Academic Radiology

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2010-04-01

7.0 Tesla MRI: The “Field of Dreams”?

John B. Weigele — 2010-04-01

The tremendous scientific and clinical impact of magnetic resonance imaging (MRI) on medicine since its introduction in the early 1970s has been revolutionary. It is remarkable (in retrospect) that Lauterbur's historic concept—that nuclear magnetic resonance could be used to generate viable images by applying magnetic gradients to assign unique magnetic field strengths to each location (voxel) within an object that could in turn be used to localize each voxel to a unique point in space—was initially met by intense skepticism . In fact, Lauterbur was so dissuaded by the contemporary scientific consensus that MRI would never be clinically useful that he did not patent his invention . Particularly relevant to the issue of field strength, one prominent criticism was that the radiofrequency (RF) signal could never be strong enough to create a useful image . Nonetheless, the technical hurdles were surmounted, and MRI proved to be an unqualified success that has become one of the most important advances in medicine during the past century.

Gold Nanoparticle Contrast in a Phantom and Juvenile Swine: Models for Molecular Imaging of Human Organs using X-ray Computed Tomography

2010-04-01

Rationale and Objectives: The purpose of this study was to demonstrate the application of gold nanoparticles (AuNP) as a contrast agent for a clinical x-ray computed tomography (CT) system using a phantom and juvenile swine.Materials and Methods: A tissue-mimicking phantom with spherical inclusions containing known concentrations of Au was scanned. Swine were injected with gum Arabic stabilized Au nanoparticles (GA-AuNP), up to 85 mg kg−1 body weight. CT scans were performed before and after the injections. Changes in Hounsfield unit (HU) values between pre- and post- injection scans were evaluated and compared to postmortem determinations of Au uptake. Average uptake of GA-AuNP in the liver of the swine was 380 μg per gram of liver and 680 μg per gram of spleen.Results: Concentrations of Au in tissues increased the CT numbers in liver by approximately 22 HU per mg Au concentration at 80 kVp and 27 HU per mg Au concentration at 140 kVp. These data were consistent with HU changes observed for similar concentrations in the phantom.Conclusions: AuNP-based contrast agents may be useful in x-ray based CT. This study provides data for determining concentrations of AuNP in comparison to other contrast materials.

Wireless Surveillance for Transjugular Intrahepatic Portosystemic Shunts (TIPS) A Feasibility Study

Ken K. Hirasaki, John A. Watts, Paul V. Suhocki — 2010-04-01

Rationale and Objectives: Shunt surveillance is a critical component of follow-up for patients with cirrhosis with transjugular intrahepatic portosystemic shunts (TIPS). Transabdominal Doppler ultrasound analysis of the shunt has been used as a noninvasive means of assessing shunt function. Doppler ultrasound analysis of the shunt is less sensitive than direct transjugular portosystemic pressure gradient measurement for detecting shunt failure. A wireless, noninvasive means of measuring the portosystemic pressure gradient in the clinic may facilitate follow-up in this group of patients. The aim of this study was to determine if two implanted wireless pressure sensors could accurately transmit a portosystemic pressure gradient across a TIPS.Materials and Methods: Two wireless microelectromechanical system pressure sensors were placed in a swine model for measuring the portosystemic pressure gradient across a TIPS. Catheter-based pressure transducers were also placed and used as the gold standard. Pressures from both systems were measured concurrently.Results: Wireless microelectromechanical system portal and systemic pressure measurements were accurate within ±2 mm Hg (mean, 0.86 mm Hg) of the gold standard.Conclusion: The use of wireless sensors may facilitate the surveillance of shunt function in patients with portal hypertension who have undergone placement of TIPS.

Imaging of Patients with Hippocampal Sclerosis at 7 Tesla: Initial Results

2009-12-17

Rationale and Objectives: Focal epilepsies potentially can be cured by neurosurgery; other treatment options usually remain symptomatic. High-resolution magnetic resonance (MR) imaging is the central imaging strategy in the evaluation of focal epilepsy. The most common substrate of temporal epilepsies is hippocampal sclerosis (HS), which cannot always be sufficiently characterized with current MR field strengths. Therefore, the purpose of our study was to demonstrate the feasibility of high-resolution MR imaging at 7 Tesla in patients with focal epilepsy resulting from a HS and to improve image resolution at 7 Tesla in patients with HS.Materials and Methods: Six patients with known HS were investigated with T1-, T2-, T2∗-, and fluid-attenuated inversion recovery–weighted sequences at 7 Tesla with an eight-channel transmit-receive head coil. Total imaging time did not exceed 90 minutes per patient.Results: High-resolution imaging at 7 Tesla is feasible and reveals high resolution of intrahippocampal structures in vivo. HS was confirmed in all patients. The maximum non-interpolated in-plane resolution reached 0.2 × 0.2 mm2 in T2∗-weighted images. The increased susceptibility effects at 7 Tesla revealed identification of intrahippocampal structures in more detail than at 1.5 Tesla, but otherwise led to stronger artifacts. Imaging revealed regional differences in hippocampal atrophy between patients. The scan volume was limited because of specific absorption rate restrictions, scanning time was reasonable.Conclusions: High-resolution imaging at 7 Tesla is promising in presurgical epilepsy imaging. “New” contrasts may further improve detection of even very small intrahippocampal structural changes. Therefore, further investigations will be necessary to demonstrate the potential benefit for presurgical selection of patients with various lesion patterns in mesial temporal epilepsies resulting from a unilateral HS.

Whole Brain Perfused Blood Volume CT: Visualization of Infarcted Tissue Compared to Quantitative Perfusion CT

2010-01-11

Rationale and Objectives: This study determines the value of whole brain color-coded three-dimensional perfused blood volume (PBV) computed tomography (CT) for the visualization of the infarcted tissue in acute stroke patients.Materials and Methods: Nonenhanced CT (NECT), perfusion CT (PCT), and CT angiography (CTA) in 48 patients with acute ischemic stroke were performed. Whole brain PBV was calculated from NECT and CTA data sets using commercial software. PBV slices in identical orientation to the PCT slices were reconstructed and the area of visual perfusion abnormality on PBV maps was measured. The infarct core in the corresponding PCT slices (CBV <2.0 mL/100 g) was measured automatically with commercial software. The ischemic area on PBV and the infarct core on quantitative PCT were compared using the Pearsons-R correlation coefficient. Significance was considered for P < .05.Results: The quantitative PCT demonstrated a mean infarct core volume of 35.48 ± 32.17 cm3, whereas the volume of visual perfusion abnormality of the corresponding PBV slices was 37.16 ± 37.59 cm3. The perfusion abnormality in PBV was highly correlated with the infarct core of quantitative PCT for area per slice (r = 0.933, P < .01) as well as volume (r = 0.922, P < .01).Conclusions: PBV can serve as surrogate marker corresponding to the infarct core in acute stroke with whole brain coverage.

Effect of Breast Compression on Lesion Characteristic Visibility with Diffraction-Enhanced Imaging

2009-12-28

Rationale and Objectives: Conventional mammography can not distinguish between transmitted, scattered, or refracted x-rays, thus requiring breast compression to decrease tissue depth and separate overlapping structures. Diffraction-enhanced imaging (DEI) uses monochromatic x-rays and perfect crystal diffraction to generate images with contrast based on absorption, refraction, or scatter. Because DEI possesses inherently superior contrast mechanisms, the current study assesses the effect of breast compression on lesion characteristic visibility with DEI imaging of breast specimens.Materials and Methods: Eleven breast tissue specimens, containing a total of 21 regions of interest, were imaged by DEI uncompressed, half-compressed, or fully compressed. A fully compressed DEI image was displayed on a soft-copy mammography review workstation, next to a DEI image acquired with reduced compression, maintaining all other imaging parameters. Five breast imaging radiologists scored image quality metrics considering known lesion pathology, ranking their findings on a 7-point Likert scale.Results: When fully compressed DEI images were compared to those acquired with approximately a 25% difference in tissue thickness, there was no difference in scoring of lesion feature visibility. For fully compressed DEI images compared to those acquired with approximately a 50% difference in tissue thickness, across the five readers, there was a difference in scoring of lesion feature visibility. The scores for this difference in tissue thickness were significantly different at one rocking curve position and for benign lesion characterizations. These results should be verified in a larger study because when evaluating the radiologist scores overall, we detected a significant difference between the scores reported by the five radiologists.Conclusions: Reducing the need for breast compression might increase patient comfort during mammography. Our results suggest that DEI may allow a reduction in compression without substantially compromising clinical image quality.

Dynamic Breast MRI in the Course of Neoadjuvant Chemotherapy: Standardized Evaluation of Tumor Size and Enhancement Parameters in Correlation to Different Histopathologic Characteristics

2010-04-01

Rationale and Objectives: Basic exploratory data analysis to evaluate enhancement and tumor size (SIZE) in contrast-enhanced breast magnetic resonance imaging (CE-MRI) during chemotherapy. Correlation with histopathology (human epidermal growth factor receptor (HER2/neu) status and estrogen receptor (ER) score).Materials and Methods: Sixty-five women (mean age 47 ± 10 years) with locally advanced breast cancer (mean SIZE 25 mL) had CE-MRI (three-dimensional fast low angle shot (FLASH); repetition time = 9.1 ms, echo time = 4.8 ms, flip angle (FA) 25°, matrix size 256 × 256 pixels, field of view 350 mm, slice thickness 2 mm, number of slices = 32, one precontrast and five postcontrast series) before and after chemotherapy. Lesion segmentation and subsequent SIZE and enhancement analysis including maximum enhancement (MAX), area under the curve (AUC), time-to-peak (TTP), and maximum upslope (MUS) were performed. Correlation with histopathology (ER score and HER2/neu status).Results: SIZE reduced significantly during therapy (25 mL vs. 5 mL, P < .0001). AUC, MAX, MUS decreased (P < .0001), TTP increased (P .01) in any of the parameters with either ER score or HER2/neu status was found. HER2/neu score equal 2+pos. or 3+ showed significantly stronger changes in SIZE (P < .01), MAX (P < .01) and AUC (P < .05) compared to lower HER2/neu score (0 to 2+neg.).Conclusions: From routine MRI protocol and semiquantitative analysis of signal enhancement curves, information about size, and hemodynamic status of tumors under treatment may be extracted. Reduction in size and maximum enhancement were complementary parameters. In the course of therapy, size and enhancement may develop differently in clinically relevant histopathological subgroups.

Time to Diagnosis and Performance Levels during Repeat Interpretations of Digital Breast Tomosynthesis: Preliminary Observations

2009-12-28

Rationale and Objectives: To compare time to interpretation and diagnostic performance levels during repeat readings of full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT) in a retrospective study.Materials and Methods: Three experienced radiologists twice interpreted 125 selected examinations, 35 with verified cancers and 90 negative for cancer during a period of 22 months using FFDM alone followed by a combined FFDM + DBT mode. Changes in time to “review and rate” these examinations as well as in diagnostic performance levels where assessed. A fixed-effect analysis accounting for cross-correlation due to the review of the same examinations by the same readers was performed.Results: The total (combined) time to review and rate an examination increased on average by 33% between the first and second readings of the same examinations (P < .001). Radiologists reduced their time to review FFDM before making the DBT available for viewing. However, they spent more time reviewing the combined FFDM + DBT mode. The recall rates for examinations depicting cancer remained largely unchanged. Among the groups of examinations with concordant and discordant recall recommendations during the two readings only the group examinations that were “newly recalled” during repeat reading, took significantly longer (P < .01).Conclusion: DBT-based breast imaging may ultimately result in a substantial increase in performance; however, without efficiency improvements DBT may take longer to interpret. Addition of “false-positive recalls” was most strongly associated with increase in interpretation time while elimination of “false-positive recalls” did not require longer interpretation time.

The Role of Parallel Diffusion-Weighted Imaging and Apparent Diffusion Coefficient (ADC) Map Values for Evaluating Breast Lesions: Preliminary Results

Guangwei Jin, Ningyu An, Michael A. Jacobs, Kuncheng Li — 2010-04-01

Rationale and Objectives: To evaluate the feasibility of using diffusion-weighted imaging (DWI) with an array spatial sensitivity encoding technique (ASSET) and apparent diffusion coefficient (ADC) map values with different b values to distinguish benign and malignant breast lesions.Materials and Methods: Fifty-six female patients with 60 histologically proven breast lesions and 20 healthy volunteers underwent magnetic resonance imaging. A subset of normal volunteers (n = 7) and patients (n = 16) underwent both conventional DWI and ASSET-DWI, and the image quality between the two methods was compared. Finally, ASSET-DWI with b = 0, 600 s/mm2, and b = 0, 1000 s/mm2, were compared for their ability to distinguish benign and malignant breast lesions.Results: The ASSET-DWI method had less distortion, fewer artifacts, and a lower acquisition time than other methods. No significant difference (P > .05) was detected in ADC map values between ASSET-DWI and conventional DWI. For ASSET-DWI, the sensitivity of ADC values for malignant lesions with a threshold of less than 1.44 × 10−3 mm2/s (b = 600 s/mm2) and 1.18 × 10−3 mm2/s (b = 1000 s/mm2) was 80% and 77.5%, respectively. The specificity of both groups was 95%.Conclusion: ASSET-DWI evaluation of breast tissue offers decreased distortion, susceptibility to artifacts, and acquisition time relative to other methods. The use of ASSET-DWI is feasible with b values ranging from 600 to 1000 s/mm2 and provides increased specificity compared to other techniques. Thus, the ADC value of a breast lesion can be used to further characterize malignant lesions from benign ones.

Complication Rates and Outcomes of 536 Implanted Subcutaneous Chest Ports: Do Rates Differ Based on the Primary Operator's Level of Training?

Anne M. Silas, Kiley D. Perrich, Eric K. Hoffer, Nancy J. McNulty — 2010-01-11

Rationale and Objectives: Totally implanted subcutaneous central venous access devices (chest ports) are an attractive option for patients in need of intermittent, recurrent venous access. In our department, these are placed by different operator types including interventional radiology (IR) attending physicians, dedicated IR nurse practitioners (NP), and IR fellows/radiology residents. The purpose of our study is to assess the rate of complications of subcutaneous chest port placement among the different operator types.Materials and Methods: A retrospective review of all subcutaneous central venous access devices implanted in our department between October 8, 2004, and October 19, 2007, was undertaken. Total numbers of port days, overall complication rates for all operators, as well as complication rates for the various operator types were calculated and were compared using the chi square test.Results: A total of 558 patients had totally implanted subcutaneous central venous access devices placed during the period of study. Of these, 536 had documented follow-up and comprise the study population. A total of 89 were placed by attending physician alone, 133 by an NP, and 314 by an IR fellow or resident, with supervision by an attending physician. Mean duration of port usage was 341 days with 182,522 total port days. A total of 39 complications occurred (7.28%), including 27 infections (5%). There was no statistically significant difference in overall complication rates, including infection rates, among operator groups (P = .925).Conclusions: Our results confirm that well-trained physician extenders and trainees can safely perform chest port placement and that these providers, under appropriate supervision, can help provide improved access to chest port placement for patients and referring clinicians.

Sensitivity of Quantitative Metrics Derived from DCE MRI and a Pharmacokinetic Model to Image Quality and Acquisition Parameters

Yue Cao, Diana Li, Zhou Shen, Daniel Normolle — 2010-04-01

Rationale and Objectives: This study aims to investigate the sensitivity of quantitative metrics derived from dynamic contrast-enhanced (DCE) magnetic resonance imaging and a pharmacokinetic (PK) model to image quality and acquisition parameters.Materials and Methods: A computer-synthesized DCE model that consisted of a large range of values of Ktrans (transfer constant of a paramagnetic contrast agent from blood to tissue), vp (fractional plasma volume), and kep (back flux rate) was created to test the reliability of quantitative metrics derived from a standard PK model. Effects of the contrast-to-noise ratio (CNR), total acquisition time, and sampling interval on the stability and bias of the derived metrics were investigated.Results: The instability and bias of the estimated Ktrans, vp, and kep values increased with sampling interval and decreased with increasing CNR. Total acquisition times had limited influence on the estimations of Ktrans and vp values, but increasing the total acquisition time improved the stability of the estimation of kep values. However, for small kep values, the stability was still poor even with a total acquisition time of 8 minutes. Also, the stability and bias of the estimated values of Ktrans, vp, and kep are interrelated.Conclusions: Our synthesized DCE model represents perfectly reproduced data except for the presence of Gaussian-distributed random noise. Our analysis suggests minimum changes that may be considered potentially significant in longitudinal therapy assessment studies. Our data are complementary to experimental data from human subjects and phantoms, and provide guidance for the design of image acquisition strategies.

Computer-Assisted Quantitative Evaluation of Therapeutic Responses for Lymphoma Using Serial PET/CT Imaging

2010-01-11

Rationale and Objectives: Molecular imaging modalities such as positron emission tomography (PET)/computed tomography (CT) have emerged as an essential diagnostic tool for monitoring treatment response in lymphoma patients. However, quantitative assessment of treatment outcomes from serial scans is often difficult, laborious, and time consuming. Automatic quantization of longitudinal PET/CT scans provides more efficient and comprehensive quantitative evaluation of cancer therapeutic responses. This study develops and validates a Longitudinal Image Navigation and Analysis (LINA) system for this quantitative imaging application.Materials and Methods: LINA is designed to automatically construct longitudinal correspondence along serial images of individual patients for changes in tumor volume and metabolic activity via regions of interest (ROI) segmented from a given time point image and propagated into the space of all follow-up PET/CT images. We applied LINA retrospectively to nine lymphoma patients enrolled in an immunotherapy clinical trial conducted at the Center for Cell and Gene Therapy, Baylor College of Medicine. This methodology was compared to the readout by a diagnostic radiologist, who manually measured the ROI metabolic activity as defined by the maximal standardized uptake value (SUVmax).Results: Quantitative results showed that the measured SUVs obtained from automatic mapping are as accurate as semiautomatic segmentation and consistent with clinical examination findings. The average of relative squared differences of SUVmax between automatic and semiautomatic segmentation was found to be 0.02.Conclusions: These data support a role for LINA in facilitating quantitative analysis of serial PET/CT images to efficiently assess cancer treatment responses in a comprehensive and intuitive software platform.

Collapsibility of Lung Volume by Paired Inspiratory and Expiratory CT Scans: Correlations with Lung Function and Mean Lung Density

2010-01-11

Rationale and Objectives: To evaluate the relationship between measurements of lung volume (LV) on inspiratory/expiratory computed tomography (CT) scans, pulmonary function tests (PFT), and CT measurements of emphysema in individuals with chronic obstructive pulmonary disease.Materials and Methods: Forty-six smokers (20 females and 26 males; age range 46–81 years), enrolled in the Lung Tissue Research Consortium, underwent PFT and chest CT at full inspiration and expiration. Inspiratory and expiratory LV values were automatically measured by open-source software, and the expiratory/inspiratory (E/I) ratio of LV was calculated. Mean lung density (MLD) and low attenuation area percent (<−950 HU) were also measured. Correlations of LV measurements with lung function and other CT indices were evaluated by the Spearman rank correlation test.Results: LV E/I ratio significantly correlated with the following: the percentage of predicted value of forced expiratory volume in the first second (FEV1), the ratio of FEV1 to forced vital capacity (FVC), and the ratio of residual volume (RV) to total lung capacity (TLC) (FEV1%P, R = −0.56, P < .0001; FEV1/FVC, r = −0.59, P < .0001; RV/TLC, r = 0.57, P < .0001, respectively). A higher correlation coefficient was observed between expiratory LV and expiratory MLD (r = −0.73, P < .0001) than between inspiratory LV and inspiratory MLD (r = −0.46, P < .01). LV E/I ratio showed a very strong correlation to MLD E/I ratio (r = 0.95, P < .0001).Conclusions: LV E/I ratio can be considered to be equivalent to MLD E/I ratio and to reflect airflow limitation and air-trapping. Higher collapsibility of lung volume, observed by inspiratory/expiratory CT, indicates less severe conditions in chronic obstructive pulmonary disease.

Lung Function Measurement of Single Lungs by Lung Area Segmentation on 2D Dynamic MRI

2010-02-08

Rationale and Objectives: Most lung disease is inhomogeneously distributed but diagnosed by global spirometry. Regional lung function might allow for earlier diagnosis. Dynamic two-dimensional magnetic resonance imaging (2D-MRI) can depict lung motion with high temporal resolution. We evaluated whether measurement of lung area on dynamic 2D-MRI has sufficient agreement with spirometry to allow for lung function testing of single lungs.Material and Methods: Ten healthy volunteers were examined in a 1.5 T MRI scanner with a Flash 2D-sequence (8.5 images per second, sagittal and coronal orientation) with simultaneous spirometry. The lung area was segmented semiautomatically and the area changes were compared with spirometric volume changes.Results: Segmentation of one time series took 191 seconds on average. Volume-time and flow-volume curves from MRI data were almost congruent with spirometric curves. Pearson correlation of MRI area with spirometry was very high (mean correlation coefficients >0.97). Bland-Altman plots showed good agreement of lung area with spirometry (95% limits of agreement below 11% in each direction). Differences between lung area and spirometry were significantly smaller for sagittal measurement of the right lung than sagittal measurement of the left lung and coronal measurement. The relative forced expiratory volume in the first second differed less than 5% between MRI and spirometry in all but one volunteer.Conclusions: Measurement of lung area on 2D-MRI allows for functional measurement of single lungs with good agreement to spirometry. Postprocessing is fast enough for application in a clinical context and possibly provides increased sensitivity for lung functional measurement of inhomogeneously distributed lung disease.

Comparison of Standard-Dose and Reduced-Dose Expiratory MDCT Techniques for Assessment of Tracheomalacia in Children

2010-04-01

Rationale and Objectives: The aim of this study was to assess the effects of radiation dose reduction on the assessment of the tracheal lumen on expiratory multidetector computed tomographic (MDCT) images of pediatric patients referred for evaluation for tracheomalacia (TM).Materials and Methods: The hospital information system was used to retrospectively identify 20 standard-dose and 20 reduced-dose paired inspiratory and expiratory MDCT studies performed for the evaluation of suspected TM in pediatric patients (aged ≤ 18 years). The reduced-dose technique used a 50% reduction of the tube current for the expiratory portion of the study compared to the standard-dose technique. Two experienced pediatric radiologists, who were blinded to the tube current of the study, reported their levels of confidence for measuring the tracheal lumen using a four-point scale ranging from zero (no confidence) to three (highest level of confidence). The difference in confidence level between the two groups of studies was analyzed using the Mann-Whitney U test. The percentage of radiation dose reduction using the reduced-dose technique in comparison to the standard-dose technique was estimated using anthropomorphic thorax phantoms. The presence or absence of TM (≥50% expiratory reduction in tracheal cross-sectional luminal area) on MDCT imaging was compared to bronchoscopic results for the subset of 32 patients who underwent both procedures.Results: A high level of confidence was reported for measuring the tracheal lumen on MDCT imaging for both standard-dose (median, 3.0) and reduced-dose (median, 3.0) expiratory sequences (P = .80). The total radiation dose of the paired inspiratory-expiratory computed tomographic (CT) exam was decreased by 23% with the reduced-dose technique. TM was diagnosed by CT imaging in seven patients who underwent standard-dose and six patients who underwent reduced-dose paired inspiratory and expiratory MDCT studies. CT results for the presence or absence of TM were concordant with the results of bronchoscopy in all 32 patients who underwent both procedures.Conclusion: The radiation dose of paired inspiratory-expiratory CT imaging can be reduced by 23% while maintaining similar diagnostic confidence for assessment of the tracheal lumen compared to a standard-dose technique in pediatric patients. Thus, a reduced-dose technique is recommended for evaluating TM in children.

Comparing Film and Digital Radiographs for Reliability of Pneumoconiosis Classifications: A Modeling Approach

2010-04-01

Rationale and Objectives: The International Labour Office (ILO) system for classifying chest radiographic changes related to inhalation of pathogenic dusts is predicated on film-screen radiography. Digital radiography has replaced film in many centers. Digital images can be printed on film (“hard copy”) or can be viewed at a computer workstation (“soft copy”). The goal of the present investigation was to compare the inter-reader and intra-reader agreement of ILO classifications for pneumoconiosis across image formats.Materials and Methods: Traditional film radiographs, hard copy digital images, and soft copy digital images from 107 subjects were read by six B readers. A multiple reader version of the inter-reader kappa statistic was compared across image formats. Intra-reader kappa comparisons were carried out using an iterative least-squares approach (unadjusted analysis) as well as a two-stage regression model adjusting for readers and subject-level covariates.Results: There were few significant differences in the inter-reader and intra-reader agreement across formats. For parenchymal abnormalities, inter-reader and intra-reader kappa values ranged from 0.536 to 0.646, and 0.65 to 0.77, respectively. In the covariate-adjusted analysis film-screen radiography was generally associated with a numerically greater reliability (ie, higher kappa values) than the other image formats, although differences were rarely statistically significant.Conclusion: Film-screen radiographs, hard copy digital images, and soft copy digital images yielded similar reliability measures. These findings provide further support to the recommendation that soft copy digital images can be used for the recognition and classification of dust-related parenchymal abnormalities using the ILO system.

Comparison between Population Average and Experimentally Measured Arterial Input Function in Predicting Biopsy Results in Prostate Cancer

Ran Meng, Silvia D. Chang, Edward C. Jones, S. Larry Goldenberg, Piotr Kozlowski — 2010-01-14

Rationale and Objectives: To test whether individually measured arterial input function (AIF) provides more accurate prostate cancer diagnosis then population average AIF when dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) data are acquired with limited temporal resolution.Materials and Methods: Twenty-six patients with a high clinical suspicion for prostate caner and no prior treatment underwent DCE MRI examination at 3.0 T before biopsy. DCE MRI data were fitted to a pharmacokinetic model using three forms of AIF: an individually measured, a local population average, and a literature double exponential population average. Receiver operating characteristic (ROC) analysis was used to correlate MRI with the biopsy results. Goodness of fit (χ2) for the three AIFs was compared using nonparametric Mann-Whitney test.Results: Average volume transfer constant (Ktrans) values were significantly higher in tumor than in normal peripheral zone for all three AIFs. The individually measured and the local population average AIFs had the highest sensitivity (76%), whereas the double exponential AIF had the highest specificity (82%). The areas under the ROC curves were not significantly different between any of the AIFs (0.81, 0.76, and 0.81 for the individually measured, local population average, and double exponential AIFs, respectively). χ2 was not significantly different for the three AIFs; however, it was significantly higher in enhancing than in nonenhancing regions for all three AIFs.Conclusions: These results suggest that, when DCE MRI data are acquired with limited temporal resolution, experimentally measured individual AIF is not significantly better than population average AIF in predicting the biopsy results in prostate cancer.

Performance of Dual-Energy CT with Tin Filter Technology for the Discrimination of Renal Cysts and Enhancing Masses

2010-04-01

Rationale and Objectives: To assess the performance of dual-energy computed tomography (DECT) equipped with the new tin filter technology to classify phantom renal lesions as cysts or enhancing masses.Materials and Methods: Forty spherical lesion proxies ranging in diameter from 6 to 27 mm were filled with either distilled water (n = 10) representing cysts or titrated iodinated contrast solutions with a concentration of 0.45 (n = 10), 0.9 (n = 10), and 1.8 mg/mL (n = 10) representing enhancing masses. The lesion proxies were placed in a 12-cm diameter renal phantom containing minced beef and submerged in a 28-cm water bath. DECT was performed using the new dual-source CT system (Definition Flash, Siemens Healthcare, Forchheim, Germany) allowing for an improved energy separation by using a tin filter. DECT was performed at tube voltages of 140/80 kV without the tin filter (protocol A) and with tin filter (protocol B). The tube current time product was selected in each protocol to achieve a constant CTDI (computed tomography dose index) with both protocols of 19 mGy (full dose), 9.5 mGy (half dose), and 4.8 mGy (quarter dose). Two blinded readers classified each lesion as a cyst or enhancing mass by using iodine overlay (IO) images. One reader measured the CT numbers of each lesion at 120 kV, in the IO, linear blending (LB), and virtual noncontrast (VNC) images.Results: The CT numbers of the lesions at 120 kV were 0.1 ± 0.7 HU (0 mg iodine/mL), 9.1 ± 0.7 HU (0.45 mg/mL), 18.1 ± 1.4 HU (0.9 mg/mL), and 37.6 ± 1.6 HU (1.8 mg/mL). Mean diameter of the lesion proxies filled with water or different iodine concentrations was similar (P = 0.38). Image noise was not significantly different in protocols A and B at the corresponding dose levels. At full dose, protocol A had a sensitivity of 93% and a specificity of 60% for discriminating renal lesions. Sensitivity and specificity declined to 84% and 38% at quarter dose. In protocol B, sensitivity was 100% and specificity was 90% at full dose and 93% and 70% at quarter dose. All misclassifications occurred in cyst or low iodine concentration (0.45 mg/mL) lesion proxies. The differences between CT numbers at 120 kV and in the IO, VNC, and AW (average weighted) images were significantly lower in protocol B compared to protocol A (each P < .05).Conclusions: DECT using the tin filter results in an improved sensitivity and specificity for discriminating renal cysts from enhancing masses in a kidney phantom model and demonstrates higher dose efficiency as compared to former dual energy technology without tin filters.

The Use of a Simulation Center to Improve Resident Proficiency in Performing Ultrasound-Guided Procedures

2010-01-25

Rationale and Objectives: With advancements in technology and push for health care reform and reduced costs, minimally invasive procedures, such as those that are ultrasound-guided, have become an essential part of radiology, and are used in many divisions of radiology. By incorporating standardized training methodologies in a risk free environment through utilization of a simulation center with phantom training, we hope to improve proficiency and confidence in procedural performance.Materials and Methods: Twenty-nine radiology residents from four levels of training were enrolled in this prospective study. The residents were given written, video, and live interactive training on the basics of ultrasound-guided procedures in our simulation center on a phantom mannequin. All of the teaching materials were created by residents and staff radiologists at the institution.Results: Residents demonstrated statistically significant improvement (P < .05) between their pre- and posttest scores on both the written and practical examinations. They also showed a trend toward improved dexterity in the technical aspects of ultrasound-guided procedures (P = .07) after training. On the survey questionnaire, residents confirm improved knowledge level, technical ability, and confidence levels pertaining to ultrasound-guided procedures.Conclusions: The use of controlled simulation based training can be an invaluable tool to improve the knowledge level, dexterity, and confidence of residents performing ultrasound-guided procedures. Additionally, a simulation model allows standardization of education.

More Mammo Squabbles

Otha Linton — 2010-04-01

For all of my years involved with radiology, I have been a strong supporter for mammography, both for clinical uses and for screening. In my assignments with the American College of Radiology (ACR), I helped encourage mammographic technique by publicizing its development and publicizing the value of periodic mammographic screening. I was not part of the science. Rather, I was part of the promotion which gained the support of the ACR, the Public Health Service, the trainers of radiologists and technologists, the manufacturers of x-ray film and equipment, other medical societies, and the science and medical writers who told the public about the value of early detection of breast cancer.

Direct Diagnosis in Radiology: Head and Neck

Mark E. Mullins — 2010-04-01

This book is part of a series of small, portable, efficient review books in radiology. In this case, the subject matter is a subset of neuroradiology, head and neck imaging. There are some positives that I found in reviewing this book: it is indeed quite portable (it could easily be carried around in a large pocket or in a bag), well organized, to the point, and well illustrated (with quite legible pictures for a small softcover book), and it includes sections such as “What does the clinician want to know?” and “Tips and Pitfalls.” I was very interested in the potential for these latter two sections in particular but was not convinced that this potential was fully realized. Moreover, there were sections titled “Pathognomonic findings,” which I personally consider to be a misnomer, especially punctuated when the authors point out in some of these how nonspecific some of the findings may be.

Emergency Ultrasound, Second Edition

Paolo Lim — 2010-04-01

Nothing induces palpitations, nausea, and lightheadedness quite like receiving your first ultrasound request as a radiology resident on the first night of call. Maybe, prior to this, you have done plenty of exams on your own with image quality equal or superior to the most experienced ultrasound techs in your department. Maybe your attending radiologists have already sung your praises for your outstanding knowledge of sonographic anatomy, physics, and artifacts. If this is the case, Emergency Ultrasound is not for you. However, if you need a basic guide for learning what you need to know to be helpful in the emergency department, this book is excellent.

2010-04-01

Academic Radiology

Cover 1

7.0 Tesla MRI: The “Field of Dreams”?

Gold Nanoparticle Contrast in a Phantom and Juvenile Swine: Models for Molecular Imaging of Human Organs using X-ray Computed Tomography

Wireless Surveillance for Transjugular Intrahepatic Portosystemic Shunts (TIPS) A Feasibility Study

Imaging of Patients with Hippocampal Sclerosis at 7 Tesla: Initial Results

Whole Brain Perfused Blood Volume CT: Visualization of Infarcted Tissue Compared to Quantitative Perfusion CT

Effect of Breast Compression on Lesion Characteristic Visibility with Diffraction-Enhanced Imaging

Dynamic Breast MRI in the Course of Neoadjuvant Chemotherapy: Standardized Evaluation of Tumor Size and Enhancement Parameters in Correlation to Different Histopathologic Characteristics

Time to Diagnosis and Performance Levels during Repeat Interpretations of Digital Breast Tomosynthesis: Preliminary Observations

The Role of Parallel Diffusion-Weighted Imaging and Apparent Diffusion Coefficient (ADC) Map Values for Evaluating Breast Lesions: Preliminary Results

Complication Rates and Outcomes of 536 Implanted Subcutaneous Chest Ports: Do Rates Differ Based on the Primary Operator's Level of Training?

Sensitivity of Quantitative Metrics Derived from DCE MRI and a Pharmacokinetic Model to Image Quality and Acquisition Parameters

Computer-Assisted Quantitative Evaluation of Therapeutic Responses for Lymphoma Using Serial PET/CT Imaging

Collapsibility of Lung Volume by Paired Inspiratory and Expiratory CT Scans: Correlations with Lung Function and Mean Lung Density

Lung Function Measurement of Single Lungs by Lung Area Segmentation on 2D Dynamic MRI

Comparison of Standard-Dose and Reduced-Dose Expiratory MDCT Techniques for Assessment of Tracheomalacia in Children

Comparing Film and Digital Radiographs for Reliability of Pneumoconiosis Classifications: A Modeling Approach

Comparison between Population Average and Experimentally Measured Arterial Input Function in Predicting Biopsy Results in Prostate Cancer

Performance of Dual-Energy CT with Tin Filter Technology for the Discrimination of Renal Cysts and Enhancing Masses

The Use of a Simulation Center to Improve Resident Proficiency in Performing Ultrasound-Guided Procedures

More Mammo Squabbles

Direct Diagnosis in Radiology: Head and Neck

Emergency Ultrasound, Second Edition

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