Danielle M. Seaman

Diffuse Cystic Lung Disease at High-Resolution CT

OBJECTIVE This article will illustrate and describe the spectrum of diseases associated with air cysts at high-resolution CT (HRCT). CONCLUSION HRCT is an important modality in the evaluation of interstitial lung disease to include cystic lung disease. Although most commonly associated with lymphangioleiomyomatosis or Langerhans cell histiocytosis, cystic lung disease is increasingly being recognized as a feature of other entities. Awareness of the spectrum of HRCT findings associated with these diseases may help the trained observer narrow the differential diagnosis.

Retrospective assessment of the utility of an iron-based agent for contrast-enhanced magnetic resonance venography in patients with endstage renal diseases.

To compare abdominopelvic and lower extremity venous enhancement in contrast‐enhanced magnetic resonance venography (ceMRV), using iron‐based ferumoxytol and gadolinium‐based gadofosveset.

Comparison of ECG‐Gated Rectilinear vs. Real‐Time Radial K‐Space Sampling Schemes in Cine True‐FISP Cardiac MRI

PURPOSE To compare three k-space sampling schemes in cine True-FISP cardiac magnetic resonance imaging and to evaluate changes in calculated quantitative functional cardiac parameters as a function of underlying k-space sampling techniques. MATERIAL AND METHODS Using a 1.5 T MR imaging system (Magnetom Sonata, Siemens Medical Solutions, Erlangen, Germany), three k-space data-sampling schemes: rectilinear (2.96 ms/1.58 ms/70 degrees /12 s TR/TE/FA/AcquisitionTime), and two radial k-space acquisitions, with filtered back-projection (RADIAL) (2.45 ms/1.25 ms/ 50 degrees /3.3 s TR/TE/FA/AT), and steady-state projection imaging with dynamic echotrain readout (SPIDER) (3.39 ms/1.62 ms/55 degrees /1.8 s TR/TE/FA/AT) of a True-FISP sequence were applied in 10 healthy volunteers. Long- and short-axis breath-hold series were acquired and signal-to-noise ratios (SNR) for blood and myocardium were determined, as was contrast-to-noise ratios (CNR). Quantitative cardiac functional analysis included: determination of end-systolic/end-diastolic volumes, ejection fraction, and left ventricular mass. Functional analysis was performed by two independent readers three times for each volunteer and k-space sampling strategy. Statistical analysis evaluated the accuracy of the measurements obtained from each of the three sampling techniques and the intra- and interobserver reliability. RESULTS Intraobserver and interobserver reliability measures of functional data were homogeneous without statistically significant differences. Intraobserver correlation coefficients ranged from 0.94-0.99; interobserver correlation coefficients ranged from 0.97-0.99. Direct comparison of SPIDER- and RADIAL-sampled True-FISP sequences showed no statistically significant differences in measured functional parameters with interstudy correlation coefficients from 0.88-0.98. RADIAL and SPIDER images had better temporal resolution and were qualitatively judged to provide superior wall/blood border definition. Statistically significant differences were identified in each volumetric functional parameter when results from the rectilinear sampling acquisitions were compared with either radial or SPIDER sampling techniques. RADIAL and SPIDER results were consistently higher than volumetric measures obtained from the rectilinear data set. CONCLUSION Employing faster sampling schemes led to enhanced signal homogeneity while maintaining the necessary CNR for estimation of functional cardiac parameters. Enhanced signal homogeneity and maintained CNR will most likely improve the accuracy of the cardiac functional parameter determination.

Occupational and environmental lung disease.

Occupational and environmental lung disease remains a major cause of respiratory impairment worldwide. Despite regulations, increasing rates of coal workers pneumoconiosis and progressive massive fibrosis are being reported in the United States. Dust exposures are occurring in new industries, for instance, silica in hydraulic fracking. Nonoccupational environmental lung disease contributes to major respiratory disease, asthma, and COPD. Knowledge of the imaging patterns of occupational and environmental lung disease is critical in diagnosing patients with occult exposures and managing patients with suspected or known exposures.

Impact of phase of respiration on central venous catheter tip position

Purpose To determine the impact of the phase of respiration on CVC tip position using cross-sectional imaging. Methods We retrospectively analyzed the CT scans of 24 consecutive patients (eight men and 16 women, mean age 56.3 years, range 18-79) who underwent a CT scan protocol that includes both imaging of the thorax in inspiration and expiration. Only patients with a central venous catheter and absence of any substantial pulmonary pathology that might affect lung volumes were included. Measurements of the catheter tip location and central venous structures were obtained from inspiratory and expiratory phase images in each patient and compared using the paired t test. Results The length of the SVC and superior mediastinum were significantly longer during inspiration compared to expiration (9 mm and 7 mm respectively, P<0.001 for both). The distance between the superior and inferior cavo-atrial junction did not change significantly with respiration. The catheter tip location moved on average 9 mm (range 0-25 mm) cephalad during inspiration compared to expiration (P=0.001) in relation to the superior cavoatrial junction. The amount of catheter tip movement correlated significantly with the degree of diaphragmatic excursion with respiration (R=0.58). During inspiration, the cavo-atrial junction was on average 11 mm inferior to the right cardiomediastinal angle observed on radiography, but was nearly identical during expiration (R=0.78, P<0.001). Conclusions The central catheter tip position varied significantly with respiratory motion, with a mean excursion of 9 mm. The right cardiomediastinal border demonstrated a strong correlation with the actual location of the superior cavo-atrial junction in expiration, but not in inspiration.

Put Your Back into It: Pathologic Conditions of the Spine at Chest CT

It is common to encounter pathologic processes of the lower cervical, thoracic, or upper lumbar spine in the course of routine computed tomography (CT) of the chest. Although magnetic resonance (MR) is the imaging modality of choice for evaluating known spinal disease, evaluation of the spine is an integral part of interpreting a chest CT study. Spinal diseases often have a characteristic CT appearance that allows the radiologist to make the diagnosis or provide a structured differential diagnosis. Pathologic conditions of the spine that can be identified at chest CT are categorized into benign or incidental findings, congenital anomalies, traumatic injuries, infectious spondylitis, primary or secondary neoplastic involvement, and associations with systemic disease. CT also provides information about bone mineralization and lesion calcification that complements the superior soft-tissue imaging capability of MR. In addition, chest CT data may be reformatted to create volumetric or multiplanar images of the spine to facilitate management decisions about spinal stabilization in symptomatic patients.

High-Pitch Dual-Source MDCT for Imaging of the Thoracoabdominal Aorta: Relationships Among Radiation Dose, Noise, Pitch, and Body Size in a Phantom Experiment and Clinical Study

OBJECTIVE The purpose of this study was to investigate, both in a phantom experiment and a within-patient clinical study the relationships among radiation dose, image noise, pitch, and body size in MDCT angiography of the thoracoabdominal aorta, with the use of high-pitch dual-source and standard-pitch single-source acquisitions. MATERIALS AND METHODS A proprietary tapered phantom consisting of four ultrahigh-molecular-weight polyethylene cylinders was used to mimic the body size ranges (small, medium, large, and extra large) of patients in the United States. The phantom was imaged using both standard-pitch (0.8) and various high-pitch (range, 2.0-3.2 [in increments of 0.4]) settings. Standard-pitch and high-pitch acquisitions were also performed in 45 patients (27 men, 18 women; mean age, 67.6 years). RESULTS At standard pitch, the volume CT dose index (CTDIvol) increased with phantom size, in a logistic sigmoid relationship. At high-pitch settings, the CTDIvol increased gradually in relation to phantom size, up to a threshold (denoted by tCTDI[pitch] ≈ 48.3-7.5 pitch), which linearly decreased (R(2) = 0.99) with pitch (maximum CTDIvol output at pitch [maxCTDI(pitch)] ≈ 18.9-3.9 pitch). A linear decrease in the size-specific dose estimate (SSDE) was observed beyond phantom size thresholds (tSSDE[pitch] ≈ 47.6-8.6 pitch) linearly decreasing (R(2) = 0.98) with pitch (maximum SSDE output at pitch [maxSSDE(pitch)] ≈ 15.5-1.3 pitch). Image noise was statistically significantly lower at standard pitch than at high-pitch settings (p = 0.01). In patients, statistically significant differences were noted between standard and high-pitch settings in the mean CTDIvol(10.8 ± 2.6 and 8.3 ± 0.7 mGy, respectively), SSDE (11.3 ± 2.1 and 8.8 ± 1.5 mGy, respectively), and noise (9.7 ± 2.2 and 14 ± 4.2, respectively) (p < .0001, for all comparisons). CONCLUSION Lower radiation dose levels achieved with the use of a high-pitch technique reflect limitations in tube output occurring for medium to large body sizes, with an associated exponential increase in noise. The standard- and high-pitch techniques yield similar radiation dose levels for small body sizes.

Effects of model-based iterative reconstruction on image quality for low-dose computed tomographic angiography of the thoracic aorta in a Swine model.

Purpose 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. Methods 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. Results 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. Conclusions 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.

Prospective optical motion correction for 3D time-of-flight angiography.

Magnetic resonance angiograms are often nondiagnostic due to patient motion. In clinical practice, the available time to repeat motion‐corrupted scans is very limited—especially in patients who suffer from acute cerebrovascular conditions. Here, the feasibility of an optical motion correction system to prospectively correct patient motion for 3D time‐of‐flight magnetic resonance angiography was investigated. Experiments were performed on five subjects with and without parallel imaging (SENSE R = 2) on a 1.5 T unit. Two human readers assessed the data and were in good agreement (kappa: 0.77). The results from this study indicate that the optical motion correction system greatly reduces motion artifacts when motion was present and did not impair the image quality in the absence of motion. Statistical analysis showed no significant difference between the (vendor‐provided) SENSE and the nonaccelerated acquisitions. In conclusion, the optical motion correction system tested in this study has the potential to greatly improve 3D time‐of‐flight angiograms regardless of whether it is used with or without SENSE. Magn Reson Med, 2013.

Imaging of Complications of Thoracic and Cardiovascular Surgery

Iatrogenic complications of thoracic and cardiovascular surgery are relatively uncommon, but contribute to potentially significant patient morbidity and mortality. The incidence of iatrogenic disease reflects the complexity of surgical procedures, including lung resection, esophagectomy, coronary artery bypass grafting, thoracic aorta repair, and cardiac valve replacement. Some iatrogenic complications are minor and common to all procedures, whereas others can be potentially devastating and are associated with precise technical components of specific surgeries. Multimodality imaging plays an important role in the diagnosis and management of operative thoracic and cardiovascular iatrogenic disease.