title: PET/MRI of Hepatic 90Y Microsphere Deposition Determines Individual Tumor Response.
abstract: OBJECTIVE
  The purpose of our study is to determine if there is a relationship between dose deposition measured by PET/MRI and individual lesion response to yttrium-90 ((90)Y) microsphere radioembolization.
  
  
  METHODS
  26 patients undergoing lobar treatment with (90)Y microspheres underwent PET/MRI within 66 h of treatment and had follow-up imaging available. Adequate visualization of tumor was available in 24 patients, and contours were drawn on simultaneously acquired PET/MRI data. Dose volume histograms (DVHs) were extracted from dose maps, which were generated using a voxelized dose kernel. Similar contours to capture dimensional and volumetric change of tumors were drawn on follow-up imaging. Response was analyzed using both RECIST and volumetric RECIST (vRECIST) criteria.
  
  
  RESULTS
  A total of 8 hepatocellular carcinoma (HCC), 4 neuroendocrine tumor (NET), 9 colorectal metastases (CRC) patients, and 3 patients with other metastatic disease met inclusion criteria. Average dose was useful in predicting response between responders and non-responders for all lesion types and for CRC lesions alone using both response criteria (p < 0.05). D70 (minimum dose to 70 % of volume) was also useful in predicting response when using vRECIST. No significant trend was seen in the other tumor types. For CRC lesions, an average dose of 29.8 Gy offered 76.9 % sensitivity and 75.9 % specificity for response.
  
  
  CONCLUSIONS
  PET/MRI of (90)Y microsphere distribution showed significantly higher DVH values for responders than non-responders in patients with CRC. DVH analysis of (90)Y microsphere distribution following treatment may be an important predictor of response and could be used to guide future adaptive therapy trials.
authors.affiliation: Department of Radiology, Washington University, Campus Box 8131, 510 S. Kingshighway Blvd, St. Louis, MO, 63110, USA.
authors.forename: Kathryn J
authors.initials: KJ
authors.lastname: Fowler
authors.affiliation: Department of Biomedical Engineering, Washington University, Campus Box 1097, 1 Brookings Dr, St. Louis, MO, 63130, USA.
authors.forename: Nichole M
authors.initials: NM
authors.lastname: Maughan
authors.affiliation: Department of Nuclear Medicine, Washington University, Campus Box 8225, 510 S. Kingshighway Blvd, St. Louis, 63110, MO, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Laforest
authors.affiliation: Department of Radiology, Washington University, Campus Box 8131, 510 S. Kingshighway Blvd, St. Louis, MO, 63110, USA.
authors.forename: Nael E
authors.initials: NE
authors.lastname: Saad
authors.affiliation: Department of Nuclear Medicine, Washington University, Campus Box 8225, 510 S. Kingshighway Blvd, St. Louis, 63110, MO, USA.
authors.forename: Akash
authors.initials: A
authors.lastname: Sharma
authors.affiliation: Department of Radiation Oncology, Washington University, Campus Box 8224, 4921 Parkview Place, St. Louis, MO, 63110, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Olsen
authors.affiliation: Department of Radiation Oncology, Washington University, Campus Box 8224, 4921 Parkview Place, St. Louis, MO, 63110, USA.
authors.forename: Christina K
authors.initials: CK
authors.lastname: Speirs
authors.affiliation: Department of Radiation Oncology, Washington University, Campus Box 8224, 4921 Parkview Place, St. Louis, MO, 63110, USA. parikh@wustl.edu.
authors.forename: Parag J
authors.initials: PJ
authors.lastname: Parikh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000379:methods*; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000532:radiotherapy*; D008279:Magnetic Resonance Imaging; D008297:Male; D008863:Microspheres; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D016896:Treatment Outcome; D015021:Yttrium Radioisotopes / Q000627:therapeutic use*
chemical_list: D015021:Yttrium Radioisotopes
keywords: Cancer; Dosimetry; Imaging; Liver/hepatic; PET; Radioembolization