Fumiko Kinoshita

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 15O-labeled compounds. Hemoglobin (Hb) concentration of blood, a primary determinant of arterial oxygen content (CaO2), influences cerebral circulation. We investigated interindividual variations of CBF, cerebral blood volume (CBV), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2) 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 CMRO2 was independent of Hb concentration. Oxygen delivery defined as a product of CaO2 and CBF (CaO2 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 CMRO2. The current findings provide important knowledge to understand the control mechanism of cerebral circulation and to interpret the 15O PET data in clinical practice.

CT-guided transthoracic needle biopsy using a puncture site-down positioning technique.

OBJECTIVE We have developed a new CT-guided technique using puncture site-down positioning during the biopsy. The goal of our study was to determine the efficacy and safety of this technique for biopsy of lung lesions compared with the standard technique. MATERIALS AND METHODS Medical records of 236 patients who underwent CT-guided transthoracic needle biopsy were retrospectively evaluated. This study included 89 cases that were biopsied using the standard technique (group A) and 147 cases that were biopsied using the puncture site-down positioning technique (group B). A 20-gauge automated cutting needle without coaxial technique was used in all patients. Medical records were reviewed for lesion size and location, biopsy results, and complications. RESULTS When using the standard technique, the sensitivity for malignant lesions was 96.1%; the sensitivity for benign lesions, 92.1%; and diagnostic accuracy, 94.4%. Thirty-seven patients (41.6%) had pneumothorax, with 16 (18.0%) requiring chest tube placement. When using the puncture site-down positioning technique, the sensitivity for malignant lesions was 95.4%; the sensitivity for benign lesions, 93.3%; and diagnostic accuracy, 94.6%. Nineteen patients (12.9%) had pneumothorax, with four (2.7%) requiring chest tube placement. Other complications were minimal. CONCLUSION CT-guided transthoracic needle biopsy using the puncture site-down positioning technique is an effective and safe procedure with a high diagnostic accuracy and low complication rate. This new technique is especially useful in reducing the rate of pneumothorax.

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.

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

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.

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.

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 15O-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.

Clinical usefulness of In-111 chloride and Tc-99m Sn colloid scintigraphy in the diagnosis of intrathoracic extramedullary hematopoiesis

We report a case of intrathoracic extramedullary hematopoiesis associated with hemolytic anemia. While the paravertebral localization of the lesions demonstrated on CT and MRI was suspicious of intrathoracic extramedullary hematopoiesis, In-111 chloride and Tc-99m Sn colloid bone marrow scintigraphies showing a bone marrow element of the lesion were useful to confirm the diagnosis.

Sequential MR imaging and SPECT studies in herpes simplex encephalitis with crossed cerebellar hyperperfusion

We report a case of herpes simplex encephalitis in which sequential MR imaging and SPECT studies showed interesting findings. SPECT in the acute stage showed wide increased uptake in the left cerebral hemisphere, as well as increased uptake in the contralateral right cerebellar hemisphere. Tl-weighted images in the subacute stage showed hyperintense signals along the cerebral cortices, but T2*-weighted gradient-echo images did not show any signal decrease caused by the magnetic susceptibility effect of hemoglobin degradation. Sequential SPECT studies in addition to MR imaging facilitate precise understanding of the pathophysiology of herpes simplex encephalitis.

Craniopharyngioma with high FDG uptake.

Craniopharyngiomas are slow-growing epithelial neoplasms in the suprasellar region. Fluorodeoxyglucose (FDG) accumulation in a craniopharyngioma has not been previously recognized. We report a case of a suprasellar craniopharyngioma with F-18 FDG positron emission tomography (PET) findings, which showed intense accumulation of FDG. Histologic examination revealed a papillary craniopharyngioma with no evidence of malignant features. Six months after excision, recurrence of the tumor was detected. FDG PET might be helpful in predicting the potential for early recurrence of craniopharyngioma. Nuclear medicine physicians should be aware that craniopharyngioma may be included in the differential diagnosis of suprasellar tumors with high FDG uptake.

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.