Biomedical subjects

Brad J Kemp

Publications and source records attributed to Brad J Kemp.

4 recordsLinked to original sources

PubMed2006

Single-photon emission computed tomography/computed tomography: basic instrumentation and innovations.

Correlation of the anatomical and functional information presented by single-photon emission computed tomography (SPECT) and computed tomography (CT) can aid in the decision-making process by enabling better localization and definition of organs and lesions and improving the precision of surgical biopsies. Technical developments over the past 20 years have led to the development of better software techniques for image fusion and, more recently, to the development of modern SPECT/CT systems. While image fusion techniques have been in clinical use for many years, the first commercial SPECT/CT system was only developed in 1999. Following the commercial success of PET/CT systems that employed multidetector CT (MDCT) scanners, there has been renewed interest in the development of comparable SPECT/CT systems. This has resulted in the development of a range of SPECT/CT devices varying from a simple CT add-on to a conventional SPECT system that can provide low-dose CT images to a full MDCT scanner integrated with a SPECT system. The advantages of combining SPECT with CT are numerous and are primarily due to the anatomic referencing and the attenuation correction capabilities of CT. Depending on system design, there are varying technical issues surrounding the different SPECT/CT devices, ranging from cost, radiation dose, planning, and siting requirements to system-specific issues such as table sag and CT artifacts due to patient motion. Motion artifacts should be less prevalent with the faster acquisition times of modern scanners, but are still problematic in the thorax and have not yet been fully resolved as they pertain to the use of CT data for cardiac attenuation correction. As this technology matures, we can expect to see a range of SPECT/CT devices available on the market that range from low-dose 1-4 slice inexpensive CT upgrades of conventional SPECT systems, to SPECT systems incorporating 64 or 128 slices CT scanners. The cost of the high-end CT scanners will exceed the cost of the SPECT scanner and hence the justification for such devices will be heavily dependent on clear demonstration of their value in clinical practice.

Equipment Design↗

PubMed2006

Reproducibility of measurements of regional myocardial blood flow in a model of coronary artery disease: Comparison of H215O and 13NH3 PET techniques.

UNLABELLED: PET absolute myocardial blood flow (MBF) with H(2)15O and 13NH3 are widely used in clinical and research settings. However, their reproducibility with a 16-myocardial segment model has not been examined in chronic coronary artery disease (CAD). We examined the short-term reproducibility of PET H(2)15O MBF and PET 13NH3 MBF in an animal model of chronic CAD. METHODS: Twelve swine (mean weight +/- SD, 38 +/- 5 kg) underwent percutaneous placement of a copper stent in the mid circumflex coronary artery, resulting in an intense inflammatory fibrotic reaction with luminal stenosis at 4 wk. Each animal underwent repeated resting MBF measurements by PET H(2)15O and PET 13NH3. Attenuation-corrected images were analyzed using commercial software to yield absolute MBF (mL/min/g) in 16 myocardial segments. MBF was also normalized to the rate.pressure product (RPP). RESULTS: By Bland-Altman reproducibility plots, the mean difference was 0.01 +/- 0.18 mL/min/g and 0.01 +/- 0.11 mL/min/g, with confidence limits of +/-0.36 and +/-0.22 mL/min/g for uncorrected regional PET H(2)15O MBF and for uncorrected regional PET 13NH3 MBF, respectively. The repeatability coefficient ranged from 0.09 to 0.43 mL/min/g for H(2)15O and from 0.09 to 0.18 mL/min/g for 13NH3 regional MBF. RPP correction did not improve reproducibility for either PET H(2)15O or PET 13NH3 MBF. The mean difference in PET H(2)15O MBF was 0.03 +/- 0.14 mL/min/g and 0.02 +/- 0.19 mL/min/g for infarcted and remote regions, respectively, and in PET 13NH3 MBF was 0.03 +/- 0.11 mL/min/g and 0.00 +/- 0.09 mL/min/g for infarcted and remote regions, respectively. CONCLUSION: PET H(2)15O and PET 13NH3 resting MBF showed excellent reproducibility in a closed-chest animal model of chronic CAD. Resting PET 13NH3 MBF was more reproducible than resting PET H(2)15O MBF. A high level of reproducibility was maintained in areas of lower flow with infarction for both isotopes.

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PubMed2006

NEMA NU 2-2001 performance measurements of an LYSO-based PET/CT system in 2D and 3D acquisition modes.

UNLABELLED: The National Electrical Manufacturers Association (NEMA) NU 2-2001 performance measurements were conducted on the Discovery RX, a whole-body PET/CT system under development by GE Healthcare. The PET scanner uses 4.2 x 6.3 x 30 mm lutetium yttrium orthosilicate (LYSO) crystals grouped in 9 x 6 blocks. There are 24 rings with 630 crystals per ring and the ring diameter is 88.6 cm. The transaxial and axial fields of view are 70.0 and 15.7 cm, respectively. The scanner has retractable septa and can operate in both 2-dimensional (2D) and 3-dimensional (3D) modes. 2D acquisitions use ring differences of +/-4 for direct and +/-5 for cross slices; 3D acquisitions use a ring difference of 23. The coincident window width is 6.5 ns and the energy window is 425-650 keV. Other than the detectors, the system uses the same hardware and software as a Discovery ST. The CT scanner is a 16-slice LightSpeed; the performance characteristics of the CT component are not included herein. METHODS: Performance measurements of sensitivity, spatial resolution, image quality, scatter fraction and counting rate performance, and image quality were obtained using NEMA methodology. RESULTS: The system sensitivity in 2D and 3D was measured as 1.7 cps/kBq and 7.3 cps/kBq, respectively. The transaxial resolution for 2D (3D) was 5.1 mm full width at half maximum (FWHM) (5.0 mm) at 1 cm from gantry center and the radial and tangential resolutions were 5.9 mm (5.9 mm) and 5.1 mm (5.2 mm) at 10 cm, respectively. The axial resolution for 2D (3D) was 4.8 mm FWHM (5.8 mm) and 6.3 mm (6.5 mm) at 1 cm and 10 cm from gantry center, respectively. The scatter fraction was 13.1% and 31.8% in 2D and 3D. The peak noise equivalent count rate (NECR) was 155 kcps at 92.1 kBq/mL in 2D and 117.7 kcps at 21.7 kBq/mL in 3D for a noise-free estimation of randoms. The contrast of the 22, 17, 13, and 10 mm hot spheres in the image quality phantom in 2D (3D) were 74.6% (72.4%), 56.7% (59.5%), 46.2% (44.6%), and 17.9% (18.0%), respectively. CONCLUSION: The Discovery RX is a scanner that possesses high NECR, low scatter fraction, and good spatial resolution characteristics.

Equipment Design↗

PubMedDate not supplied

Combined I-124 positron emission tomography/computed tomography imaging of NIS gene expression in animal models of stably transfected and intravenously transfected tumor.

PURPOSE: With the advent of replication competent viruses for cancer gene therapy, it has become imperative to monitor the biodistribution, expression and replication of these vectors in living organisms. We evaluated the potential of I-124 positron emission tomography (PET)/computed tomography (CT) imaging in gene therapy animal models utilizing the sodium iodide symporter (NIS) and compared the findings to I-123 gamma camera imaging. PROCEDURES: CB17 SCID mice were implanted with myeloma cell lines expressing NIS or infected by MV-NIS given systemically. Mice were imaged by both gamma camera (I-123) and PET/CT (I-124 ) and image quality assessed. RESULTS: NIS expressing tumors concentrated 7.1% of the injected activity while tumors infected with the control virus had only 0.3% of the activity injected. CONCLUSIONS: I-124 PET/CT in combination with NIS allows the tracking of stably transfected tumors or intravenously transfected tumors. Combined modality imaging using PET/CT allows accurate and non-invasive imaging of the distribution and gene expression of a replicating viral vector in living systems.

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