Yoshiko Ueno

Clinical utility of apparent diffusion coefficient values obtained using high b-value when diagnosing prostate cancer using 3 tesla MRI: Comparison between ultra-high b-value (2000 s/mm2) and standard high b-value (1000 s/mm2)

To determine whether the apparent diffusion coefficient (ADC) obtained using b = 2000 s/mm2 upon 3 Tesla (T) diffusion‐weighted MRI is superior to b = 1000 s/mm2 for discriminating malignant from normal prostate tissue and predicting the aggressiveness of prostate cancer, using histopathological findings of radical prostatectomy as a reference.

Value of fusion of PET and MRI for staging of endometrial cancer: Comparison with 18F-FDG contrast-enhanced PET/CT and dynamic contrast-enhanced pelvic MRI

PURPOSE To investigate the diagnostic value of retrospective fusion of pelvic MRI and (18)F-fluorodeoxyglucose ((18)F-FDG) PET images for assessment of locoregional extension and nodal staging of endometrial cancer. MATERIALS AND METHODS Thirty patients with biopsy-proven endometrial cancer underwent preoperative contrast-enhanced PET/CT (PET/ceCT) and pelvic dynamic contrast-enhanced MRI for initial staging. Diagnostic performance of PET/ceCT, contrast-enhanced MRI, and retrospective image fusion from PET and MRI (fused PET/MRI) for assessing the extent of the primary tumor (T stage) and metastasis to regional LNs (N stage) was evaluated by two experienced readers. Histopathological and follow-up imaging results were used as the gold standard. The McNemar test was employed for statistical analysis. RESULTS Fused PET/MRI and MRI detected 96.7% of the primary tumors, whereas PET/ceCT detected 93.3%. Accuracy for T status was 80.0% for fused PET/MRI, and MRI proved significantly more accurate than PET/ceCT, which had an accuracy of 60.0% (p=0.041). Patient-based sensitivity, specificity and accuracy for detecting pelvic nodal metastasis were 100%, 96.3% and 96.7% for both fused PET/MRI and PET/ceCT, and 66.7%, 100% and 96.7% for MRI, respectively. These three parameters were not statistically significant (p=1). CONCLUSION Fused PET/MRI, which complements the individual advantages of MRI and PET, is a valuable technique for assessment of the primary tumor and nodal staging in patients with endometrial cancer.

Ultra‐high b‐value diffusion‐weighted MRI for the detection of prostate cancer with 3‐T MRI

To determine, with histopathological findings of radical prostatectomy as reference, whether diffusion‐weighted imaging (DWI) using b = 2000 s/mm2 for 3‐T magnetic resonance imaging (MRI) is superior to the use of b = 1000 s/mm2 for prostate cancer detection.

Fusion of PET and MRI for staging of uterine cervical cancer: comparison with contrast-enhanced (18)F-FDG PET/CT and pelvic MRI.

PURPOSE To investigate the fusion of pelvic magnetic resonance imaging (MRI) and fluorodeoxyglucose positron emission tomography (PET) for assessment of locoregional extension and nodal staging of cervical cancer. METHODS PET/computed tomography (CT), MRI, and non-fused and fusion of PET and MRI for assessing the extent of the primary tumor and metastasis to nodes were evaluated. RESULTS Accuracy for T-status was 83.3% for fused and non-fused PET/MRI and MRI proved significantly more accurate than PET/CT (53.3%) (P=.0077). Sensitivity, specificity, and accuracy for nodal metastasis were 92.3%, 88.2%, and 90.0% for fused PET/MRI and PET/contrast-enhanced CT; 84.6%, 94.1%, and 90.0% for non-fused PET/MRI; and 69.2%, 100%, and 86.7% for MRI. CONCLUSION Fused PET/MRI combines the individual advantages of MRI and PET.

Low-dose non-enhanced CT versus full-dose contrast-enhanced CT in integrated PET/CT scans for diagnosing ovarian cancer recurrence.

OBJECTIVE To evaluate low-dose non-enhanced CT (ldCT) and full-dose contrast-enhanced CT (ceCT) in integrated 18F-fluorodeoxyglucose (FDG)-PET/CT studies for restaging of ovarian cancer. MATERIALS AND METHODS One hundred and twenty women who had undergone treatment for ovarian cancer underwent a conventional PET/CT scans with ldCT, and then ceCT. Two observers interpreted and decided in consensus on the PET/ldCT and PET/ceCT images by a 3-point scale (N: negative, E: equivocal, P: positive) per patient and lesion site. Final diagnoses were obtained by histopathological examinations, or clinical follow-up for at least 6 months. RESULTS Patient-based analysis showed that the sensitivity, specificity, and accuracy of PET/ceCT was 86.9% (40/46), 95.9% (71/74), and 92.5% (111/120), respectively, whereas those of PET/ldCT were 78.3% (36/46), 95.0% (70/74), and 88.3% (106/120), respectively. All sensitivity, specificity, and accuracy significantly differed between two methods (McNemar test, p<0.0005, p=0.023, and p<0.0001, respectively). The scales of detecting 104 recurrent lesion sites were N:14, E:6, P:84 for PET/ceCT, and N:15, E:17, P:72 for PET/ldCT, respectively. Eleven equivocal and one negative regions by PET/ldCT were correctly interpreted as positive by PET/ceCT. CONCLUSION PET/ceCT is a more accurate imaging modality with higher confidence for assessing ovarian cancer recurrence than PET/ldCT.

Do apparent diffusion coefficient (ADC) values obtained using high b-values with a 3-T MRI correlate better than a transrectal ultrasound (TRUS)-guided biopsy with true Gleason scores obtained from radical prostatectomy specimens for patients with prostate cancer?

OBJECTIVE To investigate the usefulness of apparent diffusion coefficient (ADC) values in predicting true Gleason scores from radical prostatectomy specimen (tGS), compared with systematic transrectal ultrasound (TRUS)-guided biopsy GS (bGS). MATERIALS AND METHODS One hundred and five patients with biopsy-proven prostate cancer underwent preoperative DWI (b-values of 0, 1000, and 2000s/mm(2)) of 3-T MRI. The mean and minimum ADCs of visible tumors were calculated for either of a pair of b-values: 0 and 1000s/mm(2) (ADC1000), or 0 and 2000s/mm(2) (ADC2000), and relationships between the four ADC parameters and tGS evaluated for the peripheral zone (PZ) and transition zone (TZ). For multiple tumors, the dominant tumors GS and ADCs were estimated for cancer aggressiveness assessment by computing ROC curves. RESULTS Significant negative correlations were observed between tGS and mean ADC1000, mean ADC2000, minimum ADC1000, and minimum ADC2000 (r=-0.41, -0.39, -0.39, and -0.37, respectively) of 100 visible PZ tumors and 66 visible TZ tumors (r=-0.40, -0.42, -0.29, and -0.21, respectively). For distinguishing high-grade from low/intermediate-grade PZ lesions, the areas under the curve (AUCs) of mean ADC1000 (0.751), mean ADC2000 (0.710), minimum ADC1000 (0.768), and minimum ADC2000 (0.752) were similar to that of the highest bGS (0.708) (p=0.61, p=0.98, p=0.47, and p=0.60, respectively). For distinguishing high-grade from low/intermediate-grade TZ lesions, AUCs of mean ADC1000 (0.779), and mean ADC2000 (0.811) were similar to that of the highest bGS (0.805) (p=0.83 and p=0.97). CONCLUSION Tumor ADCs obtained with high b-values could predict prostate cancer aggressiveness as effectively as systematic TRUS-guided biopsy.

Recent topics related to nephrogenic systemic fibrosis associated with gadolinium‐based contrast agents

Nephrogenic systemic fibrosis is a progressive, potentially fatal, multiorgan‐system fibrosing disease related to exposure of patients with renal failure to gadolinium‐based contrast agents used in magnetic resonance imaging. Between 1997 and 2007, more than 500 cases of nephrogenic systemic fibrosis in patients with severe renal insufficiency (glomerular filtration rate less than 30 mL/min/1.73 m2) were reported, and no known cases of nephrogenic systemic fibrosis have occurred in patients with a glomerular filtration rate of more than 30 mL/min/1.73 m2 without acute kidney injury. Additional major risk factors are use of high‐dose and specific gadolinium‐based contrast agents, a pro‐inflammatory state. Although the mechanism of nephrogenic systemic fibrosis is unclear and there is no consistently‐effective therapy, nephrogenic systemic fibrosis is an entity that can be eliminated by observing recent recommended guidelines for gadolinium‐based contrast agents and nephrogenic systemic fibrosis. This article reviews current knowledge about nephrogenic systemic fibrosis and focuses mainly on how to prevent it.

Endometrial Carcinoma: MR Imaging–based Texture Model for Preoperative Risk Stratification—A Preliminary Analysis

Purpose To evaluate the associations among mathematical modeling with the use of magnetic resonance (MR) imaging-based texture features and deep myometrial invasion (DMI), lymphovascular space invasion (LVSI), and histologic high-grade endometrial carcinoma. Materials and Methods Institutional review board approval was obtained for this retrospective study. This study included 137 women with endometrial carcinomas measuring greater than 1 cm in maximal diameter who underwent 1.5-T MR imaging before hysterectomy between January 2011 and December 2015. Texture analysis was performed with commercial research software with manual delineation of a region of interest around the tumor on MR images (T2-weighted, diffusion-weighted, and dynamic contrast material-enhanced images and apparent diffusion coefficient maps). Areas under the receiver operating characteristic curve and diagnostic performance of random forest models determined by using a subset of the most relevant texture features were estimated and compared with those of independent and blinded visual assessments by three subspecialty radiologists. Results A total of 180 texture features were extracted and ultimately limited to 11 features for DMI, 12 for LVSI, and 16 for high-grade tumor for random forest modeling. With random forest models, areas under the receiver operating characteristic curve, sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were estimated at 0.84, 79.3%, 82.3%, 81.0%, 76.7%, and 84.4% for DMI; 0.80, 80.9%, 72.5%, 76.6%, 74.3%, and 79.4% for LVSI; and 0.83, 81.0%, 76.8%, 78.1%, 60.7%, and 90.1% for high-grade tumor, respectively. Sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of visual assessment for DMI were 84.5%, 82.3%, 83.2%, 77.7%, and 87.8% (reader 3). Conclusion The mathematical models that incorporated MR imaging-based texture features were associated with the presence of DMI, LVSI, and high-grade tumor and achieved equivalent accuracy to that of subspecialty radiologists for assessment of DMI in endometrial cancers larger than 1 cm. However, these preliminary results must be interpreted with caution until they are validated with an independent data set, because the small sample size relative to the number of features extracted may have resulted in overfitting of the models.

Triexponential function analysis of diffusion‐weighted MRI for diagnosing prostate cancer

To evaluate more detailed information noninvasively through on diffusion and perfusion in prostate cancer (PCa) using triexponential analysis of diffusion‐weighted imaging (DWI).

Chemical Exchange Saturation Transfer MR Imaging: Preliminary Results for Differentiation of Malignant and Benign Thoracic Lesions

PURPOSE To prospectively evaluate the capability of amide proton transfer-weighted chemical exchange saturation transfer magnetic resonance (MR) imaging for characterization of thoracic lesions. MATERIALS AND METHODS The institutional review board approved this study, and written informed consent was obtained from 21 patients (13 men and eight women; mean age, 72 years) prior to enrollment. Each patient underwent chemical exchange saturation transfer MR imaging by using respiratory-synchronized half-Fourier fast spin-echo imaging after a series of magnetization transfer pulses. Next, a magnetization transfer ratio asymmetry at 3.5 ppm map was computationally generated. Pathology examinations resulted in a diagnosis of 13 malignant and eight benign thoracic lesions. The malignant lesions were further diagnosed as being nine lung cancers, comprising six adenocarcinomas, three squamous cell carcinomas, and four other thoracic malignancies. The Student t test was used to evaluate the capability of magnetization transfer ratio asymmetry (at 3.5 ppm), as assessed by means of region of interest measurements, for differentiating benign and malignant lesions, lung cancers and other thoracic lesions, and adenocarcinomas and squamous cell carcinomas. RESULTS Magnetization transfer ratio asymmetry (at 3.5 ppm) was significantly higher for malignant tumors (mean ± standard deviation, 3.56% ± 3.01) than for benign lesions (0.33% ± 0.38, P = .008). It was also significantly higher for other thoracic malignancies (6.71% ± 3.46) than for lung cancer (2.16% ± 1.41, P = .005) and for adenocarcinoma (2.88% ± 1.13) than for squamous cell carcinoma (0.71% ± 0.17, P = .02). CONCLUSION Amide proton transfer-weighted chemical exchange saturation transfer MR imaging allows characterization of thoracic lesions.