Materials and Methods. This retrospective study was approved by the institutional ethics committee, and informed consent was waived. Twenty consecutive patients with ischemic stroke who un- derwent CT perfusion imaging with a 320–detector row CT scanner were included. A standard acquisition proto- col was used, which was started 5 seconds after injection of a contrast agent, with a scan at 200 mAs, followed after 4 seconds by 13 scans, one every 2 seconds, at 100 mAs, and then five scans, one every 5 seconds, at 75 mAs. The total examination had an average effective dose of 5.0 mSv. For each patient, a patient-specific digital perfusion phantom was constructed to simulate the same protocol at a lower total dose (0.5–5.0 mSv, with stepped doses of 0.5 mSv). The lowest setting for which the maximum mean difference remained within 5% of the reference standard (at 5.0 mSv) was marked as the optimal setting. At the optimal setting, Xxxxxxx correlation coefficients were cal- culated to assess correlations with the reference values, and paired t tests were performed to compare the means.
Materials and Methods. The requirement for institutional review board approval was waived. Intra- and interpatient variation of PZ ADCs was determined by means of repeated measurements of normal ADCs at three magnetic resonance (MR) examina- tions in a retrospective cohort of 10 consecutive patients who had high prostate-specific antigen levels and negative findings at transrectal ultrasonographically-guided biopsy. In these patients, no signs of PZ cancer were found at all three MR imaging sessions. The effect of interpatient variation on the assessment of prostate cancer aggressive- ness was examined in a second retrospective cohort of 51 patients with PZ prostate cancer. Whole-mount step- section pathologic evaluation served as reference standard for placement of regions of interest on tumors and normal PZ. Repeated-measures analysis of variance was used to determine the significance of the interpatient variations in ADCs. Linear logistic regression was used to assess whether incorporating normal PZ ADCs improves the pre- diction of cancer aggressiveness.
Materials and Methods. SSNs on all baseline computed tomographic (CT) scans from the National Lung Cancer Trial that would have been classified as Lung-RADS category 3 or higher were iden- tified, resulting in 374 SSNs for analysis. An experienced screening radiologist volumetrically segmented all solid cores and located all malignant SSNs visible on baseline scans. Six experienced chest radiologists independently determined which nodules to upgrade to category 4X, a recently introduced category for lesions that demonstrate additional features or imaging findings that increase the suspicion of malignancy. Malignancy rates of purely size- based categories and category 4X were compared. Fur- thermore, the false-positive rates of category 4X lesions were calculated and observer variability was assessed by using Fleiss k statistics. Results: The observers upgraded 15%–24% of the SSNs to cate- gory 4X. The malignancy rate for 4X nodules varied from 46% to 57% per observer and was substantially higher than the malignancy rates of categories 3, 4A, and 4B SSNs without observer intervention (9%, 19%, and 23%, respectively). On average, the false-positive rate for cat- egory 4X nodules was 7% for category 3 SSNs, 7% for category 4A SSNs, and 19% for category 4B SSNs. Of the falsely upgraded benign lesions, on average 27% were transient. The agreement among the observers was mod- erate, with an average k value of 0.535 (95% confidence interval: 0.509, 0.561).
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Materials and Methods. The study had ethics committee approval, and a nested case-control design was used and included 55 patients with lung cancer detected at computed tomography (CT) and confirmed with histologic examination and a sample of 72 of 4873 control subjects without nodules at CT. All patients underwent direct-detector digital chest radiogra- phy in two projections within 2 months of the screening CT. Four radiologists with varying experience identified and localized potential cancers on chest radiographs by using a confidence scale of level 1 (no lesion) to 5 (defi- nite lesion). Localization receiver operating characteristic (ROC) analysis was performed. On the basis of the as- sumption that suspicious lesions seen at chest radiogra- phy would lead to further work-up with CT, the number of work-up CT examinations per detected cancer (CT exami- nations per cancer) was calculated at various confidence levels for the screening population (cancer rate in study population, 1.3%). Results: Tumor size ranged from 6.8 to 50.7 mm (median, 11.8 mm). Areas under the localization ROC curve ranged from 0.52 to 0.69. Detection rates substantially varied with the observers’ experience and confidence level: At a confidence level of 5, detection rates ranged from 18% at one CT examination per cancer to 53% at 13 CT exami- nations per cancer. At a confidence level of 2 or higher, detection rates ranged from 94% at 62 CT examinations per cancer to 78% at 44 CT examinations per cancer.
Materials and Methods. The requirement to obtain institutional review board ap- proval was waived. Fifty-one patients with prostate cancer underwent MR imaging before prostatectomy, including DW MR imaging with b values of 0, 50, 500, and 800 sec/mm2. In prostatectomy specimens, separate slice-by-slice determi- nations of Xxxxxxx grade groups were performed accord- ing to primary, secondary, and tertiary Xxxxxxx grades. In addition, tumors were classified into qualitative grade groups (low-, intermediate-, or high-grade tumors). ADC maps were aligned to step-sections and regions of inter- est annotated for each tumor slice. The median ADC of tumors was related to qualitative grade groups with lin- ear mixed-model regression analysis. The accuracy of the median ADC in the most aggressive tumor component in the differentiation of low- from combined intermediate- and high-grade tumors was summarized by using the area under the receiver operating characteristic (ROC) curve (Az). Results: In 51 prostatectomy specimens, 62 different tumors and 251 step-section tumor lesions were identified. The me- xxxx ADC in the tumors showed a negative relationship with Xxxxxxx grade group, and differences among the three quali- tative grade groups were statistically significant (P , .001). Overall, with an increase of one qualitative grade group, the median ADC (6standard deviation) decreased 0.18 3 1023 mm2/sec 6 0.02. Low-, intermediate-, and high-grade tumors had a median ADC of 1.30 3 1023 mm2/sec 6 0.30, 1.07 3 1023 mm2/sec 6 0.30, and 0.94 3 1023 mm2/sec 6 0.30, respectively. ROC analysis showed a discriminatory performance of Az = 0.90 in discerning low-grade from combined intermediate- and high-grade lesions. Conclusion: ADCs at 3.0 T showed an inverse relationship to Xxxxxxx grades in peripheral zone prostate cancer. A high discrim- inatory performance was achieved in the differentiation of low-, intermediate-, and high-grade cancer. q RSNA, 2011 Xxxxxx Xxxxxxxx, MBChB Xxxxxxxx X. Xxxxxxx, MD Xxxxxxx X. Huisman, MSEE, PhD Xxxx X. xxx Xxxx, MD, PhD
Materials and Methods. The institutional review board approved this study and waived the need for informed consent. A retrospective cohort of 70 patients (age range, 48–70 years; median, 62 years), all of whom were scheduled to undergo radi- cal prostatectomy and underwent preoperative 3-T multi- parametric magnetic resonance (MR) imaging, including T2-weighted, diffusion-weighted, and dynamic contrast material–enhanced imaging, were included. The digi- tized prostatectomy slides were annotated for cancer and noncancerous disease and coregistered to MR imaging with an interactive deformable coregistration scheme. Computer-identified features for each of the noncancer- ous disease categories (eg, benign prostatic hyperplasia [BPH], prostatic intraepithelial neoplasia [PIN], inflam- mation, and atrophy) and prostate cancer were extracted. Feature selection was performed to identify the features with the highest discriminatory power. The performance of these five features was evaluated by using the area un- der the receiver operating characteristic curve (AUC). Results: High-b-value diffusion-weighted images were more discrim- inative in distinguishing BPH from prostate cancer than apparent diffusion coefficient, which was most suitable for distinguishing PIN from prostate cancer. The focal appear- ance of lesions on dynamic contrast-enhanced images may help discriminate atrophy and inflammation from cancer. Which imaging features are discriminative for different be- nign lesions is influenced by cancer grade. The apparent diffusion coefficient appeared to be the most discriminative feature in identifying high-grade cancer. Classification re- sults showed increased performance by taking into account specific benign types (AUC = 0.70) compared with grouping all noncancerous findings together (AUC = 0.62).
Materials and Methods. As part of the ethics-committee approved Dutch-Belgian Randomised Lung Cancer Multi-Slice Screening Trial (XXXXXX), computed tomography (CT) was used to screen 2994 current or former heavy smokers, aged 50– 74 years, for lung cancer. CT was repeated after 1 and 3 years, with additional follow-up CT scans if necessary. All baseline CT scans were screened for nodules. Nodule vol- ume was determined with automated volumetric analysis. Homogeneous solid nodules, attached to a fissure with a lentiform or triangular shape, were classified as PFNs. Nodules were considered benign if they did not grow dur- ing the total follow-up period or were proved to be benign in a follow-up by a pulmonologist. Prevalence, growth, and malignancy rate of PFNs were assessed. Results: At baseline screening, 4026 nodules were detected in 1729 participants, and 19.7% (794 of 4026) of the nod- ules were classified as PFNs. The mean size of the PFNs was 4.4 mm (range: 2.8–10.6 mm) and the mean volume was 43 mm3 (range: 13–405 mm3). None of the PFNs were found to be malignant during follow-up. Between baseline and the first follow-up CT scan, 15.5% (123 of 794) were found to have grown, and 8.3% (66 of 794) had a volume doubling time of less than 400 days. One PFN was resected and proved to be a lymph node. Conclusion: PFNs are frequently found at CT scans for lung cancer. They can show growth rates in the range of malignant nodules, but none of the PFNs in the present study turned out to be malignant. Recognition of PFNs can reduce the number of follow-up examinations required for the workup of suspicious nodules. q RSNA, 2012 of Malignancy1
Materials and Methods. Twenty APEC isolates were selected and subjected to four different susceptibility tests: the quantitative microbroth dilution, agar dilution and gradient strip tests and the qualitative disk diffusion method. The experiments were performed in triplicate. Categorical agreement, essential agreement and different errors were assessed. Moreover, agreement was also evaluated by calculating intraclass correlation coefficients (ICCs) for the quantitative tests and determining the Xxxxxxx correlation coefficients for the agreement between the disk diffusion method and the quantitative tests. Results: Categorical agreement and essential agreement when compared with the microbroth technique ranged from 85-95% and 85-100%, respectively. No very major errors (false susceptible) and only one major error (false resistant) and minor errors (results involving an intermediary category) were detected. The calculated ICC values of the three quantitative tests fluctuated around 0.970 (range 0.940 to 0.988). There was a high negative correlation between the disk diffusion method and the other tests (correlation coefficients ranging from -0.979 to -0.940), indicating a clear inverse relationship between the MIC value and the zone diameter of growth inhibition.
Materials and Methods. The study design was approved by the Institutional Review Board of the Xxxxx x Xxxxx Hospital. According to Span- ish law, for this type of study, no informed consent was necessary. Five radiologists from three hospitals twice in- terpreted lumbar MR examination results in 53 patients with low back pain, with at least a 14-day interval between assessments. Radiologists were unaware of the clinical and demographic characteristics of the patients and of their colleagues’ assessments. At the second assessment, they were unaware of the results of the first assessment. Reports on Xxxxx changes, osteophytes, Schmorl nodes, diffuse defects, disk degeneration, annular tears (high- signal-intensity zones), disk contour, spondylolisthesis, and spinal stenosis were collected by using the Spanish version of the Nordic Xxxxx Consensus Group classifica- tion. The k statistic was used to assess intra- and inter- observer agreement for findings with a prevalence of 10% or greater and 90% or lower. k was categorized as almost perfect (0.81–1.00), substantial (0.61–0.80), moderate (0.41–0.60), fair (0.21–0.40), slight (0.00–0.20), or poor (,0.00).
Materials and Methods. In this ethics committee–approved study, 46 individuals with 49 computed tomographically (CT)-detected and his- tologically proved lung cancers and 65 patients without nodules at CT were retrospectively included. All subjects participated in a lung cancer screening trial. Chest radio- graphs were obtained within 2 months after screening CT. Four radiology residents and two experienced radiologists were asked to identify and localize potential cancers on the chest radiographs, first without and subsequently with the use of CAD software. A figure of merit was calculated by using free-response receiver operating characteristic analysis. Results: Tumor diameter ranged from 5.1 to 50.7 mm (median, 11.8 mm). Fifty-one percent (22 of 49) of lesions were subtle and detected by two or fewer readers. Stand-alone CAD sensitivity was 61%, with an average of 2.4 false- positive annotations per chest radiograph. Average sen- sitivity was 63% for radiologists at 0.23 false-positive annotations per chest radiograph and 49% for residents at 0.45 false-positive annotations per chest radiograph. Figure of merit did not change significantly for any of the observers after using CAD. CAD marked between five and 16 cancers that were initially missed by the readers. These correctly CAD-depicted lesions were rejected by radiolo- gists in 92% of cases and by residents in 77% of cases.