A prototype PET/SPECT/X-rays scanner dedicated for whole body small animal studies.

OBJECTIVE: To present a prototype tri-modal imaging system, consisting of a single photon emission computed tomography (SPET), a positron emission tomography (PET), and a computed tomography (CT) subsystem, evaluated in planar mode. MATERIALS AND METHODS: The subsystems are mounted on a rotating gantry, so as to be able to allow tomographic imaging in the future. The system, designed and constructed by our group, allows whole body mouse imaging of competent performance and is currently, to the best of our knowledge, unequaled in a national and regional level. The SPET camera is based on two Position Sensitive Photomultiplier Tubes (PSPMT), coupled to a pixilated Sodium Iodide activated with Thallium (NaI(Tl)) scintillator, having an active area of 5x10cm2. The dual head PET camera is also based on two pairs of PSPMT, coupled to pixelated berillium germanium oxide (BGO) scintillators, having an active area of 5x10cm2. The X-rays system consists of a micro focus X-rays tube and a complementary metal-oxide-semiconductor (CMOS) detector, having an active area of 12x12cm2. RESULTS: The scintigraphic mode has a spatial resolution of 1.88mm full width at half maximum (FWHM) and a sensitivity of 107.5cpm/0.037MBq at the collimator surface. The coincidence PET mode has an average spatial resolution of 3.5mm (FWHM) and a peak sensitivity of 29.9cpm/0.037MBq. The X-rays spatial resolution is 3.5lp/mm and the contrast discrimination function value is lower than 2%. CONCLUSION: A compact tri-modal system was successfully built and evaluated for planar mode operation. The system has an efficient performance, allowing accurate and informative anatomical and functional imaging, as well as semi-quantitative results. Compared to other available systems, it provides a moderate but comparable performance, at a fraction of the cost and complexity. It is fully open, scalable and its main purpose is to support groups on a national and regional level and provide an open technological platform to study different detector components and acquisition strategies.

Single-photon Emission Computed Tomography-Computed Tomography Using 99mTc-labeled Leukocytes for Evaluating Infection Associated with a Cranial Implant in a Rhesus Macaque (Macaca mulatta).

An adult male rhesus macaque (Macaca mulatta) that was enrolled in a study evaluating cognition and memory presented with suppurative exudate along the margins of a long-standing cranial implant that included a stainless-steel head post, plastic left-sided recording cylinder, and acrylic over a previously placed right-sided recording cylinder. Both cylinders were located at the level of the prefrontal cortex. After treatment comprising systemic antibiotics and daily cleaning with povidone-iodine for several months, the macaque underwent single-photon emission computed tomography-computed tomography (SPECT-CT) in which his neutrophils were labeled with 99mTc-hexamethylpropylene amine oxime ( 99m Tc-HMPAO) to evalu- ate for active infection below the implant. Soft tissue inflammation and osteomyelitis were found at the site of the previous right-sided recording cylinder. Cephalosporin and tetracycline antibiotics were administered for 12 wk. Follow-up SPECT-CT imaging was then performed to evaluate response to medical treatment. Results indicated no change in the degrees of soft tissue inflammation and osteomyelitis associated with the right-sided recording cylinder site. SPECT-CT imaging was used to guide the surgical removal of the implant and debridement of the infected tissue. On removal of the entire cranial implant, the osteomyelitis and soft tissue inflammation observed on the pre- and posttreatment SPECT-CT scans were confirmed. In addition, a large cavitary defect through the calvarium with suppurative exudate was discovered below the base of the head post. Infection in this defect was not apparent on SPECT; however, the bony defect was confirmed on reevaluation of the CT images. We concluded that the infection in this defect was silent on SPECT due to the limited vascularization of the sur-rounding bone and the chronicity of the infection. This case study is the first to describe the use of SPECT-CT for evaluating soft tissue inflammation and osteomyelitis beneath a cranial implant in a NHP.