Ayako Taketomi-Takahashi

The role of the ADC value in the characterisation of renal carcinoma by diffusion-weighted MRI

The purpose of this study is to evaluate the role of diffusion-weighted imaging (DWI) in combination with T(1) and T(2) weighted MRI for the characterisation of renal carcinoma. The institutional review board approved the study protocols and waived informed consent from all of the patients. 47 patients (32 male and 15 female; age range, 21-85 years; median age, 65 years) who had suspected renal lesions on abdominal CT underwent MRI for further evaluation and characterisation of the lesions from April 2005 to August 2007 in our university hospital. A region of interest was drawn around the tumour area on apparent diffusion coefficient (ADC) maps. Final diagnosis was confirmed by histological examination of surgical specimens from all patients. The ADC value was significantly higher in renal cell carcinoma (RCC) than in transitional cell carcinoma (2.71+/-2.35 x 10(-3) mm(2) s(-1) vs 1.61+/-0.80 x 10(-3) mm(2) s(-1); p = 0.022). While analysing the histological subtypes of RCC, a significant difference in ADC values between clear cell carcinoma and non-clear cell carcinoma was found (1.59+/-0.55 x 10(-3) mm(2) s(-1) vs 6.72+/-1.85 x 10(-3) mm(2) s(-1); p = 0.0004). Similarly, ADC values of RCC revealed a significant difference between positive and negative metastatic lesions (1.06+/-0.38 x 10(-3) mm(2) s(-1) vs 3.02+/-2.44 x 10(-3) mm(2) s(-1); p = 0.0004), whereas intensity on T(1) and T(2) weighted imaging did not reach statistical significance. In conclusion, DWI has clinical value in the characterisation of renal carcinomas and could be applied in clinical practice for their management.

Detection of metastatic lesions from malignant pheochromocytoma and paraganglioma with diffusion-weighted magnetic resonance imaging: comparison with 18F-FDG positron emission tomography and 123I-MIBG scintigraphy

ObjectiveTo investigate the diagnostic features of whole-body diffusion-weighted magnetic resonance imaging (DWI) as compared with 2-[18F]-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) and 123I-meta-iodo-benzyl guanidine scintigraphy (MIBG) on metastatic lesions of patients with malignant pheochromocytoma or paraganglioma.MethodsWe prospectively studied 11 patients with histologically confirmed pheochromocytoma/paraganglioma and possible metastatic lesions. FDG-PET, MIBG, and DWI examinations were performed within 1 week, and the images were visually interpreted. Abnormal positive uptake either on MIBG or on FDG-PET was considered as metastases. Abnormal high signal intensities on DWI were considered as metastases using conventional T1-and T2-weighted images as reference.ResultsFDG-PET and DWI demonstrated metastatic lesions in all 11 patients, but MIBG showed no metastatic lesions in two patients. The numbers of lymph node metastases depicted on FDG-PET, MIBG, and DWI were 19, 6, and 39; bone metastases were 50, 49, and 60; liver metastases were 9, 9, and 15; lung metastases were 5, 7, and 5, respectively. MIBG failed to demonstrate many metastatic lesions, which were demonstrated on FDG-PET or DWI, although two mediastinal lymph node metastases, three lung metastases, and six bone metastases, which were not seen on DWI, were clearly demonstrated on MIBG. DWI showed 15 liver metastases, but 6 of them were not seen on FDG-PET or MIBG.ConclusionsDWI may be particularly advantageous in depicting lymph node and liver metastases and may have a higher rate of detecting metastatic lesions when compared with MIBG or FDG-PET. The limitations of DWI were possible false-positive finding, and probable lower detectability of mediastinal lymph node and lung metastasis.

Reliable Measurement Procedure of Virtual Touch Tissue Quantification With Acoustic Radiation Force Impulse Imaging

The purpose of this study was to find a reliable procedure for performing virtual touch tissue quantification of the liver.

Radiation Exposure from CT Examinations in Japan

BackgroundComputed tomography (CT) is the largest source of medical radiation exposure to the general population, and is considered a potential source of increased cancer risk. The aim of this study was to assess the current situation of CT use in Japan, and to investigate variations in radiation exposure in CT studies among institutions and scanners.MethodsData-sheets were sent to all 126 hospitals and randomly selected 14 (15%) of 94 clinics in Gunma prefecture which had CT scanner(s). Data for patients undergoing CT during a single month (June 2008) were obtained, along with CT scan protocols for each institution surveyed. Age and sex specific patterns of CT examination, the variation in radiation exposure from CT examinations, and factors which were responsible for the variation in radiation exposure were determined.ResultsAn estimated 235.4 patients per 1,000 population undergo CT examinations each year, and 50% of the patients were scanned in two or more anatomical locations in one CT session. There was a large variation in effective dose among hospitals surveyed, particularly in lower abdominal CT (range, 2.6-19.0 mSv). CT examinations of the chest and upper abdomen contributed to approximately 73.2% of the collective dose from all CT examinations. It was estimated that in Japan, approximately 29.9 million patients undergo CT annually, and the estimated annual collective effective dose in Japan was 277.4 *103 Sv person. The annual effective dose per capita for Japan was estimated to be 2.20 mSv.ConclusionsThere was a very large variation in radiation exposure from CT among institutions surveyed. CT examinations of the chest and upper abdomen were the predominant contributors to the collective dose.

MR signal of the solid portion of pilocytic astrocytoma on T2-weighted images : is it useful for differentiation from medulloblastoma?

Background and purpose: Although imaging features of cerebellar pilocytic astrocytoma and medulloblastoma have been described in many texts, original comparisons of magnetic resonance intensity between these two tumours are limited. In the present study the results of magnetic resonance imaging (MRI) were reviewed, focusing especially on the signal intensity of the solid portion of these neoplasms. Methods: MR images of ten cerebellar pilocytic astrocytomas and ten medulloblastomas were reviewed. The signal intensities of the solid components were graded on a scale of 1 to 5, with higher scores indicating a signal intensity closer to that of water. The degree of enhancement, tumour cysts and peripheral oedema were evaluated on MR images. When the solid portion was heterogeneous (i.e. mixed signal intensity or degree of enhancement), the dominant area was selected for evaluation. Results: On T2-weighted images, the signal intensity of the solid portion was equal to that of cerebrospinal fluid (CSF) in 50% of pilocytic astrocytomas. No medulloblastomas showed such hyperintensity. Most medulloblastomas (80%) were isointense to grey matter. On T1-weighted images, the signal intensity varied widely in pilocytic astrocytomas; however, all medulloblastomas were iso- or hypointense to grey matter. The MR enhancement pattern, cystic component and peripheral oedema all varied in both tumour types and no specific features were identified. Conclusion: A signal intensity of the solid portion isointense to CSF on T2-weighted images was characteristic of cerebellar pilocytic astrocytomas; this was not observed in medulloblastomas. Attention to T2-weighted imaging of the solid portions of a tumour is easy and helpful in differentiating between cerebellar pilocytic astrocytoma and medulloblastoma.

Diagnostic reference level of computed tomography (CT) in japan

Optimisation of computed tomography (CT) parameters is important in avoiding excess radiation exposure. The aim of this study is to establish the diagnostic reference levels (DRL) of CT in Japan by using dose-length product (DLP). Datasheets were sent to all hospitals/clinics which had CT scanner(s) in Gunma prefecture. Data were obtained for all patients who underwent CT during a single month (June 2010), and the distributions of DLP were evaluated for eight anatomical regions and five patient age groups. The DRL was defined as the 25th and 75th percentiles of DLP. Datasheets were collected from 80 of 192 hospitals/clinics (26 090 patients). DLP for head CT of paediatric patients tended to be higher in Japan compared with DRLs of paediatric head CTs reported from the EU or Syria. Although this study was performed with limited samples, DLP for adult patients were at comparable levels for all anatomical regions.

Breakthrough reactions of iodinated and gadolinium contrast media after oral steroid premedication protocol

BackgroundAdverse reactions to iodinated and gadolinium contrast media are an important clinical issue. Although some guidelines have proposed oral steroid premedication protocols to prevent adverse reactions, some patients may have reactions to contrast media in spite of premedication (breakthrough reaction; BTR).The purpose of this study was to assess the frequency, type and severity of BTR when following an oral steroid premedication protocol.MethodsAll iodinated and gadolinium contrast-enhanced radiologic examinations between August 2011 and February 2013 for which the premedication protocol was applied in our institution were assessed for BTRs.ResultsThe protocol was applied to a total of 252 examinations (153 patients, ages 15–87 years; 63 males, 90 females). Of these, 152 were for prior acute adverse reactions to contrast media, 85 were for a history of bronchial asthma, and 15 were for other reasons. There were 198 contrast enhanced CTs and 54 contrast enhanced MRIs. There were nine BTR (4.5%) for iodinated contrast media, and only one BTR (1.9%) for gadolinium contrast media: eight were mild and one was moderate. No patient who had a mild index reaction (IR) had a severe BTR.ConclusionIncidence of BTRs when following the premedication protocol was low. This study by no means proves the efficacy of premedication, but provides some support for following a premedication protocol to improve safety of contrast-enhanced examinations when prior adverse reactions are mild, or when there is a history of asthma.

Prevalence of abnormal findings on brain magnetic resonance (MR) examinations in adult participants of brain docking

BackgroundTo determine the prevalence of abnormal findings on brain magnetic resonance (MR) examinations in adult participants of brain docking in order to assess its usefulness.MethodsWe analyzed screening brain MR examinations for 1113 adults (age, 52.6+/-8.5 years; range, 22–84; 761 male and 352 female) performed during 6-year period from April 1998 to March 2004. All participants voluntarily sought a brain MR examination at their own expense. All subjects were studied using the same 1.0-T MR scanner, on axial T1-weighted spin echo (SE) images, proton-density-weighted and T2-weighted fast SE images, and intracranial MR angiography (MRA). All abnormal findings were classified into three basic categories: (1) findings with no referral necessary; (2) findings not requiring further evaluation, but which needed to be reported to the referring physician; (3) findings requiring further evaluation.ResultsParticipants with abnormal MR findings requiring further evaluation accounted for 1.3 %, but five of seven suspected intracranial aneurysms were not confirmed by other imaging modalities (false positive). No malignant tumors or other life-threatening pathology was detected, and only three participants (0.27 %) with abnormalities underwent surgical treatment. No participant groups were identified from our data as being high risk for MR abnormal findings requiring further evaluation.ConclusionBrain-docking participants had a variety of abnormalities on brain MR examinations, but only a small percentage of these findings required further evaluation. The usefulness of the brain docking with MRI and MRA has yet to be proven, and at this time we cannot approve this screening procedure.

Reliable Measurement by Virtual Touch Tissue Quantification With Acoustic Radiation Force Impulse Imaging Phantom Study

The purpose of this study was to evaluate the factors that may affect shear wave velocity (SWV) measurements by using a phantom.

Feasibility of measuring human pancreatic perfusion in vivo using imaging techniques.

Objective: The objective of this study was to demonstrate the feasibility of pancreatic perfusion computed tomography (CT) and review pancreatic perfusion measurements by various imaging modalities. Methods: Dynamic CT data from 8 patients (4 men; mean age, 64.8 [SD, 12.1] years; range, 40-80 years) with normal pancreas were analyzed using 2 analytical models: the maximum-slope and compartment-model methods. Literature search was also performed. Results: Although the perfusion value estimated by the maximum-slope method (88.1 [SD, 42.1] mL/min per 100 mL) was significantly smaller than that of the compartment-model method (127.0 [SD, 70.5]; P < 0.001), there was a linear correlation between them (r = 0.97, P < 0.001). In the literature review, 15 studies that reported the absolute values of normal pancreatic perfusion, by using perfusion CT, dynamic magnetic resonance imaging, hydrogen gas clearance method, and 15O-H2O-positron emission tomography were found. The reported mean values of normal pancreatic perfusion ranged from 38.4 to 356 mL/min per 100 mL, and there was a great deal of individual variation. Conclusions: Perfusion CT may provide reliable perfusion measurements of the pancreas, and the normal value was estimated at around 100 mL/min per 100 mL with a great deal of individual variation. The maximum-slope method may provide a lower perfusion value compared with the compartment-model method.