Makoto Sakane

Clinical evaluation of image quality and radiation dose reduction in upper abdominal computed tomography using model-based iterative reconstruction; comparison with filtered back projection and adaptive statistical iterative reconstruction

PURPOSE To evaluate the image quality of upper abdominal CT images reconstructed with model-based iterative reconstruction (MBIR) in comparison with filtered back projection (FBP) and adaptive statistical iterative reconstruction (ASIR) on scans acquired with various radiation exposure dose protocols. MATERIALS AND METHODS This prospective study was approved by our institutional review board, and informed consent was obtained from all 90 patients who underwent both control-dose (CD) and reduced-dose (RD) CT of the upper abdomen (unenhanced: n=45, contrast-enhanced: n=45). The RD scan protocol was randomly selected from three protocols; Protocol A: 12.5% dose, Protocol B: 25% dose, Protocol C: 50% dose. Objective image noise, signal-to-noise (SNR) ratio for the liver parenchyma, visual image score and lesion conspicuity were compared among CD images of FBP and RD images of FBP, ASIR and MBIR. RESULTS RD images of MBIR yielded significantly lower objective image noise and higher SNR compared with RD images of FBP and ASIR for all protocols (P<.01) and CD images of FBP for Protocol C (P<.05). Although the subjective image quality of RD images of MBIR was almost acceptable for Protocol C, it was inferior to that of CD images of FBP for Protocols A and B (P<.0083). The conspicuity of the small lesions in RD images of MBIR tended to be superior to that in RD images of FBP and ASIR and inferior to that in CD images for Protocols A and B, although the differences were not significant (P>.0083). CONCLUSION Although 12.5%-dose MBIR images (mean size-specific dose estimates [SSDE] of 1.13mGy) yielded objective image noise and SNR comparable to CD-FBP images, at least a 50% dose (mean SSDE of 4.63mGy) would be needed to maintain the subjective image quality and the lesion conspicuity.

Correlation between apparent diffusion coefficients on diffusion-weighted MRI and standardized uptake value on FDG-PET/CT in pancreatic adenocarcinoma

Background Diffusion-weighted magnetic resonance imaging (DW-MRI) and 2-deoxy-2-[18F]fluoro-D-glucose–positron emission tomography/computed tomography (PET/CT) is increasingly recognized as important for assessing tumor malignancy in oncology. Apparent diffusion coefficient (ADC) and standardized uptake value (SUV) are negatively correlated in some types of cancer based on tumor aggressiveness. Purpose To evaluate relationships between ADC of magnetic resonance imaging and SUV of PET/CT in pancreatic adenocarcinomas. Material and Methods Twenty-nine patients histopathologically diagnosed with pancreatic adenocarcinomas were evaluated. ADC maps were generated from 3 T-MRI using b values (b = 0, 800 s/mm2). PET/CT was performed 60 min after intravenous injection of FDG (3.7 MBq/kg). The margins of tumors on DW-MRI and PET/CT were assessed to measure ADC and SUV of tumor appropriately. For tumors considered well-marginated, minimal and mean ADC as well as maximal and mean SUV were measured. The correlation of ADC and SUV were statistically evaluated and survival period stratified on ADC and SUV also evaluated. Results Twenty-two tumors on DW-MRI and 25 on PET/CT were deemed well-marginated. Minimal ADC was significantly and negatively correlated with maximal and mean SUV (r = −0.61, P = 0.0040; r = −0.66, P = 0.0015), and mean ADC also showed significantly and negatively correlation with maximal and mean SUV (r = −0.50, P = 0.024; r = −0.54, P = 0.012). There was no significant difference on overall survival stratified on ADC and SUV. Conclusion ADC and SUV were significantly correlated in pancreatic adenocarcinomas, although no significant findings were observed in overall survival.

Assessment of combination of contrast-enhanced magnetic resonance imaging and positron emission tomography/computed tomography for evaluation of ovarian masses.

ObjectivesThe objectives of this study were to correlate fluorodeoxyglucose uptake in ovarian masses on positron emission tomography/computed tomography (PET/CT) with pathological grades of malignancy and subtypes and to determine the appropriate approach for combining PET/CT and contrast-enhanced magnetic resonance imaging (CE-MRI) to characterize ovarian masses. Materials and MethodsA retrospective study was conducted including 127 patients who underwent surgical resection of an ovarian mass (30 benign, 31 borderline, 66 malignant). Maximum standardized uptake values (SUVmax) obtained with PET/CT were compared between pathological grades of malignancy and subtypes. Two radiologists each independently conducted a blind evaluation of CE-MRI for all lesions and classified them by the grade of malignancy as determinate (benign, borderline, or malignant) or indeterminate and by subtype as mucinous or nonmucinous. The appropriate approach for combining CE-MRI and PET/CT was determined by comparing the combined diagnostic ability with that of CE-MRI alone. ResultsThe SUVmax of malignant tumors was significantly higher than that of benign and borderline lesions (mean, 7.8, 1.7, 2.4; P < 0.05). Among malignant tumors, SUVmax was significantly lower in mucinous adenocarcinomas compared with nonmucinous malignant tumors (mean, 3.3, 8.4; P < 0.05) and lower in clear cell adenocarcinomas compared with other subtypes of nonmucinous malignant tumors (mean, 6.0, 9.4; P < 0.05). The SUVmax cutoff that best differentiated malignant lesions from benign/borderline lesions was 2.4 for mucinous and 4.0 for nonmucinous tumors. These cutoffs correctly classified lesions as malignant or not in 88.2% of cases (112/127). When PET/CT was combined with CE-MRI, the readers correctly classified 85% (34/40) and 86.5% (32/37) of indeterminate lesions on CE-MRI. However, PET/CT was not useful for classifying determinate lesions on CE-MRI, particularly because PET/CT correctly classified only 70.1% (12/17) of clear cell adenocarcinomas, whereas CE-MRI alone correctly classified 94.1% (1617). Thus, compared with CE-MRI alone, the diagnostic accuracy of CE-MRI + PET/CT when PET/CT was added only for indeterminate lesions on CE-MRI was significantly higher for both readers for differentiating between benign and borderline/malignant (P < 0.05), as well as between benign/borderline and malignant (P < 0.01). ConclusionFluorodeoxyglucose uptake in ovarian masses correlates with pathological subtypes as well as the grade of malignancy. Furthermore, the combination of CE-MRI and PET/CT is a highly accurate method for characterizing ovarian masses because PET/CT can be used as a complement to classify indeterminate lesions as malignant or not based on appropriate cutoff SUVmax for mucinous and nonmucinous tumors.

Preoperative staging of endometrial cancer using reduced field-of-view diffusion-weighted imaging: a preliminary study

ObjectivesTo compare the image quality and diagnostic performance of reduced field-of-view (rFOV) versus conventional full field-of-view (fFOV) diffusion-weighted (DW) imaging of endometrial cancer.MethodsFifty women with endometrial cancer underwent preoperative rFOV and fFOV DW imaging. Two radiologists compared the image qualities of both techniques, and five radiologists assessed superficial and deep myometrial invasion using both techniques. The statistical analysis included the Wilcoxon signed-rank test and paired t-test for comparisons of image quality and mean diagnostic values.ResultsDistortion, tumour delineation, and overall image quality were significantly better with rFOV DW imaging, compared to fFOV DW imaging (P < 0.05); however, the former was inferior in noise (P < 0.05). Regarding superficial invasion, the mean accuracies of the techniques did not differ statistically (rFOV, 58.0% versus fFOV, 56.0%; P = 0.30). Regarding deep myometrial invasion, rFOV DW imaging yielded significantly better mean accuracy, specificity, and positive predictive values (88.4%, 97.8%, and 91.7%, respectively), compared with fFOV DW imaging (84.8%, 94.1%, and 77.4%, respectively; P = 0.009, 0.005, and 0.011, respectively).ConclusionsCompared with fFOV DW imaging, rFOV DW imaging yielded less distortion, improved image quality and, consequently, better diagnostic performance for deep myometrial invasion of endometrial cancer.Key Points• rFOV DWI yields better assessment of deep myometrial invasion in endometrial cancer.• rFOV DWI could not sufficiently evaluate superficial invasion in endometrial cancer.• Distortion, tumour delineation, and overall image quality were improved with rFOV DWI.

Low-Dose Pelvic Computed Tomography Using Adaptive Iterative Dose Reduction 3-Dimensional Algorithm: A Phantom Study

Objective To evaluate the image quality and radiation dose reduction in pelvic computed tomography (CT) achieved with an adaptive iterative dose reduction 3-dimensional (AIDR 3D) algorithm using a phantom model. Methods Two phantoms were scanned using a 320-detector row CT scanner with 8 tube current levels, and the images were reconstructed with a standard filtered back projection (FBP) algorithm and with an AIDR 3D algorithm. Results Compared with FBP, AIDR 3D reduced image noise and improved contrast-to-noise ratios. The diagnostic performance for detection of low-contrast targets of AIDR 3D images obtained with 100 mA at 120 kVp was almost as good as that of the FBP images obtained with 200 mA. Conclusions The AIDR 3D algorithm substantially reduced image noise and improved the image quality of pelvic CT images compared with those obtained with the FBP algorithm and can thus be considered a promising technique for low-dose pelvic CT examinations.

Application of non-Gaussian water diffusional kurtosis imaging in the assessment of uterine tumors: A preliminary study

Objectives To evaluate the interobserver reliability and value of diffusional kurtosis imaging (DKI) in the assessment of uterine tumors compared with those of conventional diffusion-weighted imaging (DWI). Methods This retrospective study was approved by our institutional review board, which waived the requirement for informed consent. Fifty-eight women (mean age: 55.0 ± 13.6 years; range: 30–89 years) with suspected malignant uterine tumors underwent 3-T magnetic resonance imaging using DKI and DWI. Twelve had coexisting leiomyoma. Two observers analyzed region-of-interest measurements of diffusivity (D), kurtosis (K), and the apparent diffusion coefficient (ADC) of uterine lesions and healthy adjacent tissues. Interobserver agreement was evaluated using the intra-class correlation coefficient (ICC). The mean values were compared using one-way analysis of variance with a post-hoc Tukey’s honestly significant difference test. The diagnostic accuracy of D and ADC in differentiating malignant tumors from benign leiomyomas was analyzed using receiver operating characteristic (ROC) analysis. Results The ICCs between the two observers in evaluating D, K, and the ADC of the malignant tumors were higher than 0.84, suggesting excellent interobserver agreements. The mean D (×10−3 mm2/s) of uterine cancers (1.05 ± 0.41 and 1.09 ± 0.40 for observers 1 and 2, respectively) were significantly lower than those of leiomyoma (1.40 ± 0.37 and 1.56 ± 0.33, respectively; P < 0.05), healthy myometrium (1.72 ± 0.27 and 1.69 ± 0.30, respectively; P < 0.001), and healthy endometrium (1.53 ± 0.35 and 1.42 ± 0.37, respectively; P < 0.005). There was no significant difference in the area under the ROC curve between D and ADC. The mean K of uterine cancers (0.88 ± 0.28 and 0.90 ± 0.23, respectively) were higher than those of myometrium (0.72 ± 0.10 and 0.73 ± 0.10, respectively; P < 0.001), healthy endometrium (0.65 ± 0.13 and 0.60 ± 0.18, respectively; P < 0.001), and leiomyoma (0.76 ± 0.14 and 0.77 ± 0.16, respectively; not significant, P > 0.1). Conclusions Interobserver agreements in evaluating D, K, and ADC were moderate to excellent. D performed equally to conventional DWI in differentiating between benign and malignant uterine lesions. The mean K of malignant uterine lesions was significantly higher than that of non-tumorous myometrium or endometrium.

Volumetric parameters of 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/computed tomography can predict histopathologic treatment response after neoadjuvant chemoradiotherapy in pancreatic adenocarcinoma

PURPOSE The purpose of this study was to investigate the clinical potential of 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography/computed tomography (FDG PET/CT) to evaluate histopathologic effects of preoperative chemoradiotherapy (CRT) in pancreatic adenocarcinoma, with particular focus on volumetric PET/CT parameters. MATERIAL AND METHODS This study included 25 patients with pancreatic adenocarcinoma who underwent radical surgery after gemcitabine- and S-1-based preoperative-CRT. The extent of residual tumor was graded using the Evans grading systems, and patients with more than 50% destruction of tumor cells were defined as responder. Peak SUV corrected for lean body mass (SULpeak), metabolic tumor volume (MTV) with a threshold of SUV=2.0, total lesion glycolysis (TLG) of pre- and post-CRT, and reduction rates of SULpeak in those parameters were assessed by PET/CT. These parameters were compared using the students t-test between responder and non-responder. The treatment effect was also assessed by contingency table analysis divided with median value of each parameter using chi-square tests. RESULTS Eight patients (32%) showed histopathologic poor response (Evans grade I), 11 cases (44%) had mild response (Evans grade IIa), and six cases (24%) had moderate response (Evans grade IIb); therefore, six cases (24%) were assigned to responders and others 19 cases (76%) were non-responders. With regards to volumetric PET parameters, post-CRT SULpeak of responders was significantly lower than that of non-responders (p=0.013). Post-CRT MTV and TLG were negative for all six cases of responders. There were significant differences between responder and non-responder on the contingency table analysis of post-CRT MTV and TLG status (p=0.014 for both). CONCLUSIONS This study demonstrated that the volumetric PET/CT parameters, higher post-treatment SULpeak and positive MTV/TLG could predict the unfavorable histopathological effects of CRT in patients with pancreatic adenocarcinoma.

Single-breath-hold thin-slice gadoxetic acid-enhanced hepatobiliary MR imaging using a newly developed three-dimensional fast spoiled gradient-echo sequence.

PURPOSE To prospectively evaluate the efficacy of a new three-dimensional gradient-echo sequence (Turbo LAVA) that uses undersampled k-space acquisition combined with a two-dimensional parallel imaging technique for hepatobiliary MRI. MATERIALS AND METHODS Sixty patients underwent T1-weighted gadoxetic acid-enhanced hepatobiliary axial MRI during a single breath-hold using both Turbo LAVA (thickness/interval=1.6/0.8mm) and conventional three-dimensional gradient-echo (4/2mm; LAVA) sequences at 3T. Axial 4-mm-thick reformation was performed from Turbo LAVA images. Portal vein-to-liver contrast (PLC), bile duct-to-liver contrast (BLC), and lesion-to-liver contrast (LLC) were compared. Two radiologists independently assessed image quality using a five-point scale. Sagittal 4-mm-thick multiplanar reconstructions (MPR) were performed from both sequences and assessed together with directly obtained 4-mm-thick sagittal LAVA images in terms of sharpness. The paired t-test was used to compare PLC, BLC, and LLC. The Wilcoxon signed rank test was used to compare five-point scales. RESULTS The mean PLC (P<0.001), BLC (P<0.001), and LLC (P<0.005) were significantly higher for Turbo LAVA than for LAVA; the scores for image noise and sharpness were inferior (P=0.000 and 0.005) and superior (0.005 and 0.157) for Turbo LAVA. There were no significant differences in the scores for bile duct visualization, artifacts, fat suppression quality, overall quality, and focal lesion conspicuity. For sagittal images, MPR Turbo LAVA showed significantly better sharpness than MPR LAVA but showed significantly worse sharpness compared with directly obtained LAVA. CONCLUSION High-spatial-resolution single-breath-hold hepatobiliary MRI using Turbo LAVA was feasible. Diagnostic-quality MPR images can be obtained using this sequence.

Combined hepatocellular-cholangiocarcinoma with stem cell features, cholangiolocellular subtype after inferior vena cava stent placement for a patient with Budd–Chiari syndrome:

We report a case of combined hepatocellular-cholangiocarcinoma with stem cell features, cholangiolocellular subtype arising about 15 years after placement of an inferior vena cava stent for primary Budd–Chiari syndrome. Pre-surgical differentiation of the tumor from hepatocellular carcinoma was difficult because of elevated levels of alpha-fetoprotein and hypervascularity in the arterial phase. Histopathological examination revealed atypical cells forming ductal and alveolar structures showing a vague border with the surrounding liver. Immunostaining showed positive results for epithelial membrane antigen, mainly localized to the apical surface of the tubules, representing a characteristic finding for combined hepatocellular-cholangiocarcinoma with stem cell features, cholangiolocellular subtype. Combined hepatocellular-cholangiocarcinoma with stem cell features arising in the liver with hepatic damage from Budd–Chiari syndrome is not common, but diagnosis is important to manage the malignancy, which shows different clinical behaviors from hepatocellular carcinoma.

Imaging findings of ovarian dysgerminoma with emphasis on multiplicity and vascular architecture: pathogenic implications

We report the imaging findings of three ovarian dysgerminomas that coexisted with other germ cell tumors or gonadoblastomas, focusing on the distribution of tumor nests and vascular architecture, which might provide information about the pathogenesis of dysgerminomas. In a 14-year-old female with dysgerminoma and coexisting gonadoblastomas, contrast-enhanced magnetic resonance imaging (MRI) demonstrated a solid mass in the right ovary, which presented as hyperintense lobules on diffusion-weighted imaging separated by fibrovascular septa. Some small nodules were found to exist separately from the lobules (multiplicity) and to include pathological remnants of gonadoblastoma. Large tumor vessels were present at the center of the mass (central blood vessels), which were in direct contact with the ovarian veins and radiated peripherally through the fibrovascular septa. In a 35-year-old female, a mixed germ cell tumor, which was mainly composed of dysgerminoma and yolk sac tumor foci, exhibited the same vascular architecture pattern as the first dysgerminoma on contrast-enhanced computed tomography. In a 10-year-old female with a mixed germ cell tumor, contrast-enhanced MRI revealed an enlarged left ovary, which contained a large heterogeneous mass and multiple tiny nodules (multiplicity). Microscopically, the former corresponded to a yolk sac tumor, and the latter corresponded to a dysgerminoma containing remnants of gonadoblastoma. Based on these cases, the presence of tumor nest multiplicity and central blood vessels might aid the diagnosis of dysgerminoma, and these imaging findings might be indicative of the synchronous development of multiple dysgerminomas from primordial germ cells or gonadoblastomas.