Bone material analogues for PET/MRI phantoms. Issue 5 (13th March 2020)

• Record Type: Journal Article
• Authors: Chandramohan, Dharshan; Cao, Peng; Han, Misung; An, Hongyu; Sunderland, John J.; Kinahan, Paul E.; Laforest, Richard; Hope, Thomas A.; Larson, Peder E. Z.
• Other Names: El Naqa Issam guestEditor.; Das Shiva K. guestEditor.
• Is Part Of: Medical physics. Volume 47:Issue 5(2020)
• Page Start: 2161
• Page End: 2170
• Publication Date: 2020-03-13
• Subjects: attenuation correction -- bone materials -- doped plaster -- PET/MRI; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1002/mp.14079
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: To develop bone material analogues that can be used in construction of phantoms for simultaneous PET/MRI systems. Methods: Plaster was used as the basis for the bone material analogues tested in this study. It was mixed with varying concentrations of an iodinated CT contrast, a gadolinium‐based MR contrast agent, and copper sulfate to modulate the attenuation properties and MRI properties (T1 and T2*). Attenuation was measured with CT and 68 Ge transmission scans, and MRI properties were measured with quantitative ultrashort echo time pulse sequences. A proof‐of‐concept skull was created by plaster casting. Results: Undoped plaster has a 511 keV attenuation coefficient (~0.14 cm −1 ) similar to cortical bone (0.10–0.15 cm −1 ), but slightly longer T1 (~500 ms) and T2* (~1.2 ms) MR parameters compared to bone (T1 ~ 300 ms, T2* ~ 0.4 ms). Doping with the iodinated agent resulted in increased attenuation with minimal perturbation to the MR parameters. Doping with a gadolinium chelate greatly reduced T1 and T2*, resulting in extremely short T1 values when the target T2* values were reached, while the attenuation coefficient was unchanged. Doping with copper sulfate was more selective for T2* shortening and achieved comparable T1 and T2* values to bone (after 1 week of drying), while the attenuation coefficient was unchanged. Conclusions: Plaster doped with copper sulfate is a promising bone material analogue for a PET/MRI phantom, mimicking the MR properties (T1 and T2*) and 511 keV attenuation coefficient of human cortical bone.