Japanese
TitlePETを用いた局所脳血流量の定量測定における部分容積効果の評価
Subtitle原著
Authors成田雄一郎*,**, 飯田秀博*, Babak A.ARDEKANI*,***, 畑澤順*, 菅野巖*, 中村尚司****, 上村和夫*****
Authors(kana)
Organization*秋田県立脳血管研究センター放射線医学研究部, **東北大学大学院工学科原子核工学専攻, ***Department of Applied Physics, University of Technology, ****東北大学サイクロトロン・ラジオアイソトープセンター放射線管理研究部, *****秋田県立脳血管研究センター所長
Journal核医学
Volume32
Number2
Page163-172
Year/Month1995/2
Article原著
Publisher日本核医学会
Abstract「要旨」15O標識水とポジトロンエミッショントモグラフィ (PET) を用いた局所脳血流測定法において, 部分容積効果の影響を評価した. 灰白質, 白質, および脳髄液の3成分からなる脳解剖数値ファントムを使い, 15O標識水の入力関数に対する放射能濃度分布画像を作成, PET装置の空間分解能に対応する画像の平滑化を行った後, 種々のトレーサ動態モデルにて局所血流量画像を計算し, 血流量値のモデル依存性を調べた. 画像の平滑化により, 灰白質領域の放射能濃度は系統的に過小評価, 白質および脊髄領域では過大評価した. これにともなって, 得られた血流量値も, 灰白質および白質実質の血流量値と比べると, それぞれ過小あるいは過大評価した. しかし, 血流画像をそのまま平滑化した定量値と比べると, 系統的に小さく評価した. この過小評価の程度は, 平滑化の程度および使用するモデルに大きく依存しており, 灰白質と白質の混合領域ではSteady state法で約20%, Autoradiography法およびWeighted integration法で約9%, Non-linear least square法で約2%であった. また, 脳髄液が含まれる領域では, Steady state法およびAutoradiography法でその誤差が拡大した. PETを用いた局所脳血流量の定量解析においては, 以上のような過小評価の存在, およびこれのモデル依存性は, 重要な因子であり, 注意を要することが示された.
Practice臨床医学：一般
KeywordsPositron CT, 15O-Water, Cerebral blood flow, Microsphere model, Autoradiograph, Weighted integration, Steady state, Non-linear least square fitting
English
TitleEvaluation of Partial Volume Effect in Quantitative Measurement of Regional Cerebral Blood Flow Using Positron Emission Tomography
Subtitle
AuthorsYuichiro NARITA*,**, Hidehiro IIDA*, Babak A.ARDEKANI*,***, Jun HATAZAWA*, Iwao KANNO*, Takashi NAKAMURA****, Kazuo UEMURA*****
Authors(kana)
Organization*Department of Radiology and Nuclear Medicine, Akita Research Institute of Brain and Blood Vessels, **Department of Atomic Engineering, Tohoku University, ***Department of Applied Physics, University of Technology, ****Division of Radiation Protection, Cycrotron and Radioisotope Center, Tohoku University, *****Akita Research Institute of Brain and Blood Vessels
JournalThe Japanese Journal of nuclear medicine
Volume32
Number2
Page163-172
Year/Month1995/2
ArticleOriginal article
PublisherTHE JAPANESE SOCIETY OF NUCLEAR MEDICINE
Abstract[Summary] Effects of limited spatial resolution of the positron emission tomography (PET) scanner on the quantitative measurement of regional cerebral blood flow (rCBF) was investigated for various tracer kinetic models with use of 15O labeled water and PET. Using a numerical brain phantom consisting of a gray matter, white matter and cerebrospinal fluid components, dynamical tracer distribution images were calculated for the H215O bolus injection and for the C15O2 gas inhalation protocols. The tracer distribution images were convoluted with a 2 dimensional gaussian function with full-width at half maximum (FWHM) of 4, 7, 12 mm to simulate a limited spatial resolution of the PET scanner, and rCBF images were calculated according to some kinetic models. Smoothing the tracer distribution images caused a heterogeneous structure (tissue mixture) in a given volume element. rCBF values calculated by models with use of 15O-water and PET were found to provide rCBF values that were systematically underestimated compared with those obtained by the microsphere moldel for a mixed tissue region. Moreover, the magnitude of the underestimation was shown to be highly dependent on the tracer kinetic models employed, those errors for mixed tissue of gray and white matter were 20% on steady state, 9% on autoradiography and on weighted integration method, and 2% on non-linear least squares fitting, compared with microsphere model. More errors obserbed by steady state method and autoradiography method happened for tissue mixture consisting gray matter, white matter and cerebrospinal fluid components. It is important to take into account for difference of the partial volume effect for each models in calculated rCBF.
PracticeClinical medicine
KeywordsPositron CT, 15O-Water, Cerebral blood flow, Microsphere model, Autoradiograph, Weighted integration, Steady state, Non-linear least square fitting

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