Tetsu Niwa

Complementary Roles of Whole-Body Diffusion-Weighted MRI and 18F-FDG PET: The State of the Art and Potential Applications

18F-FDG PET is an established functional imaging modality for the evaluation of human disease. Diffusion-weighted MRI (DWI) is another rapidly evolving functional imaging modality that can be used to evaluate oncologic and nononcologic lesions throughout the body. The information provided by 18F-FDG PET and DWI can be complementary, because the 2 methods are based on completely different biophysical underpinnings. This article will describe the basic principles, clinical applications, and limitations of DWI. In addition, the available evidence that correlates and compares 18F-FDG PET and DWI will be reviewed.

Syndromes Associated with Vascular Tumors and Malformations: A Pictorial Review

Use of the International Society for the Study of Vascular Anomalies (ISSVA) classification system has been strongly recommended in recent years because of the need for separate therapeutic measures for patients with vascular tumors and malformations. In the ISSVA classification system, vascular tumors, which are neoplastic, are distinguished from vascular malformations, which are caused by vascular structural anomalies and are not neoplastic, on the basis of the presence or absence of neoplastic proliferation of vascular endothelial cells. It is important that radiologists be familiar with the development, diagnosis, and treatment of vascular tumors and malformations, especially the imaging features of low- and high-flow vascular malformations. Some vascular tumors and malformations develop in isolation, whereas others develop within the phenotype of a syndrome. Syndromes that are associated with vascular tumors include PHACE syndrome. Syndromes that are associated with vascular malformations include Sturge-Weber, Klippel-Trénaunay, Proteus, blue rubber bleb nevus, Maffucci, and Gorham-Stout syndromes, all of which demonstrate low flow, and Rendu-Osler-Weber, Cobb, Wyburn-Mason, and Parkes Weber syndromes, all of which demonstrate high flow. Because imaging findings may help identify such syndromes as systemic, it is important that radiologists familiarize themselves with these conditions.

Congenital absence of the portal vein: clinical and radiologic findings.

Congenital absence of the portal vein (CAPV) is a rare anomaly in which the intestinal and splenic venous drainage bypasses the liver and drains into the systemic veins through various venous shunts. In patients with CAPV, the portosystemic shunting causes disruption of the enterohepatic circulation and leads to various clinical manifestations. CAPV can be diagnosed without invasive techniques. This article illustrates the clinical and radiologic findings (including ultrasound, CT, and MRI) of CAPV.

NUT midline carcinoma: report of 2 cases suggestive of pulmonary origin.

In this study, we report 2 pediatric cases of nuclear protein of the testis (NUT) midline carcinoma (NMC) suggestive of pulmonary origin: case 1 was a 14-year-old Japanese boy and case 2 was a 7-year-old Japanese girl. Initial symptoms of both cases were prolonged cough and chest pain, and the case 2 patient also complained of lumbago and lumbar mass due to bone metastases. Imaging studies revealed that pulmonary tumors from both patients were located at the hilar region of the lower lobe. Biopsies of the tumors showed undifferentiated carcinoma in case 1 and combined undifferentiated and squamous cell carcinoma in case 2. Despite intensive treatment with chemotherapy and radiation, progression of neither tumor was controlled, and both patients died of the tumors at 1 year (case 1) and 4 months (case 2) after onset of disease. Both tumors were diffusely positive for p63 and NUT expression and were partially positive for various cytokeratins. Reverse transcription polymerase chain reaction analysis and subsequent direct sequencing revealed that the bromodomain-containing protein 4-NUT chimeric gene was present in tumor tissue of both patients, leading to a diagnosis of NMC. The tumor cells of case 1 were also positive for thyroid transcription factor-1 expression, but those of case 2 were negative. Histologic examination of the surgically removed lung tumor of case 1 indicated that the origin of the tumor was basal cells of the bronchiolar epithelia.

Susceptibility-Weighted Imaging Findings of Cortical Laminar Necrosis in Pediatric Patients

BACKGROUND AND PURPOSE: MR susceptibility-weighted imaging (SWI) is a highly sensitive technique for detection of hemorrhage, but its utility in the evaluation of children with laminar necrosis is not yet known. We assessed whether cortical laminar necrosis in pediatric patients contains hemorrhage on SWI. MATERIALS AND METHODS: “Cortical laminar necrosis” was defined as a hyperintense cortical lesion on T1-weighted imaging in the subacute or chronic phase of brain damage in some foci involving the cerebral cortex and white matter such as hypoxic-ischemic incidents and encephalopathy. Medical records, CT, and MR images were retrospectively analyzed. Fifteen patients (7 boys, 8 girls; age range, 0–13 years) were included. The areas of signal-intensity loss on SWI that were considered to be hemorrhage were correlated with the laminar necrosis. CT was assessed to correlate with the presence of calcification at the location of the signal-intensity loss on SWI. To assess appearance or signal-intensity changes of hemorrhage in the laminar necrosis, follow-up SWI was performed. RESULTS: The causes of laminar necrosis included infarction in 4 patients, ischemic changes from Moyamoya disease in 2, meningoencephalitis in 2, hypoxic-ischemic encephalopathy in 2, shaken baby syndrome in 1, encephalopathy from severe infection in 1, status epilepticus in 1, citrullinemia in 1, and brain injury with posterior reversible encephalopathy syndrome in 1. T1-weighted imaging showed focal laminar necrosis in 8, multifocal laminar necrosis in 2, and diffuse laminar necrosis in 5. SWI findings correlated with laminar necrosis included the following: no hemorrhage in 13 patients (80.0%), dotted hemorrhage in 2 (13.3%), and laminar hemorrhage in 1 (6.7%). Follow-up SWI performed in 6 patients showed no additional hemorrhage. CONCLUSION: Most areas of cortical laminar necrosis in pediatric patients showed no hemorrhage on SWI.

The correlation of diffusion-weighted magnetic resonance imaging in cervical compression myelopathy with neurologic and radiologic severity.

Study Design. A retrospective evaluation of diffusion-weighted imaging, apparent diffusion coefficient (ADC) maps, and T2-weighted images in patients with cervical compression myelopathy. Objective. To correlate high signal intensity on ADC maps and T2-weighted images to neurologic severity and radiologic spinal cord compression. Summary of Background Data. Previous studies indicated that the ADC map was more sensitive in detection of cervical compressive myelopathy than T2-weighted imaging. The relationship to neurologic severity has not been previously published. Methods. In 100 patients with or without cervical compressive myelopathy, the magnetic resonance appearance of the spinal cord on ADC maps and T2-weighted images was evaluated independently by 2 readers. On the basis of the presence or absence of abnormality, patients were categorized into 4 groups by type of intramedullary change. The degree of canal compression and the Japanese Orthopedic Association (JOA) score for cervical myelopathy were compared among the 4 types. Results. The type I group consisted of 32 patients without signal change on either ADC maps or T2-weighted images. The type II group had 33 patients with high signal intensity only on the ADC map. The type III group contained 28 patients with high signal intensity on both the ADC map and the T2-weighted images. The type IV group comprised 7 patients with high signal intensity only on T2-weighted images. The degree of canal compression and the JOA scores were significantly different among the 4 groups (P < 0.005). Most type III (25 of 28) and type IV (7 of 7) patients had severe cord compression. Average JOA scores in each type were (I) 16.0, (II) 14.7, (III) 11.7, and (IV) 8.7. Conclusion. ADC maps demonstrated internal changes in the early stages of chronic spinal cord compression, but had limitations for the detection of intramedullary changes in late-stage myelopathy.

Abnormal Basiocciput Development in CHARGE Syndrome

BACKGROUND AND PURPOSE: The causative gene of the common congenital malformation referred to as CHARGE syndrome is CHD7. Affected individuals often undergo head and neck imaging to assess abnormalities of the olfactory structures, hypothalamus-pituitary axis, and inner ear. We encountered a few children with severe hypoplasia of the basiocciput during a radiologic assessment of patients with CHARGE syndrome. To our knowledge, this anomaly has not been reported. Our purpose was to evaluate the incidence and severity of this anomaly in this syndrome. MATERIALS AND METHODS: Sagittal MR images of 8 patients with CHARGE syndrome were retrospectively reviewed by 2 radiologists who consensually evaluated the status of the basiocciput of the patients with CHARGE syndrome, as either normal or hypoplastic; and associated anomalies, which include basilar invagination, Chiari type I malformation, and syringomyelia, as either present or absent. The length between the basion (Ba) and the endo-sphenobasion (Es) and between the basion and the exo-sphenobasion (Xs) was measured on midsagittal MR images of the 8 patients and 70 age-matched controls. We searched for trends related to age in the length of Ba-Es and Ba-Xs of the control children by using a matched t test. RESULTS: Basioccipital hypoplasia was identified in 7 of the 8 patients with CHARGE syndrome and was severe in 6. Of those, 5 had associated basilar invagination and 1 had Chiari type I malformation with syringomyelia. CONCLUSIONS: Basioccipital hypoplasia and basilar invagination are prevalent in patients with CHARGE syndrome.

Scurvy in a child with autism: magnetic resonance imaging and pathological findings.

We present a case of scurvy in a 6-year-old boy with autism and an unbalanced diet. The patient was admitted with difficulties in walking. Magnetic resonance imaging findings of the thigh showed diffuse signal abnormality in the bone marrow, periosteum, and the femoral muscle. A biopsy specimen of the femur showed hematoma, proliferative fibroblasts, and few collagen fibers, which suggested a deficiency of vitamin C. Although recurrent periosteal hematoma may be suggestive of scurvy, this finding was subtle in the current case. It is important to be aware of this rare disease because it is easily cured with vitamin C supplementation.

Imaging and clinical characteristics of children with multiple foci of microsusceptibility changes in the brain on susceptibility-weighted MRI

BackgroundMicrosusceptibility changes in the brain are well known to correspond with microbleeds or micrometal fragments in adults, but this phenomenon has not been explored well in children.ObjectiveTo assess imaging and clinical characteristics of children with multiple foci of microsusceptibility changes using susceptibility-weighted imaging (SWI).Materials and methodsBetween 2006 and 2008, 12 children with multiple foci of microsusceptibility on SWI without corresponding abnormal signal on conventional MRI were identified and were retrospectively assessed.ResultsThe locations of foci of microsusceptibility included the cerebral white matter, basal ganglia, brainstem and cerebellar white matter, without any clear systematic anatomic distribution. CT (n = 5) showed no calcification at the locations corresponding to the microsusceptibility on SWI. Conventional MR imaging showed white matter volume loss (n = 5), delayed myelination (n = 2), acute infarction (n = 1), chronic infarction (n = 1), meningitis (n = 1), slight signal abnormality in the white matter (n = 1) and no abnormal findings (n = 1). Follow-up SWI (n = 3) showed no change of the microsusceptibility foci. Interestingly, all children had a history of heart surgery under extracorporeal circulation for congenital heart disease.ConclusionMultiple foci of microsusceptibility can be seen in the brain on SWI in children with congenital heart disease who underwent heart surgery with extracorporeal circulation.

Treatment Outcomes, Growth Height, and Neuroendocrine Functions in Patients With Intracranial Germ Cell Tumors Treated With Chemoradiation Therapy

PURPOSE We carried out a retrospective review of patients receiving chemoradiation therapy (CRT) for intracranial germ cell tumor (GCT) using a lower dose than those previously reported. To identify an optimal GCT treatment strategy, we evaluated treatment outcomes, growth height, and neuroendocrine functions. METHODS AND MATERIALS Twenty-two patients with GCT, including 4 patients with nongerminomatous GCT (NGGCT) were treated with CRT. The median age at initial diagnosis was 11.5 years (range, 6-19 years). Seventeen patients initially received whole brain irradiation (median dose, 19.8 Gy), and 5 patients, including 4 with NGGCT, received craniospinal irradiation (median dose, 30.6 Gy). The median radiation doses delivered to the primary site were 36 Gy for pure germinoma and 45 Gy for NGGCT. Seventeen patients had tumors adjacent to the hypothalamic-pituitary axis (HPA), and 5 had tumors away from the HPA. RESULTS The median follow-up time was 72 months (range, 18-203 months). The rates of both disease-free survival and overall survival were 100%. The standard deviation scores (SDSs) of final heights recorded at the last assessment tended to be lower than those at initial diagnosis. Even in all 5 patients with tumors located away from the HPA, final height SDSs decreased (p = 0.018). In 16 patients with tumors adjacent to the HPA, 8 showed metabolic changes suggestive of hypothalamic obesity and/or growth hormone deficiency, and 13 had other pituitary hormone deficiencies. In contrast, 4 of 5 patients with tumors away from the HPA did not show any neuroendocrine dysfunctions except for a tendency to short stature. CONCLUSIONS CRT for GCT using limited radiation doses resulted in excellent treatment outcomes. Even after limited radiation doses, insufficient growth height was often observed that was independent of tumor location. Our study suggests that close follow-up of neuroendocrine functions, including growth hormone, is essential for all patients with GCT.