Lynne M Hurwitz

Duke University Medical Center, Durham, North Carolina, United States

Are you Lynne M Hurwitz?

Claim your profile

Publications (50)112.87 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of the study was to assess the image quality of multi-detector-row computed tomography (CT) angiographic images of the thoracic aorta reconstructed with filtered back projection (FBP), adaptive statistical iterative reconstruction, and model-based iterative reconstruction (MBIR) at different kVp and mA settings. A healthy 56.1-kg Yorkshire pig underwent sequential arterial CT angiograms on a 64-slice multi-detector-row CT scanner (Discovery CT 750HD; GE Healthcare Inc, Milwaukee, Wis) at progressively lower kVp and mA settings. At 120-, 100-, and 80-kVp levels, the pig was scanned at 700, 400, 200, 100, and 50 mA at, for a total of 15 scans. Each scan was reconstructed with FBP, adaptive statistical iterative reconstruction (50% blend), and MBIR. Relative noise and contrast-to-noise ratio (CNR) were calculated from regions of interest over the aorta and paraspinous muscle. In addition, selected axial and oblique sagittal images were scored subjectively for both aortic wall visibility and for overall image quality. Averaged across all kVp and mA variations, MBIR reduced relative noise by 73.9% and improved CNR by 227% compared with FBP; MBIR reduced relative noise by 63.4% and improved CNR by 107% compared with ASIR. The effects were more pronounced in lower tube output settings. At 100 kVp/700 mA, MBIR reduced noise by 57% compared with FBP and 40% compared with ASIR. At 100 kVp/50 mA, MBIR reduced noise by 82% compared with FBP and 75% compared with ASIR. Subjective improvements in image quality were noted only in higher noise settings. Model-based iterative reconstruction reduces relative noise and improves CNR compared with ASIR and FBP at all kVp and mA settings, which were significantly greater at lower mA settings.
    Journal of computer assisted tomography. 12/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Purpose To determine the effectiveness of radiologists' search, recognition, and acceptance of lung nodules on computed tomographic (CT) images by using eye tracking. Materials and Methods This study was performed with a protocol approved by the institutional review board. All study subjects provided informed consent, and all private health information was protected in accordance with HIPAA. A remote eye tracker was used to record time-varying gaze paths while 13 radiologists interpreted 40 lung CT images with an average of 3.9 synthetic nodules (5-mm diameter) embedded randomly in the lung parenchyma. The radiologists' gaze volumes ( GV gaze volume s) were defined as the portion of the lung parenchyma within 50 pixels (approximately 3 cm) of all gaze points. The fraction of the total lung volume encompassed within the GV gaze volume s, the fraction of lung nodules encompassed within each GV gaze volume (search effectiveness), the fraction of lung nodules within the GV gaze volume detected by the reader (recognition-acceptance effectiveness), and overall sensitivity of lung nodule detection were measured. Results Detected nodules were within 50 pixels of the nearest gaze point for 990 of 992 correct detections. On average, radiologists searched 26.7% of the lung parenchyma in 3 minutes and 16 seconds and encompassed between 86 and 143 of 157 nodules within their GV gaze volume s. Once encompassed within their GV gaze volume , the average sensitivity of nodule recognition and acceptance ranged from 47 of 100 nodules to 103 of 124 nodules (sensitivity, 0.47-0.82). Overall sensitivity ranged from 47 to 114 of 157 nodules (sensitivity, 0.30-0.73) and showed moderate correlation (r = 0.62, P = .02) with the fraction of lung volume searched. Conclusion Relationships between reader search, recognition and acceptance, and overall lung nodule detection rate can be studied with eye tracking. Radiologists appear to actively search less than half of the lung parenchyma, with substantial interreader variation in volume searched, fraction of nodules included within the search volume, sensitivity for nodules within the search volume, and overall detection rate. © RSNA, 2014 Online supplemental material is available for this article.
    Radiology 10/2014; · 6.34 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Preprocedural multidetector computed tomography (MDCT) may identify patients at risk for mechanical complications during lead extraction.
    Pacing and Clinical Electrophysiology 09/2014; · 1.75 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This retrospective study assessed whether dual-source high-pitch computed tomographic angiography (CTA) offered advantages over single-source standard-pitch techniques in the evaluation of the ascending aorta. Twenty patients who received both thoracic dual-source high-pitch and single-source standard-pitch CTAs within 1 year were assessed. Dual-source CTAs were performed; standard-pitch imaging used dose-modulated 120 kVp/150 mAs and 0.8 pitch compared with high-pitch protocols employing dose-modulated 120 kVp/250 mAs and 2.4 target pitch. Radiation dose was documented. Contrast-to-noise ratios (CNRs) at sinuses of the Valsalva (CNRValsalva) and ascending aorta (CNRAorta) were calculated. Dose/CNR for each technique was compared with paired t-tests. Motion at aortic valve, aortic root and ascending aorta were assessed with four-point scales and Mann-Whitney U tests; longitudinal extension of motion was compared with paired t-tests. Significantly lower motion scores for high-pitch, compared with standard-pitch acquisitions for aortic annulus, 0 vs. 2, aortic root, 0 vs. 3, and ascending aorta, 0 vs. 2, were achieved. Significantly reduced longitudinal extension of motion at aortic root, 4.9 mm vs 15.7 mm, and ascending aorta, 4.9 mm vs 21.6 mm, was observed. Contrast was not impacted: CNRValsalva, 45.6 vs 46.3, and CNRAorta, 45.3 vs 47.1. CTDIvol was significantly decreased for high-pitch acquisitions, 13.9 mGy vs 15.8 mGy. Dual-source high-pitch CTAs significantly decreased motion artefact without negatively impacting vascular contrast and radiation dose. • Dual-source high-pitch CTA significantly decreased motion artefact of the ascending aorta. • Dual-source high-pitch CTA did not negatively impact on vascular contrast. • Dual-source high-pitch CTA significantly decreased radiation dose compared with single-source standard-pitch acquisitions.
    European Radiology 02/2014; · 4.34 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE To investigate within the same patient the relationship between radiation dose and noise to patient body size in thoracoabdominal aortic CT angiography (CTA), using non-ECG-assisted high-pitch dual-source and standard-pitch acquisitions. METHOD AND MATERIALS This HIPAA-compliant retrospective study received IRB approval with a waiver of informed consent. Fifty consecutive patients (29 men, 21 women; mean age, 68 years ± 13 standard deviation [SD]; mean body mass index [BMI], 29.9 kg/m2 ± 7) underwent clinically-indicated CTA of the thoracoabdominal aorta using a second-generation dual-source scanner. Standard-pitch (pitch=0.8) unenhanced acquisition was followed by a non-ECG-assisted high-pitch (pitch=1.6-3.0;mean,2.8±0.2) dual-source contrast-enhanced acquisition. Radiation dose was calculated for each patient as CTDIvol and size-specific dose estimate (SSDE). Noise was measured as voxel SD from a region-of-interest in the subcutaneous fat of the thoracic and abdominal wall. The relationship between CTDIvol, SSDE, and noise as a function of BMI was assessed using linear regression models. RESULTS Mean CTDIvol and SSDE (±SD) were significantly lower with high-pitch compared to standard-pitch acquisition (8.2±1.0 vs 10.6±3.0 mGy and 9.0±1.5 vs 11.2±2.1 mGy, respectively [P<.0001]). For each patient, noise was higher with high-pitch compared to standard-pitch (mean noise [±SD], 11.3±2.1 vs 8.7±1.6 in the thorax and 12.6±2.9 vs 9.6±2.5 in the abdomen [P<.0001]). Linear regression analysis showed a significantly positive correlation between CTDIvol and BMI for both standard-pitch (R2=0.47) and high-pitch (R2=0.02). While SSDE was independent of BMI with a standard-pitch, the high-pitch acquisition showed significantly negative correlation between SSDE and BMI (R2=0.33), likely reflecting limitation of the scanner output. Noise showed a significantly positive correlation with BMI for both acquisitions, though the higher slope at high-pitch suggests higher dependency on patient body size. CONCLUSION Non-ECG-assisted high-pitch dual-source acquisition for aortic CTA yields lower radiation dose, at the cost of higher noise in large patients. CLINICAL RELEVANCE/APPLICATION Radiologists should be aware of the higher noise using high-pitch settings in large patients, likely reflecting limitation of the scanner output.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: Although frailty has recently been examined in various populations as a predictor of morbidity and mortality, its effect on thoracic aortic surgery outcomes has not been studied. The objective of the present study was to evaluate the role of frailty in predicting postoperative morbidity and mortality in patients undergoing proximal aortic replacement surgery. A retrospective analysis of a prospectively maintained database was performed for all patients undergoing elective and nonelective proximal aortic operations (root, ascending aorta, and/or arch) at a single-referral institution from June 2005 to December 2012. A total of 581 patients underwent proximal aortic surgery, of whom 574 (98.8%) were included in the present analysis; 7 were excluded because of incomplete data. Frailty was evaluated using an index consisting of age >70 years, body mass index <18.5 kg/m(2), anemia, history of stroke, hypoalbuminemia, and total psoas volume in the bottom quartile of the population. One point was given for each criterion met to determine a frailty score of 0 to 6. Frailty was defined as a score of ≥2. Risk models for length of stay >14 days, discharge to other than home, 30-day composite major morbidity, 30-day composite major morbidity/mortality, and 30-day and 1-year mortality were calculated using multivariate regression modeling. Of the 574 patients, 148 (25.7%) were defined as frail (frailty score ≥2). The unadjusted 30-day/in-hospital and long-term outcomes were significantly worse for the frail versus nonfrail patients in all but 1 of the outcomes analyzed; no difference was found in the 30-day readmission rates between the 2 groups. In the multivariate model, a frailty score of ≥2 was associated with discharge to other than home and 30-day and 1-year mortality. Frailty, as defined using a 6-component frailty index, can serve as an independent predictor of discharge disposition and early and late mortality risk in patients undergoing proximal aortic surgery. These frailty markers, all of which are easily assessed preoperatively, could provide valuable information for patient counseling and risk stratification before proximal aortic replacement.
    The Journal of thoracic and cardiovascular surgery 10/2013; · 3.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Aortic stenosis affects many people worldwide with a significant impact on morbidity and mortality with uncorrected, symptomatic aortic valve stenosis carrying mortality of 50 % at one year. Degenerative calcific pathology, the most common cause of aortic stenosis, increases in prevalence with age; estimated prevalence of 5 % in individuals over 75 years of age. Despite the malignant prognosis without valve replacement, many patients are not offered surgery due to advanced age and co-existing medical conditions; reported to be a third of symptomatic patients. In the last several years, transcatheter aortic valve replacement has emerged as an alternative treatment in patients with high or prohibitive open surgical risk. The PARTNER cohort B data, employing the Sapien valve, demonstrated a 20 % absolute mortality benefit at one year compared with medical therapy. In this review, we provide an update of this technology and discuss patient selection, procedural planning, complications, and look toward the future of transcatheter heart valves in the treatment of aortic stenosis.
    Current Cardiology Reports 06/2013; 15(6):367.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Advances in computed tomography (CT) scanners and electrocardiographic gating techniques have resulted in superior image quality of the ascending aorta and increased the use of CT angiography for evaluating the postoperative ascending aorta. Several abnormalities of the ascending aorta and aortic arch often require surgery, and various open techniques may be used to reconstruct the aorta, such as the Wheat procedure, in which both an ascending aortic graft and an aortic valve prosthesis are implanted; the Cabrol and modified Bentall procedures, in which a composite synthetic ascending aorta and aortic valve graft are placed; the Ross procedure, in which the aortic valve and aortic root are replaced with the patient's native pulmonary valve and proximal pulmonary artery; valve-sparing procedures such as the T. David-V technique, which leaves the native aortic valve intact; and more extensive arch repair procedures such as the elephant trunk and arch-first techniques, in which interposition or inclusion grafts are implanted, with or without replacement of the aortic valve. Normal postoperative imaging findings, such as hyperattenuating felt pledgets, prosthetic conduits, and reanastomosis sites, may mimic pathologic processes. Postoperative complications seen at CT angiography that require further intervention include pseudoaneurysms, anastomotic stenoses, dissections, and aneurysms. Radiologists must be familiar with these procedures and their imaging features to identify normal postoperative appearances and complications.
    Radiographics 01/2013; 33(1):73-85. · 2.79 Impact Factor
  • Conference Paper: Cardiac PET
    [Show abstract] [Hide abstract]
    ABSTRACT: LEARNING OBJECTIVES 1) To understand the complimentary role of anatomic and functional imaging in the assessment of CAD and its implications for patient management. ABSTRACT Detection of significant luminal narrowing has been the hallmark to characterize presence and extent of coronary artery disease (CAD) for decades. However, it is now known that characterizations of systemic atherosclerosis burden and inflammation as well as local quality of plaque composition and morphology allow for better characterization of CAD and thus may improve prediction of adverse cardiovascular events. Plaques characterized histologically as thin fibrous cap atheromas with a thin fibrous cap, underlying lipid rich necrotic core, and inflammatory activity have been recognized as vulnerable or high risk plaques. Both positron emission tomography (PET) and cardiac computed tomography (CT) are novel non-invasive technologies that provide morphological (CT) and metabolic (PET) information on atherosclerotic plaque. PET allows for the quantification of 18F-fluorodeoxyglucose (FDG) uptake within the arterial wall, which provides a measure of macrophages activity within atheromatous plaque. Coronary CTA allows for the visualisation of plaque morphology and composition. Thus, integrated imaging by PET/CT permits for co-registration of FGD activity with presence and morphology of plaque and may lead to improved charcaterization of vulnerable plaque and/or vulnerable patients. This course details the methodology and principles of cardiac FDG-PET and coronary CTA and provides an overview on the research with an emphasis on the detection and characterization of vulnerable plaque.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE To identify the optimal monochromatic energy level for visualization of the hepatic arteries on dual energy CT angiographic (CTA) volume rendered (VR) images. METHOD AND MATERIALS This is an IRB-approved study of 29 patients who underwent arterial phase CT of the upper abdomen with dual kVp switching (80 kVp/140 kVp) on a Discovery CT 750HD scanner (GE Healthcare). Datasets were processed with Gemstone Spectral Imaging (GSI) software to derive calculated monochromatic image sets at 40, 50, 60, 70, and 80 keV, from which noise (SD) and contrast-to-noise ratios (CNR) were determined. Standardized volume rendered images from monochromatic 40, 60 and 80 keV, datasets were scored subjectively on a 7 point scale for visualization of the left and right hepatic arteries (1=not visible; 2=visible, but contour difficult to trace; 3=visible with moderate discontinuity; 4=mild discontinuity; 5=continuous with moderate wall irregularity; 6=mild wall irregularity; 7=smooth vessel walls), and a 5 point scale for for overall image quality (1=poor, nondiagnostic image quality; 2=marginal image quality with limited diagnostic value; 3=good image quality with mild noise/artifact; 4=very good image quality typical of ideal standard clinical practice; 5=superior image quality). RESULTS Compared to 80 kEv, average aortic enhancement at 40 keV increased by 346%. Concurrently, noise increased by 170%, and CNR improved by 89%. Compared to 80 kEv, subjective scores for visibility of the left and right hepatic arteries at 40 kEv improved by 15% and 8%, respectively. Overall VR image quality scores improved by 19% from a mean of 3.3 to 3.9. CONCLUSION As the keV is lowered, the attenuation and CNR of contrast-enhanced vessels increase substantially. Less dramatic, but still significant, improvements in subjective hepatic arterial visibility and overall image quality with volume rendering were also seen. These data show that reconstructing monochromatic images for volume rendering appears beneficial, and that using the lowest keV of 40 is optimal. CLINICAL RELEVANCE/APPLICATION Low keV monochromatic image sets reconstructed from dual energy hepatic CTAs improve contrast-to-noise ratios, subjective VR vessel visibility, and overall subjective VR image quality.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE To evaluate the quality of aortic CT angiographic images reconstructed with filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and model-based iterative reconstruction (MBIR) scanned at progressively lower radiation doses. METHOD AND MATERIALS A healthy 56.1 kg Yorkshire pig underwent successive thoracic arterial CT angiography on a Discovery CT 750HD MDCT scanner (GE Healthcare) at progressively lower radiation doses while under general anesthesia. The pig was scanned at 700, 400, 200, 100, and 50 mA at 120, 100, and 80 kVp, for a total of 15 scans. Each scan was reconstructed with FBP, ASIR (50% blend) and MBIR. Noise (SD) and contrast-to-noise ratios (CNR) were calculated from ROIs over the aorta and paraspinous muscle. In addition, selected axial and oblique sagittal images were scored subjectively from 1 to 5 for both aortic wall visibility (1-aortic wall margin difficult or impossible to asses; 5-superior aortic wall visualization) and for overall image quality (1-poor quality, nondiagnostic; 4-good image quality typical of expected clinical practice; 5-superior image quality with no significant noise or artifact). RESULTS Averaged across all doses, MBIR reduced noise by 73% and improved CNR by 227% compared to FBP; MBIR reduced noise by 69% and improved CNR by 107% compared to ASIR. The effect was more pronounced in higher noise settings. At 120 kVp/400 mA, MBIR reduced noise by 50% compared to FBP and 30% compared to ASIR. At 80 kVp/50 mA MBIR reduced noise by 81% compared to FBP and 74% compared to ASIR. Subjective improvements in image quality were only noted in higher noise settings. At 120 kVp/400 mA, readers scored FBP, ASIR, and MBIR images equally. At 120 kVp/50 mA, readers scored FBP and ASIR images as nondiagnostic, while MBIR images were considered of moderate quality but remained diagnostic. At very low doses (80 KvP/50 mA), FBP, ASIR, and MBIR were nondiagnostic. CONCLUSION MBIR reduced image noise compared to ASIR and FBP across all dose levels. Reductions in noise were significantly greater in lower dose settings. While quantitative data suggest that large dose reductions may be possible, qualitative data is more tempered, particularly at very low doses. CLINICAL RELEVANCE/APPLICATION Subjective data suggest that, while still beneficial, the dramatic dose reductions for MBIR implied by quantitative data may be tempered by the waxy appearance of MBIR images at low doses.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
  • Jared Dean Christensen, Lynne Michelle Hurwitz, Daniel Tobias Boll
    [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE CTA evaluation of the aorta can be problematic due to cardiac motion artifact during conventional non-ECG gated helical single source standard pitch (SS SP) CTA acquisition. Dual source non-ECG gated high pitch (DS HP) CTA is an alternative technique that may reduce motion artifact without increasing radiation dose or compromising diagnostic image quality. This study compares dose and image quality of DS HP vs SS SP CTA of the thoracic aorta. METHOD AND MATERIALS In this IRB-approved study we evaluated 20 patients who had both a DS HP and comparison SS SP CTA of the thoracic aorta. HP exams were performed on a dual source 64 MDCT scanner (Definition, Siemens Medical Systems) with the following settings: 120 kVp, qual ref mAs 250, automatic pitch adjustment (1.85-2.4), rotation time 0.33 s. SS SP CTAs were acquired on a 64 MDCT with identical parameters except for pitch (1.375) and rotation time, 0.5-0.8 s. Weight-based contrast dosing of IsoVue 370 was used for all scans at the same injection rate. CTDIvol was recorded for all exams. Quantitative image quality was assessed by calculating contrast to noise (CNR) at the sinuses of Valsalva (CNRv) and ascending aorta (CNRa). Qualitative assessment was performed by randomized, blinded dual reader consensus for wall motion artifact at the aortic valve annulus, sinuses of Valsalva and ascending aorta on a 4-point scale (0=no motion, 3=severe). Statistical analysis with paired t-test evaluated corresponding qualitative and quantitative parameters. RESULTS Mean CTDI for DS HP vs. SS SP CTA was lower (13.9±2.4 vs. 15.9±4.0, respectively, p=0.08). CNR analysis showed a marginal increase in mean CNRv (46.3 vs. 45.6, p=0.79), and mean CNRa (47.1 vs. 45.3, p=0.52), for the HP protocol. There were, however, significant improvements in image quality in relation to motion for DS HP vs. SS SP technique (p<0.05), with mean scores assessing wall motion artifacts at the level of the annulus (0.4 vs. 1.8), sinuses of Valsalva (0.7 vs. 2.0), and ascending aorta (0.6 vs. 1.8). CONCLUSION DS HP CTA significantly decreases motion-related artifact of the thoracic aortic without decreasing CNR compared to SS SP CTA at comparable radiation dose levels. CLINICAL RELEVANCE/APPLICATION DS HP CTA may result in decreased motion artifact of the thoracic aorta thereby potentially improving diagnostic accuracy without negatively impacting CNR or patient radiation dose.
    Single Tube Standard Pitch Computed Tomographic Angiography (CTA) of the Thoracic Aorta: Quantitative and Qualitative Assessment of Image Quality and Radiation Dose. Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to investigate gray-scale inversion in nodule detection on chest radiography. Simulated nodules were superimposed randomly onto normal chest radiographs. Six radiologists interpreted 144 chest radiographs during three reading sessions: traditional presentation, inverted gray-scale, and a choice session allowing use of traditional and gray-scale inverted views. Sensitivity and specificity were used to assess accuracy based on presence or absence of a nodule. Gray-scale inversion and choice display sessions resulted in significantly higher nodule detection specificity and decreased sensitivity compared to traditional display. Gray-scale inversion may decrease false-positive nodule findings during chest X-ray interpretation.
    Clinical imaging 09/2012; 36(5):515-21. · 0.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to assess the radiation dose distribution and image quality for organ-based dose modulation during adult thoracic MDCT. Organ doses were measured using an anthropomorphic adult female phantom containing 30 metal oxide semiconductor field-effect transistor detectors on a dual-source MDCT scanner with two protocols: standard tube current modulation thoracic CT and organ-based dose modulation using a 120° radial arc. Radiochromic film measured the relative axial dose. Noise was measured to evaluate image quality. Breast tissue location across the anterior aspect of the thorax was retrospectively assessed in 100 consecutive thoracic MDCT examinations. There was a 17-47% decrease (p = < 0.05) in anterior thoracic organ dose and a maximum 52% increase (p = < 0.05) in posterior thoracic organ dose using organ-based dose modulation compared with tube current modulation. Effective dose (SD) for tube current modulation and organ-based dose modulation were 5.25 ± 0.36 mSv and 4.42 ± 0.30 mSv, respectively. Radiochromic film analysis showed a 30% relative midline anterior-posterior gradient. There was no statistically significant difference in image noise. Adult female breast tissue was located within an average anterior angle of 155° (123-187°). Organ-based dose modulation CT using an anterior 120° arc can reduce the organ dose in the anterior aspect of the thorax with a compensatory organ dose increase posteriorly without impairment of image quality. Laterally located breast tissue will have higher organ doses than medially located breast tissue when using organ-based dose modulation. The benefit of this dose reduction must be clinically determined on the basis of the relationship of the irradiated organs to the location of the prescribed radial arc used in organ-based dose modulation.
    American Journal of Roentgenology 07/2012; 199(1):W65-73. · 2.90 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to assess the difference in absorbed organ dose and image quality for MDCT neck protocols using automatic tube current modulation alone compared with organ-based dose modulation and in-plane thyroid bismuth shielding. An anthropomorphic female phantom with metal oxide semiconductor field effect transistor (MOSFET) detectors was scanned on a 64-MDCT scanner. The protocols included a reference neck CT protocol using automatic tube current modulation and three modified protocols: organ-based dose modulation, automatic tube current modulation with thyroid shield, and organ-based dose modulation with thyroid shield. Image noise was evaluated quantitatively with the SD of the attenuation value, and subjectively by two neuroradiologists. Organ-based dose modulation, automatic tube current modulation with thyroid shield, and organ-based dose modulation with thyroid shield protocols reduced the thyroid dose by 28%, 33%, and 45%, respectively, compared with the use of automatic tube current modulation alone (p ≤ 0.005). Organ-based dose modulation also reduced the radiation dose to the ocular lens (33-47%) compared with the use of automatic tube current modulation (p ≤ 0.04). There was no significant difference in measured noise and subjective image quality between the protocols. Both organ-based dose modulation and thyroid shields significantly reduce the thyroid organ dose without degradation of subjective image quality compared with automatic tube current modulation. Organ-based dose modulation has the additional benefit of dose reduction to the ocular lens.
    American Journal of Roentgenology 05/2012; 198(5):1132-8. · 2.90 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to assess the effect of peak kilovoltage on radiation dose and image quality in adult neck MDCT. An anthropomorphic phantom with metal oxide semiconductor field effect transistor detectors was imaged with a 64-MDCT scanner. The reference CT protocol called for 120 kVp, and images obtained with that protocol were compared with CT images obtained with protocols entailing 80, 100, and 140 kVp. All imaging was performed with automatic tube current modulation. Organ dose and effective dose were determined for each protocol and compared with those obtained with the 120-kVp protocol. Image noise was evaluated objectively and subjectively for each protocol. The highest organ doses for all protocols were to the thyroid, ocular lens, skin, and mandible. The greatest reductions in organ dose were for the bone marrow of the cervical spine and mandible: 43% and 35% with the 100-kVp protocol and 63% and 53% with the 80-kVp protocol. Effective dose decreased as much as 9% with the 100-kVp protocol and 12% with the 80-kVp protocol. Use of the 140-kVp protocol was associated with an increase in organ dose as high as 64% for bone marrow in the cervical spine and a 19% increase in effective dose. Image noise increased with lower peak kilovoltage. The measured noise difference was greatest at 80 kVp, absolute increases were less than 2.5 HU. There was no difference in subjective image quality among protocols. Reducing the voltage from 120 to 80 kVp for neck CT can result in greater than 50% reduction in the absorbed organ dose to the bone marrow of the cervical spine and mandible without impairment in subjective image quality.
    American Journal of Roentgenology 03/2012; 198(3):621-7. · 2.90 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pulmonary embolism (PE) is a leading cause of maternal mortality in the developed world. Along with appropriate prophylaxis and therapy, prevention of death from PE in pregnancy requires a high index of clinical suspicion followed by a timely and accurate diagnostic approach. To provide guidance on this important health issue, a multidisciplinary panel of major medical stakeholders was convened to develop evidence-based guidelines for evaluation of suspected pulmonary embolism in pregnancy using the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) system. In formulation of the recommended diagnostic algorithm, the important outcomes were defined to be diagnostic accuracy and diagnostic yield; the panel placed a high value on minimizing cumulative radiation dose when determining the recommended sequence of tests. Overall, the quality of the underlying evidence for all recommendations was rated as very low or low, with some of the evidence considered for recommendations extrapolated from studies of the general population. Despite the low-quality evidence, strong recommendations were made for three specific scenarios: performance of chest radiography (CXR) as the first radiation-associated procedure; use of lung scintigraphy as the preferred test in the setting of a normal CXR; and performance of computed-tomographic pulmonary angiography (CTPA) rather than digital subtraction angiography (DSA) in a pregnant woman with a nondiagnostic ventilation-perfusion (V/Q) result. The recommendations presented in this guideline are based upon the currently available evidence; availability of new clinical research data and development and dissemination of new technologies will necessitate a revision and update.
    American Journal of Respiratory and Critical Care Medicine 11/2011; 184(10):1200-8. · 11.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to identify an optimal cross-sectional neck diameter that correlates with image quality and radiation exposure in MDCT examinations of the neck performed with automatic tube current modulation. Ninety-six adults underwent 64-MDCT of the neck with automatic tube current modulation at the same noise setting. On frontal and lateral scout images, maximal body diameters were measured in the transverse and anteroposterior planes at two levels: just below the mandible (upper neck) and at the lung apex (lower neck). Neck diameters were correlated with image quality on a subjective 4-point scale and with radiation exposure (volume CT dose index). As continuous variables, both anteroposterior and transverse diameters in the lower neck were associated with image quality (p ≤ 0.0012). Diameters in the upper neck were not associated with image quality. When diameters in the lower neck were categorized into small, medium, and large, image quality grades were higher for smaller patients (p < 0.001). Images of 81% of small patients (lower neck transverse diameter < 40 cm) had a high image quality grade, compared with images of 7-20% of large patients (diameter > 48 cm). Transverse diameter in the lower neck correlated best with radiation dose measured as volume CT dose index (r = 0.78). When transverse diameter in the lower neck was used to categorize patients' size, the mean volume CT dose index for small patients was 34.1 mSv and that for large patients was 63.5 mSv. Lower neck transverse diameter on the CT scout image best correlates with image quality and radiation exposure for neck MDCT examinations performed with automatic tube current modulation. Images of patients with a lower neck transverse diameter less than 40 cm are of higher quality than those of larger patients. Individualized dose reduction techniques therefore may be appropriate for smaller patients.
    American Journal of Roentgenology 11/2011; 197(5):W904-9. · 2.90 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this article is to compare the radiation dose of conventional fluoroscopy-guided lumbar epidural steroid injections (ESIs) and CT fluoroscopy (CTF)-guided lumbar ESI using both clinical data and anthropomorphic phantoms. We performed a retrospective review of dose parameters for 14 conventional fluoroscopy ESI procedures performed by one proceduralist and 42 CTF-guided ESIs performed by three proceduralists (14 each). By use of imaging techniques similar to those for our clinical cohorts, a commercially available anthropomorphic male phantom with metal oxide semiconductor field effect transistor detectors was scanned to obtain absorbed organ doses for conventional fluoroscopy-guided and CTF-guided ESIs. Effective dose (ED) was calculated from measured organ doses. The mean conventional fluoroscopy time for ESI was 37 seconds, and the mean procedural CTF time was 4.7 seconds. Calculated ED for conventional fluoroscopy was 0.85 mSv compared with 0.45 mSv for CTF. The greatest contribution to the radiation dose from CTF-guided ESI came from the planning lumbar spine CT scan, which had an ED of 2.90 mSv when z-axis ranged from L2 to S1. This resulted in a total ED for CTF-guided ESI (lumbar spine CT scan plus CTF) of 3.35 mSv. The ED for the CTF-guided ESI was almost half that of conventional fluoroscopy because of the shorter fluoroscopy time. However, the overall radiation dose for CTF-guided ESIs can be up to four times higher when a full diagnostic lumbar CT scan is performed as part of the procedure. Radiation dose reduction for CTF-guided ESI is best achieved by minimizing the dose from the preliminary planning lumbar spine CT scan.
    American Journal of Roentgenology 10/2011; 197(4):778-82. · 2.90 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this article is to assess whether iopamidol-370 provides superior vascular contrast of the coronaries and depiction of anatomic detail without affecting heart rate and beat-to-beat variability during coronary dual-source MDCT compared with iodixanol-320. In this prospective trial, coronary CT angiography was performed on 60 adult patients using either iopamidol-370 or iodixanol-320. Cohorts were matched by age, habitus, sex, and baseline heart rate, with cohort sizes determined by power analysis. All studies were performed on a dual-source MDCT scanner with retrospective ECG-gating utilizing automatic pitch adjustment. Data assessment focused on heart rate variability during contrast administration statistically evaluated as Student t test comparisons within and between cohorts, coronary contrast-to-noise ratio analysis of the main coronary arteries utilizing Student t test comparisons between cohorts, and coronary branch depiction and distribution analysis in dual-reader consensus decisions between cohorts. Thirty patients matched for age, habitus, sex, and heart rate were evaluated in each cohort. ECG analyses found a statistically significant (p = 0.013) decrease in heart rate during administration of iodixanol-320. Beat-to-beat variations, expressed as coefficient of variation, within and among cohorts were low (coefficient of variation, < 0.05). Contrast-to-noise ratio was significantly increased for iopamidol-370 versus iodixanol-320 (aortic root, p = 0.021; left main, p = 0.032; left anterior descending, p = 0.033; left circumflex, p = 0.039; and right, p = 0.009). Analysis of coronary branch visualization revealed improved depiction for iopamidol-370 compared with iodixanol-320. Iopamidol-370, with its higher iodine concentration, provided greater vascular contrast of the arterial coronary tree and improved depiction of anatomic detail without significantly impacting cardiac heart rate during coronary MDCT imaging, as compared with iodixanol-320.
    American Journal of Roentgenology 09/2011; 197(3):W445-51. · 2.90 Impact Factor