English / 日本語
Miho Kita MD,PhD (Department of Radiology, Seichokai Fuchu Hospital)
Kazuhiro Kawano RT, Katsuya Kometani RT
Daichi Tamagaki, Tomomi Tani
The inversion time at the null point (TInull) varies depending on the imaging parameters in inversion recovery (IR) sequences.
This web page provides a free tool for immediate calculation of the optimal TInull which adequately nulls the signal of fat or CSF, according to the imaging protocol1) .
1) Miho Kita, et al.: Online tool for calculating null points in various inversion recovery sequences. Magn Reson Imaging 2013; 31: 1631-1639.
How to use this calculation tool :
Please enter the imaging parameters and T1 value※ of fat or CSF (listed below for reference) into the blank cells and click on the “Calculate” button, then calculated TInull will be instantly displayed. The calculated value of TInull can be subsequently applied to clinical imaging by setting it as the inversion time on the MR scanner.
Reference values of T1 of fat and CSF depending on static magnetic field strength are listed below, for ease of reference.
※T1 relaxation times (ms) ［Reference values］
| 1.5T | 3T | |
|---|---|---|
| Fat | 260 （240～280） | 340 （320～370） |
| CSF | 4500 （4200～4700） | 4700 （4500～4900） |
Calculation tool for null point :
各空欄に、T1値（上記の表を参照）や撮像パラメーター（ＭＲ装置に表示）を半角で入力してください。その後計算ボタンをクリックすると、TI null の欄にTInull計算値が表示されます。得られたTInullの値をinversion delayとして入力してから、撮像開始してください。
なお、SPAIRの場合は、inversion delayの値を変更すると、連動してpackage数やSPAIR TRが変化する場合がありますので、そのような場合には、TRなどの設定を再調整し、SPAIR TRとinversion delayの関係が計算通りとなっていることを確認したうえで、撮像を開始してください。
Abbreviations:
T1 — longitudinal relaxation time
TR — repetition time
TE — echo time
ES — echo space
ETL — echo train length
TRSPAIR — interval of SPAIR pulse application
（1）SPAIR併用拡散強調像
SPAIR併用2D-TSE法
各空欄にT1値・TR・SPAIR TRを入力
（2）STIR拡散強調像
各空欄にT1値・TR・TEを入力
（3）FLAIR-TSE法
各空欄にT1値・TR・ES・ETLを入力
The equations programmed in this tool, assuming the inversion pulse is perfect, are as follows:
(1) Sequences having a train of multiple SPAIR pulses (with no spin echo) before the next IR pulse
[2D multi-slice SPAIR-DWI, 2D multi-slice SPAIR-TSE]
where TRSPAIR is the interval of SPAIR pulse application given by:
with the only exception of single-shot 2D multi-slice SPAIR-TSE, for which TRSPAIR=TR.
(2) Sequences having a single spin echo before the next IR pulse
[STIR-DWI (single-shot SE-EPI), FLAIR-SE，STIR-SE]
(3) Sequences having multiple spin echoes before the next IR pulse
[FLAIR-TSE（T1-FLAIR,T2-FLAIR）, STIR-TSE, 3D SPAIR-TSE, 2D single-slice SPAIR-TSE]
When the inversion pulse is imperfect, the equations become:
where α is the ratio of longitudinal magnetization after the inversion pulse to that before the pulse. When the inversion pulse is perfect , α=-1.