Kazuhiro Kitajima

High Signal Intensity in the Dentate Nucleus and Globus Pallidus on Unenhanced T1-weighted MR Images: Relationship with Increasing Cumulative Dose of a Gadolinium-based Contrast Material

PURPOSE To explore any correlation between the number of previous gadolinium-based contrast material administrations and high signal intensity (SI) in the dentate nucleus and globus pallidus on unenhanced T1-weighted magnetic resonance (MR) images. MATERIALS AND METHODS The institutional review board approved this study, waiving the requirement to obtain written informed consent. A group of 381 consecutive patients who had undergone brain MR imaging was identified for cross-sectional analysis. For longitudinal analysis, 19 patients who had undergone at least six contrast-enhanced examinations were compared with 16 patients who had undergone at least six unenhanced examinations. The mean SIs of the dentate nucleus, pons, globus pallidus, and thalamus were measured on unenhanced T1-weighted images. The dentate nucleus-to-pons SI ratio was calculated by dividing the SI in the dentate nucleus by that in the pons, and the globus pallidus-to-thalamus SI ratio was calculated by dividing the SI in the globus pallidus by that in the thalamus. Stepwise regression analysis was undertaken in the consecutive patient group to detect any relationship between the dentate nucleus-to-pons or globus pallidus-to-thalamus SI ratio and previous gadolinium-based contrast material administration or other factors. A random coefficient model was used to evaluate for longitudinal analysis. RESULTS The dentate nucleus-to-pons SI ratio showed a significant correlation with the number of previous gadolinium-based contrast material administrations (P < .001; regression coefficient, 0.010; 95% confidence interval [CI]: 0.009, 0.011; standardized regression coefficient, 0.695). The globus pallidus-to-thalamus SI ratio showed a significant correlation with the number of previous gadolinium-based contrast material administrations (P < .001; regression coefficient, 0.004; 95% CI: 0.002, 0.006; standardized regression coefficient, 0.288), radiation therapy (P = .009; regression coefficient, -0.014; 95% CI: -0.025, -0.004; standardized regression coefficient, -0.151), and liver function (P = .031; regression coefficient, 0.023; 95% CI: 0.002, 0.044; standardized regression coefficient, 0.107). The dentate nucleus-to-pons and globus pallidus-to-thalamus SI ratios in patients who had undergone contrast-enhanced examinations were significantly greater than those of patients who had undergone unenhanced examinations (P < .001 for both). CONCLUSION High SI in the dentate nucleus and globus pallidus on unenhanced T1-weighted images may be a consequence of the number of previous gadolinium-based contrast material administrations.

Gadolinium-based Contrast Agent Accumulates in the Brain Even in Subjects without Severe Renal Dysfunction: Evaluation of Autopsy Brain Specimens with Inductively Coupled Plasma Mass Spectroscopy

PURPOSE To use inductively coupled plasma mass spectroscopy (ICP-MS) to evaluate gadolinium accumulation in brain tissues, including the dentate nucleus (DN) and globus pallidus (GP), in subjects who received a gadolinium-based contrast agent (GBCA). MATERIALS AND METHODS Institutional review board approval was obtained for this study. Written informed consent for postmortem investigation was obtained either from the subject prior to his or her death or afterward from the subjects relatives. Brain tissues obtained at autopsy in five subjects who received a linear GBCA (GBCA group) and five subjects with no history of GBCA administration (non-GBCA group) were examined with ICP-MS. Formalin-fixed DN tissue, the inner segment of the GP, cerebellar white matter, the frontal lobe cortex, and frontal lobe white matter were obtained, and their gadolinium concentrations were measured. None of the subjects had received a diagnosis of severely compromised renal function (estimated glomerular filtration rate <45 mL/min/1.73 m(2)) or acute renal failure. Fisher permutation test was used to compare gadolinium concentrations between the two groups and among brain regions. RESULTS Gadolinium was detected in all specimens in the GBCA agent group (mean, 0.25 µg per gram of brain tissue ± 0.44 [standard deviation]), with significantly higher concentrations in each region (P = .004 vs the non-GBCA group for all regions). In the GBCA group, the DN and GP showed significantly higher gadolinium concentrations (mean, 0.44 µg/g ± 0.63) than other regions (0.12 µg/g ± 0.16) (P = .029). CONCLUSION Even in subjects without severe renal dysfunction, GBCA administration causes gadolinium accumulation in the brain, especially in the DN and GP.

Prostate cancer detection with 3 T MRI: Comparison of diffusion‐weighted imaging and dynamic contrast‐enhanced MRI in combination with T2‐weighted imaging

To evaluate the diagnostic ability of diffusion‐weighted imaging (DWI) and dynamic contrast‐enhanced imaging (DCEI) in combination with T2‐weighted imaging (T2WI) for the detection of prostate cancer using 3 T magnetic resonance imaging (MRI) with a phased‐array body coil.

Accuracy of 18F-FDG PET/CT in Detecting Pelvic and Paraaortic Lymph Node Metastasis in Patients with Endometrial Cancer

OBJECTIVE The objective of our study was to evaluate the accuracy of integrated PET and CT (PET/CT) using (18)F-FDG in detecting pelvic and paraaortic lymph node metastasis in patients with endometrial cancer, using surgical and histopathologic findings as the reference standard. SUBJECTS AND METHODS Forty patients with clinical stages IA to IIIC underwent radical hysterectomy, including pelvic lymphadenectomy with or without paraaortic lymphadenectomy, after FDG PET/CT. Lymphadenectomy involved removing all visible lymph nodes in the surgical fields. PET/CT findings were interpreted by two experienced radiologists in consensus and compared with histopathologic results. The criterion for malignancy on PET/CT images was increased radiotracer uptake by a lymph node independent of node size. RESULTS In total, 62 pathologically positive nodes were found in 10 patients and 60 of 62 dissected metastatic nodes were identified on the CT component. The overall node-based sensitivity, specificity, and accuracy of PET/CT for detecting nodal metastases were 53.3% (32/60), 99.6% (1,419/1,424), and 97.8% (1,451/1,484), respectively. The sensitivity for detecting metastatic lesions 4 mm or less in diameter was 16.7% (4/24), that for lesions between 5 and 9 mm was 66.7% (14/21), and that for lesions 10 mm or larger was 93.3% (14/15). The overall patient-based sensitivity, specificity, and accuracy were 50% (5/10), 86.7% (26/30), and 77.5% (31/40), respectively. CONCLUSION Integrated FDG PET/CT is superior to conventional imaging techniques, but it is only moderately sensitive in predicting lymph node metastasis preoperatively in patients with endometrial cancer. Even PET/CT should not replace lymphadenectomy.

Diagnostic accuracy of integrated FDG-PET/contrast-enhanced CT in staging ovarian cancer: comparison with enhanced CT

PurposeThe purpose of the study is to evaluate the accuracy of integrated positron emission tomography and computed tomography (PET/CT) with 18F-fluorodeoxyglucose (FDG) with IV contrast for preoperative staging of ovarian cancer, in comparison with enhanced CT, using surgical and histopathological findings as the reference standard.Materials and methodsForty patients with ovarian cancer underwent FDG-PET/contrast-enhanced CT scans for staging before primary debulking surgery. PET/CT and the CT component separately, were interpreted by two experienced radiologists by consensus for each investigation. Status with regard to lesion inside and outside the pelvis was determined on the basis of histopathology. The significance of differences between the two imaging modalities was determined using the McNemar test.ResultsStaging revealed stage I in 18 patients (IA, n = 9; IB, n = 3; IC, n = 6), stage II in seven (IIA, n = 2; IIB, n = 3; IIC, n = 2), stage III in 14 (IIIA, n = 1; IIIB, n = 3; IIIC, n = 10), and stage IV in one. The results of CT and PET/CT were concordant with the final pathological staging in 22 out of 40 (55%) and 30 out of 40 (75%) cases, respectively. The overall lesion-based sensitivity improved from 37.6% (32 out of 85) to 69.4% (59 out of 85), specificity from 97.1% (578 out of 595) to 97.5% (580 out of 595), and accuracy from 89.7% (610 out of 680) to 94.0% (639 out of 680) between CT and PET/CT. There were significant differences in sensitivity and accuracy, with p values of 5.6 × 10−7 and 1.2 × 10−7, respectively.ConclusionIntegrated FDG-PET/contrast-enhanced CT is a more accurate imaging modality for staging ovarian cancer and useful for selecting appropriate treatment than enhanced CT.

Spectrum of FDG PET/CT findings of uterine tumors

OBJECTIVE The purpose of this article is to review FDG PET/CT and MRI findings in a variety of benign and malignant tumors of the uterus and to become familiar with the wide variety of FDG PET/CT findings of this entity. CONCLUSION Benign uterine tumors generally have mild FDG uptake, and leiomyoma rarely shows high uptake. Uterine malignant tumors generally have intense FDG uptake, whereas malignant uterine tumors that are small or that have low cellular density often show minimal uptake.

Brain gadolinium deposition after administration of gadolinium-based contrast agents

Gadolinium-based contrast agents (GBCAs) consist of gadolinium ions and a chelating agent that binds the gadolinium ion tightly so that its toxicity is not manifested. However, in 2013, an association between brain MRI abnormalities and a history of GBCA administration was first reported. Even in patients with normal renal function, increased signal intensity in the dentate nucleus and globus pallidus on unenhanced T1-weighted images showed a positive correlation with previous exposure to linear chelate type GBCAs, but not to macrocyclic chelate type ones. This difference of GBCAs is speculated to reflect the stability of GBCAs, and de-chelated gadolinium deposition has been strongly suspected. Using inductively coupled plasma mass spectroscopy, gadolinium was detected from patients’ brains with a history of repeated GBCA administration. In some cases, the gadolinium concentration of a patient’s brain with normal renal function exceeded the gadolinium concentration of the skin in nephrogenic systemic fibrosis patients, but without any histological change. The actual risk has not been documented yet, but it seems important to consider the potential unknown risks of residual gadolinium in our decisions regarding GBCA administration, and to make efforts to minimize any residual gadolinium in the patient’s body.

FDG-PET for the diagnosis of fever of unknown origin: a Japanese multi-center study.

ObjectiveTo evaluate the clinical value of 2-[18F]fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) for the diagnosis of fever of unknown origin (FUO), we performed a Japanese multi-center retrospective survey.MethodsA total of 81 consecutive patients with FUO who underwent FDG-PET at 6 institutions between July 2006 and December 2007 were retrospectively evaluated. FDG uptake was visually evaluated using a 4-grade scale. The efficacy of FDG-PET for the evaluation of FUO, the provision of additional diagnostic information, the clinical impact on therapeutic decisions (4-grade scale), and the diagnostic performance compared with the final diagnosis were evaluated.ResultsThe diagnostic results were analyzed according to 4 groups of final diagnoses: infection, arthritis/vasculitis/autoimmune/collagen disease (A/V), tumor/granuloma (T/G), and other/unknown (O/U). Sensitivity was highest in T/G, followed by infection, A/V and O/U [100%(7/7), 89%(24/27), 65%(11/17), 0%(0/1) respectively]. Clinical impact and mean FDG score showed the same tendency. Additional information was highest in infection followed by T/G, A/V, and O/U [76%(22/29), 75%(6/8), 43%(9/21), 23%(5/22), respectively]. The O/U group showed a high specificity (84%, 16/19) and accurately excluded active focal inflammatory diseases and malignancy. The use of steroids for the treatment of fever seemed to mask the lesions and modified the results, especially in the A/V group (4 false negatives in 8 steroid users out of 21 A/V patients). The prevalence of each disease in each hospital significantly affected the effectiveness of FDG-PET for the diagnosis of FUO. The mean FDG uptake score and additional information (70%, 31/44 vs. 30%, 11/37, respectively) in national hospital (NH) was significantly higher than in university hospitals (UH). A Grade 3 clinical impact, in which the FDG PET results changed the clinical decision, was seen in 50% (22/44) of the patients in the NH group and 13.5% (5/37) of the patients in the UH group. The sensitivity (91%, 30/33; 63%, 12/19) and specificity (60%, 6/10; 86%, 12/14) of the results in the NH and UH groups differed. The total sensitivity was 81% (42/52), specificity was 75% (18/24). The NH group included a large number of cases with infectious diseases (50%, 23/44), while the UH group included a large number of A/V cases (38%, 14/37) and O/U cases (41%, 15/37).ConclusionFDG-PET for the diagnosis of FUO provided additional diagnostic information and had a high clinical impact, especially among patients with infectious diseases. It was also helpful in cases with unknown or other miscellaneous diseases by allowing the exclusion of focally active diseases. The prevalence of diseases in hospitals significantly affected the effectiveness of FDG-PET for the diagnosis of FUO. FDG-PET is a useful examination providing various degrees of clinical impact for the management of FUO, depending on the characteristics of the patient and the hospital.

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.

Performance of FDG-PET/CT for diagnosis of recurrent uterine cervical cancer

The purpose is to evaluate the accuracy of integrated FDG-PET/CT, compared with PET alone, for diagnosis of suspected recurrence of uterine cervical cancer. Fifty-two women who had undergone treatment for histopathologically proven cervical cancer received PET/CT with suspected recurrence. PET-alone and integrated PET/CT images were evaluated by two different experienced radiologists by consensus for each investigation. A final diagnosis was confirmed by histopathology, radiological imaging, and clinical follow-up for over 1 year. Patient-based analysis showed that the sensitivity, specificity, and accuracy of PET/CT were 92.0% (23/25), 92.6% (25/27), and 92.3% (48/52), respectively, while for PET, the corresponding figures were 80.0% (20/25), 77.8% (21/27), and 78.8% (41/52), respectively. PET/CT resolved the false-positive PET results due to hypermetabolic activity of benign/inflammatory lesions and physiological variants, and was able to detect lung metastasis, local recurrence, peritoneal dissemination, para-aortic lymph node metastasis, and pelvic lymph node metastasis missed by PET alone. However, tiny local recurrence and lymph node metastasis could not be detected even by PET/CT. FDG-PET/CT is a useful complementary modality for providing good anatomic and functional localization of sites of recurrence during follow-up of patients with cervical cancer.