JP2006116137A5 - - Google Patents

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JP2006116137A5
JP2006116137A5 JP2004308364A JP2004308364A JP2006116137A5 JP 2006116137 A5 JP2006116137 A5 JP 2006116137A5 JP 2004308364 A JP2004308364 A JP 2004308364A JP 2004308364 A JP2004308364 A JP 2004308364A JP 2006116137 A5 JP2006116137 A5 JP 2006116137A5
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ray
ray tube
tube current
value
image noise
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JP4731151B2 (en
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Ｘ線ＣＴ装置のＸ線管に流すＸ線管電流を決定するＸ線ＣＴ装置のＸ線管電流決定方法であって、
Ｘ線管及びＸ線検出器を回転させずに被検体を一方向のみ走査し、この走査時に前記Ｘ線検出器から得られたスキャノグラムデータから被検体断面モデルを求める工程と、
前記被検体断面モデルに基づいて各ビューごとに変化させるＸ線管電流のＸ線管電流標準変調曲線を決定する工程と、
前記Ｘ線管電流標準変調曲線上のＸ線管電流を使用した場合の各ビューの画像ノイズ分散寄与値と、前記各ビューに対して適用されるビュー方向重みとに基づいて再構成画像の画像ノイズ分散値を推定する工程と、
操作者が設定した画像ノイズ目標値から定まる目標の画像ノイズ分散値と、前記推定した画像ノイズ分散値との比に基づいて前記Ｘ線管電流標準変調曲線上のＸ線管電流を修正する工程と、
を含むことを特徴とするＸ線ＣＴ装置のＸ線管電流決定方法。 An X-ray tube current determining method for an X-ray CT apparatus for determining an X-ray tube current to be passed through an X-ray tube of an X-ray CT apparatus,
Scanning the subject only in one direction without rotating the X-ray tube and the X-ray detector, and obtaining a subject cross-sectional model from the scanogram data obtained from the X-ray detector at the time of scanning;
Determining an X-ray tube current standard modulation curve of an X-ray tube current to be changed for each view based on the subject cross-sectional model;
The image of the reconstructed image based on the image noise variance contribution value of each view when the X-ray tube current on the X-ray tube current standard modulation curve is used and the view direction weight applied to each view Estimating a noise variance value;
Correcting the X-ray tube current on the X-ray tube current standard modulation curve based on a ratio between a target image noise variance value determined from an image noise target value set by an operator and the estimated image noise variance value When,
A method for determining an X-ray tube current of an X-ray CT apparatus. 使用可能な管電圧ごと及びＣＴＤＩの基準となるファントム別に、（式１）における基準ＣＴＤＩｖｏｌ値The reference CTDIvol value in (Equation 1) for each usable tube voltage and for each phantom that is the reference for CTDI
（式１）管電流１ｍＡ・照射時間１ｓ・移動ピッチ（スキャナ１回転あたりの天板ｚ移動量／Ｘ線ビーム厚さ）＝１ (Formula 1) Tube current 1 mA, irradiation time 1 s, movement pitch (top plate z movement amount per scanner rotation / X-ray beam thickness) = 1
を予め格納しておき、Is stored in advance,
前記基準ＣＴＤＩｖｏｌ値と、前記修正されたＸ線管電流標準変調曲線上のＸ線管電流とに基づいて被曝線量の予測値を算出し、表示する工程を更に含む、Calculating and displaying a predicted value of the exposure dose based on the reference CTDIvol value and the X-ray tube current on the modified X-ray tube current standard modulation curve;
ことを特徴とする請求項１に記載のＸ線ＣＴ装置のＸ線管電流決定方法。The X-ray tube current determination method for an X-ray CT apparatus according to claim 1. Ｘ線を照射するＸ線管球と、前記Ｘ線管を制御するＸ線管制御装置と、を備えたＸ線源と、An X-ray source comprising: an X-ray tube that emits X-rays; and an X-ray tube control device that controls the X-ray tube;
被検体をはさんで前記Ｘ線源に対向し、Ｘ線を検出して撮影データを出力するＸ線検出器と、An X-ray detector facing the X-ray source across the subject, detecting X-rays and outputting imaging data;
前記Ｘ線源及び前記Ｘ線検出器を搭載して所定角度毎に回転可能な回転板と、A rotating plate mounted with the X-ray source and the X-ray detector and capable of rotating at predetermined angles;
前記撮影データに基づいて再構成演算処理を行う画像処理装置と、An image processing device that performs reconstruction calculation processing based on the imaging data;
を備えたＸ線ＣＴ装置であって、An X-ray CT apparatus comprising:
Ｘ線管及びＸ線検出器を回転させずに被検体を一方向のみ走査し、この走査時に前記Ｘ線検出器から得られたスキャノグラムデータから被検体断面モデルを求める手段と、Means for scanning the subject only in one direction without rotating the X-ray tube and the X-ray detector, and obtaining a subject cross-sectional model from the scanogram data obtained from the X-ray detector at the time of scanning;
前記被検体断面モデルに基づいて各ビューごとに変化させるＸ線管電流のＸ線管電流標準変調曲線を決定する手段と、Means for determining an X-ray tube current standard modulation curve of an X-ray tube current to be changed for each view based on the subject cross-sectional model;
前記Ｘ線管電流標準変調曲線上のＸ線管電流を使用した場合の各ビューの画像ノイズ分散寄与値を推定する手段と、Means for estimating an image noise variance contribution value of each view when using an X-ray tube current on the X-ray tube current standard modulation curve;
前記推定した各ビューの画像ノイズ分散寄与値と、各ビューに対して適用されるビュー方向重みとに基づいて再構成画像の画像ノイズ分散値を推定する手段と、Means for estimating the image noise variance value of the reconstructed image based on the estimated image noise variance contribution value of each view and the view direction weight applied to each view;
操作者が設定した画像ノイズ目標値から定まる目標の画像ノイズ分散値と、前記推定した画像ノイズ分散値との比に基づいて前記Ｘ線管電流標準変調曲線上のＸ線管電流を修正する手段と、Means for correcting an X-ray tube current on the X-ray tube current standard modulation curve based on a ratio between a target image noise variance value determined from an image noise target value set by an operator and the estimated image noise variance value When,
を備えることを特徴とするＸ線ＣＴ装置。An X-ray CT apparatus comprising: 使用可能な管電圧ごと及びＣＴＤＩの基準となるファントム別に、（式２）における基準ＣＴＤＩｖｏｌ値Reference CTDIvol value in (Equation 2) for each usable tube voltage and for each phantom that is the reference for CTDI
（式２）管電流１ｍＡ・照射時間１ｓ・移動ピッチ（スキャナ１回転あたりの天板ｚ移動量／Ｘ線ビーム厚さ）＝１ (Formula 2) Tube current 1 mA, irradiation time 1 s, movement pitch (top plate z movement amount per scanner rotation / X-ray beam thickness) = 1
を格納する手段と、Means for storing
前記基準ＣＴＤＩｖｏｌ値と、前記修正されたＸ線管電流標準変調曲線上のＸ線管電流とに基づいて被曝線量の予測値を算出し、表示する手段と、を更に含む、Means for calculating and displaying a predicted value of the exposure dose based on the reference CTDIvol value and the X-ray tube current on the modified X-ray tube current standard modulation curve;
ことを特徴とする請求項３に記載のＸ線ＣＴ装置。The X-ray CT apparatus according to claim 3.
JP2004308364A 2004-10-22 2004-10-22 X-ray tube current determination method and X-ray CT apparatus Active JP4731151B2 (en)

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