Jong Hyo Kim

Chronic Obstructive Pulmonary Disease: Quantitative and Visual Ventilation Pattern Analysis at Xenon Ventilation CT Performed by Using a Dual-Energy Technique

PURPOSEnTo evaluate the potential of xenon ventilation computed tomography (CT) in the quantitative and visual analysis of chronic obstructive pulmonary disease (COPD).nnnMATERIALS AND METHODSnThis study was approved by the institutional review board. After informed consent was obtained, 32 patients with COPD underwent CT performed before the administration of xenon, two-phase xenon ventilation CT with wash-in (WI) and wash-out (WO) periods, and pulmonary function testing (PFT). For quantitative analysis, results of PFT were compared with attenuation parameters from prexenon images and xenon parameters from xenon-enhanced images in the following three areas at each phase: whole lung, lung with normal attenuation, and low-attenuating lung (LAL). For visual analysis, ventilation patterns were categorized according to the pattern of xenon attenuation in the area of structural abnormalities compared with that in the normal-looking background on a per-lobe basis: pattern A consisted of isoattenuation or high attenuation in the WI period and isoattenuation in the WO period; pattern B, isoattenuation or high attenuation in the WI period and high attenuation in the WO period; pattern C, low attenuation in both the WI and WO periods; and pattern D, low attenuation in the WI period and isoattenuation or high attenuation in the WO period.nnnRESULTSnAmong various attenuation and xenon parameters, xenon parameters of the LAL in the WO period showed the best inverse correlation with results of PFT (P < .0001). At visual analysis, while emphysema (which affected 99 lobes) commonly showed pattern A or B, airway diseases such as obstructive bronchiolitis (n = 5) and bronchiectasis (n = 2) and areas with a mucus plug (n = 1) or centrilobular nodules (n = 5) showed pattern D or C.nnnCONCLUSIONnWI and WO xenon ventilation CT is feasible for the simultaneous regional evaluation of structural and ventilation abnormalities both quantitatively and qualitatively in patients with COPD.

Breast Cancer: Radiogenomic Biomarker Reveals Associations among Dynamic Contrast-enhanced MR Imaging, Long Noncoding RNA, and Metastasis

PURPOSEnTo perform a radiogenomic analysis of women with breast cancer to study the multiscale relationships among quantitative computer vision-extracted dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging phenotypes, early metastasis, and long noncoding RNA (lncRNA) expression determined by means of high-resolution next-generation RNA sequencing.nnnMATERIALS AND METHODSnIn this institutional review board-approved study, an automated image analysis platform extracted 47 computational quantitative features from DCE MR imaging data in a training set (n = 19) to screen for MR imaging biomarkers indicative of poor metastasis-free survival (MFS). The lncRNA molecular landscape of the candidate feature was defined by using an RNA sequencing-specific negative binomial distribution differential expression analysis. Then, this radiogenomic biomarker was applied prospectively to a validation set (n = 42) to allow prediction of MFS and lncRNA expression by using quantitative polymerase chain reaction analysis.nnnRESULTSnThe quantitative MR imaging feature, enhancing rim fraction score, was predictive of MFS in the training set (P = .007). RNA sequencing analysis yielded an average of 55.7 × 10(6) reads per sample and identified 14 880 lncRNAs from a background of 189 883 transcripts per sample. Radiogenomic analysis allowed identification of three previously uncharacterized and five named lncRNAs significantly associated with high enhancing rim fraction, including Homeobox transcript antisense intergenic RNA (HOTAIR) (P < .05), a known predictor of poor MFS in patients with breast cancer. Independent validation confirmed the association of the enhancing rim fraction phenotype with both MFS (P = .002) and expression of four of the top five differentially expressed lncRNAs (P < .05), including HOTAIR.nnnCONCLUSIONnThe enhancing rim fraction score, a quantitative DCE MR imaging lncRNA radiogenomic biomarker, is associated with early metastasis and expression of the known predictor of metastatic progression, HOTAIR.

Multilevel analysis of spatiotemporal association features for differentiation of tumor enhancement patterns in breast DCE-MRI

PURPOSEnAnalyzing spatiotemporal enhancement patterns is an important task for the differential diagnosis of breast tumors in dynamic contrast-enhanced MRI (DCE-MRI), and yet remains challenging because of complexities in analyzing the time-series of three-dimensional image data. The authors propose a novel approach to breast MRI computer-aided diagnosis (CAD) using a multilevel analysis of spatiotemporal association features for tumor enhancement patterns in DCE-MRI.nnnMETHODSnA database of 171 cases consisting of 111 malignant and 60 benign tumors was used. Time-series contrast-enhanced MR images were obtained from two different types of MR scanners and protocols. The images were first registered for motion compensation, and then tumor regions were segmented using a fuzzy c-means clustering-based method. Spatiotemporal associations of tumor enhancement patterns were analyzed at three levels: Mapping of pixelwise kinetic features within a tumor, extraction of spatial association features from kinetic feature maps, and extraction of kinetic association features at the spatial feature level. A total of 84 initial features were extracted. Predictable values of these features were evaluated with an area under the ROC curve, and were compared between the spatiotemporal association features and a subset of simple form features which do not reflect spatiotemporal association. Several optimized feature sets were identified among the spatiotemporal association feature group or among the simple feature group based on a feature ranking criterion using a support vector machine based recursive feature elimination algorithm. A least-squares support vector machine (LS-SVM) classifier was used for tumor differentiation and the performances were evaluated using a leave-one-out testing.nnnRESULTSnPredictable values of the extracted single features ranged in 0.52-0.75. By applying multilevel analysis strategy, the spatiotemporal association features became more informative in predicting tumor malignancy, which was shown by a statistical testing in ten spatiotemporal association features. By using a LS-SVM classifier with the optimized second and third level feature set, the CAD scheme showed Az of 0.88 in classification of malignant and benign tumors. When this performance was compared to the same LS-SVM classifier with simple form features which do not reflect spatiotemporal association, there was a statistically significant difference (0.88 vs 0.79, p <0.05), suggesting that the multilevel analysis strategy yields a significant performance improvement.nnnCONCLUSIONSnThe results suggest that the multilevel analysis strategy characterizes the complex tumor enhancement patterns effectively with the spatiotemporal association features, which in turn leads to an improved tumor differentiation. The proposed CAD scheme has a potential for improving diagnostic performance in breast DCE-MRI.

Computer-aided detection of colonic polyps at CT colonography using a Hessian matrix-based algorithm: preliminary study.

OBJECTIVEnThe purpose of our study was to develop a Hessian matrix-based computer-aided detection (CAD) algorithm for polyp detection on CT colonography (CTC) and to analyze its performance in a high-risk population.nnnSUBJECTS AND METHODSnThe CTC data sets of 35 patients with at least one colonoscopically proven polyp were interpreted with a Hessian matrix-based CAD algorithm, which was designed to depict bloblike structures protruding into the lumen. Our gold standard was a combination of segmental unblinded optical colonoscopy and retrospective unblinded consensus review by two radiologists. Sensitivity of CAD for polyp detection was evaluated on both per-polyp and per-patient bases. The average number of false-positive detections was calculated, and the causes of false-positives and false-negatives were analyzed.nnnRESULTSnNinety-four polyps were identified on colonoscopy. Forty-six polyps were smaller than 6 mm and 48 were 6 mm or larger. Seventy-five (79.8%) of these 94 polyps were identified by radiologists in a retrospective review. When colonoscopy was used as a standard of reference, the sensitivity of CAD was 77.1% for polyps 6 mm or larger. For large polyps (> or = 6 mm) that could be identified on retrospective review, the CAD algorithm achieved sensitivities of 92.5% (37/40) and 91.7% (22/24), respectively, on per-polyp and per-patient bases. There were an average of 5.5 false-positive detections per patient and 3.1 false-positive detections per data set for CAD. The two most frequent causes of false-positives on CAD were prominent or converging fold (78/191) and feces (50/191). Of the three polyps 6 mm or larger that were missed by CAD, two had a flat appearance on colonoscopy and the remaining one was located in the narrow area between the rectal tube and the rectal wall.nnnCONCLUSIONnA Hessian matrix-based CAD algorithm for CTC has the potential to depict polyps larger than or equal to 6 mm with high sensitivity and an acceptable false-positive rate.

Xenon-Enhanced Dual-Energy CT of Patients With Asthma: Dynamic Ventilation Changes After Methacholine and Salbutamol Inhalation

OBJECTIVEnThe purpose of this study was to evaluate the use of xenon-enhanced dual-energy CT of the chest to assess ventilation changes after methacholine and salbutamol inhalation in subjects with asthma and healthy subjects.nnnSUBJECTS AND METHODSnTwenty-five subjects with asthma and 10 healthy subjects underwent three-phase (basal, after methacholine inhalation, after salbutamol inhalation) xenon-enhanced chest CT. Each phase was composed of wash-in and washout scans. For visual analysis, two radiologists evaluated ventilation defects and gas trapping lobe by lobe on a 10-point scale. Total ventilation defect and gas trapping scores were calculated by adding ventilation defect and gas trapping scores. Xenon and total lung volume were quantified automatically. Total xenon concentration index was calculated as total xenon concentration divided by lung volume. Repeated measures analysis of variance and Student t test were used for comparisons of total ventilation defect score, total gas trapping score, and total xenon concentration index between the two groups. The Friedman test was used for within-group analysis.nnnRESULTSnIn the basal state, subjects with asthma had a higher total ventilation defect score (p = 0.004) and higher total gas trapping score (p = 0.05) than did healthy subjects. On washout images, total ventilation defect score, total gas trapping score, and total xenon concentration index after methacholine and salbutamol inhalation were statistically different between the two groups (p < 0.05). However, total xenon concentration index on wash-in images was not significantly different between the two groups. In within-group analysis, total ventilation defect score and total gas trapping score in subjects with asthma and total ventilation defect score in healthy subjects increased significantly after methacholine inhalation and decreased significantly after salbutamol inhalation (p < 0.05).nnnCONCLUSIONnXenon-enhanced chest CT may be a useful technique for visualizing dynamic changes in airflow in response to methacholine and salbutamol inhalation in patients with asthma. Optimization of the protocol for radiation exposure is warranted.

Effects of Spatial Resolution and Tube Current on Computer-aided Detection of Polyps on CT Colonographic Images: Phantom Study

PURPOSEnTo prospectively evaluate the effects of z-axis spatial resolution and tube current on the sensitivity of a commercially available computed tomographic (CT) colonography computer-aided diagnosis (CAD) system for polyp detection by using pig colon phantoms.nnnMATERIALS AND METHODSnNinety-six polyps were created and analyzed in 14 pig colon phantoms. CT colonography was performed by using a 16-detector CT scanner at 0.75-mm collimation; 10, 50, 100, and 160 mAs; and a pitch of 1.5. At each milliampere-second setting, the CT images were reconstructed with a section thickness (ST) of 1.5 mm and a reconstruction increment (RI) of 1.3 mm. To evaluate the effect of z-axis spatial resolution, CT images were also reconstructed at 100 mAs with various SI and RI combinations (respectively: 1.0 and 0.7 mm, 3.0 and 2.0 mm, 3.0 and 3.0 mm, 5.0 and 5.0 mm). The phantom data were then analyzed by using a CAD program. CAD performance with different CT parameters was calculated and compared in terms of per-polyp sensitivity and number of false-positive (FP) findings per data set.nnnRESULTSnAt a constant tube current of 100 mAs, the polyp detection rate was significantly higher in data sets obtained with SI and RI combinations of 1.0 and 0.7 mm, respectively (81% [78/96]), and 1.5 and 1.3 mm, respectively (75% [72/96]), than in those obtained with the three thicker ST-RI settings (27% [26/96] to 64% [61/96]) (P < .01). A similar trend was observed, regardless of polyp size or morphology. However, the number of FP findings at the 1.0 mm and 0.7 mm setting (8.9 per phantom) was also significantly greater than that at the thicker ST-RI settings (4.0-6.1 per phantom) (P < .05). At a constant z-axis spatial resolution (1.5-mm ST, 1.3-mm RI), CAD polyp detection rate and number of FP findings per phantom remained nearly constant-close to 78% (75/96) and 6.1, respectively-at various tube current settings.nnnCONCLUSIONnCAD performance in polyp detection at CT colonography is highly dependent on z-axis spatial resolution. However, tube current is not an influencing factor in CAD performance at a given z-axis spatial resolution.nnnSUPPLEMENTAL MATERIALnhttp://radiology.rsnajnls.org/cgi/content/full/2482071025/DC1.

Differentiation of small hyperechoic renal cell carcinoma from angiomyolipoma: computer-aided tissue echo quantification.

To assess the value of computer‐aided tissue echo quantification in differentiating small hyperechoic renal cell carcinomas from angiomyolipomas, we studied ultrasonographic images of 15 renal cell carcinomas and 20 angiomyolipomas. After digitizing the images, we measured the absolute gray scale values of the renal cortex, central echo complex, and mass. The relative gray scale value (%) of the mass was calculated by setting the gray scale value of the cortex as 0% and the central echo complex as 100%. The relative gray scale value of renal cell carcinomas was in the range of 12 to 73% (mean, 28%), whereas that of angiomyolipomas was 30 to 204% (mean, 130%). The differentiation between small hyperechoic renal cell carcinomas and angiomyolipomas can be facilitated by computer‐aided tissue echo quantification.

Comparison of fundamental sonography, tissue-harmonic sonography, fundamental compound sonography, and tissue-harmonic compound sonography for focal hepatic lesions.

Image qualities of fundamental, tissue-harmonic, fundamental compound, and tissue-harmonic compound sonography for evaluating focal hepatic lesions were compared. Two radiologists, blinded to the type of techniques and to the final diagnosis, independently evaluated 384 images of 96 hepatic lesions: hemangiomas (n=35), hepatic cystic lesions (n=28), cirrhosis-related nodules (n=22), focal nodular hyperplasia (n=1), and metastases (n=10). All images were graded in terms of lesion conspicuity, margin sharpness, and overall image quality using a 4- or 5-point scale. In the cases of cystic lesions, posterior acoustic enhancement and internal artifacts were also analyzed. A Friedman test was used for multiple statistical comparisons of the four techniques for all parameters. Compound imaging was significantly superior to fundamental imaging regarding lesion conspicuity, margin sharpness, and overall quality (P<0.05). For posterior enhancement and internal artifacts within the cyst, harmonic ultrasonography (US) was significantly better than fundamental US (P<0.05). For evaluating focal hepatic lesions on US, compound imaging provided better lesion conspicuity, better margin sharpness, and better overall image quality than fundamental imaging did. Tissue harmonic imaging also provided better posterior enhancement and fewer internal artifacts of the cyst than fundamental imaging.

Realistic simulation of reduced-dose CT with noise modeling and sinogram synthesis using DICOM CT images.

PURPOSEnReducing the patient dose while maintaining the diagnostic image quality during CT exams is the subject of a growing number of studies, in which simulations of reduced-dose CT with patient data have been used as an effective technique when exploring the potential of various dose reduction techniques. Difficulties in accessing raw sinogram data, however, have restricted the use of this technique to a limited number of institutions. Here, we present a novel reduced-dose CT simulation technique which provides realistic low-dose images without the requirement of raw sinogram data.nnnMETHODSnTwo key characteristics of CT systems, the noise equivalent quanta (NEQ) and the algorithmic modulation transfer function (MTF), were measured for various combinations of object attenuation and tube currents by analyzing the noise power spectrum (NPS) of CT images obtained with a set of phantoms. Those measurements were used to develop a comprehensive CT noise model covering the reduced x-ray photon flux, object attenuation, system noise, and bow-tie filter, which was then employed to generate a simulated noise sinogram for the reduced-dose condition with the use of a synthetic sinogram generated from a reference CT image. The simulated noise sinogram was filtered with the algorithmic MTF and back-projected to create a noise CT image, which was then added to the reference CT image, finally providing a simulated reduced-dose CT image. The simulation performance was evaluated in terms of the degree of NPS similarity, the noise magnitude, the bow-tie filter effect, and the streak noise pattern at photon starvation sites with the set of phantom images.nnnRESULTSnThe simulation results showed good agreement with actual low-dose CT images in terms of their visual appearance and in a quantitative evaluation test. The magnitude and shape of the NPS curves of the simulated low-dose images agreed well with those of real low-dose images, showing discrepancies of less than +/-3.2% in terms of the noise power at the peak height and +∕-1.2% in terms of the spatial frequency at the peak height. The magnitudes of the noise measured for 12 different combinations the phantom size, tube current, and reconstruction kernel for the simulated and real low-dose images were very similar, with differences of 0.1 to 4.7%. The p value for a statistical testing of the difference in the noise magnitude ranged from 0.99 to 0.11, showing that there was no difference statistically between the noise magnitudes of the real and simulated low-dose images using our method. The strength and pattern of the streak noise in an anthropomorphic phantom was also consistent with expectations.nnnCONCLUSIONSnA novel reduced-dose CT simulation technique was developed which uses only CT images while not requiring raw sinogram data. Our method can provide realistic simulation results under reduced-dose conditions both in terms of the noise magnitude and the textual appearance. This technique has the potential to promote clinical research for patient dose reductions.

Quantitative analysis of dynamic airway changes after methacholine and salbutamol inhalation on xenon-enhanced chest CT

ObjectivesTo investigate the dynamic changes in airways in response to methacholine and salbutamol inhalation and to correlate the xenon ventilation index on xenon-enhanced chest CTs in asthmatics.MethodsThirty-one non-smokers (6 normal, 25 asthmatics) underwent xenon-enhanced chest CT and pulmonary function tests. Images were obtained at three stages (basal state, after methacholine inhalation and after salbutamol inhalation), and the total xenon ventilation index (TXVI) as well as airway values were measured and calculated. The repeated measures ANOVA and Spearman’s correlation coefficient were used for statistical analysis.ResultsTXVI in the normal group did not significantly change (Pu2009>u20090.05) with methacholine and salbutamol. For asthmatics, however, the TXVI significantly decreased after methacholine inhalation and increased after salbutamol inhalation (Pu2009<u20090.05). Of the airway parameters, the airway inner area (IA) significantly increased after salbutamol inhalation in all airways (Pu2009<u20090.01) in asthmatics. Airway IA, wall thickness and wall area percentage did not significantly decrease after methacholine inhalation (Pu2009>u20090.05). IA of the large airways was well correlated with basal TXVI, FEV1 and FVC (Pu2009<u20090.05).ConclusionsAirway IA is the most reliable parameter for reflecting the dynamic changes after methacholine and salbutamol inhalation, and correlates well with TXVI in asthmatics on xenon-enhanced CT.Key Points• In asthmatics, xenon ventilation decreases after methacholine and increases after salbutamol inhalation.• Inner airway area (IA) correlates well with xenon ventilation.• IA is the most reliable parameter reflecting airway changes in drug responses.