Modified ACR Phantom for Assessing Quantitation Paul Kinahan Feb 29, 2008 The ACR PET phantom shown below is increasingly being used by PET imaging centers for ACR accreditation of the imaging facility. There are similarities between the ACR and SNM (NEMA-IQ) phantoms. The differences are that the NEMA-IQ phantom is more representative of an abdominal cross section, while ROI placement on the small cylinders of the ACR phantom is simpler than the small spheres of the NEMA-IQ phantom. In addition the entire volume of the SNM modification of the NEMA-IQ phantom is filled with Ge-68 in epoxy, making relatively radioactive and heavy. With the modified ACR phantom, Ge-68 in epoxy in only in the small cylinders reducing weight and radioactivity substantially. The tradeoff is that the main background portion of the cylinder has to be filled with a carefully measured amount of F-18 to obtained the desired target:background ratio. A worksheet that calculates the necessary amount of F-18 in the background for a 4:1 target:background ratio is shown with sample PET and CT images.
Teflon A B Water C D Air
Table 1: Excel spreadsheet method for determining activity to be injected in main chamber to archive a 4:1 cylinder:background ratio. Two methods are shown