Quantitative and qualitative assessment of Yttrium-90 PET/CT imaging.

Ali Asgar Attarwala,Gerhard Glatting,Flavia Molina-Duran,Dale L Bailey,Stefan O Schönberg,Karen-Anett Büsing,Kathy Willowson,Ramasamy Paulmurugan

doi:10.1371/journal.pone.0110401

Abstract

Yttrium-90 is known to have a low positron emission decay of 32 ppm that may allow for personalized dosimetry of liver cancer therapy with 90Y labeled microspheres. The aim of this work was to image and quantify 90Y so that accurate predictions of the absorbed dose can be made. The measurements were performed within the QUEST study (University of Sydney, and Sirtex Medical, Australia). A NEMA IEC body phantom containing 6 fillable spheres (10–37 mm ∅) was used to measure the 90Y distribution with a Biograph mCT PET/CT (Siemens, Erlangen, Germany) with time-of-flight (TOF) acquisition. A sphere to background ratio of 8∶1, with a total 90Y activity of 3 GBq was used. Measurements were performed for one week (0, 3, 5 and 7 d). he acquisition protocol consisted of 30 min-2 bed positions and 120 min-single bed position. mages were reconstructed with 3D ordered subset expectation maximization (OSEM) and point spread function (PSF) for iteration numbers of 1–12 with 21 (TOF) and 24 (non-TOF) subsets and CT based attenuation and scatter correction. Convergence of algorithms and activity recovery was assessed based on regions-of-interest (ROI) analysis of the background (100 voxels), spheres (4 voxels) and the central low density insert (25 voxels). For the largest sphere, the recovery coefficient (RC) values for the 30 min –2-bed position, 30 min-single bed and 120 min-single bed were 1.12±0.20, 1.14±0.13, 0.97±0.07 respectively. For the smaller diameter spheres, the PSF algorithm with TOF and single bed acquisition provided a comparatively better activity recovery. Quantification of Y-90 using Biograph mCT PET/CT is possible with a reasonable accuracy, the limitations being the size of the lesion and the activity concentration present. At this stage, based on our study, it seems advantageous to use different protocols depending on the size of the lesion.

Highlights

Liver cancer is a very frequent cancer, and liver metastases from tumors of other origin are a very common problem in oncology
Selective Internal Radiation Therapy (SIRT) is based on microspheres containing radioactive 90Y, which are directly administered via super selective injection into selected branches of the hepatic artery, providing a highly localized dose to shrink the tumor before surgery or chemotherapy [11,12]
In 2004 Nickles et al demonstrated the possibility of quantifying 90Y distribution using positron emission tomography (PET)[18]

Summary

Introduction

Liver cancer is a very frequent cancer, and liver metastases from tumors of other origin are a very common problem in oncology. Treatment options include external beam radiotherapy, chemotherapy or surgery. SIRT is based on microspheres containing radioactive 90Y, which are directly administered via super selective injection into selected branches of the hepatic artery, providing a highly localized dose to shrink the tumor before surgery or chemotherapy [11,12]. Until recently was performed using the bremsstrahlung spectrum of 90Y captured with single photon emission computed tomography (SPECT) [13,14]. In 2004 Nickles et al demonstrated the possibility of quantifying 90Y distribution using positron emission tomography (PET)[18]. In 2010, Lhommel et al performed a feasibility study to obtain the biodistribution of 90Y using time of flight (TOF) PET/CT and showed that this method provides higher accuracy for dose distribution assessments [20]

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