Showing papers in "Journal of Computer Assisted Tomography in 2012"

Radiation dose reduction with Sinogram Affirmed Iterative Reconstruction technique for abdominal computed tomography.

Abstract: Purpose: The objective of this study was to assess the effect of Sinogram Affirmed Iterative Reconstruction (SAFIRE) and filtered back-projection (FBP) techniques on abdominal computed tomography (CT) performed with 50% and 75% radiation dose reductionsMethods: Twenty-four patients (mean age, 64 ± 14 years; male-female ratio, 10:14) gave informed consent for an institutional review board–approved prospective study involving acquisition of additional research images through the abdomen on 128-slice multi–detector-row CT (SOMATOM Definition Flash) at quality reference mAs of 100 (50% lower dose) and 50 (75% lower dose) over a scan length of 10 cm using combined modulation (CARE Dose 4D) Standard-of-care abdominal CT was performed at 200 quality reference mAs, with remaining parameters held constant The 50- and 100-mAs data sets were reconstructed with FBP and at 4 SAFIRE settings (S1, S2, S3, S4) Higher number of SAFIRE settings denotes increased strength of the algorithm resulting in lower image noise Two abdominal radiologists independently compared the FBP and SAFIRE images for lesion number, location, size and conspicuity, and visibility of small structures, image noise, and diagnostic confidence Objective noise and Hounsfield units (HU) were measured in the liver and the descending aortaResults: All 43 lesions were detected on both FBP and SAFIRE images Minor blocky, pixelated appearance of 50% and 75% reduced dose images was noted at S3 and S4 SAFIRE but not at S1 and S2 settings Subjective noise was suboptimal in both 50% and 75% lower-dose FBP images but was deemed acceptable on all SAFIRE settings Sinogram Affirmed Iterative Reconstruction images were deemed acceptable in all patients at 50% lower dose and in 22 of 24 patients at 75% lower dose As compared with 75% reduced dose FBP, objective noise was lower by 228% (229/297), 35% (193/297), 443% (167/293), and 548% (134/297) on S1 to S4 settings, respectively (P < 0001)Conclusions: Sinogram Affirmed Iterative Reconstruction–enabled reconstruction provides abdominal CT images without loss in diagnostic value at 50% reduced dose and in some patients also at 75% reduced dose

Comparison of hybrid and pure iterative reconstruction techniques with conventional filtered back projection: dose reduction potential in the abdomen.

Abstract: PURPOSE Assess the effect of filtered back projection (FBP) and hybrid (adaptive statistical iterative reconstruction [ASIR]) and pure (model-based iterative reconstruction [MBIR]) iterative reconstructions on abdominal computed tomography (CT) acquired with 75% radiation dose reduction. MATERIALS AND METHODS In an institutional review board-approved prospective study, 10 patients (mean [standard deviation] age, 60 (8) years; 4 men and 6 women) gave informed consent for acquisition of additional abdominal images on 64-slice multidetector-row CT (GE 750HD, GE Healthcare). Scanning was repeated over a 10-cm scan length at 200 and 50 milliampere second (mA s), with remaining parameters held constant at 120 kilovolt (peak), 0.984:1 pitch, and standard reconstruction kernel. Projection data were deidentified, exported, and reconstructed to obtain 4 data sets (200-mA s FBP, 50-mA s FBP, 50-mA s ASIR, 50-mA s MBIR), which were evaluated by 2 abdominal radiologists for lesions and subjective image quality. Objective noise and noise spectral density were measured for each image series. RESULTS Among the 10 patients, the maximum weight recorded was 123 kg, with maximum transverse diameter measured as 43.7 cm. Lesion conspicuity at 50-mA s MBIR was better than on 50-mA s FBP and ASIR images (P < 0.01). Image noise was rated as suboptimal on low-dose FBP and ASIR but deemed acceptable in MBIR images. Objective noise with 50-mA s MBIR was 2 to 3 folds lower compared to 50-mA s ASIR, 50-mA s FBP, and 200-mA s FBP (P < 0.0001). Noise spectral density analyses demonstrated that ASIR retains the noise spectrum signature of FBP, whereas MBIR has much lower noise with a more regularized noise spectrum pattern. CONCLUSION Model-based iterative reconstruction renders acceptable image quality and diagnostic confidence in 50- mA s abdominal CT images, whereas FBP and ASIR images are associated with suboptimal image quality at this radiation dose level.

Development and validation of a practical lower-dose-simulation tool for optimizing computed tomography scan protocols.

Abstract: Objective The objective of this study was to develop and validate a novel noise insertion method that can accurately simulate lower-dose images from existing standard-dose computed tomography (CT) data. Methods The noise insertion method incorporates the effects of the bowtie filter, automatic exposure control, and electronic noise. We validated this tool using both phantom and patient studies. The phantom study compared simulated lower-dose images with the actually acquired lower-dose images. The patient studies included 105 pediatric and 24 adult CT body examinations. Results The noise level in the simulated images was within 3.2% of the actual lower-dose images in phantom experiments. Noise power spectrum also demonstrated excellent agreement. For the patient examinations, a mean difference of noise level between 2.0% and 9.7% was observed for simulated dose levels between 75% and 30% of the original dose. Conclusions An accurate technique for simulating lower-dose CT images was developed and validated, which can be used to retrospectively optimize CT protocols.

Diffusion-weighted magnetic resonance imaging of the prostate: improved robustness with stretched exponential modeling.

Abstract: Purpose: This study aimed to compare the intraclass correlation coefficients of parameters estimated with stretched exponential and biexponential diffusion models of in vivo diffusion-weighted magnetic resonance imaging (MRI) of the prostate. Methods: After the institutional review board issued a waiver of informed consent for this Health Insurance Portability and Accountability ActYcompliant study, 25 patients with biopsy-proven prostate cancer underwent 3T endorectal MRI and diffusion-weighted MRI of the prostate at 10 b values (0, 45, 75, 105, 150, 225, 300, 600, 900, and 1200 s/mm 2 ). The full set of b values was collected twice within a single acquisition. Intraclass correlation coefficients were calculated for intra-acquisition variability. From the biexponential model, the quantitative parameters diffusion coefficient (D), perfusion coefficient (D*), and perfusion fraction ( f ) were estimated. From the stretched exponential model, the quantitative parameters Kohlrausch decay constant (DK) and alpha (>) were estimated. Results: For the 25 patient data sets, the average intraclass correlation coefficients for DK and > were 95.8%, and 64.1%, respectively, whereas those for D, D*, and f were 84.4%, 25.3%, and 41.3%, respectively. Conclusions: The stretched exponential diffusion model captures the nonlinear effects of intravoxel incoherent motion in the prostate. The parameters derived from this model are more reliable and reproducible than the parameters derived from the standard, widely used biexponential diffusion/perfusion model.

Typical and atypical imaging findings of intrahepatic cholangiocarcinoma using gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging.

Abstract: Purpose The objective of this study was to examine the imaging features of classic mass-forming intrahepatic cholangiocarcinoma (MICC) and nonclassic hypervascular MICC on gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging. Methods Twenty pathologically confirmed MICCs were included. Two radiologists retrospectively reviewed the imaging characteristics on T2-weighted imaging, diffusion-weighted imaging, dynamic contrast-enhanced images, and hepatobiliary phase (HBP) of each MICC. For the morphologic feature of defect, HBP signal intensity (SI) ratio was calculated by dividing the SI of the MICC by nearby normal liver parenchyma SI. Results Classic MICCs (n = 14) showed classic rim or peripheral enhancement at arterial dominant phase with centripetal enhance in the delayed phases. Hypervascular MICCs (n = 6) showed complete (n = 4) or near-complete (n = 2) arterial enhancement and washout (n = 6) on delayed phases. On HBP, 13 classic MICCs (93%) and 2 hypervascular MICCs (33%) showed cloud-like SI in the center ("EOB cloud") with peripheral defect. Mean SI ratio was 0.77 in classic MICCs and 0.59 in hypervascular MICC (P = 0.057). Conclusions Classic MICCs (70%) frequently showed progressive centripetal enhancement on dynamic phase, and central EOB-cloud appearance with distinct peripheral defect on HBP. Nonclassic hypervascular MICCs comprised 30% of the MICCs in this study. Compared with classic MICCs, hypervascular MICCs showed wash-in on arterial dominant phase and washout on delayed phase.

Computed tomography perfusion analysis of pancreatic carcinoma.

Abstract: OBJECTIVE The purpose of this study was to evaluate CT perfusion of pancreatic carcinomas using the Patlak model for assessing perfusion, permeability, and blood volume. METHODS A total of 25 patients with pancreatic carcinoma were examined prospectively with a 64-slice computed tomography (CT) using a dynamic sequence after intravenous injection of 80-mL contrast material (370 mg/mL; flow rate, 5 mL/s). Eighty-kilovolt (peak) perfusion acquisitions were evaluated for estimating perfusion parameters for carcinoma and healthy tissue using a 2-compartment model (Patlak model). RESULTS Twenty patients had hypodense tumors; in 5 patients, the tumor could not be delineated in contrast-enhanced CT. All carcinomas could be identified clearly in the color-coded perfusion maps. Perfusion, permeability, and blood volume values were significant lower in pancreatic carcinomas compared to healthy pancreatic tissue (0.27 ± 0.20 vs 0.89 ± 0.19 min, P < 0.0001; 0.43 ± 0.20 vs 0.75 ± 0.16 × 0.5 min, P < 0.0001; and 38.9 ± 20.7 vs 117.8 ± 46.9 mL/100 mL, P < 0.0001). CONCLUSION Computed tomographic perfusion of the pancreas using a 2-compartment perfusion model is feasible. Color-coded perfusion maps could be a helpful tool to delineate pancreatic carcinomas even if they are not visible in contrast-enhanced CT.

Validation of dual-source single-tube reconstruction as a method to obtain half-dose images to evaluate radiation dose and noise reduction: phantom and human assessment using CT colonography and sinogram-affirmed iterative reconstruction (SAFIRE).

Abstract: OBJECTIVE: To evaluate a method for obtaining half-dose CT images for observer studies evaluating lower-dose CT. METHODS: Phantoms of varying sizes were scanned at multiple tube potentials using dose-matched dual-source (DS) and single-source (SS) protocols. Images from single-tube reconstruction of DS data were compared with SS images acquired at half-original CTDIvol. Thirty patients underwent supine SS and dose-matched prone DS CT colonography (CTC). Half-dose prone images were reconstructed with sinogram-affirmed iterative reconstruction (SAFIRE). Two radiologists scored image quality on 2-dimensional (2D) and 3D images. RESULTS: Image noise was similar between half-dose SS images and DS images reconstructed from one tube only with tube potential of 120 kV or more for phantoms 40 cm or smaller (P < 0.05). For both readers, the patients' CTC image quality scores were more than 84% concordant between SS or DS CTC images, and half-dose-prone CTC images with SAFIRE had 84% or more concordance with routine-dose CTC except for 3D image noise. CONCLUSIONS: In appropriately sized patients, DS acquisition with single-tube reconstruction can create half-dose images, permitting comparison to full-dose images. For CTC, there is comparable image quality for colonic evaluation between full-dose and half-dose images reconstructed with SAFIRE.

Magnetic resonance imaging patterns of tumor regression after neoadjuvant chemotherapy in breast cancer patients: correlation with pathological response grading system based on tumor cellularity

Abstract: PURPOSE The objectives of the study were to analyze the tumor shrinkage pattern on magnetic resonance imaging (MRI) after neoadjuvant chemotherapy and to evaluate whether there is any difference in shrinkage pattern between pathological responder and nonresponder groups. In addition, we wanted to compare tumor diameter obtained from MRI with histological diameter according to the tumor shrinkage pattern. METHODS Between July 2008 and December 2010, 55 consecutive patients (56 lesions) with pathologically proven breast cancer who underwent neoadjuvant chemotherapy followed by surgery were retrospectively enrolled. The shrinkage pattern was classified into 4 categories: I (concentric shrinkage without surrounding lesion), II (concentric shrinkage with surrounding lesions), III (shrinkage with residual multinodular lesions, and IV (diffuse contrast enhancement in whole quadrants). Histological regression was scored on a 5-point scale regarding tumor cellularity reduction (Miller-Payne grading system). Patients with Miller-Payne grade 1 or 2 were classified into the nonresponder group, and patients with grade 3, 4, or 5 were in the responder group. RESULTS Of 56 lesions, pattern I was seen in 29 lesions, pattern II in 13 lesions, pattern III in 5 lesions, and pattern IV in 4 lesions. Three lesions were not visualized on MRI after neoadjuvant chemotherapy, and 2 lesions were increased in size. There was a statistically significant difference in the tumor shrinkage pattern between responder and nonresponder groups (P = 0.017). All 5 lesions with type III shrinkage pattern were found in the responder group, and all 4 lesions with pattern IV were in the nonresponder group. Magnetic resonance imaging diameter of lesions with types I, II, and IV patterns showed significant correlation with the histological diameter. Among them, the correlation factor was highest in pattern IV (ρ = 0.94, P < 0.001) followed by pattern I (ρ = 0.67, P < 0.01) and pattern II (ρ = 0.502, P = 0.08). However, in type III shrinkage pattern, tumor size measured on MRI was not significantly correlated with histological size (P = 0.87). CONCLUSIONS Types III and I shrinkage patterns were more frequently observed in the pathological responder group, and type IV was more frequently noted in the nonresponder group. Tumor diameter measured on MRI showed strong correlation with histological diameter in lesions with types I and IV shrinkage patterns, whereas lesions with type III did not show significant correlation. Type II pattern showed similar frequencies between the 2 groups and moderate correlation between sizes obtained from MRI and histology.

"Sweet spot" for endoleak detection: optimizing contrast to noise using low keV reconstructions from fast-switch kVp dual-energy CT.

Abstract: OBJECTIVE To assess endoleak detection and conspicuity using low-kiloelectron volt (keV) monochromatic reconstructions of single-source (fast-switch kilovolt [peak]) dual-energy data sets. METHODS With approval of the institutional review board, multiphasic dual-energy computed tomographic (CT) scans for aortic endograft surveillance were retrospectively reviewed for 39 patients. Two abdominal radiologists each performed 2 separate reading sessions, at 55-keV and standard 75-keV reconstruction, respectively. The readers tabulated endoleak presence, conspicuity on 1-to-5 scale, and type overall and in arterial and venous phases. Originally, dictated reports in medical records were used as criterion standard. RESULTS Original dictations identified 19 endoleaks (9 abdominal and 10 thoracic), 13 of which were type II. The blinded readers (R1 and R2) exhibited good to very good intraobserver and interobserver agreement. Endoleak detection was higher at 55 keV than at 75 keV (sensitivity, 100% (95% confidence interval [CI], 82.4%-100.0%) and 84.2% (95% CI, 60.4-96.6%) at 55 keV vs 79% (95% CI, 54.4-94.0%) and 68.4% (95% CI, 43.5%-87.4%) at 75 keV in venous phase). Further, endoleak conspicuity ratings (where original dictation showed positive leak) were higher at 55 keV than at 75 keV, which was a significant difference for R2 in the overall ratings (P = 0.03) and for both readers in the venous phase ratings (R1, P = 0.01; R2, P = 0.004). There was no difference in endoleak type characterization between the kiloelectron volt levels. CONCLUSION Sensitivity for endoleak detection and overall endoleak conspicuity ratings were both higher at 55 keV than 75 keV, favoring the inclusion of a lower-energy monochromatic reconstruction for endoleak surveillance protocols with dual-energy computed tomography.

Computed tomographic evaluation of mesentery: diagnostic value in acute mesenteric ischemia.

Abstract: OBJECTIVE To evaluate the computed tomographic appearances of mesentery in acute mesenteric ischemia (AMI) to recognize characteristic features and their prognostic values. METHODS Computed tomographic examinations of 34 patients with a confirmed diagnosis of AMI were retrospectively reviewed to evaluate the number of mesenteric vessels, diameter of the superior mesenteric artery and superior mesenteric vein, mesenteric fat stranding, mesenteric vessel pneumatosis and ascites. RESULTS Overall, at least one of these mesenteric signs was present in all but 1 patient. In all AMI of arterial occlusive type and in 68% of nonocclusive mesenteric ischemia, the number of arterial vessels was reduced (P = 0.067). Mesenteric vessel pneumatosis and reduced number of venous vessels were significantly associated with higher mortality (P = 0.027 and P = 0.042, respectively). Reperfusion signs were associated with a reduced mortality (28.7% vs 65.5%). CONCLUSION Considering its characteristic features and its possible prognostic value, the evaluation of mesentery will supply additional information in the interpretation of computed tomography in AMI.

Adaptive statistical iterative reconstruction and Veo: assessment of image quality and diagnostic performance in CT colonography at various radiation doses.

Abstract: Objectives To evaluate the diagnostic performance of computed tomography (CT) colonography (CTC) reconstructed with different levels of adaptive statistical iterative reconstruction (ASiR, GE Healthcare) and Veo (model-based iterative reconstruction, GE Healthcare) at various tube currents in detection of polyps in porcine colon phantoms. Methods Five porcine colon phantoms with 46 simulated polyps were scanned at different radiation doses (10, 30, and 50 mA s) and were reconstructed using filtered back projection (FBP), ASiR (20%, 40%, and 60%) and Veo. Eleven data sets for each phantom (10-mA s FBP, 10-mA s 20% ASiR, 10-mA s 40% ASiR, 10-mA s 60% ASiR, 10-mA s Veo, 30-mA s FBP, 30-mA s 20% ASiR, 30-mA s 40% ASiR, 30-mA s 60% ASiR, 30-mA s Veo, and 50-mA s FBP) yielded a total of 55 data sets. Polyp detection sensitivity and confidence level of 2 independent observers were evaluated with the McNemar test, the Fisher exact test, and receiver operating characteristic curve analysis. Comparative analyses of overall image quality score, measured image noise, and interpretation time were also performed. Results Per-polyp detection sensitivities and specificities were highest in 10-mA s Veo, 30-mA s FBP, 30-mA s 60% ASiR, and 50-mA s FBP (sensitivity, 100%; specificity, 100%). The area-under-the-curve values for the overall performance of each data set was also highest (1.000) at 50-mA s FBP, 30-mA s FBP, 30-mA s 60% ASiR, and 10-mA s Veo. Images reconstructed with ASiR showed statistically significant improvement in per-polyp detection sensitivity as the percent level of per-polyp sensitivity increased (10-mA s FBP vs 10-mA s 20% ASiR, P = 0.011; 10-mA s FBP vs 10-mA s 40% ASiR, P = 0.000; 10-mA s FBP vs 10-mA s 60% ASiR, P = 0.000; 10-mA s 20% ASiR vs 40% ASiR, P = 0.034). Overall image quality score was highest at 30-mA s Veo and 50-mA s FBP. The quantitative measurement of the image noise was lowest at 30-mA s Veo and second lowest at 10-mA s Veo. There was a trend of decrease in time required for image interpretation as the percent level of ASiR increased, and ASiR or Veo was used instead of FBP. However, differences from comparative analyses of overall image quality score, measured image noise, and interpretation time did not reach statistical significance. Conclusion ASiR and Veo showed improved diagnostic performance with excellent sensitivity and specificity with less image noise and good image quality compared with FBP reconstruction of same radiation dose. Our study confirmed feasibility of low-dose CTC with iterative reconstruction as a promising screening tool with excellent diagnostic performance similar to that of the standard-dose CTC with FBP.

Improvement of image quality at low-radiation dose and low-contrast material dose abdominal CT in patients with cirrhosis: intraindividual comparison of low tube voltage with iterative reconstruction algorithm and standard tube voltage.

Abstract: OBJECTIVE To intraindividually compare a low-tube voltage, low-contrast material dose computed tomography (CT) reconstructed with iterative reconstruction (IR) algorithm at standard tube voltage reconstructed with filtered back projection (FBP) and standard-contrast material dose during liver dynamic CT. MATERIALS AND METHODS Twenty-five patients with liver cirrhosis underwent 64-section multidetector CT. One hundred twenty kilovolt (peak) (kV[p]) with standard contrast material dose of 600 mg of iodine per kilogram (protocol A) and 80 kV(p) with low-contrast material dose of 450 mg of iodine per kilogram (protocol B) CT image sets were reconstructed by using FBP algorithm and that of using IR algorithm with a 60%/40% blend of IR-FBP reconstruction at 80-kV(p) image set (protocol C). Scans obtained during 3 hepatic phases were subjected to quantitative and qualitative analysis. RESULTS The mean radiation dose and the contrast medium dose were significantly lower under protocols B and C than under protocol A. In all hepatic phases, all signal-to-noise and contrast-to-noise ratios were greater under protocol C than under other protocols at all anatomic sites. Qualitative analysis showed that image noise and diagnostic acceptability were significantly higher under protocol C. CONCLUSION In all hepatic phases, a low-tube voltage, low-contrast material dose CT with IR algorithm yielded better contrast enhancement and image quality than a standard tube voltage, standard contrast material dose CT with FBP in thin adult patients.

Utility of pretreatment mean apparent diffusion coefficient and apparent diffusion coefficient histograms in prediction of outcome to chemoradiation in head and neck squamous cell carcinoma

Abstract: PURPOSE This study aimed to evaluate pretreatment whole-tumor mean apparent diffusion coefficient (ADC) and ADC histogram as predictors of outcome to chemoradiation in patients with head and neck squamous cell carcinoma (HNSCC). MATERIALS AND METHODS Patients with HNSCC underwent pretreatment 3-T diffusion-weighted magnetic resonance imaging with calculation of mean ADC and ADC histograms. Outcomes were determined 2 years after chemoradiation. Positive outcome was defined as no abnormal 18-fluoro deoxy glucose uptake on posttherapy computed tomography-positron emission tomography (or abnormal uptake that was proven benign), no locoregional recurrence or metastatic disease, and no requirement for salvage surgery. Negative outcome was defined as residual abnormal 18-fluoro deoxy glucose avidity that was proven malignant, salvage surgery requirement, locoregional recurrence or metastatic disease, death, or a combination of these. A 2-sample t test was used to compare the mean ADC between patients with positive and negative outcomes. The ADC cut point for dividing the groups was determined by looking at its distribution. A Kaplan-Meier plot was produced, and a log-rank test was conducted with calculation of sensitivity, specificity, and positive and negative predictive values. RESULTS Nine patients showed positive and 8 showed negative outcomes. Significant difference (P = 0.03) was seen in mean ADC (in 10 mm/s) between patients showing positive and negative outcomes (1.18 and 1.43, respectively). According to the log-rank test, tumors with greater than 45% of their volume below the ADC threshold of 1.15 × 10 mm/s were more likely to have a positive outcome (accuracy, 77%). CONCLUSIONS Patients with HNSCC demonstrating lower pretreatment ADC and with greater than 45% of volume below ADC threshold of 1.15 × 10 mm/s may have better outcome to chemoradiation at 2 years.

Comprehensive comparative study of computed tomography-based estimates of split renal function for potential renal donors: modified ellipsoid method and other CT-based methods.

Abstract: OBJECTIVE To investigate a new modified computed tomographic (CT) ellipsoid method of split renal function and to compare results from this method with other CT-derived metrics METHODS Thirty-eight potential renal donors with both CT and nuclear renography were retrospectively evaluated for estimated split function using 6 CT methods to determine accuracy For the CT methods, correlation, reproducibility, ease in image post-processing, and the ability of CT-derived methods to determine the dominant kidney before renal transplantation were evaluated using a nuclear renography reference standard RESULTS Four of the 6 CT methods (split renal volume, modified ellipsoid method, parenchymal area, attenuation capacity) showed similar strong correlation (r = 084-079) Bland-Altman analysis revealed similar performance in differences (SDs <30%) between those CT measures and reference standard, as well as good interobserver agreement for the modified ellipsoid and parenchymal area methods The technically simpler methods had inferior performance Post-processing time for the modified ellipsoid method was significantly shorter than semiautomated split renal volume or parenchymal area method (P < 001) Each CT-based method showed excellent agreement (100% or 974%) with renography regarding the determination of dominant kidney CONCLUSIONS Excellent correlation with nuclear split renal function supports the use of CT alone for the imaging assessment for many potential renal donors, including the decision of which kidney to harvest Among the CT-based methods, the modified ellipsoid method can be performed rapidly with high accuracy and reproducibility

Detection of prostate cancer with magnetic resonance imaging: optimization of T1-weighted, T2-weighted, dynamic-enhanced T1-weighted, diffusion-weighted imaging apparent diffusion coefficient mapping sequences and MR spectroscopy, correlated with biopsy and histopathological findings.

Abstract: PURPOSE The aim of this study was to optimize and predict the most efficient magnetic resonance imaging (MRI) sequences; T1-weighted (T1W), T2-weighted (T2W), dynamic contrast-enhanced (DCE) T1W, diffusion-weighted imaging (DWI) apparent diffusion coefficient (ADC) mapping sequences and proton MR spectroscopy (H-MRS) for the detection of prostate cancer. MATERIALS AND METHODS After institutional review board approval and informed consent taken from all the patients, 40 patients with prostate cancer were included in this research. Two readers independently evaluated the results of T1W, T2W, DCE T1W, and DWI-ADC mapping sequences and proton H-MRS for the depiction of prostate cancer. Reference standard was the transrectal ultrasonography-guided biopsy and the surgical histopathological results. Statistical analysis was assessed by the Fisher exact t test, Wilcoxon signed rank test, variance analysis test with kappa (κ) values and receiver operating characteristics (ROC) curve for ADC values, choline (Cho)/citrate (Cit) and Cho+creatine (Cre)/Cit ratios for each observer. RESULTS Based on both readers' results, sensitivity declined to 31% and specificity to 75% for the T1W sequence, sensitivity declined to 43% and specificity to 67% for the DCE T1W sequence, sensitivity declined to 46% and specificity to 68% for the T2W sequence, sensitivity declined to 29% and specificity to 82% for the DWI-ADC mapping; and specificity was 49% for the Cho/Cit and Cho+Cre/Cit ratios, sensitivity was 69% for the Cho/Cit ratio, and sensitivity was 70% for the Cho+Cre/Cit ratio for H-MRS. The T2W sequence and H-MRS presented significant statistical differences for the depiction of prostatic cancer (P < 0.05), the most efficient sequence to detect prostatic cancer was H-MRS: Cho+Cre/Cit and Cho/Cit ratios. CONCLUSION Instead of using either sequences alone owing to low sensitivity and specificity rates, combined use of MRI techniques could easily improve the detection and staging of prostate cancer.

Imaging studies of intraductal tubulopapillary neoplasms of the pancreas: 2-tone duct sign and cork-of-wine-bottle sign as indicators of intraductal tumor growth.

Abstract: Objective The objective of this study was to describe the imaging findings for intraductal tubulopapillary neoplasms of the pancreas. Methods Eleven pancreatic tumors pathologically confirmed as intraductal tubulopapillary neoplasm were retrospectively collected. The dynamic contrast-enhanced computed tomography (CT), magnetic resonance (MR) imaging including MR cholangiopancreatography (MRCP), ultrasound, and endoscopic retrograde cholangiopancreatography (ERCP) results were reviewed. The 2-tone duct sign and cork-of-wine-bottle sign were reviewed as indicators of intraductal tumor growth on CT/MR and MRCP/ERCP images, respectively. Results A 2-tone duct sign was noted on the dynamic CT images (7/10, 70%) and on the MR imaging (5/8, 63%). The distal main pancreatic duct was dilated in all the patients except one, who had a branch duct lesion. A cork-of-wine-bottle sign was observed on the MRCP image (3/8, 38%) and on the ERCP image (3/6, 50%). Conclusions Intraductal tubulopapillary neoplasms are rare tumors showing characteristic imaging findings such as the 2-tone duct sign and the cork-of-wine-bottle sign that represent their intraductal growth.

Hepatocellular carcinoma presenting at contrast-enhanced multi-detector-row computed tomography or gadolinium-enhanced magnetic resonance imaging as a small (2 cm), indeterminate nodule: growth rate and optimal interval time for imaging follow-up.

Abstract: OBJECTIVE: The objective of the study was to measure growth rate and to determine the optimal interval time for imaging follow-up of hepatocellular carcinomas (HCCs) presenting at multi-detector-row computed tomography (MDCT) or magnetic resonance imaging (MRI) as small, indeterminate lesions. METHODS: We included patients with cirrhosis with HCC initially presenting as indeterminate lesion of 2 cm or less at MDCT or MRI August 2005 to August 2009 and with available imaging follow-up. Measures of tumor growth included tumor volume doubling time (TVDT), tumor percentual diameter increase, and tumor percentual volume increase. RESULTS: We examined 48 patients (mean age, 64 years) with 69 HCCs. At index examination, mean (SD) maximum transverse diameter and volume of lesions were 1.2 (SD, 0.3) cm and 0.6 (SD, 0.7) cm, respectively. Median TVDT was 210 days. Tumors with follow-up longer than 365 days had significant increase in tumor percentual diameter increase and tumor percentual volume increase. CONCLUSIONS: Median TVDT of 210 days suggests extended follow-up of 6 months for small, indeterminate liver nodules detected at MDCT or MRI.

Computed tomographic perfusion imaging for the therapeutic response of chemoembolization for hepatocellular carcinoma.

Abstract: BACKGROUND Computed tomographic (CT) perfusion imaging has been applied in many clinical areas, but few studies have addressed the values of CT perfusion imaging in evaluating the therapeutic response of chemoembolization for hepatocellular carcinoma (HCC). OBJECTIVE To assess the perfusion changes of HCC after transarterial chemoembolization, and to investigate the values of CT perfusion imaging in chemoembolization procedure. METHODS Multidetector computed tomographic perfusion imaging was performed in 24 patients with HCC 1 week before and 4 weeks after chemoembolization. The CT perfusion parameters, including hepatic arterial perfusion (HAP), hepatic portal perfusion (HPP), total liver perfusion (TLP), and hepatic arterial perfusion index (HAPI), were calculated by using the slope method. The t statistic was used to analysis the difference of CT perfusion parameter values before and after chemoembolization therapy. RESULTS The values of HAP, TLP, and HAPI in tumors 4 weeks after chemoembolization were significantly decreased than those before chemoembolization (P 0.05). CONCLUSION Computed tomographic perfusion imaging has the ability to evaluate the perfusion changes in HCC after chemoembolization, which can be used to evaluate the therapeutic response of chemoembolization for hepatocellular carcinoma.

Diffusion tensor imaging provides an insight into the microstructure of meningiomas, high-grade gliomas, and peritumoral edema.

Abstract: OBJECTIVE Fractional anisotropy (FA) is a measure for the degree of microstructural organization. Several studies have used FA values to assess microstructural organization of brain tumors and peritumoral edema. The purpose of our study was to validate FA and apparent diffusion constant (ADC) values in the diagnosis of meningiomas versus high-grade glial tumors, with the focus on the ability of diffusion tensor imaging (DTI) to reveal tumor ultrastructure. Our hypothesis was that FA and ADC values significantly differ between high-grade gliomas and meningiomas, and in the peritumoral edema. METHODS Diffusion tensor imaging values were obtained from 20 patients with meningiomas (21 tumors) and 15 patients with high-grade gliomas. Regions of interest were outlined in FA and ADC maps for solid-enhancing tumor tissue and peritumoral edema. Fractional anisotropy and ADC values were normalized by comparison to normal-appearing white matter (NAWM) in the contralateral hemisphere. Differences between meningiomas and high-grade gliomas were statistically analyzed. RESULTS Meningiomas showed a significantly higher FA tumor/FA NAWM ratio (P = 0.0001) and lower ADC tumor/ADC NAWM ratio (P = 0.0008) compared to high-grade gliomas. On average, meningiomas also showed higher FA values in peritumoral edema than high-grade gliomas (P = 0.016). Apparent diffusion constant values of peritumoral edema for the 2 tumor groups did not differ significantly (P = 0.5). CONCLUSIONS Diffusion tensor imaging can be used to reveal microstructural differences between meningiomas and high-grade gliomas and may contribute toward predicting the histopathology of intracranial tumors. We advocate that diffusion tensor imaging should be included in the standard imaging protocol for patients with intracranial tumors.

Computed inverse resonance imaging for magnetic susceptibility map reconstruction.

Abstract: OBJECTIVE This article reports a computed inverse magnetic resonance imaging (CIMRI) model for reconstructing the magnetic susceptibility source from MRI data using a 2-step computational approach. METHODS The forward T2*-weighted MRI (T2*MRI) process is broken down into 2 steps: (1) from magnetic susceptibility source to field map establishment via magnetization in the main field and (2) from field map to MR image formation by intravoxel dephasing average. The proposed CIMRI model includes 2 inverse steps to reverse the T2*MRI procedure: field map calculation from MR-phase image and susceptibility source calculation from the field map. The inverse step from field map to susceptibility map is a 3-dimensional ill-posed deconvolution problem, which can be solved with 3 kinds of approaches: the Tikhonov-regularized matrix inverse, inverse filtering with a truncated filter, and total variation (TV) iteration. By numerical simulation, we validate the CIMRI model by comparing the reconstructed susceptibility maps for a predefined susceptibility source. RESULTS Numerical simulations of CIMRI show that the split Bregman TV iteration solver can reconstruct the susceptibility map from an MR-phase image with high fidelity (spatial correlation ≈ 0.99). The split Bregman TV iteration solver includes noise reduction, edge preservation, and image energy conservation. For applications to brain susceptibility reconstruction, it is important to calibrate the TV iteration program by selecting suitable values of the regularization parameter. CONCLUSIONS The proposed CIMRI model can reconstruct the magnetic susceptibility source of T2*MRI by 2 computational steps: calculating the field map from the phase image and reconstructing the susceptibility map from the field map. The crux of CIMRI lies in an ill-posed 3-dimensional deconvolution problem, which can be effectively solved by the split Bregman TV iteration algorithm.

Multidetector computed tomography for detection and characterization of pulmonary hypertension in consideration of WHO classification.

Abstract: OBJECTIVE We evaluated the reliability of various multidetector computed tomography (MDCT) parameters for diagnosis and severity assessment of pulmonary hypertension (PH) with consideration of World Health Organization (WHO) classification. METHODS A total of 172 patients were included in this retrospective study. One hundred fourteen patients had a diagnosis of PH (mean pulmonary artery pressure ≥25 mm Hg), and 58 patients without PH (mean pulmonary artery pressure <20 mm Hg) served as control subjects. The patients with PH were grouped according to the WHO classification based on PH etiology. RESULTS The patients with PH had significantly greater main, left, and right pulmonary artery diameters than the control subjects (P < 0.001). No significant differences within the PH subgroups were found. Receiver operating characteristic analysis showed reasonable sensitivity and specificity for selected MDCT parameters. The severity of PH did not correlate with MDCT parameters. CONCLUSIONS Easy-to-determine MDCT parameters allow detection of PH independent of the WHO group. In patients with dilated aorta, the vertebra can be an alternative internal standard. Severity of PH cannot be estimated by MDCT parameters.

Deformable anatomic templates embed knowledge into patient's brain images: Part 1. Construction and display.

Abstract: OBJECTIVE This paper describes the methods used to create annotated deformable anatomic templates (DATs) and display them in a patient's axial 2-dimensional and reformatted volume brain images. METHODS A senior neuroradiologist annotated and manually segmented 1185 color-coded structures on axial magnetic resonance images of a normal template brain using domain knowledge from multiple medical specialties. Besides the visible structures, detailed pathways for vision, speech, cognition, and movement were charted. This was done by systematically joining visible anatomic anchor points and selecting the best fit based on comparisons with cadaver dissections and the constraints defined on the companion 2-dimensional images. RESULTS The DAT is commercially available for use on a picture archiving and communication system or as a standalone workstation. CONCLUSIONS The DAT can quickly embed extensive, clinically useful functional neuroanatomic knowledge into the patient's brain images. Besides labeling visible structures, DAT displays clinically important, previously uncharted subdivisions of the fiber tracts.

The new 4-dimensional computed tomographic scanner allows dynamic visualization and measurement of normal acromioclavicular joint motion in an unloaded and loaded condition.

Abstract: OBJECTIVE Using 4-dimensional computed tomographic scanner to determine the motion pattern of the acromioclavicular (AC) joint during adduction of the arm, with and without resisted superior elevation. METHODS Sixteen healthy volunteers (5 women and 11 men; mean ± SD age, 42 ± 11 years). Four different motions were measured: AC joint width, anteroposterior translation, superoinferior translation, and opening of the superior aspect of the joint. Measurements between arm positions of neutral, adduction, and loaded were compared. RESULTS Predominant movement is posterior translation (1.1 ± 0.9 mm, P = 0.001); in the coronal plane, superior translation of the clavicle (0.6 ± 0.5 mm, P = 0.001) and some opening of the superior joint space. Changes in the AC joint width and anteroposterior translation were significantly related to age (P = 0.016 and P = 0.006). CONCLUSIONS Four-dimensional computed tomographic scans record the motion pattern of an asymptomatic AC joint and demonstrated that in adduction plus resisted elevation of the arm, the main movement of the AC joint is posterior and superior translation of the clavicle.

Organ-based computed tomographic (CT) radiation dose reduction to the lenses: impact on image quality for CT of the head.

Abstract: PURPOSE Recently, a new specific organ dose adaption and reduction protocol, or SODAR tool (X-CARE, Siemens Healthcare), which reduces dose to the anterior aspect of the body of patients, was installed on our computed tomographic scanner. The purpose of this pilot project was to evaluate image quality and dose distribution in the acquired data with the new protocol. MATERIALS AND METHODS Sixteen consecutive patients were scanned with the new SODAR head protocol. The findings were compared with 16 matched patients who were imaged with the standard computed tomographic head trauma protocol. Image quality was assessed qualitatively using a scale of 1 to 4 (1, excellent; 2, good; 3, fair; 4, nondiagnostic). Additionally, 1-cm regions of interest were placed in the white matter of the cerebral hemispheres, the cerebellar hemispheres, and the brain stem at the level of the pons for a quantitative analysis. The standard deviation of each measurement was recorded as an indicator for image noise. Dose measurement trials were performed using optically stimulated luminescence dosimeters on head phantoms and then on patients. RESULTS Subjective image quality ranged between 1 and 3; no scan areas were considered nondiagnostic. Overall image quality of the posterior fossa averaged at 1.656 was slightly reduced compared to the cerebral hemispheres (mean, 1.141). The mean standard protocol brain stem image quality was 1.604, with only minimal deterioration to 1.708 in the SODAR group.No significant difference in image noise could be found between the SODAR group with a mean noise of 4.515 and standard images with a mean of 4.721 (P > 0.05).The dose to the anterior aspect of the patient was lowered to 3.2 mGy compared to 4.5 mGy on the lateral aspect of the scan (P > 0.05). To compensate for the photon loss in the posterior aspect, the dose has to be slightly increased to a mean of 6 mGy, but overall, a significant dose reduction with stable image quality could be achieved by reducing the dose length product from 1489 to 1347 mGy·cm using SODAR (P < 0.0001). CONCLUSION Using the SODAR protocol resulted not only in an impressive 46% to 59% frontal dose reduction but also in the overall dose reduction. This dose reduction was obtained without sacrificing image quality, providing diagnostic images of the brain while protecting radiosensitive structures like the eye lenses in trauma brain imaging. Future applications will be reducing dose to other radiosensitive structures such as the thyroid gland and breast tissue from potentially harmful low-energy radiation without compromising image quality.

Multifocal micronodular pneumocyte hyperplasia: computed tomographic appearance and follow-up in tuberous sclerosis complex.

Abstract: Objective To characterize pulmonary nodules in patients with tuberous sclerosis complex (TSC) using computed tomography. Methods We retrospectively reviewed chest computed tomographic images of 73 patients with TSC (22 males and 51 females; mean ± SD age, 31.5 ± 13.2 years; range, 13.8-63.5 years). Results Multiple pulmonary nodules were identified in 42 (58%) of 73 patients (mean ± SD size, 6.6 ± 3.0 mm; range, 2-14 mm). Solid nodules were present in 11 (26%) of 42 patients, ground-glass nodules were present in 3 (7%) of 42 patients, and both solid and ground-glass nodules were present in 28 (67%) of 42 patients. The presence of multiple nodules was independent of sex and lymphangioleiomyomatosis. Follow-up images were available for 22 patients with multiple nodules (mean ± SD follow-up, 2.0 ± 1.1 years; range, 0.9-4.9 years), none of whom had change in nodule size or number. Conclusions Most men and women with TSC have multiple pulmonary nodules, which likely represent multifocal micronodular pneumocyte hyperplasia in the absence of known predisposing factors.

Diffusion tensor magnetic resonance imaging of rat glioma models: A correlation study of MR imaging and histology

Abstract: Introduction Diffusion tensor magnetic resonance (MR) imaging (DTI) can be used to characterize the microstructures of ordered biological tissues. This study was designed to assess histological features of gliomas and surrounding brain tissues in rats using DTI. Methods Three types of tumors, a 9L gliosarcoma (n = 8), a F98 glioma (n = 5), and a human glioblastoma xenograft (GBM22; n = 8) were incubated in rat brains and underwent conventional MRI and DTI scanning using a 4.7-T animal MRI system. Fractional anisotropy (FA), isotropic apparent diffusion coefficient, parallel diffusivity (λ//), and perpendicular diffusivity (λ⊥), as well as histological features within several regions of interest were analyzed. Results All tumor masses consisted of low-FA central zones (tumor center) and high-FA peripheral regions (tumor rim). Histological examination revealed the existence of highly coherent tumor organizations (circular for 9L and F98 or radial for GBM22) in the tumor rims. There were higher apparent diffusion coefficient, λ⊥, and λ// in the peritumoral edema compared to the contralateral gray matter. There were significantly lower FA and higher λ⊥ in the ipsilateral white matter than in the contralateral white matter for the GBM22 tumor, whereas there were no differences for the 9L and F98 tumors. Histologic examination showed GBM22 tumor infiltration into the ipsilateral damaged white matter. Conclusions Quantitative analysis of DTI indices provides useful information for assessing tumor microstructure and tumor cell invasion into the adjacent gray matter and white matter.

Computed tomography findings of influenza A (H1N1) pneumonia in adults: pattern analysis and prognostic comparisons.

Abstract: AIM The aim of this study was to evaluate retrospectively the chest computed tomography findings of influenza A (H1N1) pneumonia and their relationship with clinical outcome. METHODS Chest computed tomography findings and clinical outcomes of 76 patients with influenza A (H1N1) pneumonia were assessed. Computed tomography findings were evaluated for the presence and distribution of parenchymal abnormalities, which were then classified into 3 patterns: bronchopneumonia, cryptogenic organizing pneumonia (COP), and acute interstitial pneumonia (AIP) patterns. Clinical courses were divided into 2 groups on the basis of necessitating admission to intensive care unit or mechanical ventilation therapy (group 1) or not (group 2). RESULTS Lung abnormalities consisted of ground-glass opacity (93%, 71 patients), consolidation (66%, 50 patients), small nodules (61%, 46 patients), and tree-in-bud sign (22%, 17 patients). Lesions were classified into bronchopneumonia (49%, 37 patients), COP (30%, 23 patients), AIP (18%, 14 patients), and unclassifiable (3%, 2 patients) patterns. Patients with AIP pattern had a tendency to belonging to group 1, accounting for 40% (8 of 20 patients) of group 1 course and only 11% (6 of 56 patients) of group 2 course (P = 0.004). CONCLUSIONS Computed tomography findings of influenza A (H1N1) pneumonia in adults can be classified into COP, AIP, and bronchopneumonia patterns. Patients presenting with AIP pattern have a tendency to show poor prognosis.

Imaging features and pathologic characteristics of ovarian thecoma.

Abstract: Objective To analyze the imaging findings of ovarian thecoma and to better understand the tumor features based on aspect of computed tomography and magnetic resonance images. Methods Nineteen ovarian thecomas confirmed by histopathologic examination were analyzed retrospectively. Image characteristics were analyzed and compared with those of the pathologic features. Results The mean diameter of tumors was 9.6 cm. The masses were well defined (n = 17) or ill defined (n = 2) and appeared solid with cystic areas (n = 11), entirely solid (n = 4), or cystic with solid components (n = 4). On T2-weighted/spectral adiabatic inversion recovery (T2WI/SPAIR) images, 12 cases appeared isointense or slightly hyperintense. Of the 12 cases, 8 had patchy hypersignal areas. On computed tomographic images, 7 cases showed hypodensity or isodensity. All tumors exhibited mild enhancement. On pathologic examination, the tumor was composed of spindle cells with a moderate amount of cytoplasm. Conclusion Imaging manifestations of ovarian thecoma are various and nonspecific. However, a large, well-defined mildly enhanced solid mass with cystic areas and especially isointense or slightly hyperintense on T2WI/SPAIR sequence in pelvic cavity may suggest the diagnosis of ovarian thecoma.

Toward biphasic computed tomography (CT) enteric contrast: material classification of luminal bismuth and mural iodine in a small-bowel phantom using dual-energy CT.

Abstract: OBJECTIVE: To develop dual-energy computed tomography methods for identification of hyperenhancing, hypoenhancing, and nonenhancing small-bowel pathologies. METHODS: Small-bowel phantoms simulating varying patient sizes and polyp types (hyperenhancing, hypoenhancing, and nonenhancing) contained bismuth suspension in the lumen. Dual-energy CT was performed at 80/140 kV and 100/140 kV. Computed tomographic number ratios (CT numbers at low/high kilovoltage) were calculated. Two radiologists evaluated polyp detection and conspicuity using bismuth-only, iodine-only, iodine-overlay, and mixed-kilovoltage displays. RESULTS: Computed tomographic ratios for bismuth and iodine did not overlap. For hyperenhancing and nonenhancing polyps at 80/140 kV, iodine-overlay display yielded higher detection rate (96%, 94%) and conspicuity score (3.5, 3.1) than mixed-kilovoltage images (88%, 68%; 1.5, 2.7). Mixed-kV images performed slightly better for hypoenhancing polyps (92%, 3.4 vs. <80%, <2.9). Similar results were observed at 100/140kV. CONCLUSIONS: Dual-energy CT and a bismuth-containing enteric contrast permitted simultaneous identification of hyperenhancing, hypoenhancing, and nonenhancing polyps over a range of patient sizes.

Effect of in utero exposure of iodinated intravenous contrast on neonatal thyroid function.

Abstract: Purpose Administration of radioactive iodine to a pregnant woman for thyroid ablation has been shown to affect neonatal thyroid levels. Thus, there is a theoretical risk in affecting a neonate's thyroid level upon birth with prior administration of intravenous contrast containing iodine to a pregnant woman during a computed tomographic scan. However, there is no literature to support this theoretical risk. This study attempted to determine if there is any effect on a newborn's thyroid levels after exposure to this type of contrast material in utero. Materials and methods The medical charts of 96 pregnant women during the years 2004 through 2009 on whom computed tomographic scans were performed were reviewed. A total of 29 charts were excluded secondary to missing neonatal records, missed abortions, and intrauterine fetal demise. The rest were subdivided into those who received intravenous (IV) ± oral contrast material and those who did not. The medical records of the newborns of these patients were also reviewed. The subject group consisted of 61 pregnant women who received IV ± oral contrast and their 64 neonates. The control group consisted of 6 pregnant patients who did not receive IV contrast and their 6 neonates. Results Of the 64 neonates in the subject group, only one neonate was found to have a low thyroxine level with a normal thyroid stimulating hormone level. This infant was severely premature, being born at the 25th week of gestation, and developed respiratory distress syndrome and sepsis, which were potential confounding factors. All of the 6 neonates in the control group had normal thyroid levels. Conclusion This study concludes that there is no significant adverse clinical risk of thyroid function abnormalities to the fetus after IV iodinated contrast material to their mothers.