This report describes our initial experience using positron emission tomography (PET) scanning in... more This report describes our initial experience using positron emission tomography (PET) scanning in esophageal cancer patients. In two patients PET identified distant metastatic disease missed by conventional staging. Laparoscopic biopsy provided histological confirmation of metastases. In the third patient, locoregional lymph nodes were identified by PET and confirmed by surgical staging. In this preliminary report, PET appears to be a promising new noninvasive modality for staging patients with esophageal cancer.
The Standardized Uptake Value (SUV) is often used in positron emission tomography (PET) to differ... more The Standardized Uptake Value (SUV) is often used in positron emission tomography (PET) to differenciate malignant from benign tumors, and to monitor the progress of the patient response to therapy. Despite its name, SUV may depend on both PET scanner hardware and software details, and will depend on the imaging protocol. In this paper, we present a study of the SUV variability according to these external factors. To study the influence of the PET device, phantom studies were performed on two different combined PET/CT scanners. SUVs were obtained using several reconstruction algorithms and different reconstruction matrix sizes. To study the influence of the imaging protocol, patients were injected with 370 MBq of 18F-FDG and scanned at 60 and 90 min post-injection. SUVs were obtained applying several clinical image reconstruction algorithms. Significant differences in SUVs were obtained depending on the PET scanner, reconstruction method, and imaging protocol. It is essential, therefore, to follow a strict protocol in order to reliably compare FDG uptake with SUVs. Our results may have a significant clinical impact in order to provide an unbiased SUV thereshold to determine malignancy.
1993 IEEE Conference Record Nuclear Science Symposium and Medical Imaging Conference, 1993
Two methods for attenuation correction in 3D positron emission tomography have been compared. The... more Two methods for attenuation correction in 3D positron emission tomography have been compared. The first method, which is referred to here as the direct method, estimates the attenuation correction factors from the ratio of the blank and transmission scan. The second method, referred to here as the reconstruction-reprojection method is based on the reconstruction and forward projection of a transmission
Conference Record of the 1991 IEEE Nuclear Science Symposium and Medical Imaging Conference, 1991
Following previous reports of the NEC gain for a PET (positron emission tomography) scanner with ... more Following previous reports of the NEC gain for a PET (positron emission tomography) scanner with retractable septa (Siemens-CTI 953B), methods for 3-D normalization and attenuation correction from 2-D datasets were developed. Physical performance and system calibration were reevaluated for 3-D reconstructed data for this scanner. Normalization is performed by measuring the direct plane sinograms (no cross-plane contribution) with septa in
Conference Record of the 1991 IEEE Nuclear Science Symposium and Medical Imaging Conference, 1991
A positron emission tomography (PET) scanner with a reduced number of detectors per ring subtendi... more A positron emission tomography (PET) scanner with a reduced number of detectors per ring subtending two opposing arcs of 60° and mounted on a circular support was developed. Projection data at all angles are acquired by rotating the detector assembly. The scanner has no septa, and data from the equivalent of 16 full rings of detectors are collected and sorted
Continental shelf waters from the Labrador Sea to the Mid-Atlantic Bight experienced significant ... more Continental shelf waters from the Labrador Sea to the Mid-Atlantic Bight experienced significant freshening in the late 1990s, likely caused by increasing glacial melting and enhanced precipitation and river runoff at higher latitudes (as a result of climate change). The freshening of the ocean can alter circulation and stratification of shelf waters and may influence the phytoplankton dynamics and ecosystem
IEEE Symposium Conference Record Nuclear Science 2004., 2004
Evaluation and follow up of small pulmonary nodules has become commonplace with advancing PET and... more Evaluation and follow up of small pulmonary nodules has become commonplace with advancing PET and CT technology. Limits in system resolution, recovery coefficient estimations and transaxial ROI determinations often make obtaining useful SUV data difficult. We demonstrate a method which may be more accurate for making these determinations. It is assumed that the nodule can be distinguished clearly on CT
Proceedings of 1994 IEEE Nuclear Science Symposium - NSS'94, 1995
The use of X-ray CT for Attenuation Correction of PET Data ... Thomas Beyer, Paul E. Kinahan, Dav... more The use of X-ray CT for Attenuation Correction of PET Data ... Thomas Beyer, Paul E. Kinahan, David W. Townsend, and Donald Sashin Department of Radiology, University of Pittsburgh, Pittsburgh, PA 15213-2582 ... This paper presents the results of evaluating ...
Performance characteristics of a new commercial design of positron tomograph with retractable sep... more Performance characteristics of a new commercial design of positron tomograph with retractable septa for brain imaging have been studied. The device, composed of block BGO detectors (8 x 8 elements per block), has a ring diam of 76cm and an axial FOV of 10.8cm (slice thickness 4.3" with septa). The in-plane resolution is less than 5mm with wobble sampling. Its
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 2000
The availability of accurately aligned, whole-body anatomical (CT) and functional (PET) images co... more The availability of accurately aligned, whole-body anatomical (CT) and functional (PET) images could have a significant impact on diagnosing and staging malignant disease and on identifying and localizing metastases. Computer algorithms to align CT and PET images acquired on different scanners are generally successful for the brain, whereas image alignment in other regions of the body is more problematic. A combined PET/CT tomograph with the unique capability of acquiring accurately aligned functional and anatomical images for any part of the human body has been designed and built. The PET/CT scanner was developed as a combination of a Siemens Somatom AR.SP spiral CT and a partial-ring, rotating ECAT ART PET scanner. All components are mounted on a common rotational support within a single gantry. The PET and CT components can be operated either separately, or in combined mode. In combined mode, the CT images are used to correct the PET data for scatter and attenuation. Fully quanti...
The physical PET performance of the first prototype of the recently introduced Biograph mCT TOF P... more The physical PET performance of the first prototype of the recently introduced Biograph mCT TOF PET/CT scanner (Siemens Molecular Imaging) has been evaluated. The PET component incorporates 192 detector blocks, 5.4 cm x 5.4 cm in cross-section; each block comprises a 13 x 13 matrix of 4 x 4 x 20 mm3 crystal elements. The four detector block rings cover
1999 IEEE Nuclear Science Symposium. Conference Record. 1999 Nuclear Science Symposium and Medical Imaging Conference (Cat. No.99CH37019), 1999
... Blank and transmission data were acquired in standard 2D (ring difference 5, span of 11) and ... more ... Blank and transmission data were acquired in standard 2D (ring difference 5, span of 11) and true modes, using 3 rotating %e rod sources (activity around 10 mCi), and a 7 bin wide rod mask, which produced scatter free 2D attenuation correction. B. Experimental protocols ...
This report describes our initial experience using positron emission tomography (PET) scanning in... more This report describes our initial experience using positron emission tomography (PET) scanning in esophageal cancer patients. In two patients PET identified distant metastatic disease missed by conventional staging. Laparoscopic biopsy provided histological confirmation of metastases. In the third patient, locoregional lymph nodes were identified by PET and confirmed by surgical staging. In this preliminary report, PET appears to be a promising new noninvasive modality for staging patients with esophageal cancer.
The Standardized Uptake Value (SUV) is often used in positron emission tomography (PET) to differ... more The Standardized Uptake Value (SUV) is often used in positron emission tomography (PET) to differenciate malignant from benign tumors, and to monitor the progress of the patient response to therapy. Despite its name, SUV may depend on both PET scanner hardware and software details, and will depend on the imaging protocol. In this paper, we present a study of the SUV variability according to these external factors. To study the influence of the PET device, phantom studies were performed on two different combined PET/CT scanners. SUVs were obtained using several reconstruction algorithms and different reconstruction matrix sizes. To study the influence of the imaging protocol, patients were injected with 370 MBq of 18F-FDG and scanned at 60 and 90 min post-injection. SUVs were obtained applying several clinical image reconstruction algorithms. Significant differences in SUVs were obtained depending on the PET scanner, reconstruction method, and imaging protocol. It is essential, therefore, to follow a strict protocol in order to reliably compare FDG uptake with SUVs. Our results may have a significant clinical impact in order to provide an unbiased SUV thereshold to determine malignancy.
1993 IEEE Conference Record Nuclear Science Symposium and Medical Imaging Conference, 1993
Two methods for attenuation correction in 3D positron emission tomography have been compared. The... more Two methods for attenuation correction in 3D positron emission tomography have been compared. The first method, which is referred to here as the direct method, estimates the attenuation correction factors from the ratio of the blank and transmission scan. The second method, referred to here as the reconstruction-reprojection method is based on the reconstruction and forward projection of a transmission
Conference Record of the 1991 IEEE Nuclear Science Symposium and Medical Imaging Conference, 1991
Following previous reports of the NEC gain for a PET (positron emission tomography) scanner with ... more Following previous reports of the NEC gain for a PET (positron emission tomography) scanner with retractable septa (Siemens-CTI 953B), methods for 3-D normalization and attenuation correction from 2-D datasets were developed. Physical performance and system calibration were reevaluated for 3-D reconstructed data for this scanner. Normalization is performed by measuring the direct plane sinograms (no cross-plane contribution) with septa in
Conference Record of the 1991 IEEE Nuclear Science Symposium and Medical Imaging Conference, 1991
A positron emission tomography (PET) scanner with a reduced number of detectors per ring subtendi... more A positron emission tomography (PET) scanner with a reduced number of detectors per ring subtending two opposing arcs of 60° and mounted on a circular support was developed. Projection data at all angles are acquired by rotating the detector assembly. The scanner has no septa, and data from the equivalent of 16 full rings of detectors are collected and sorted
Continental shelf waters from the Labrador Sea to the Mid-Atlantic Bight experienced significant ... more Continental shelf waters from the Labrador Sea to the Mid-Atlantic Bight experienced significant freshening in the late 1990s, likely caused by increasing glacial melting and enhanced precipitation and river runoff at higher latitudes (as a result of climate change). The freshening of the ocean can alter circulation and stratification of shelf waters and may influence the phytoplankton dynamics and ecosystem
IEEE Symposium Conference Record Nuclear Science 2004., 2004
Evaluation and follow up of small pulmonary nodules has become commonplace with advancing PET and... more Evaluation and follow up of small pulmonary nodules has become commonplace with advancing PET and CT technology. Limits in system resolution, recovery coefficient estimations and transaxial ROI determinations often make obtaining useful SUV data difficult. We demonstrate a method which may be more accurate for making these determinations. It is assumed that the nodule can be distinguished clearly on CT
Proceedings of 1994 IEEE Nuclear Science Symposium - NSS'94, 1995
The use of X-ray CT for Attenuation Correction of PET Data ... Thomas Beyer, Paul E. Kinahan, Dav... more The use of X-ray CT for Attenuation Correction of PET Data ... Thomas Beyer, Paul E. Kinahan, David W. Townsend, and Donald Sashin Department of Radiology, University of Pittsburgh, Pittsburgh, PA 15213-2582 ... This paper presents the results of evaluating ...
Performance characteristics of a new commercial design of positron tomograph with retractable sep... more Performance characteristics of a new commercial design of positron tomograph with retractable septa for brain imaging have been studied. The device, composed of block BGO detectors (8 x 8 elements per block), has a ring diam of 76cm and an axial FOV of 10.8cm (slice thickness 4.3" with septa). The in-plane resolution is less than 5mm with wobble sampling. Its
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 2000
The availability of accurately aligned, whole-body anatomical (CT) and functional (PET) images co... more The availability of accurately aligned, whole-body anatomical (CT) and functional (PET) images could have a significant impact on diagnosing and staging malignant disease and on identifying and localizing metastases. Computer algorithms to align CT and PET images acquired on different scanners are generally successful for the brain, whereas image alignment in other regions of the body is more problematic. A combined PET/CT tomograph with the unique capability of acquiring accurately aligned functional and anatomical images for any part of the human body has been designed and built. The PET/CT scanner was developed as a combination of a Siemens Somatom AR.SP spiral CT and a partial-ring, rotating ECAT ART PET scanner. All components are mounted on a common rotational support within a single gantry. The PET and CT components can be operated either separately, or in combined mode. In combined mode, the CT images are used to correct the PET data for scatter and attenuation. Fully quanti...
The physical PET performance of the first prototype of the recently introduced Biograph mCT TOF P... more The physical PET performance of the first prototype of the recently introduced Biograph mCT TOF PET/CT scanner (Siemens Molecular Imaging) has been evaluated. The PET component incorporates 192 detector blocks, 5.4 cm x 5.4 cm in cross-section; each block comprises a 13 x 13 matrix of 4 x 4 x 20 mm3 crystal elements. The four detector block rings cover
1999 IEEE Nuclear Science Symposium. Conference Record. 1999 Nuclear Science Symposium and Medical Imaging Conference (Cat. No.99CH37019), 1999
... Blank and transmission data were acquired in standard 2D (ring difference 5, span of 11) and ... more ... Blank and transmission data were acquired in standard 2D (ring difference 5, span of 11) and true modes, using 3 rotating %e rod sources (activity around 10 mCi), and a 7 bin wide rod mask, which produced scatter free 2D attenuation correction. B. Experimental protocols ...
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Papers by David Townsend