, 24 women; mean age, 64 ± 9.5 [SD] years) who underwent 83 treatments with Y-90 transarterial radioembolization for primary or secondary malignancies of the liver with a PLSF ≥ 7.5% were retrospectively evaluated. The patients mapping technetium 99 m (Tc-99 m) macroaggregated albumin (MAA) PLSF and SLSF were calculated and compared to the post Y-90 delivery SLSF. A model using modern dose thresholds was created to identify patients who would require dose reduction due to a lung dose ≥ 30 Gy, with patients who required >50% dose reduction considered to be delivery cancelations.

Results

A significant difference was found between mean PLSF (14.7 ± 11.6 [SD]%; range: 7.5–84.1%) and mean SLSF (8.7 ± 8.5 [SD]%; range: 1.7–73.5) (P < 0.001). The mean realized LSF (7.1 ± 3 [SD]%; range:1.5–17.6) was significantly less than the PLSF (P <0.001) but not the SLSF (P = 0.07). PLSF significantly overestimated the realized LSF by more than the SLSF (8.5 ± 5.3 [SD] % [range: -0.1–21.7] vs. 0.8 ± 3.6 [SD] % [range: -5–13.2], respectively) (P < 0.001). Based on the clinical significance model, 20 patients (20/83, 24.1%) would have required dose reduction or cancelation when using PLSF but would not require even a dose reduction when using the SLSF. Significantly more deliveries would have been be canceled if PLSF was used as compared to SLSF (22/83 [26.5%] vs. 6/83 [7.2%], respectively) (P < 0.001).

Conclusion

SLSF is significantly more accurate at predicting realized LSF than PLSF and this difference is of clinical significance in a number of patients with a PLSF ≥ 7.5%.

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Keywords : Dosimetry, Hepatocellular carcinoma, Lung shunt fraction, Transarterial radioembolization

Abbreviations : Y-90, CBCT, CT, LSF, HCC, IQR, MAA, MIRD, PLSF, ROI, SD, SLSF, SPECT, TARE, Tc-99 m