[Evaluation of Low-dose Whole-body FDG PET with SiPM-based PET/CT Scanner: Visual and Semi-quantitative Analyses Using Random Sampling from Full-dose Scan Data].

PURPOSE: Sensitivity and count rate performance of the latest PET/CT scanners with a silicon photomultiplier (SiPM) have been substantially improved compared to scanners with a photomultiplier tube (PMT), thereby promising a low-dose whole-body PET scan with maintaining image quality. However, it is ethically difficult to verify the low-dose protocol in actual clinical settings. In this study, we investigated the effect of dose reduction on reconstructed images by using a low-dose simulation technique, i.e., reducing the number of events from the acquired data. METHOD: For 21 subjects who underwent whole-body 18F-FDG PET examination with an SiPM-based PET/CT scanner, Biograph Vision (Siemens Healthineers, Erlangen, Germany), at a dosage of 3.5 MBq/kg and a continuous bed motion speed of 1.1 mm/sec (the standard protocol in our hospital), the number of events in acquired list data (100%; "full-dose") was reduced to 50%, 25%, 12.5%, and 6.25% ("low-dose"). The low-dose reconstructed images were evaluated visually and physically with reference to the full-dose images. The physical evaluation was performed by calculating differences in SUVmax at abnormal uptake (n=54) between the full-dose and low-dose images. RESULT: The 25% data images were visually acceptable, and the difference in SUVmax between the 100% and 25% data images was 9.8±13.5%. CONCLUSION: Our results suggest that Biograph Vision is a feasible method to reduce conventional dose with the potential use of 25% data images.

Spontaneous intraperitoneal renal rupture with urinoma formation in the fetus.

Spontaneous intraperitoneal renal rupture with urinoma formation in fetuses is an unusual condition that is caused by upper or lower urinary tract obstruction. We report the case of a neonatal male infant who presented with a spontaneous intraperitoneal right renal rupture accompanying ipsilateral ureterovesical junction obstruction (UVJO). Fetuses with UVJO accompanying contralateral multicystic dysplastic kidney should be observed carefully because of the risk of spontaneous renal rupture.

Usefulness of deep learning-assisted identification of hyperdense MCA sign in acute ischemic stroke: comparison with readers' performance.

PURPOSE: To evaluate the usefulness of deep learning-assisted diagnosis for identifying hyperdense middle cerebral artery sign (HMCAS) on non-contrast computed tomography in comparison with the diagnostic performance of neuroradiologists. MATERIALS AND METHODS: We obtained 46 HMCAS-positive and 52 HMCAS-negative test samples extracted using 50-pixel-diameter circular regions of interest. Five neuroradiologists undertook an initial diagnostic performance test by describing the HMCAS-positive prediction rate in each sample. Their diagnostic performance was compared with that of a deep convolutional neural network (DCNN) model that had been trained using another dataset in our previous study. In the second test, readers could reference the prediction rate of the DCNN model in each sample. RESULTS: The diagnostic performance of the DCNN for HMCAS showed an accuracy of 81.6% and area under the receiver-operating characteristic curve (AUC) of 0.869, whereas the initial diagnostic performance of neuroradiologists showed an accuracy of 78.8% and AUC of 0.882. The second diagnostic test of neuroradiologists with reference to the results of the DCNN model showed an accuracy of 84.7% and AUC of 0.932. In all readers, AUC values were higher in the second test than the initial test. CONCLUSION: The ability of DCNN to identify HMCAS is comparable with the diagnostic performance of neuroradiologists.

Viral Etiology of Acute Lower Respiratory Tract Infections in Hospitalized Children in Nagasaki, a Regional City of Japan in 2013-2015.

BACKGROUND: Acute lower respiratory tract infections (ALRIs) are the most common disease for hospitalized children in Japan. The aim of this study was to identify viruses in children hospitalized for ALRIs and to demonstrate epidemiologic and clinical characteristics in Japan. METHODS: During a 2-year period from February 2013 to January 2015, we collected nasopharyngeal swab specimens from almost all hospitalized children with ALRIs in Nagasaki, a regional city of Japan, and its environs. Viruses were detected by multiplex polymerase chain reaction from these samples. RESULTS: We detected one or more viruses from 259 (69%) of 374 patients, 227 of whom were infected with a single virus, 30 with 2, and 2 with 3 viruses. Detected viruses in this study were rhinovirus (46.4%), respiratory syncytial virus (29.7%), human metapneumovirus (6.8%), parainfluenza virus (5.5%), enterovirus D68 (3.4%), influenza virus (2.7%), adenovirus (2.4%), bocavirus (2.0%) and Coxsackie virus (1.0%). We detected a seasonal shift in respiratory syncytial virus outbreaks from the 2013-2014 to the 2014-2015 seasons. There was no significant difference in clinical course and severity among those viruses. Patients with a history of asthma or underlying diseases were older and more frequently required oxygen therapy than previously healthy patients. CONCLUSIONS: Viral etiology in hospitalized children with ALRIs in Nagasaki, Japan, was similar to that in many other countries. Enterovirus D68, which was recently recognized as a causative agent of severe ALRIs, was also identified in this study area. Severity of ALRIs may depend on underlying disease rather than type of etiologic virus.

Identification of 11p14.1-p15.3 deletion probably associated with short stature, relative macrocephaly, and delayed closure of the fontanelles.

We herein report a de novo hemizygous 9.2-Mb interstitial deletion of chromosome 11p14.1-15.3 in a 3-year-old Japanese girl with short stature, relative macrocephaly, and delayed closure of cranial fontanelles and sutures. She did not show either any motor or mental development delay. This deletion involves 25 genes including NELL1. The loss of the Nell1 function leads to skeletal defects in the cranial vault and vertebral column, and overexpression of Nell1 causes craniosynostosis in mice. These results imply that short stature and an abnormality of membranous ossification could be explained by haploinsufficiency of NELL1 on 11p14.1-p15.3. Further studies are needed to clarify the phenotype in patients with an 11p14.1-15.3 deletion and the pathogenesis of NELL1. © 2016 Wiley Periodicals, Inc.

Does respiratory virus coinfection increases the clinical severity of acute respiratory infection among children infected with respiratory syncytial virus?

BACKGROUND: Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory infection in children less than 5 years of age. The impact of non-RSV respiratory virus coinfection on the severity of RSV disease is unknown. METHODS: This hospital-based prospective study was conducted in Nagasaki, Japan, on all children less than 5 years of age with acute respiratory infection (ARI) who had undergone a rapid RSV diagnostic test between April 2009 and March 2010. Thirteen respiratory viruses were identified from nasopharyngeal swab samples using a multiplex polymerase chain reaction; polymerase chain reaction-positive samples were considered as confirmed respiratory virus infections. The cases were classified into 3 categories (pneumonia, moderate-to-severe nonpneumonic ARI and mild ARI) according to the findings of the chest radiograph and the hospitalization records. RESULTS: Among 384 cases enrolled, 371 were eligible for analysis, of whom 85 (23%) were classified as pneumonia cases; 137 (37%) as moderate-to-severe nonpneumonic ARI cases and 162 (40%) as mild ARI cases. RSV was detected in 172 cases (61.6%), and 31 cases (18.0%) had double or triple infections with other respiratory viruses. RSV infection was more frequently observed in pneumonia cases (odds ratio [OR]: 2.3; 95% confidence interval [CI]: 1.31-3.9) and moderate-to-severe nonpneumonic ARI cases (OR: 2.95; 95% CI: 1.82-4.78) than in mild ARI cases. The association with moderate-to-severe nonpneumonic ARI cases was stronger with RSV/non-RSV respiratory virus coinfection (adjusted OR: 4.91; 95% CI: 1.9-12.7) than with RSV single infection (adjusted OR: 2.77; 95% CI: 1.64-4.7). CONCLUSIONS: Non-RSV respiratory virus coinfection is not uncommon in RSV-infected children and may increase the severity of RSV disease.

Hypertrophic olivary degeneration after surgical resection of brain tumors.

BACKGROUND: Hypertrophic olivary degeneration (HOD) can be seen as high signal intensity with enlargement of the inferior olivary nucleus (ION) on T2-weighted magnetic resonance (MR) images 4-6 months after injury of the Guillain-Mollaret triangle. To the best of our knowledge, there has been no systematic evaluation with regard to the relationship between neurosurgical intervention affecting this pathway and the appearance of HOD. PURPOSE: To evaluate MR findings of HOD after surgical resection of brain tumors with the temporal evolution in focus. MATERIAL AND METHODS: MR images of seven patients that showed signal changes in the ION after surgical resection of brain tumors in the posterior fossa were retrospectively reviewed. T1-weighted imaging with and without gadolinium (Gd) contrast enhancement and T2-weighted imaging were performed in all patients before and after surgery. RESULTS: Before surgery, no patient had a signal change in the ION. T2-high signal intensity of the ION initially appeared 5 days to 2.5 months after surgery. Five patients showed enlargement of the ION with T2-high signal intensity 11 days to 3.5 months after surgery: three patients showed the enlargement of the ION subsequent to the T2-signal change on serial follow-up MR images. On Gd-enhanced T1-weighted images, there was no enhancement at the ION in any patient. Each signal change of the ION was consistent with HOD, according to the relationship between the resection site of the tumor and the Guillain-Mollaret triangle on follow-up MRI. CONCLUSION: HOD can be caused after neurosurgical intervention of brain tumors involving the Guillain-Mollaret triangle. It is important for radiologists to distinguish HOD from tumor recurrence.

Impact of subject head motion on quantitative brain (15)O PET and its correction by image-based registration algorithm.

OBJECTIVE: Subject head motion during sequential (15)O positron emission tomography (PET) scans can result in artifacts in cerebral blood flow (CBF) and oxygen metabolism maps. However, to our knowledge, there are no systematic studies examining this issue. Herein, we investigated the effect of head motion on quantification of CBF and oxygen metabolism, and proposed an image-based motion correction method dedicated to (15)O PET study, correcting for transmission-emission mismatch and inter-scan mismatch of emission scans. METHODS: We analyzed (15)O PET data for patients with major arterial steno-occlusive disease (n = 130) to determine the occurrence frequency of head motion during (15)O PET examination. Image-based motion correction without and with realignment between transmission and emission scans, termed simple and 2-step method, respectively, was applied to the cases that showed severe inter-scan motion. RESULTS: Severe inter-scan motion (>3 mm translation or >5° rotation) was observed in 27 of 520 adjacent scan pairs (5.2 %). In these cases, unrealistic values of oxygen extraction fraction (OEF) or cerebrovascular reactivity (CVR) were observed without motion correction. Motion correction eliminated these artifacts. The volume-of-interest (VOI) analysis demonstrated that the motion correction changed the OEF on the middle cerebral artery territory by 17.3 % at maximum. The inter-scan motion also affected CBV, CMRO2 and CBF, which were improved by the motion correction. A difference of VOI values between the simple and 2-step method was also observed. CONCLUSIONS: These data suggest that image-based motion correction is useful for accurate measurement of CBF and oxygen metabolism by (15)O PET.

Hypertrophic olivary degeneration after gamma-knife radiosurgery for pontine metastasis.

We present a case of a 57-year-old woman who underwent gamma-knife radiosurgery (GKRS) for pontine metastasis. Magnetic resonance (MR) imaging 2.8 months after GKRS showed T2 hyperintensity and hypertrophy of the left inferior olivary nucleus (ION) without gadolinium enhancement and smaller pontine metastasis. We diagnosed the signal change in the left ION as hypertrophic olivary degeneration (HOD) resulting from damage to the left central tegmental tract. We believe this is the first report to describe HOD after GKRS for pontine metastasis.

Pancreatic head resection preserving the main pancreatic duct for congenital hyperinsulinism of infancy.

Surgical intervention for congenital hyperinsulinism with an unclear focal lesion in the pancreatic head sometimes require the resection of most of the pancreas head and pancreaticojejunotomy. This report presents the case of a patient that underwent pancreatic head resection preserving the main pancreatic duct to avoid pancreaticojejunostomy.

Changes in susceptibility signs on serial T2*-weighted single-shot echo-planar gradient-echo images in acute embolic infarction: comparison with recanalization status on 3D time-of-flight magnetic resonance angiography.

INTRODUCTION: The present study compares changes in susceptibility signs on follow-up single-shot echo-planar gradient-echo T2*-weighted images (GRE-EPI) with vascular status on follow-up magnetic resonance angiography (MRA) in acute embolic infarction. METHODS: Twenty consecutive patients with acute embolic infarction repeatedly underwent MR imaging including GRE-EPI and MRA using a 1.5-T MR superconducting system. All patients underwent initial MR examination within 24 h of onset and follow-up MR imaging within 1 month after onset. RESULTS: Changes in susceptibility signs on follow-up GRE-EPI were compatible with vascular status on follow-up MRA in 19 of the 20 patients. Susceptibility signs disappeared with complete recanalization in 13 patients, migrated with partial recanalization in 3, did not change together with the absence of recanalization in 2, and became extended together with the absence of recanalization in 1. Cerebral hemorrhage obscured susceptibility signs in the one remaining patient. CONCLUSION: Susceptibility signs on follow-up GRE-EPI can reflect changes in an acute embolus, such as recanalization or migration, in this study. Serial GRE-EPI in acute embolism complements the diagnostic certainty of MRA by directly detecting an embolus as a susceptibility sign.

The effect of activity outside the field-of-view on image signal-to-noise ratio for 3D PET with (15)O.

Activity outside the field-of-view (FOV) degrades the count rate performance of 3D PET and consequently reduces signal-to-noise ratios (SNRs) of reconstructed images. The aim of this study was to evaluate a neck-shield installed in a 3D PET scanner for reducing the effect of the outside FOV activity. Specifically, we compared brain PET scans ((15)O(2) and H(2)(15)O) with and without the use of the neck-shield. Image SNRs were directly estimated by a sinogram bootstrap method. The bootstrap analysis showed that the use of the neck-shield improved the SNR by 8% and 19% for H(2)(15)O and (15)O(2), respectively. The SNR improvements were predominantly due to the reduction of the random count rates. Noise equivalent count rate (NECR) analysis provided SNR estimates that were very similar with the bootstrap-based results for H(2)(15)O, but not for (15)O(2). This discrepancy may be due to the fundamental difference between the two methods: the bootstrap method directly calculates the local SNR of reconstructed images, whereas the NECR calculation is based on the whole-gantry count rates, indicating a limitation of the conventional NECR-based method as a tool for assessing the image SNR. Although quantitative parameters, e.g. cerebral blood flow, did not differ when examined with and without the neck-shield, the use of the shield for brain (15)O study is recommended in terms of the image SNR.

Whole-brain perfusion measurement using 320-detector row computed tomography in patients with cerebrovascular steno-occlusive disease: comparison with 15O-positron emission tomography.

OBJECTIVE: The 320-detector row computed tomography (CT) can provide whole-brain CT perfusion (CTP) maps with continuous angiographic images by performing a single dynamic scan. We investigated the reliability of CTP cerebral blood flow (CTP-CBF) with 320-detector row CT by comparing findings with O-positron emission tomography (PET-CBF). METHODS: Whole-brain CTP and PET were performed in 10 patients with chronic unilateral steno-occlusive disease. We compared absolute and relative CBF values of bilateral middle cerebral artery territories between CTP and PET. RESULTS: Although mean CTP-CBF values were approximately 30% lower than mean PET-CBF values, the mean ischemic-to-nonischemic CBF ratios of CTP and PET were almost identical (P = 0.804). Regression analysis showed a significant correlation between CTP-CBF and PET-CBF values for each patient (r = 0.52-0.85, P < 0.001). CONCLUSIONS: Whole-brain CTP using 320-detector row CT is useful for evaluating the degree of ischemia for the entire brain with chronic cerebrovascular disease.

Thoracolithiasis: 11 cases with a calcified intrapleural loose body.

PURPOSE: To describe clinical and imaging characteristics of thoracolithiasis. MATERIALS AND METHODS: Medical records from our center from September 2005 to March 2007 were reviewed. A definitive diagnosis was made by multidetector-row computed tomography studies of the chest, which revealed in each patient an intrapleural calcified nodular opacity, which changed in intrapleural location on serial examinations. Eleven patients fulfilled this criteria. The images were analyzed by experienced radiologists, who focused on the distribution, size, and shape of the thoracolithiasis. RESULTS: The incidence of thoracolithiasis was 0.086% (11 of 12,835 individuals). All the patients were asymptomatic and did not have any history of intrathoracic disease. The nodules ranged in size from 5 to 15 mm (median 8 mm), and were ovoid and smoothly marginated. Each nodule contained homogeneous diffuse calcification. Eight nodules occurred in the left pleural space and 3 in the right. Their locations varied, which included on the diaphragm, along the posterior chest wall of the lower lung, abutting the left cardiac margin, and near the paraspinal space of the lower thoracic spine. Each of the calcified pleural bodies changed in intrapleural location on follow-up computed tomography examination. CONCLUSIONS: The calcified intrapleural nodular opacities of thoracolithiasis tended to be located inferiorly, presumably secondary to the effects of gravity, and they seemed to migrate freely within the pleural cavity.

Interindividual variations of cerebral blood flow, oxygen delivery, and metabolism in relation to hemoglobin concentration measured by positron emission tomography in humans.

Regional cerebral blood flow (CBF) and oxygen metabolism can be measured by positron emission tomography (PET) with (15)O-labeled compounds. Hemoglobin (Hb) concentration of blood, a primary determinant of arterial oxygen content (C(a)O(2)), influences cerebral circulation. We investigated interindividual variations of CBF, cerebral blood volume (CBV), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO(2)) in relation to Hb concentration in healthy human volunteers (n=17) and in patients with unilateral steno-occlusive disease (n=44). For the patients, data obtained only from the contralateral hemisphere (normal side) were analyzed. The CBF and OEF were inversely correlated with Hb concentration, but CMRO(2) was independent of Hb concentration. Oxygen delivery defined as a product of C(a)O(2) and CBF (C(a)O(2) CBF) increased with a rise of Hb concentration. The analysis with a simple oxygen model showed that oxygen diffusion parameter (L) was constant over the range of Hb concentration, indicating that a homeostatic mechanism controlling CBF is necessary to maintain CMRO(2). The current findings provide important knowledge to understand the control mechanism of cerebral circulation and to interpret the (15)O PET data in clinical practice.

F-18 FDG-PET imaging of dysembryoplastic neuroepithelial tumor-like astrocytoma.

Cerebral astrocytoma needs to be distinguished from dysembryoplastic neuroepithelial tumor (DNT) when a well-demarcated, cortically based and pseudo-cystic tumor with minimal mass effect is demonstrated on magnetic resonance imaging. We report an unusual case of DNT-like astrocytoma. 18F fluoro-deoxy-glucose (FDG) positron emission tomography showed a focal increase of FDG uptake in a deep part of the tumor. Histologic examination revealed predominantly microcystic change with oligodendrocyte-like cells, leading to a diagnosis of DNT. However, increased cellularity and nuclear atypia of astrocytes within the tumor were conspicuous as for DNT. Four years after excision, tumor recurrence was detected. FDG-positron emission tomography is useful for identifying the malignant potential of DNT-like astrocytoma.

Late-presenting posterior transdiaphragmatic (Bochdalek) hernia in adults: prevalence and MDCT characteristics.

PURPOSE: The objective of our study was to determine the prevalence of posterior transdiaphragmatic hernia in a large normal adult population. We also performed volume measurements and described its characteristics and sequential changes. MATERIALS AND METHODS: We prospectively evaluated 3107 chest computed tomography screenings obtained at our center between September 2005 and March 2006. The images were analyzed by experienced radiologists, who focused on the distribution, size, content, and sequential changes of the diaphragmatic hernia. Volumetric measurement was used to evaluate the size of the hernia. We also performed a chart review for each case and recorded the sex, age, symptoms, and clinical history. RESULTS: A total of 525 hernias were identified in 396 of 3107 persons, representing an incidence of 12.7%. Age ranges were 36 to 86 years and average was 62.8 years. The prevalence of the posterior diaphragmatic hernias in the 50s, 60s, and 70s age groups was 10.5% (168/1596), 13.7% (137/1003), and 20.3% (80/394), respectively. All persons were asymptomatic. In 93.7% (492/525) of the hernias, only fat was observed, whereas kidney involvement was observed in 5.5% (29/525). Protruded hernia content extended along the diaphragm, thoracoabdominal wall, and in the intermediate position between these 2 structures in 53.7%, 32.8%, and 13.5% of the hernias, respectively. No significant sequential changes were observed (P=0.082) during our follow-up period (12 to 27 mo). CONCLUSIONS: Incidentally observed posterior transdiaphragmatic hernias are a common finding on multidetector-row computed tomography, occurring in up to 20% of persons by age 70 years.