title: Micro insert: a prototype full-ring PET device for improving the image resolution of a small-animal PET scanner.
abstract: A full-ring PET insert device should be able to enhance the image resolution of existing small-animal PET scanners.
  
  
  METHODS
  The device consists of 18 high-resolution PET detectors in a cylindric enclosure. Each detector contains a cerium-doped lutetium oxyorthosilicate array (12 x 12 crystals, 0.72 x 1.51 x 3.75 mm each) coupled to a position-sensitive photomultiplier tube via an optical fiber bundle made of 8 x 16 square multiclad fibers. Signals from the insert detectors are connected to the scanner through the electronics of the disabled first ring of detectors, which permits coincidence detection between the 2 systems. Energy resolution of a detector was measured using a (68)Ge point source, and a calibrated (68)Ge point source stepped across the axial field of view (FOV) provided the sensitivity profile of the system. A (22)Na point source imaged at different offsets from the center characterized the in-plane resolution of the insert system. Imaging was then performed with a Derenzo phantom filled with 19.5 MBq of (18)F-fluoride and imaged for 2 h; a 24.3-g mouse injected with 129.5 MBq of (18)F-fluoride and imaged in 5 bed positions at 3.5 h after injection; and a 22.8-g mouse injected with 14.3 MBq of (18)F-FDG and imaged for 2 h with electrocardiogram gating.
  
  
  RESULTS
  The energy resolution of a typical detector module at 511 keV is 19.0% +/- 3.1%. The peak sensitivity of the system is approximately 2.67%. The image resolution of the system ranges from 1.0- to 1.8-mm full width at half maximum near the center of the FOV, depending on the type of coincidence events used for image reconstruction. Derenzo phantom and mouse bone images showed significant improvement in transaxial image resolution using the insert device. Mouse heart images demonstrated the gated imaging capability of the device.
  
  
  CONCLUSIONS
  We have built a prototype full-ring insert device for a small-animal PET scanner to provide higher-resolution PET images within a reduced imaging FOV. Development of additional correction techniques are needed to achieve quantitative imaging with such an insert.
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri, USA.
authors.forename: Heyu
authors.initials: H
authors.lastname: Wu
authors.forename: Debashish
authors.initials: D
authors.lastname: Pal
authors.forename: Tae Yong
authors.initials: TY
authors.lastname: Song
authors.forename: Joseph A
authors.initials: JA
authors.lastname: O'Sullivan
authors.forename: Yuan-Chuan
authors.initials: YC
authors.lastname: Tai
mesh_terms: D000465:Algorithms; D000818:Animals; D003952:Diagnostic Imaging / Q000295:instrumentation / Q000379:methods; D004562:Electrocardiography / Q000379:methods; D004867:Equipment Design; D005462:Fluorine Radioisotopes / Q000494:pharmacology; D019788:Fluorodeoxyglucose F18 / Q000494:pharmacology; D007091:Image Processing, Computer-Assisted; D051379:Mice; D009683:Nuclear Medicine / Q000379:methods; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation* / Q000379:methods*
chemical_list: D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18
references.citation: Ann Med. 1999 Dec;31(6):432-7
references.pmid: 10680858
references.citation: Phys Med Biol. 1995 Jun;40(6):1105-26
references.pmid: 7659733
references.citation: J Nucl Med. 2008 Jan;49(1):79-87
references.pmid: 18077526
references.citation: J Nucl Med. 2005 Mar;46(3):455-63
references.pmid: 15750159
references.citation: J Nucl Med. 2000 Apr;41(4):661-81
references.pmid: 10768568
references.citation: J Nucl Med. 2008 Mar;49(3):471-9
references.pmid: 18287272
references.citation: Mol Imaging. 2005 Apr-Jun;4(2):117-27
references.pmid: 16105510
references.citation: Phys Med Biol. 2005 Jan 21;50(2):179-95
references.pmid: 15742938
references.citation: Annu Rev Biomed Eng. 2005;7:255-85
references.pmid: 16004572
references.citation: Phys Med Biol. 2003 Jun 7;48(11):1519-37
references.pmid: 12817935
references.citation: Radiology. 2001 May;219(2):316-33
references.pmid: 11323453
references.citation: Phys Med Biol. 1999 Mar;44(3):781-99
references.pmid: 10211810
references.citation: J Nucl Med. 1987 Nov;28(11):1717-24
references.pmid: 3499493
references.citation: Phys Med Biol. 2007 Jul 21;52(14):4293-310
references.pmid: 17664609