Yoshiharu Ohno

ADC Measurement of Abdominal Organs and Lesions Using Parallel Imaging Technique

OBJECTIVE The purpose of our study was to assess the reliability and usefulness of parallel imaging for apparent diffusion coefficient (ADC) measurement of abdominal organs and lesions. MATERIALS AND METHODS Single-shot spin-echo echo-planar diffusion-weighted MRI (TE = 66, b = 0, 600 s/mm2) was performed in phantom and clinical studies. The b value was set to minimize the effects of perfusion in tissue and to maintain signal-to-noise ratio. Bottle phantoms were scanned with and without parallel imaging and with various parallel imaging factors and at various positions to evaluate the effects of parallel imaging on ADCs. In 200 consecutive clinical patients (122 men and 78 women: mean age, 61.9 years), ADCs were calculated for liver (four segments), spleen, pancreas (head, body, tail), gallbladder, renal parenchyma, and back muscle, and then compared to evaluate the reliability of clinical ADC measurements with parallel imaging. ADCs were also calculated for diffuse diseases and focal lesions (94 malignant and 93 benign) of abdominal organs to evaluate the clinical usefulness of ADC. RESULTS Location-dependent changes in water ADCs were minimal with parallel imaging factors first of 3, then of 4, and were small except for measurements at the image periphery. Acetone ADCs were saturated at 4.00 x 10(-3) mm2/s. Degraded image quality prevented ADC measurement of the left hepatic lobe and pancreas in 7-18 patients. There was no significant difference among ADCs of four liver segments (1.50 +/- 0.24 [SD] x 10(-3) mm2/s - 1.56 +/- 0.31 x 10(-3) mm2/s) and between ADCs of the right and left kidneys (2.65 +/- 0.30 x 10(-3) mm2/s, 2.59 +/- 0.33 x 10(-3) mm2/s). ADC of the pancreas tail (1.65 +/- 0.37 x 10(-3) mm2/s) was significantly lower than those of the head (1.81 +/- 0.40 x 10(-3) mm2/s) and body (1.81 +/- 0.41 x 10(-3) mm2/s) (p < 0.005). Renal ADCs were significantly lower in patients with renal failure (right: 2.15 +/- 0.30 x 10(-3) mm2/s; left: 2.11 +/- 0.25 x 10(-3) mm2/s) than in those without disease (right: 2.67 +/- 0.29 x 10(-3) mm2/s; left: 2.60 +/- 0.32 x 10(-3) mm2/s) (p < 0.005). ADC of pancreatic cancer was significantly higher than that of healthy pancreas (p < 0.05). ADC of renal angiomyolipoma was significantly lower than those of renal cell carcinoma and healthy renal parenchyma (p < 0.0005). CONCLUSION Clinical ADC measurements of abdominal organs and lesions using parallel imaging appear to be reliable and useful, and the effect of parallel imaging on calculated values is considered to be minimal.

Non–Small Cell Lung Cancer: Whole-Body MR Examination for M-Stage Assessment—Utility for Whole-Body Diffusion-weighted Imaging Compared with Integrated FDG PET/CT

PURPOSE To prospectively and directly compare the capability of whole-body diffusion-weighted (DW) imaging, whole-body magnetic resonance (MR) imaging with and that without DW imaging, and integrated fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) for M-stage assessment in non-small cell lung cancer (NSCLC) patients. MATERIALS AND METHODS The institutional review board approved this study; informed consent was obtained from patients. A total of 203 NSCLC patients (109 men, 94 women; mean age, 72 years) prospectively underwent whole-body DW imaging, whole-body MR imaging, and FDG PET/CT. Final diagnosis of the M-stage in each patient was determined on the basis of results of all radiologic and follow-up examinations. Two chest radiologists and two nuclear medicine physicians independently assessed all examination results and used a five-point visual scoring system to evaluate the probability of metastases. Final diagnosis based on each of the methods was made by consensus of two readers. Receiver operating characteristic (ROC) analysis was used to compare the capability for M-stage assessment among whole-body DW imaging, whole-body MR imaging with and that without DW imaging, and PET/CT on a per-patient basis. Sensitivity, specificity, and accuracy were compared with the McNemar test. RESULTS Area under ROC curve (A(z)) values of whole-body MR imaging with DW imaging (A(z) = 0.87, P = .04) and integrated FDG PET/CT (A(z) = 0.89, P = .02) were significantly larger than that of whole-body DW imaging (A(z) = 0.79). Specificity and accuracy of whole-body MR imaging with (specificity, P = .02; accuracy, P < .01) and that without DW imaging (specificity, P = .02; accuracy, P = .01) and integrated FDG PET/CT (specificity, P < .01; accuracy, P < .01) were significantly higher than those of whole-body DW imaging. CONCLUSION Whole-body MR imaging with DW imaging can be used for M-stage assessment in NSCLC patients with accuracy as good as that of PET/CT.

Radiation Dose Reduction in Chest CT: A Review

OBJECTIVE This article aims to summarize the available data on reducing radiation dose exposure in routine chest CT protocols. First, the general aspects of radiation dose in CT and radiation risk are discussed, followed by the effect of changing parameters on image quality. Finally, the results of previous radiation dose reduction studies are reviewed, and important information contributing to radiation dose reduction will be shared. CONCLUSION A variety of methods and techniques for radiation dose reduction should be used to ensure that radiation exposure is kept as low as is reasonably achievable.

Quantitative assessment of regional pulmonary perfusion in the entire lung using three-dimensional ultrafast dynamic contrast-enhanced magnetic resonance imaging: Preliminary experience in 40 subjects.

To assess regional differences in quantitative pulmonary perfusion parameters, i.e., pulmonary blood flow (PBF), mean transit time (MTT), and pulmonary blood volume (PBV) in the entire lung on a pixel‐by‐pixel basis in normal volunteers and pulmonary hypertension patients.

Detection of bone metastases in non-small cell lung cancer patients: comparison of whole-body diffusion-weighted imaging (DWI), whole-body MR imaging without and with DWI, whole-body FDG-PET/CT, and bone scintigraphy.

To prospectively compare the capability for bone metastasis assessment of whole‐body diffusion‐weighted imaging (DWI), magnetic resonance imaging (MRI) without and with DWI, [18F] fluoro‐2‐D‐glucose positron emission tomography with computed tomography (FDG‐PET/CT) and bone scintigraphy in non‐small cell carcinoma (NSCLC) patients.

Dynamic oxygen-enhanced MRI reflects diffusing capacity of the lung

The purpose of this study was to demonstrate the feasibility of dynamic oxygen‐enhanced MRI in a clinical setting. We hypothesized that dynamic oxygen enhancement can reflect the regional diffusing capacity of the lung. Ten patients with pulmonary emphysema and seven healthy volunteers were examined with a respiratory‐synchronized inversion recovery single‐shot turbo spin‐echo sequence (TR = 3200–5000 ms, TE = 16 ms, TI = 720 ms, ETS = 4 ms) following 100% oxygen inhalation, using a 1.5 T whole‐body scanner. Maximum mean relative enhancement ratios calculated by averaging six defined regions of interest (ROIs) in both lungs were statistically compared between healthy volunteers and patients, and were correlated with diffusing lung capacity (%DLCO). In patients with pulmonary emphysema, maximum mean relative enhancement ratios were significantly decreased compared to those in healthy volunteers (P = 0.0008). Maximum mean relative enhancement ratio had excellent correlation with % DLC0 (r2 = 0.83). Dynamic oxygen‐enhanced MRI may reflect the diffusing capacity of the lung; therefore, imaging of oxygen enhancement with MRI may provide maps of the diffusing capacity. Magn Reson Med 47:1139–1144, 2002.

Primary pulmonary hypertension: 3D dynamic perfusion MRI for quantitative analysis of regional pulmonary perfusion.

OBJECTIVE The purpose of this study was to determine whether quantitative pulmonary perfusion parameters obtained from 3D dynamic contrast-enhanced MR perfusion data can be used to assess the severity of primary pulmonary hypertension (PPH) as indicated by pulmonary vascular resistance (PVR) and mean pulmonary artery pressure (MPAP). CONCLUSION Three-dimensional dynamic contrast-enhanced MRI has potential for assessment of disease severity as indicated by PVR and MPAP in patients with PPH.

Ultra-short echo time (UTE) MR imaging of the lung: Comparison between normal and emphysematous lungs in mutant mice

To investigate the utility of ultra‐short echo time (UTE) sequence as pulmonary MRI to detect non‐uniform disruption of lung architecture that is typical of emphysema.

Diffusion-weighted MRI versus 18F-FDG PET/CT: performance as predictors of tumor treatment response and patient survival in patients with non-small cell lung cancer receiving chemoradiotherapy.

OBJECTIVE The purpose of this study was to compare the predictive capabilities of diffusion-weighted MRI (DWI) and 18F-FDG PET/CT for tumor response to therapy and survival in patients with non-small cell lung cancer (NSCLC) receiving chemoradiotherapy. SUBJECTS AND METHODS The study included 64 patients with NSCLC diagnosed as stage III who underwent pretherapeutic DWI and FDG PET/CT and were treated with chemoradiotherapy. For quantitative prediction, apparent diffusion coefficient (ADC) for DWI and maximum standardized uptake value (SUVmax) for PET/CT were measured at all targeted lesions and averaged to obtain final values for each patient. To evaluate the predictive capability of either index for distinguishing partial response and nonresponse (stable or progressive disease) groups, receiver operating characteristic analysis was performed, and sensitivity, specificity, and accuracy of the two modalities were compared using the McNemar test. Finally, overall and progression-free survival curves divided by the corresponding threshold value were compared by means of the log-rank test. RESULTS The area under the curve (Az) for ADC (Az=0.84) was significantly larger than that for SUVmax (Az=0.64, p<0.05). The application of feasible threshold values resulted in specificity (44.4%) and accuracy (76.6%) of DWI becoming significantly higher than those of PET/CT (specificity, 11.1%; p<0.05 and accuracy, 67.2%, p<0.05). In addition, only overall survival and progression-free survival of the two groups divided by ADC at 2.1×10(-3) mm2/s and SUVmax at 10 showed a significant difference (p<0.05). CONCLUSION DWI may have better potential than FDG PET/CT for prediction of tumor response to therapy in NSCLC patients before chemoradiotherapy.

Differentiation of Malignant and Benign Pulmonary Nodules with Quantitative First-Pass 320–Detector Row Perfusion CT versus FDG PET/CT

PURPOSE To prospectively compare the capability of quantitative first-pass perfusion 320-detector row computed tomography (CT) (ie, area-detector CT) with that of combined positron emission tomography and CT (PET/CT) for differentiation between malignant and benign pulmonary nodules. MATERIALS AND METHODS This prospective study was approved by the institutional review board, and written informed consent was obtained from 50 consecutive patients with 76 pulmonary nodules. All patients underwent dynamic area-detector CT, PET/CT, and microbacterial and/or histopathologic examinations. All pulmonary nodules were divided into three groups: malignant nodules (n = 43), benign nodules with low biologic activity (n = 6), and benign nodules with high biologic activity (n = 27). For each dynamic area-detector CT data set, the perfusion derived by using the maximum slope model (PF(MS)), extraction fraction derived by using the Patlak plot model (EF(PP)), and blood volume derived by using the Patlak plot model (BV(PP)) were calculated. These parameters were statistically compared among the three nodule groups. Receiver operating characteristic (ROC) analyses were used to compare the diagnostic capability of the CT and PET/CT indexes. Finally, the sensitivity, specificity, and accuracy of each index were compared by using the McNemar test. RESULTS All indexes in the malignant nodule group were significantly different from those in the low-biologic-activity benign nodule group (P < .05). Areas under the ROC curve for PF(MS) and EF(PP) were significantly larger than those for BV(PP) (P < .05) and maximal standard uptake value (SUV(max)) (P < .05). The specificity and accuracy of PF(MS) and EF(PP) were significantly higher than those of BV(PP) and SUV(max) (P < .05). CONCLUSION Dynamic first-pass area-detector perfusion CT has the potential to be more specific and accurate than PET/CT for differentiating malignant from benign pulmonary nodules. SUPPLEMENTAL MATERIAL http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.10100245/-/DC1.