Investigative Radiology (INVEST RADIOL )

Publisher: Association of University Radiologists


Investigative Radiology publishes original, peer-reviewed reports on clinical and laboratory investigations in diagnostic imaging, the diagnostic use of radioactive isotopes, computed tomography, positron emission tomography, magnetic resonance imaging, ultrasound, digital subtraction angiography, and related modalities. Emphasis is on early and timely publication. Primarily research-oriented, the journal also includes a wide variety of features of interest to clinical radiologists.

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Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to evaluate the effects on objective and subjective image quality of virtual monoenergetic reconstructions at various energy levels of dual-energy computed tomography (DECT) in patients with head and neck cancer.
    Investigative Radiology 05/2014;
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    Investigative Radiology 02/2014; IN PRESS.
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    ABSTRACT: The purpose of this study was to investigate whether quantification of pulmonary perfusion from dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) yields more reproducible results with data acquired during free breathing than with data from conventional breath-hold measurements. Ten healthy male volunteers underwent 2 imaging sessions at a clinical 1.5-T MRI system, separated by a week ± 1 day. Each of these sessions comprised 2 DCE MRI acquisitions: one performed during breath-hold and one during free, shallow breathing; both acquisitions were separated by at least 20 minutes. For all DCE MRI measurements, a standard dose of gadobutrol was used. Breath-hold measurements lasted 53 seconds; free-breathing acquisitions were performed in a total acquisition time of 146 seconds.Lung tissue was segmented automatically to minimize user influence, and pulmonary plasma flow (PPF) and volume (PPV) were quantified on a per-pixel basis with a 1-compartment model. Free-breathing measurements were analyzed twice, (a) including data from the entire acquisition duration and (b) after truncation to the duration of the breath-hold measurements. For further statistical analysis, median values of the resulting parameter maps were determined. To assess intraindividual reproducibility, intraclass correlation coefficients and coefficients of variation between the first and second measurements were calculated for breath-hold, truncated, and full free-breathing measurements, respectively. Differences in the coefficients of variation were assessed with a nonparametric 2-sided paired Wilcoxon signed rank test. All 40 measurements were completed successfully. Maps of PPF and PPV could be calculated from both measurement techniques; PPF and PPV in the breath-hold measurements were significantly lower (P < 0.001) than in truncated and full free-breathing measurements. Both evaluations of the free-breathing measurements yielded higher intraclass correlation coefficients and lower coefficients of variation between the first and second measurements than the breath-hold measurements. Besides offering substantially higher patient comfort, free-breathing DCE MRI acquisitions allow for pixelwise quantification of pulmonary perfusion and hence generation of parameter maps. Moreover, quantitative perfusion estimates derived from free-breathing DCE MRI measurements have better reproducibility than estimates from the conventionally used breath-hold measurements.
    Investigative Radiology 01/2014;
  • Investigative Radiology 09/2013;
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    ABSTRACT: The purpose of the study was to compare the performance of late iodine-enhancement (LIE) dual-energy computed tomography (DECT) linear blending and selective myocardial iodine mapping for the detection of chronic myocardial infarction (CMI) with late gadolinium-enhancement (LGE) 3-T magnetic resonance imaging. This study was approved by the institutional review board, and the patients gave informed consent. A total of 20 patients with a history of CMI underwent cardiac LIE-DECT and LGE-MRI. Images of the LIE-DECT were reconstructed as 100 kilovolt (peak) (kV[p]), 140 kV(p), and weighted-average (WA; linear blending) images from low- and high-kilovoltage peak data using 3 different weighting factors (0.8, 0.6, 0.3). Additional color-coded myocardial iodine distribution maps were calculated. The images were reviewed for the presence of late enhancement, transmural extent, signal characteristics, infarct volume, and subjective image quality. Segmental analysis of LIE-DECT data from 100 kV(p), WA of 0.8, and WA of 0.6 showed identical results for the identification of CMI (89% sensitivity, 98% specificity, 96% accuracy) and correctly identified all segments with transmural scarring detected through LGE-MRI. Weighted average of 0.6 received the best subjective image quality rating (15/20 votes) and average measured infarct size correlated best with LGE-MRI (5.7% difference). In comparison with LGE-MRI, iodine distribution maps were susceptible to false-positive and false-negative findings (52% sensitivity, 88% specificity, 81% accuracy), overestimating quantity of transmural scars by 78% while underestimating infarct volume by 55%. Late iodine enhancement cardiac dual-energy computed tomography correlates well with LGE-MRI for detecting CMI, whereas iodine distribution analysis provides inferior accuracy. Linear blending further improves image quality and enables more precise estimation of scar volume.
    Investigative Radiology 07/2013;
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    ABSTRACT: INTRODUCTION: Renal ischemia reperfusion injury leads to acute kidney injury (AKI) and is associated with tissue edema, inflammatory cell infiltration, and subsequent development of interstitial renal fibrosis and tubular atrophy. The purpose of this study was to investigate the value of the functional magnetic resonance imaging (MRI) techniques, T2 mapping, and diffusion-weighted imaging (DWI) in characterizing acute and chronic pathology after unilateral AKI in mice. MATERIALS AND METHODS: Moderate or severe AKIs were induced in C57Bl/6 mice through transient unilateral clamping of the renal pedicle for 35 minutes (moderate AKI) or 45 minutes (severe AKI), respectively. Magnetic resonance imaging was performed in 10 animals with moderate AKI and 7 animals with severe AKI before surgery and at 5 time points thereafter (days 1, 7, 14, 21, 28) using a 7-T magnet. Fat-saturated T2-weighted images, multiecho turbo spin echo, and diffusion-weighed sequences (7 b values) were acquired in matching coronal planes. Parameter maps of T2 relaxation time and apparent diffusion coefficient (ADC) were calculated, and mean values were determined for the renal cortex, the outer medulla, and the inner medulla. Inflammatory cell infiltration with monocytes/macrophages (F4/80), T-lymphocytes (CD4, CD8), and dendritic cells (CD11c) as well as the degree of interstitial fibrosis 4 weeks after AKI were determined through renal histology and immunohistochemistry. Statistical analysis comprised unpaired t tests for group comparisons and correlation analysis between MRI parameters and kidney volume loss. RESULTS: Increase of T2 relaxation time, indicating tissue edema, was most pronounced in the outer medulla and reached maximum values at d7 after AKI. At this time point, T2 values in the outer medulla were significantly increased to 53.8 ± 2.5 milliseconds after the severe AKI and to 46.3 ± 2.3 milliseconds after the moderate AKI when compared with the respective contralateral normal kidneys (40.9 ± 0.9 and 36.4 ± 1.2 milliseconds, respectively; P < 0.01). The T2 values reached baseline by d28. Medullary ADC was significantly reduced at all time points after AKI; restriction of diffusion was significantly more pronounced after the severe AKI than after the moderate AKI at d14 and d28. Changes of renal T2 and ADC values were associated with the severity of AKI as well as the degree of inflammatory cell infiltration and interstitial renal fibrosis 4 weeks after AKI. Furthermore, relative changes of both MRI parameters significantly correlated with kidney volume loss 4 weeks after AKI. DISCUSSION: Measuring T2 and ADC values through MRI is a noninvasive way to determine the presence and severity of acute and chronic renal changes after AKI in mice. Thus, the method should prove useful in animal and human clinical studies.
    Investigative Radiology 07/2013;
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    ABSTRACT: OBJECTIVES: The aim of this study was to evaluate free-breathing single-shot real-time cine imaging for functional cardiac imaging at 3 T with increased spatial resolution. Special emphasis of this study was placed on the influence of parallel imaging techniques. MATERIALS AND METHODS: Gradient echo phantom images were acquired with GRAPPA and modified SENSE reconstruction using both integrated and separate reference scans as well as TGRAPPA and TSENSE. In vivo measurements were performed for GRAPPA reconstruction with an integrated and a separate reference scan, as well as TGRAPPA using balanced steady-state free precession protocols. Three clinical protocols, rtLRInt (Tres = 51.3 milliseconds; voxel, 2.5 × 5.0 × 10 mm), rtMRSep (Tres = 48.8 milliseconds; voxel, 1.9 × 3.1 × 10 mm), and rtHRSep (Tres = 48.3 milliseconds; voxel, 1.6 × 2.6 × 10 mm), were investigated on 20 volunteers using GRAPPA reconstruction with internal as well as separate reference scans. End-diastolic volume, end-systolic volume, ejection fraction, peak ejection rate, peak filling rate, and myocardial mass were evaluated for the left ventricle and compared with an electrocardiogram-triggered segmented readout cine protocol used as standard of reference. All studies were performed at 3 T. RESULTS: Phantom and in vivo data demonstrate that the combination of GRAPPA reconstruction with a separate reference scan provides an optimal compromise of image quality as well as spatial and temporal resolution. Functional values (P values) for the standard of reference, rtLRInt, rtMRSep, and rtHRSep end-diastolic volume were 141 ± 24 mL, 138 ± 21 mL, 138 ± 19 mL, and 128 ± 33 mL, respectively (P = 0.7, 0.7, 0.4); end-systolic volume, 55 ± 15 mL, 61 ± 14 mL, 58 ± 12 mL, and 55 ± 20 mL, respectively (P = 0.23, 0.43, 0.62); ejection fraction, 61% ± 5%, 57% ± 5%, 58% ± 4%, and 56% ± 8%, respectively (P = 0.01, 0.11, 0.06); peak ejection rate, 481 ± 73 mL/s, 425 ± 62 mL/s, 434 ± 67 mL/s, and 381 ± 86 mL/s, respectively (P = 0.03, 0.04, 0.01); peak filling rate, 555 ± 80 mL/s, 480 ± 70 mL/s, 500 ± 70 mL/s, and 438 ± 108 mL/s, respectively (P= 0.007, 0.05, 0.004); and myocardial mass, 137 ± 26 g, 141 ± 25 g, 141 ± 23 g, and 130 ± 31 g, respectively (P = 0.62, 0.54, 0.99). CONCLUSIONS: Using a separate reference scan and high acceleration factors up to R = 6, single-shot real-time cardiac imaging offers adequate temporal and spatial resolution for accurate assessment of global left ventricular function in free breathing with short examination times.
    Investigative Radiology 01/2013; 48(3):158-166.
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    ABSTRACT: Diffusion-weighted imaging (DWI) and the introduction of the intravoxel incoherent motion (IVIM) model have provided a unique method for evaluating perfusion and diffusion within a tissue without the need for a contrast agent. Despite its relevance, cardiac DWI has thus far been limited by low b values because of signal loss induced by physiological motion. The goal of this study was to develop a methodology for estimating IVIM parameters of in vivo cardiac magnetic resonance imaging using an efficient DWI acquisition framework. This was achieved by investigating various acquisition strategies (principal component analysis [PCA] filtering and temporal maximum intensity projection [PCATMIP] and single trigger delay [TD]) and fitting methods. Simulations were performed on a synthetic dataset of diffusion-weighted signal intensity (SI) to determine the fitting method that would yield IVIM parameters with the greatest accuracy. The required number of b values to correctly estimate IVIM parameters was also investigated. Breath-hold DWI scans were performed for 12 volunteers to collect several TD values during diastole. Thirteen b values ranging from 0 to 550 s/mm were used. The IVIM parameters derived using the data from all the acquired TDs (PCATMIP technique) were compared with those derived using a single acquisition performed at an optimized diastolic time point (1TD). The main result of this study was that PCATMIP, when combined with a fitting model that accounted for T1 and T2 relaxation, provided IVIM parameters with less variability. However, an acquisition performed with 1 optimized diastolic TD provided results that were as good as those provided using PCATMIP if the R-R variability during the acquisition was sufficiently low (±5%). Furthermore, the use of only 9 b values (that could be acquired in 2 breath-holds), instead of 13 b values (requiring 3 breath-holds), was sufficient to determine the IVIM parameters. This study demonstrates that IVIM is technically feasible invivo and reports for the first time the perfusion fraction, f, and the diffusion coefficients, D and D*, for the cardiac DWI of healthy volunteers. Motion-induced signal loss, which is the main problem associated with cardiac DWI, could be avoided with the combined use of sliding acquisition during the cardiac cycle and image postprocessing with the PCATMIP algorithm. This study provides new perspectives for perfusion imaging without a contrast agent and demonstrates that IVIM parameters can act as promising tools to further characterize microvascular abnormalities or dysfunction.
    Investigative Radiology 11/2012;
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    ABSTRACT: The aim of this study was to assess the effectiveness of a model-based iterative reconstruction (MBIR) in improving image quality and diagnostic performance of ultralow-dose computed tomography (ULDCT) of the lung. The institutional review board approved this study, and all patients provided written informed consent. Fifty-two patients underwent low-dose computed tomography (LDCT) (screening-dose, 50 mAs) and ULDCT (4 mAs) of the lung simultaneously. The LDCT images were reconstructed with filtered back projection (LDCT-FBP images) and ULDCT images were reconstructed with both MBIR (ULDCT-MBIR images) and FBP (ULDCT-FBP images). On all the 156 image series, objective image noise was measured in the thoracic aorta, and 2 blinded radiologists independently assessed subjective image quality. Another 2 blinded radiologists independently evaluated the ULDCT-MBIR and ULDCT-FBP images for the presence of noncalcified and calcified pulmonary nodules; LDCT-FBP images served as the reference. Paired t test, Wilcoxon signed rank sum test, and free-response receiver-operating characteristic analysis were used for statistical analysis of the data. Compared with LDCT-FBP and ULDCT-FBP, ULDCT-MBIR had significantly reduced objective noise (both P <; 0.001). Subjective noise on the ULDCT-MBIR images was comparable with that on the LDCT-FBP images but lower than that on the ULDCT-FBP images (P <; 0.001). Artifacts on ULDCT-MBIR images were more numerous than those on the LDCT-FBP images (P = 0.007) but fewer than those on the ULDCT-FBP images (P <; 0.001). Compared with the LDCT-FBP images, ULDCT-MBIR and ULDCT-FBP images showed reduced image sharpness (both P <; 0.001). All the ULDCT-MBIR images showed a blotchy pixelated appearance; however, the performance of ULDCT-MBIR was significantly superior to that of ULDCT-FBP for the detection of noncalcified pulmonary nodules (P = 0.002). The average true-positive fractions for significantly sized noncalcified nodules (≥4 mm) and small noncalcified nodules (<;4 mm) on the ULDCT-MBIR images were 0.944 and 0.884, respectively, when LDCT-FBP images were used as reference. All of the calcified nodules were detected by both the observers on both the ULDCT-MBIR and ULDCT-FBP images. As compared with FBP, MBIR enables significant reduction of the image noise and artifacts and also better detection of noncalcified pulmonary nodules on ULDCT of the lung. Compared with LDCT-FBP images, ULDCT-MBIR images showed significantly reduced objective noise and comparable subjective image noise. Almost all of the noncalcified nodules and all of the calcified nodules could be detected on the ULDCT-MBIR images, when LDCT-FBP images were used as the reference.
    Investigative Radiology 08/2012; 47(8):482-9.
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    ABSTRACT: The purpose of this study was to select the optimal monochromatic level for virtual monochromatic spectral (VMS) imaging to minimize the image noise of the liver parenchyma and to acquire a high contrast-to-noise ratio (CNR) of hypovascular hepatic metastases in the portal-dominant phase. This study was conducted with the approval of our institutional review board, and written informed consent was obtained from all the participating patients. Ninety patients with hepatic metastases were scanned by fast kilovoltage switching dual-energy computed tomography in the portal-dominant phase. One hundred one sets of VMS images in the range of 40 to 140 keV at 1-keV intervals were reconstructed. The image noise of the liver parenchyma in each patient and the CNR of each metastasis (n = 303) were measured on all the 101 VMS image sets. Data were analyzed by the paired t test and mixed-effects model. Bonferroni's method was used for multiple comparisons. The lowest noise of the liver parenchyma was obtained in 6, 15, 31, 29, 7, 1, and 1 patient at 67, 68, 69, 70, 71, 72, and 73 keV, respectively. The mean noise of the liver parenchyma on the 69-keV VMS images in all 90 patients was significantly lower than that on the 67-, 68-, 71-, 72-, and 73-keV VMS images (P < 0.001); however, there was no significant difference in the mean noise of the liver parenchyma between the 69-keV and 70-keV VMS images (P = 0.279). For 95% of the hepatic metastases (288/303 metastases), the highest metastasis-to-liver CNR was obtained in the 66- to 71- keV VMS images. The mean metastasis-to-liver CNR for the 303 metastases was numerically highest at 68 keV; however, there was no significant difference in the mean metastasis-to-liver CNR between the 68-keV and 69-keV images (P = 0.737) or between the 68-keV and 70-keV images (P = 0.103). VMS imaging at approximately 70 keV (69-70 keV) yielded the lowest image noise of the liver parenchyma and a high CNR for hypovascular hepatic metastases in the portal-dominant phase.
    Investigative Radiology 05/2012; 47(5):292-8.
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    ABSTRACT: Purpose: To evaluate the stand-alone performance of a computer-aided detection (CAD) algorithm for colorectal polyps in a large heterogeneous CT colonography (CTC) database that included both tagged and untagged datasets. Methods: Written, informed consent was waived for this institutional review board-approved, HIPAA-compliant retrospective study. CTC datasets from 2063 patients were assigned to training (n = 374) and testing (n = 1689). The test set consisted of 836 untagged and 853 tagged examinations not used for CAD training. Examinations were performed at 15 sites in the United States, Asia, and Europe, using 4- to 64-multidetector-row computed tomography and various acquisition parameters. CAD sensitivities were calculated on a per-patient and per-polyp basis for polyps measuring ≥6 mm. The reference standard was colonoscopy in 1588 (94%) and consensus interpretation by expert radiologists in 101 (6%) patients. Statistical testing employed χ2, logistic regression, and Mann-Whitney U tests. Results: In 383 of 1689 individuals, 564 polyps measuring ≥6 mm were identified by the reference standard (347 polyps: 6–9 mm and 217 polyps: ≥10 mm). Overall, CAD per-patient sensitivity was 89.6% (343/383), with 89.0% (187/210) for untagged and 90.2% (156/173) for tagged datasets (P = 0.72). Overall, per-polyp sensitivity was 86.9% (490/564), with 84.4% (270/320) for untagged and 90.2% (220/244) for tagged examinations (P = 068). The mean false-positive rate per patient was 5.14 (median, 4) in untagged and 4.67 (median, 4) in tagged patient datasets (P = 0.353). Conclusion: Stand-alone CAD can be applied to both tagged and untagged CTC studies without significant performance differences. Detection rates are comparable to human readers at a relatively low false-positive rate, making CAD a useful tool in clinical practice.
    Investigative Radiology 01/2012; 47(2):99–108.
  • Investigative Radiology 01/2012;
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    ABSTRACT: To investigate dynamic contrast-enhanced computed tomography (DCE-CT) for monitoring the effects of sorafenib on experimental prostate carcinomas in rats by quantitative assessments of tumor microcirculation parameters with immunohistochemical validation. Prostate carcinoma allografts (MLLB-2) implanted subcutaneously in male Copenhagen rats (n=16) were imaged at baseline and after a 1-week treatment course of sorafenib using DCE-CT with iopromide (Ultravist 370, Bayer Pharma, Berlin, Germany) on a dual-source 128-slice CT (Somatom Definition FLASH, Siemens Healthcare, Forchheim, Germany). Scan parameters were as follows: detector width, 38.4 mm; contrast agent volume, 2 mL/kg bodyweight; injection rate, 0.5 mL/s; scan duration, 90 seconds; and temporal resolution, 0.5 seconds. The treatment group (n=8) received daily applications of sorafenib (10 mg/kg bodyweight) via gavage. Quantitative parameters of tumor microcirculation (plasma flow, mL/100 mL/min), endothelial permeability-surface area product (PS, mL/100 mL/min), and tumor vascularity (plasma volume, %) were calculated using a 2-compartment uptake model. DCE-CT parameters were correlated with immunohistochemical assessments of tumor vascularity (RECA-1), cell proliferation (Ki-67), and apoptosis (TUNEL). Sorafenib significantly (P < 0.05) suppressed tumor perfusion (25.1 ± 9.8 to 9.5 ± 6.0 mL/100 mL/min), tumor vascularity (15.6% ± 11.4% to 5.4% ± 2.1%), and PS (8.7 ± 4.5 to 2.7 ± 2.5 mL/100 mL/min) in prostate carcinomas during the treatment course. Immunohistochemistry revealed significantly lower tumor vascularity in the therapy group than in the control group (RECA-1; 181 ± 24 vs. 314 ± 47; P < 0.05). In sorafenib-treated tumors, significantly more apoptotic cells (TUNEL; 7132 ± 3141 vs. 3722 ± 1445; P < 0.05) and significantly less proliferating cells (Ki-67; 9628 ± 1.298 vs. 17,557 ± 1446; P < 0.05) were observed than those in the control group. DCE-CT tumor perfusion correlated significantly (P < 0.05) with tumor cell proliferation (Ki-67; r=0.55). DCE-CT tumor vascularity correlated significantly (P < 0.05) with immunohistochemical tumor cell apoptosis (TUNEL; r=-0.59) and tumor cell proliferation (Ki-67; r=0.68). DCE-CT endothelial PS correlated significantly (P < 0.05) with immunohistochemical tumor cell apoptosis (TUNEL; r=-0.6) and tumor vascularity (RECA-1; r=0.53). While performing corrections for multiple comparisons, we observed a significant correlation only between DCE-CT tumor vascularity (RECA-1) and tumor cell proliferation (Ki-67). Sorafenib significantly suppressed tumor perfusion, tumor vascularity, and PS quantified by DCE-CT in experimental prostate carcinomas in rats. These functional CT surrogate markers showed moderate correlations with antiangiogenic, antiproliferative, and proapoptotic effects observed by immunohistochemistry. DCE-CT may be applicable for the quantification of noninvasive imaging biomarkers of therapy response to antiangiogenic therapy.
    Investigative Radiology 09/2011; 47(1):49-57.
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    ABSTRACT: Comparison of 3 optimized pulse sequences for thoracoabdominal contrast-enhanced magnetic-resonance angiography by signal-to-noise measurements and time-dependent T1 mapping in the steady state after injection of 0.03 mmol/kg BW gadofosveset. After institutional review board approval, 15 healthy volunteers (19-46 years, mean age: 31.5 years) were included in this prospective, intraindividual comparison study. All examinations were performed at 1.5 T. Three pulse sequences: volume interpolated breath-hold examination (VIBE) sequences as VIBESEMI (echo time [TE]: 1.64 milliseconds, repetition time [TR]: 3.77 milliseconds, FA: 15 degrees, voxel size: 1.2 × 1.2 × 1.2 mm) with short TR, VIBEOPT (TE: 2.2 milliseconds, TR: 5.2, FA: 15 degree, voxel size: 1.2 × 1.2 × 1.2 mm) with long TR, and a typical 3-dimensional fast low angle shot (FLASH) sequence (TE: 1.39 milliseconds, TR: 3.77 milliseconds, FA: 25 degree, voxel size: 1.0 × 0.8 × 1.0 mm) were repeated 10, 20, 30, and 40 minutes after the injection of 0.03 mmol/kg BW gadofosveset (mean dose: 9.7 mL). Mean signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were computed for the aorta and the inferior vena cava (IVC). Three-dimensional gradient echo sequences with variable flip angles were performed for T1 mapping 0 to 50 minutes postinjection (p.i.). Additional phantom measurements were performed to compare the sequences. Significantly higher SNR values of the FLASH were found at every point compared with VIBEOPT (P = 0.002-P = 0.004), but only 10, respectively, 20 minutes p.i. to VIBESEMI. No significant differences of SNR were obtained between VIBESEMI and VIBEOPT. In the aorta, the maximal percentage gain of SNR was 29.2% for 3D-FLASH compared with VIBESEMI. Similar, but mostly not significant, results were obtained regarding the SNR in the IVC with the 3D-FLASH sequence yielding higher SNR versus both comparators (P = 0.007-P = 0.466). Except 10 minutes p.i., CNR analysis yielded higher values for the VIBESEMI versus both comparators in the aorta as well as in the IVC. No statistical significant difference was found for the VIBESEMI versus the 3D-FLASH sequence in all comparisons. Regarding the phantom measurements, statistically significant higher SNR was found for the VIBESEMI versus the 3D-FLASH. The T1 time in the aorta decreased p.i. from 1227 ± 383 milliseconds to 141 ± 27 milliseconds and showed over the time a slow reincrease to 175 ± 29 milliseconds at 50 minutes p.i. Ten to 30 minutes after injection of gadofosveset, a relatively constant longitudinal relaxation is given. In this steady state, no additional improvements were obtained by theoretically optimized sequence parameters in the VIBEOPT with a longer TR.
    Investigative Radiology 06/2011; 46(11):678-85.
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    ABSTRACT: : To evaluate the diagnostic performance of fast scanning tomosynthesis in comparison with that of chest radiography for the detection of pulmonary nodules, using multidetector-row computed tomography (MDCT) as the reference, and to assess the association of the true-positive fraction (TPF) with the size, CT attenuation value, and location of the nodules. : The institutional review board approved this study, and written informed consent was obtained from all patients. Fifty-seven patients with and 59 without pulmonary nodules underwent chest MDCT, fast scanning tomosynthesis, and radiography. The images of tomosynthesis and radiography were randomly read by 3 blinded radiologists; MDCT served as the reference standard. Free-response receiver-operating characteristic (FROC) and receiver-operating characteristic (ROC) analyses, Cochran-Armitage trend or Fisher exact test, a conditional logistic regression model, and McNemar test were used. : Both FROC and ROC analyses revealed significantly better performance (P < 0.01) of fast scanning tomosynthesis than radiography for the detection of pulmonary nodules. For fast scanning tomosynthesis, the average TPF and false-positive rate as determined by FROC analysis were 0.80 and 0.10, respectively. For both fast scanning tomosynthesis and radiography, the average TPF increased with increasing nodule size and CT attenuation values, and was lower for subpleural nodules (all P < 0.01). : The diagnostic performance of fast scanning tomosynthesis for the detection of pulmonary nodules was significantly superior to that of radiography. The TPF was affected by the size, CT attenuation value, and location of the nodule, in both fast scanning tomosynthesis and radiography.
    Investigative Radiology 04/2011; 46(8):471-7.
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    ABSTRACT: To investigate changes of diffusion tensor imaging (DTI) parameters (mean apparent diffusion coefficient [ADC], fractional anisotropy [FA], and first eigenvector) with increasing proteoglycan (PG) extraction of articular cartilage. Twelve cylindrical cartilage-on-bone samples were drilled from 4 human patellae (3 per patella). Each sample was divided into 2 pieces. One piece underwent histologic examination to assess the PG content of the native sample by safranin-O staining and its collagen architecture by polarized light microscopy. The other underwent magnetic resonance imaging (MRI) at 17.6 T for DTI measurement. After MRI, 2 of the 3 samples from each patella were immersed in a dilute trypsin solution (0.1 mg/mL), whereas the third sample was kept as a negative control in physiological saline. After incubation (6, 48, 72, and 96 hours), the samples were reimaged, stained for PG content and for the collagen orientation. Maps of ADC, FA, and the orientation of the first eigenvector as well as histology were available for each sample before and after incubation. PG loss led to increased ADC and reduced safranin-O staining from the articular surface to the bone-cartilage interface. A significant correlation (r(2) = 0.86, P < 0.01) was observed between the change in bulk ADC and PG loss. Regional analysis from the articular surface to the tide mark demonstrated depth dependent significant correlations of ADC and PG loss. FA and first eigenvector as well as polarized light microscopy showed only small changes in the order of magnitude of measurement errors, not correlating with PG loss. Mean diffusivity evidence by the ADC is linearly correlated to progressive PG extraction in articular cartilage. FA and the first eigenvector seem to be specific to the collagen architecture of cartilage. DTI has the potential to become a valuable biomarker for the workup of cartilage degeneration in osteoarthritis, since evaluation of the PG content and collagen architectural properties of cartilage can be performed with a single, non–contrast-enhanced proton-based MRI measurement.
    Investigative Radiology 03/2011; 46(6):401-9.

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