Cynthia McCollough | Mayo Clinic (original) (raw)

Papers by Cynthia McCollough

Medical Physics, 2015

The spatial resolution of iterative reconstruction (IR) in computed tomography (CT) is contrast- ... more The spatial resolution of iterative reconstruction (IR) in computed tomography (CT) is contrast- and noise-dependent because of the nonlinear regularization. Due to the severe noise contamination, it is challenging to perform precise spatial-resolution measurements at very low-contrast levels. The purpose of this study was to measure the spatial resolution of a commercially available IR method using ensemble-averaged images acquired from repeated scans. A low-contrast phantom containing three rods (7, 14, and 21 HU below background) was scanned on a 128-slice CT scanner at three dose levels (CTDIvol = 16, 8, and 4 mGy). Images were reconstructed using two filtered-backprojection (FBP) kernels (B40 and B20) and a commercial IR method (sinogram affirmed iterative reconstruction, SAFIRE, Siemens Healthcare) with two strength settings (I40-3 and I40-5). The same scan was repeated 100 times at each dose level. The modulation transfer function (MTF) was calculated based on the edge profile measured on the ensemble-averaged images. The spatial resolution of the two FBP kernels, B40 and B20, remained relatively constant across contrast and dose levels. However, the spatial resolution of the two IR kernels degraded relative to FBP as contrast or dose level decreased. For a given dose level at 16 mGy, the MTF50% value normalized to the B40 kernel decreased from 98.4% at 21 HU to 88.5% at 7 HU for I40-3 and from 97.6% to 82.1% for I40-5. At 21 HU, the relative MTF50% value decreased from 98.4% at 16 mGy to 90.7% at 4 mGy for I40-3 and from 97.6% to 85.6% for I40-5. A simple technique using ensemble averaging from repeated CT scans can be used to measure the spatial resolution of IR techniques in CT at very low contrast levels. The evaluated IR method degraded the spatial resolution at low contrast and high noise levels.

Seminars in roentgenology, 2015

Academic radiology, 2014

Nephrosclerosis occurs with aging and is characterized by increased kidney subcapsular surface ir... more Nephrosclerosis occurs with aging and is characterized by increased kidney subcapsular surface irregularities at autopsy. Assessments of cortical roughness in vivo could provide an important measure of nephrosclerosis. The purpose of this study was to develop and validate an image-processing algorithm for quantifying renal cortical surface roughness in vivo and determine its association with age. Renal cortical surface roughness was measured on contrast-enhanced abdominal computed tomography (CT) images of potential living kidney donors. A roughness index was calculated based on geometric curvature of each kidney from three-dimensional images and compared to visual observation scores. Cortical roughness was compared between the oldest and youngest donors, and its interaction with cortical volume and age assessed. The developed quantitative roughness index identified significant differences in kidneys with visual surface roughness scores of 0 (minimal), 1 (mild), and 2 (moderate; P &...

Radiology, Jan 26, 2015

Purpose To determine the dose reduction that could be achieved without degrading low-contrast spa... more Purpose To determine the dose reduction that could be achieved without degrading low-contrast spatial resolution (LCR) performance for two commercial iterative reconstruction (IR) techniques, each evaluated at two strengths with many repeated scans. Materials and Methods Two scanner models were used to image the American College of Radiology (ACR) CT accreditation phantom LCR section at volume CT dose indexes of 8, 12, and 16 mGy. Images were reconstructed by using filtered back projection (FBP) and two manufacturers' IR techniques, each at two strengths (moderate and strong). Data acquisition and reconstruction were repeated 100 times for each, yielding 1800 images. Three diagnostic medical physicists reviewed the LCR images in a blinded fashion and graded the visibility of four 6-mm rods with a six-point scale. Noninferiority and inferiority-superiority analyses were used to interpret the differences in LCR relative to FBP images acquired at 16 mGy. Results LCR decreased with ...

Dual-energy CT scanning has significant potential for disease identification and classification. ... more Dual-energy CT scanning has significant potential for disease identification and classification. However, it dramatically increases the amount of data collected and therefore impacts the clinical workflow. One way to simplify image review is to fuse CT datasets of different tube energies into a unique blended dataset with desirable properties.

Radiologic clinics of North America, 2012

This article discusses modern dual-energy computed tomography (DECT) and the unique material-spec... more This article discusses modern dual-energy computed tomography (DECT) and the unique material-specific information these scanners can provide. A description of the technical aspects of the various DECT techniques is provided. Specific clinical applications in urologic imaging, including chemical composition of urolithiasis, evaluation of renal masses, detection of urothelial neoplasms, and adrenal adenoma imaging, are discussed. The unique postprocessed image sets, including virtual noncontrast, iodine overlay, and stone composition, are described.

Radiology, Jan 25, 2015

Purpose To develop software to automatically calculate size-specific dose estimates (SSDEs) and t... more Purpose To develop software to automatically calculate size-specific dose estimates (SSDEs) and to assess the effect of variations in water-equivalent diameter (Dw) along the z-axis on SSDE for computed tomographic (CT) examinations of the torso. Materials and Methods In this institutional review board-approved, HIPAA-compliant, retrospective study, a software program was used to calculate Dw at each image position in 102 consecutive CT examinations of the combined chest, abdomen, and pelvis. SSDE was calculated by multiplying the size-dependent conversion factor and volume CT dose index (CTDIvol) at each image position. The variations in Dw along the z-axis were determined for six hypothetical scanning ranges: chest alone; abdomen alone; pelvis alone; chest and abdomen; abdomen and pelvis; and chest, abdomen, and pelvis. Mean SSDE was calculated in two ways: (a) from the SSDE at each position and (b) from the mean CTDIvol over each scan range and the conversion factor corresponding...

Cardiology Clinics, 2003

CT data acquisition and image reconstruction techniques are closely related to image quality and ... more CT data acquisition and image reconstruction techniques are closely related to image quality and patient radiation dose. There is little question that technological developments currently underway will change the nature of both, and result in improved quality and diagnostic value of cardiovascular CT images while hopefully minimizing radiation dose to the patient.

Optimal noise control is important for improving image quality and reducing radiation dose in com... more Optimal noise control is important for improving image quality and reducing radiation dose in computed tomography. Here we investigated two image space based nonlinear filters for noise reduction: the bilateral filter (BF) and the nonlocal means (NLM) algorithm. Images from both methods were compared against those from a commercially available weighted filtered backprojection (WFBP) method. A standard phantom for quality assurance testing was used to quantitatively compare noise and spatial resolution, as well as low contrast detectability (LCD). Additionally, an image dataset from a patient's abdominal CT exam was used to assess the effectiveness of the filters on full dose and simulated half dose acquisitions. We found that both the BF and NLM methods improve the tradeoff between noise and high contrast spatial resolution with no significant difference in LCD. Results from the patient dataset demonstrated the potential of dose reduction with the denoising methods. Care must be taken when choosing the NLM parameters in order to minimize the generation of artifacts that could possibly compromise diagnostic value.

Medical Imaging 2009: Physics of Medical Imaging, 2009

Dual-source computed tomography (CT) utilizes two x-ray tubes and two detectors simultaneously fo... more Dual-source computed tomography (CT) utilizes two x-ray tubes and two detectors simultaneously for the purpose of obtaining 83 msec temporal resolution, 160 kW of x-ray power reserve, or dual-kV (dual-energy) scan capabilities. One inherent constraint of such a design is cross-scatter radiation, which occurs when x-rays from tube A are scattered by the patient and detected by detector B, or

Journal of Thoracic Imaging, 2007

Computed tomography (CT) angiography of the coronaries has the ability to depict extracardiac les... more Computed tomography (CT) angiography of the coronaries has the ability to depict extracardiac lesions in the visualized thorax and upper abdomen. These incidental lesions can often present a challenge to physicians. We performed a retrospective review of 100 consecutive patients referred for 64-multidetector CT coronary CT angiography performed on a 64-slice CT scanner. Two fellowship trained cardiac radiologists reviewed each study by consensus on a CT postprocessing workstation using commercially available software. Extracardiac CT findings (ECF) were classified as benign, indeterminate, or of clinical significance at the time of image evaluation. Benign findings were those considered to be of little clinical significance with no follow-up needed. Indeterminate findings were those deemed of potential clinical importance, requiring correlation of the patient history or a follow-up study. Clinically significant findings were those felt to be of definite clinical importance requiring immediate evaluation or intervention. The study cohort consisted of 68 males (68%) and 32 females (32%) with a mean (+/-standard deviation) age of 63.4+/-14.5 years and a range of 23 to 87 years. A total of 145 ECF were found in 67 patients (67%), 50 males and 17 females, with a mean age of 68.0+/-11.8 years and a range of 23 to 87 years. Of those, 107 (73.8%) were considered benign, 22 (15.2%) indeterminate, and 16 clinically significant findings (11.0%). By significance, a total of 107 benign ECF were found in 61 patients, 46 males and 15 females, with a mean age of 67.7+/-12.2 years and a range of 23 to 87 years. Only 22 ECF indeterminate findings were present, distributed in 21 patients, of which there were 17 males and 5 females, with a mean age of 68.5+/-13.9 and a range of 23 to 82 years. The 16 clinically significant ECF were distributed in 11 patients, all males, with a mean age of 68.0+/-8.8 and a range of 55 to 87 years. The presence of ECF in our daily practice is frequent, and not limited to the identification of pulmonary nodules, and reinforces the notion that all the organs in the scan should be thoroughly and methodically evaluated.

Urology, 2015

Non-enhanced CT exams were acquired using a 64-channel spiral CT scanner (Sensation-64 or Definit... more Non-enhanced CT exams were acquired using a 64-channel spiral CT scanner (Sensation-64 or Definition-64, Siemens Healthcare, Forchheim, Germany) with 64 x 0.6 collimation, a pitch of 1.2, 120 kVp, and quality reference mAs of 240. In addition a modulated tube current (CARE Dose) was applied to lower radiation exposure. 1 For the stone quantification, reconstructions of 2 mm slice thickness at 2 mm increments were used with a B40 (medium sharp) reconstruction algorithm.

Skeletal Radiology, 2007

Objective High-resolution real-time three-dimensional (3D) imaging of the moving wrist may provid... more Objective High-resolution real-time three-dimensional (3D) imaging of the moving wrist may provide novel insights into the pathophysiology of joint instability. The purpose of this work was to assess the feasibility of using retrospectively gated spiral computed tomography (CT) to perform four-dimensional (4D) imaging of the moving wrist joint. Materials and methods A cadaver forearm from below the elbow was mounted on a motion simulator which performed radioulnar deviation of the wrist at 30 cycles per minute. An electronic trigger from the simulator provided the "electrocardiogram" (ECG) signal required for gated reconstructions. Four-dimensional and 3D images were compared by a blinded observer for image quality and presence of artifacts. Results Image quality of 4D images was found to be excellent at the extremes of radial and ulnar deviation (end-motion phases). Some artifacts were seen in mid-motion phases.

Seminars in Respiratory and Critical Care Medicine, 2014

Chest computed tomography (CT) is a useful tool for diagnosing various thoracic conditions and ha... more Chest computed tomography (CT) is a useful tool for diagnosing various thoracic conditions and has become the diagnostic imaging modality of choice for many diseases. Recent discussions about the radiation dose from CT have attracted the attention of medical professionals and the general public. This article discusses radiation dose with an emphasis on chest CT and on current techniques for patient dose reduction. Four techniques are discussed in detail, including tube current modulation, automatic exposure control, automatic tube voltage selection, and iterative image reconstruction. Adopting these techniques in routine clinical practice can dramatically reduce radiation dose levels.

Radiologic Clinics of North America, 2009

Dual-energy CT refers to the use of CT data representing two different energy spectra and allows ... more Dual-energy CT refers to the use of CT data representing two different energy spectra and allows for the possibility of differentiating and classifying tissue to obtain material-specific images. Dual-energy CT data can be acquired using various CT hardware platforms, with numerous approaches also existing for display of anatomic and material-specific dual-energy information. Dual-source CT refers to the use of two x-ray sources and two x-ray detectors mounted on a single CT gantry and can be used in either a dual-energy or single-energy mode. This article summarizes and reviews current and potential applications for dual-energy and dual-source CT in the abdomen and pelvis.

Radiologic Clinics of North America, 2009

Physics in Medicine and Biology, 2009

Tube current modulation was designed to reduce radiation dose in CT imaging while maintaining ove... more Tube current modulation was designed to reduce radiation dose in CT imaging while maintaining overall image quality. This study aims to develop a method for evaluating the effects of tube current modulation (TCM) on organ dose in CT exams of actual patient anatomy. This method was validated by simulating a TCM and a fixed tube current chest CT exam on 30 voxelized patient models and estimating the radiation dose to each patient's glandular breast tissue. This new method for estimating organ dose was compared with other conventional estimates of dose reduction. Thirty detailed voxelized models of patient anatomy were created based on image data from female patients who had previously undergone clinically indicated CT scans including the chest area. As an indicator of patient size, the perimeter of the patient was measured on the image containing at least one nipple using a semi-automated technique. The breasts were contoured on each image set by a radiologist and glandular tissue was semi-automatically segmented from this region. Previously validated Monte Carlo models of two multidetector CT scanners were used, taking into account details about the source spectra, filtration, collimation and geometry of the scanner. TCM data were obtained from each patient's clinical scan and factored into the model to simulate the effects of TCM. For each patient model, two exams were simulated: a fixed tube current chest CT and a tube current modulated chest CT. X-ray photons were transported through the anatomy of the voxelized patient models, and radiation dose was tallied in the glandular breast tissue. The resulting doses from the tube current modulated simulations were compared to the results obtained from simulations performed using a fixed mA value. The average radiation dose to the glandular breast tissue from a fixed tube current scan across all patient models was 19 mGy. The average reduction in breast dose using the tube current modulated scan was 17%. Results were size dependent with smaller patients getting better dose reduction (up to 64% reduction) and larger patients getting a smaller reduction, and in some cases the dose actually increased when using tube current modulation (up to 41% increase). The results indicate that radiation dose to glandular breast tissue generally decreases with the use of tube current modulated CT acquisition, but that patient size (and in some cases patient positioning) may affect dose reduction.

Pediatric Radiology, 2010

Medical Physics, 2003

The purpose of this document is to provide the medical physicist with a framework and guidance fo... more The purpose of this document is to provide the medical physicist with a framework and guidance for establishment of a comprehensive quality assurance ͑QA͒ program for computed-tomography-͑CT͒ scanners used for CTsimulation, CT-simulation software, and the CT-simulation process. The CT-simulator is a CT scanner equipped with a flat tabletop and, preferably, external patient positioning lasers. The scanner is accompanied with specialized software which allows treatment planning on volumetric patient CT scans in a manner consistent with conventional radiation therapy simulators. 1-12 The CT scanner used in the CTsimulation process can be located in the radiation oncology department or in the diagnostic radiology department. Depending on the CT-scanner location and primary use, acceptance testing, commissioning, and QA can be the responsibility of a therapy medical physicist, diagnostic physicist, or a joint responsibility of diagnostic and therapy physicists. The commissioning and periodic QA of the accompanying software and the QA of the CT-simulation process is always the responsibility of the therapy physicist. This report does not address each of the two scenarios individually ͑scanner located in diagnostic radiology or radiation oncology͒, but rather establishes a set of QA procedures that are applicable to scanners used for CT-simulation regardless of their location and primary purpose. It is the responsibility of the respective diagnostic and therapy physicists to determine how the QA program is implemented and how the responsibilities are assigned. The primary responsibility for implementation of recommendations for QA of scanners used for CTsimulation in this document rests with the radiation oncology Quality Assurance Committee ͑QAC͒ as specified by the AAPM Task Group 40. 13 Further discussion of QA program responsibilities is provided in Appendix A. If the scanner is located in the radiation oncology department, a therapy medical physicist can perform QA of the CT-scanner and of the simulation process independently. It is recommended that the therapy physicist solicit help from a diagnostic physicist for the establishment of a QA program and scanner commissioning if he or she has limited CT experience. Likewise, if the CT-scanner is located in the diagnostic radiology department, the primary responsibility for the scanner QA rests with the diagnostic physicist. It is then the responsibility of the radiation oncology physicist to assure that the recommendations of this task group are implemented by either diagnostic radiology or the radiation oncology physicist or a designate.

Medical Physics, 2015

The spatial resolution of iterative reconstruction (IR) in computed tomography (CT) is contrast- ... more The spatial resolution of iterative reconstruction (IR) in computed tomography (CT) is contrast- and noise-dependent because of the nonlinear regularization. Due to the severe noise contamination, it is challenging to perform precise spatial-resolution measurements at very low-contrast levels. The purpose of this study was to measure the spatial resolution of a commercially available IR method using ensemble-averaged images acquired from repeated scans. A low-contrast phantom containing three rods (7, 14, and 21 HU below background) was scanned on a 128-slice CT scanner at three dose levels (CTDIvol = 16, 8, and 4 mGy). Images were reconstructed using two filtered-backprojection (FBP) kernels (B40 and B20) and a commercial IR method (sinogram affirmed iterative reconstruction, SAFIRE, Siemens Healthcare) with two strength settings (I40-3 and I40-5). The same scan was repeated 100 times at each dose level. The modulation transfer function (MTF) was calculated based on the edge profile measured on the ensemble-averaged images. The spatial resolution of the two FBP kernels, B40 and B20, remained relatively constant across contrast and dose levels. However, the spatial resolution of the two IR kernels degraded relative to FBP as contrast or dose level decreased. For a given dose level at 16 mGy, the MTF50% value normalized to the B40 kernel decreased from 98.4% at 21 HU to 88.5% at 7 HU for I40-3 and from 97.6% to 82.1% for I40-5. At 21 HU, the relative MTF50% value decreased from 98.4% at 16 mGy to 90.7% at 4 mGy for I40-3 and from 97.6% to 85.6% for I40-5. A simple technique using ensemble averaging from repeated CT scans can be used to measure the spatial resolution of IR techniques in CT at very low contrast levels. The evaluated IR method degraded the spatial resolution at low contrast and high noise levels.

Seminars in roentgenology, 2015

Academic radiology, 2014

Nephrosclerosis occurs with aging and is characterized by increased kidney subcapsular surface ir... more Nephrosclerosis occurs with aging and is characterized by increased kidney subcapsular surface irregularities at autopsy. Assessments of cortical roughness in vivo could provide an important measure of nephrosclerosis. The purpose of this study was to develop and validate an image-processing algorithm for quantifying renal cortical surface roughness in vivo and determine its association with age. Renal cortical surface roughness was measured on contrast-enhanced abdominal computed tomography (CT) images of potential living kidney donors. A roughness index was calculated based on geometric curvature of each kidney from three-dimensional images and compared to visual observation scores. Cortical roughness was compared between the oldest and youngest donors, and its interaction with cortical volume and age assessed. The developed quantitative roughness index identified significant differences in kidneys with visual surface roughness scores of 0 (minimal), 1 (mild), and 2 (moderate; P &...

Radiology, Jan 26, 2015

Purpose To determine the dose reduction that could be achieved without degrading low-contrast spa... more Purpose To determine the dose reduction that could be achieved without degrading low-contrast spatial resolution (LCR) performance for two commercial iterative reconstruction (IR) techniques, each evaluated at two strengths with many repeated scans. Materials and Methods Two scanner models were used to image the American College of Radiology (ACR) CT accreditation phantom LCR section at volume CT dose indexes of 8, 12, and 16 mGy. Images were reconstructed by using filtered back projection (FBP) and two manufacturers' IR techniques, each at two strengths (moderate and strong). Data acquisition and reconstruction were repeated 100 times for each, yielding 1800 images. Three diagnostic medical physicists reviewed the LCR images in a blinded fashion and graded the visibility of four 6-mm rods with a six-point scale. Noninferiority and inferiority-superiority analyses were used to interpret the differences in LCR relative to FBP images acquired at 16 mGy. Results LCR decreased with ...

Dual-energy CT scanning has significant potential for disease identification and classification. ... more Dual-energy CT scanning has significant potential for disease identification and classification. However, it dramatically increases the amount of data collected and therefore impacts the clinical workflow. One way to simplify image review is to fuse CT datasets of different tube energies into a unique blended dataset with desirable properties.

Radiologic clinics of North America, 2012

This article discusses modern dual-energy computed tomography (DECT) and the unique material-spec... more This article discusses modern dual-energy computed tomography (DECT) and the unique material-specific information these scanners can provide. A description of the technical aspects of the various DECT techniques is provided. Specific clinical applications in urologic imaging, including chemical composition of urolithiasis, evaluation of renal masses, detection of urothelial neoplasms, and adrenal adenoma imaging, are discussed. The unique postprocessed image sets, including virtual noncontrast, iodine overlay, and stone composition, are described.

Radiology, Jan 25, 2015

Purpose To develop software to automatically calculate size-specific dose estimates (SSDEs) and t... more Purpose To develop software to automatically calculate size-specific dose estimates (SSDEs) and to assess the effect of variations in water-equivalent diameter (Dw) along the z-axis on SSDE for computed tomographic (CT) examinations of the torso. Materials and Methods In this institutional review board-approved, HIPAA-compliant, retrospective study, a software program was used to calculate Dw at each image position in 102 consecutive CT examinations of the combined chest, abdomen, and pelvis. SSDE was calculated by multiplying the size-dependent conversion factor and volume CT dose index (CTDIvol) at each image position. The variations in Dw along the z-axis were determined for six hypothetical scanning ranges: chest alone; abdomen alone; pelvis alone; chest and abdomen; abdomen and pelvis; and chest, abdomen, and pelvis. Mean SSDE was calculated in two ways: (a) from the SSDE at each position and (b) from the mean CTDIvol over each scan range and the conversion factor corresponding...

Cardiology Clinics, 2003

CT data acquisition and image reconstruction techniques are closely related to image quality and ... more CT data acquisition and image reconstruction techniques are closely related to image quality and patient radiation dose. There is little question that technological developments currently underway will change the nature of both, and result in improved quality and diagnostic value of cardiovascular CT images while hopefully minimizing radiation dose to the patient.

Optimal noise control is important for improving image quality and reducing radiation dose in com... more Optimal noise control is important for improving image quality and reducing radiation dose in computed tomography. Here we investigated two image space based nonlinear filters for noise reduction: the bilateral filter (BF) and the nonlocal means (NLM) algorithm. Images from both methods were compared against those from a commercially available weighted filtered backprojection (WFBP) method. A standard phantom for quality assurance testing was used to quantitatively compare noise and spatial resolution, as well as low contrast detectability (LCD). Additionally, an image dataset from a patient's abdominal CT exam was used to assess the effectiveness of the filters on full dose and simulated half dose acquisitions. We found that both the BF and NLM methods improve the tradeoff between noise and high contrast spatial resolution with no significant difference in LCD. Results from the patient dataset demonstrated the potential of dose reduction with the denoising methods. Care must be taken when choosing the NLM parameters in order to minimize the generation of artifacts that could possibly compromise diagnostic value.

Medical Imaging 2009: Physics of Medical Imaging, 2009

Dual-source computed tomography (CT) utilizes two x-ray tubes and two detectors simultaneously fo... more Dual-source computed tomography (CT) utilizes two x-ray tubes and two detectors simultaneously for the purpose of obtaining 83 msec temporal resolution, 160 kW of x-ray power reserve, or dual-kV (dual-energy) scan capabilities. One inherent constraint of such a design is cross-scatter radiation, which occurs when x-rays from tube A are scattered by the patient and detected by detector B, or

Journal of Thoracic Imaging, 2007

Computed tomography (CT) angiography of the coronaries has the ability to depict extracardiac les... more Computed tomography (CT) angiography of the coronaries has the ability to depict extracardiac lesions in the visualized thorax and upper abdomen. These incidental lesions can often present a challenge to physicians. We performed a retrospective review of 100 consecutive patients referred for 64-multidetector CT coronary CT angiography performed on a 64-slice CT scanner. Two fellowship trained cardiac radiologists reviewed each study by consensus on a CT postprocessing workstation using commercially available software. Extracardiac CT findings (ECF) were classified as benign, indeterminate, or of clinical significance at the time of image evaluation. Benign findings were those considered to be of little clinical significance with no follow-up needed. Indeterminate findings were those deemed of potential clinical importance, requiring correlation of the patient history or a follow-up study. Clinically significant findings were those felt to be of definite clinical importance requiring immediate evaluation or intervention. The study cohort consisted of 68 males (68%) and 32 females (32%) with a mean (+/-standard deviation) age of 63.4+/-14.5 years and a range of 23 to 87 years. A total of 145 ECF were found in 67 patients (67%), 50 males and 17 females, with a mean age of 68.0+/-11.8 years and a range of 23 to 87 years. Of those, 107 (73.8%) were considered benign, 22 (15.2%) indeterminate, and 16 clinically significant findings (11.0%). By significance, a total of 107 benign ECF were found in 61 patients, 46 males and 15 females, with a mean age of 67.7+/-12.2 years and a range of 23 to 87 years. Only 22 ECF indeterminate findings were present, distributed in 21 patients, of which there were 17 males and 5 females, with a mean age of 68.5+/-13.9 and a range of 23 to 82 years. The 16 clinically significant ECF were distributed in 11 patients, all males, with a mean age of 68.0+/-8.8 and a range of 55 to 87 years. The presence of ECF in our daily practice is frequent, and not limited to the identification of pulmonary nodules, and reinforces the notion that all the organs in the scan should be thoroughly and methodically evaluated.

Urology, 2015

Non-enhanced CT exams were acquired using a 64-channel spiral CT scanner (Sensation-64 or Definit... more Non-enhanced CT exams were acquired using a 64-channel spiral CT scanner (Sensation-64 or Definition-64, Siemens Healthcare, Forchheim, Germany) with 64 x 0.6 collimation, a pitch of 1.2, 120 kVp, and quality reference mAs of 240. In addition a modulated tube current (CARE Dose) was applied to lower radiation exposure. 1 For the stone quantification, reconstructions of 2 mm slice thickness at 2 mm increments were used with a B40 (medium sharp) reconstruction algorithm.

Skeletal Radiology, 2007

Objective High-resolution real-time three-dimensional (3D) imaging of the moving wrist may provid... more Objective High-resolution real-time three-dimensional (3D) imaging of the moving wrist may provide novel insights into the pathophysiology of joint instability. The purpose of this work was to assess the feasibility of using retrospectively gated spiral computed tomography (CT) to perform four-dimensional (4D) imaging of the moving wrist joint. Materials and methods A cadaver forearm from below the elbow was mounted on a motion simulator which performed radioulnar deviation of the wrist at 30 cycles per minute. An electronic trigger from the simulator provided the "electrocardiogram" (ECG) signal required for gated reconstructions. Four-dimensional and 3D images were compared by a blinded observer for image quality and presence of artifacts. Results Image quality of 4D images was found to be excellent at the extremes of radial and ulnar deviation (end-motion phases). Some artifacts were seen in mid-motion phases.

Seminars in Respiratory and Critical Care Medicine, 2014

Chest computed tomography (CT) is a useful tool for diagnosing various thoracic conditions and ha... more Chest computed tomography (CT) is a useful tool for diagnosing various thoracic conditions and has become the diagnostic imaging modality of choice for many diseases. Recent discussions about the radiation dose from CT have attracted the attention of medical professionals and the general public. This article discusses radiation dose with an emphasis on chest CT and on current techniques for patient dose reduction. Four techniques are discussed in detail, including tube current modulation, automatic exposure control, automatic tube voltage selection, and iterative image reconstruction. Adopting these techniques in routine clinical practice can dramatically reduce radiation dose levels.

Radiologic Clinics of North America, 2009

Dual-energy CT refers to the use of CT data representing two different energy spectra and allows ... more Dual-energy CT refers to the use of CT data representing two different energy spectra and allows for the possibility of differentiating and classifying tissue to obtain material-specific images. Dual-energy CT data can be acquired using various CT hardware platforms, with numerous approaches also existing for display of anatomic and material-specific dual-energy information. Dual-source CT refers to the use of two x-ray sources and two x-ray detectors mounted on a single CT gantry and can be used in either a dual-energy or single-energy mode. This article summarizes and reviews current and potential applications for dual-energy and dual-source CT in the abdomen and pelvis.

Radiologic Clinics of North America, 2009

Physics in Medicine and Biology, 2009

Tube current modulation was designed to reduce radiation dose in CT imaging while maintaining ove... more Tube current modulation was designed to reduce radiation dose in CT imaging while maintaining overall image quality. This study aims to develop a method for evaluating the effects of tube current modulation (TCM) on organ dose in CT exams of actual patient anatomy. This method was validated by simulating a TCM and a fixed tube current chest CT exam on 30 voxelized patient models and estimating the radiation dose to each patient's glandular breast tissue. This new method for estimating organ dose was compared with other conventional estimates of dose reduction. Thirty detailed voxelized models of patient anatomy were created based on image data from female patients who had previously undergone clinically indicated CT scans including the chest area. As an indicator of patient size, the perimeter of the patient was measured on the image containing at least one nipple using a semi-automated technique. The breasts were contoured on each image set by a radiologist and glandular tissue was semi-automatically segmented from this region. Previously validated Monte Carlo models of two multidetector CT scanners were used, taking into account details about the source spectra, filtration, collimation and geometry of the scanner. TCM data were obtained from each patient's clinical scan and factored into the model to simulate the effects of TCM. For each patient model, two exams were simulated: a fixed tube current chest CT and a tube current modulated chest CT. X-ray photons were transported through the anatomy of the voxelized patient models, and radiation dose was tallied in the glandular breast tissue. The resulting doses from the tube current modulated simulations were compared to the results obtained from simulations performed using a fixed mA value. The average radiation dose to the glandular breast tissue from a fixed tube current scan across all patient models was 19 mGy. The average reduction in breast dose using the tube current modulated scan was 17%. Results were size dependent with smaller patients getting better dose reduction (up to 64% reduction) and larger patients getting a smaller reduction, and in some cases the dose actually increased when using tube current modulation (up to 41% increase). The results indicate that radiation dose to glandular breast tissue generally decreases with the use of tube current modulated CT acquisition, but that patient size (and in some cases patient positioning) may affect dose reduction.

Pediatric Radiology, 2010

Medical Physics, 2003

The purpose of this document is to provide the medical physicist with a framework and guidance fo... more The purpose of this document is to provide the medical physicist with a framework and guidance for establishment of a comprehensive quality assurance ͑QA͒ program for computed-tomography-͑CT͒ scanners used for CTsimulation, CT-simulation software, and the CT-simulation process. The CT-simulator is a CT scanner equipped with a flat tabletop and, preferably, external patient positioning lasers. The scanner is accompanied with specialized software which allows treatment planning on volumetric patient CT scans in a manner consistent with conventional radiation therapy simulators. 1-12 The CT scanner used in the CTsimulation process can be located in the radiation oncology department or in the diagnostic radiology department. Depending on the CT-scanner location and primary use, acceptance testing, commissioning, and QA can be the responsibility of a therapy medical physicist, diagnostic physicist, or a joint responsibility of diagnostic and therapy physicists. The commissioning and periodic QA of the accompanying software and the QA of the CT-simulation process is always the responsibility of the therapy physicist. This report does not address each of the two scenarios individually ͑scanner located in diagnostic radiology or radiation oncology͒, but rather establishes a set of QA procedures that are applicable to scanners used for CT-simulation regardless of their location and primary purpose. It is the responsibility of the respective diagnostic and therapy physicists to determine how the QA program is implemented and how the responsibilities are assigned. The primary responsibility for implementation of recommendations for QA of scanners used for CTsimulation in this document rests with the radiation oncology Quality Assurance Committee ͑QAC͒ as specified by the AAPM Task Group 40. 13 Further discussion of QA program responsibilities is provided in Appendix A. If the scanner is located in the radiation oncology department, a therapy medical physicist can perform QA of the CT-scanner and of the simulation process independently. It is recommended that the therapy physicist solicit help from a diagnostic physicist for the establishment of a QA program and scanner commissioning if he or she has limited CT experience. Likewise, if the CT-scanner is located in the diagnostic radiology department, the primary responsibility for the scanner QA rests with the diagnostic physicist. It is then the responsibility of the radiation oncology physicist to assure that the recommendations of this task group are implemented by either diagnostic radiology or the radiation oncology physicist or a designate.