Leticia Taeubert1,2,3, Yannick Berker4,5, Bettina Beuthien-Baumann6,7, Aswin L Hoffmann8,9,10, Esther G C Troost8,9,10,11,12, Marc Kachelrieß4,13, Clarissa Gillmann1,2. 1. Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany. 2. National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany. 3. Author to whom any correspondence should be addressed. 4. Division of X-ray Imaging and Computed Tomography, German Cancer Research Center (DKFZ), Heidelberg, Germany. 5. Current affiliation: Translational Pediatric Pharmacology, Clinical Cooperation Unit Pediatric Oncology, German Cancer Research Center (DKFZ) and Hopp Children's Cancer Center Heidelberg (KiTZ), Heidelberg, Germany. 6. Division of Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany. 7. National Center for Tumor Diseases (NCT), Partner Site, Heidelberg, Germany. 8. OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany. 9. Department for Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Dresden, Dresden, Germany. 10. Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology - OncoRay, Dresden, Germany. 11. German Cancer Consortium (DKTK), Partner Site Dresden, and German Cancer Research Center (DKFZ), Heidelberg, Germany. 12. National Center for Tumor Diseases (NCT), Partner Site, Dresden, Germany: German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany, and; Helmholtz Association/Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany. 13. Medical Faculty of Heidelberg, Heidelberg University, Heidelberg, Germany.
Abstract
OBJECTIVE: To implement computed tomography (CT)-based attenuation maps of radiotherapy (RT) positioning hardware and radiofrequency (RF) coils to enable hybrid positron emission tomography/magnetic resonance imaging (PET/MRI)-based RT treatment planning. MATERIALS AND METHODS: The RT positioning hardware consisted of a flat RT table overlay, coil holders for abdominal scans, coil holders for head and neck scans and an MRI compatible hip and leg immobilization device. CT images of each hardware element were acquired on a CT scanner. Based on the CT images, attenuation maps of the devices were created. Validation measurements were performed on a PET/MR scanner using a 68Ge phantom (48 MBq, 10 min scan time). Scans with each device in treatment position were performed. Then, reference scans containing only the phantom were taken. The scans were reconstructed online (at the PET/MRI scanner) and offline (via e7tools on a PC) using identical reconstruction parameters. Average reconstructed activity concentrations of the device and reference scans were compared. RESULTS: The device attenuation maps were successfully implemented. The RT positioning devices caused an average decrease of reconstructed PET activity concentration in the range between -8.3 ± 2.1% (mean ± SD) (head and neck coil holder with coils) to -1.0 ± 0.5% (abdominal coil holder). With attenuation correction taking into account RT hardware, these values were reduced to -2.0 ± 1.2% and -0.6 ± 0.5%, respectively. The results of the offline and online reconstructions were nearly identical, with a difference of up to 0.2%. CONCLUSION: The decrease in reconstructed activity concentration caused by the RT positioning devices is clinically relevant and can successfully be corrected using CT-based attenuation maps. Both the offline and online reconstruction methods are viable options.
OBJECTIVE: To implement computed tomography (CT)-based attenuation maps of radiotherapy (RT) positioning hardware and radiofrequency (RF) coils to enable hybrid positron emission tomography/magnetic resonance imaging (PET/MRI)-based RT treatment planning. MATERIALS AND METHODS: The RT positioning hardware consisted of a flat RT table overlay, coil holders for abdominal scans, coil holders for head and neck scans and an MRI compatible hip and leg immobilization device. CT images of each hardware element were acquired on a CT scanner. Based on the CT images, attenuation maps of the devices were created. Validation measurements were performed on a PET/MR scanner using a 68Ge phantom (48 MBq, 10 min scan time). Scans with each device in treatment position were performed. Then, reference scans containing only the phantom were taken. The scans were reconstructed online (at the PET/MRI scanner) and offline (via e7tools on a PC) using identical reconstruction parameters. Average reconstructed activity concentrations of the device and reference scans were compared. RESULTS: The device attenuation maps were successfully implemented. The RT positioning devices caused an average decrease of reconstructed PET activity concentration in the range between -8.3 ± 2.1% (mean ± SD) (head and neck coil holder with coils) to -1.0 ± 0.5% (abdominal coil holder). With attenuation correction taking into account RT hardware, these values were reduced to -2.0 ± 1.2% and -0.6 ± 0.5%, respectively. The results of the offline and online reconstructions were nearly identical, with a difference of up to 0.2%. CONCLUSION: The decrease in reconstructed activity concentration caused by the RT positioning devices is clinically relevant and can successfully be corrected using CT-based attenuation maps. Both the offline and online reconstruction methods are viable options.
Authors: Constantin Lapa; Ursula Nestle; Nathalie L Albert; Christian Baues; Ambros Beer; Andreas Buck; Volker Budach; Rebecca Bütof; Stephanie E Combs; Thorsten Derlin; Matthias Eiber; Wolfgang P Fendler; Christian Furth; Cihan Gani; Eleni Gkika; Anca-L Grosu; Christoph Henkenberens; Harun Ilhan; Steffen Löck; Simone Marnitz-Schulze; Matthias Miederer; Michael Mix; Nils H Nicolay; Maximilian Niyazi; Christoph Pöttgen; Claus M Rödel; Imke Schatka; Sarah M Schwarzenboeck; Andrei S Todica; Wolfgang Weber; Simone Wegen; Thomas Wiegel; Constantinos Zamboglou; Daniel Zips; Klaus Zöphel; Sebastian Zschaeck; Daniela Thorwarth; Esther G C Troost Journal: Strahlenther Onkol Date: 2021-07-14 Impact factor: 3.621