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3T MR ½ºÇÉ¿¡ÄÚ T1°­Á¶¿µ»ó¿¡¼­ ÀûÁ¤ÀÇ ¼÷ÀÓ°¢

3T MR Spin Echo T1 Weighted Image at Optimization of Flip Angle

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¹è¼ºÁø ( Bae Sung-Jin ) - °è¸í´ëÇб³ µ¿»êº´¿ø ¿µ»óÀÇÇаú

ÀÓûȯ ( Lim Cheong-Hwan ) - ÇѼ­´ëÇб³ ¹æ»ç¼±Çаú

Abstract

¸ñÀû: ¿µ»óÁø´Ü¿µ¿ª¿¡¼­ ÀÌ¿ëµÇ°í ÀÖ´Â 3T(T, tesla) MRÀÇ ½ºÇÉ¿¡ÄÚ(SE, spin echo) T1°­Á¶¿µ»ó(T1-Weighted image)±â¹ý¿¡¼­ ¼÷ÀÓ°¢(FA, flip angle)ÀÇ º¯È­¿¡ µû¸¥ ¿µ»óÀÇ ÁúÀ» ³ªÅ¸³»´Â ½ÅÈ£´ë ÀâÀ½ºñ(SNR, signal to noise ratio), ´ëÁ¶µµ ÀâÀ½ºñ(CNR, contrast to noise ratio)¸¦ Æò°¡ÇÑ ÈÄ Æ¯ÀÌÈí¼öÀ²(SAR, specific absorption rate)À» ÁÙÀ̸鼭 CNR¸¦ Çâ»ó½Ãų ¼ö ÀÖ´Â ÀûÁ¤ÀÇ ¼÷ÀÓ°¢À» ¾Ë¾Æº¸°íÀÚ ÇÏ¿´´Ù.

´ë»ó ¹× ¹æ¹ý: °í½ÄÀû ½ºÇÉ¿¡ÄÚ¿¡¼­ Åë»óÀûÀ¸·Î »ç¿ëÇÏ´Â 90 RF pulse ´ë½Å 50 RF pulse¿¡¼­ 130±îÁö 10¾¿ Áõ°¡½ÃŰ¸é¼­ ´ë³ú T1°­Á¶¿µ»óÀ» ȹµæÇÏ¿´´Ù. ÀÌ ¿µ»óµé¿¡¼­ ¹éÁú(WM, white matter), ȸ¹éÁú(GM, gray matter)°ú ¹è°æ(background)¿¡¼­ °¢°¢ ½ÅÈ£°­µµ¸¦ ÃøÁ¤ÇÏ¿© SNR¸¦ ±¸ÇÏ¿´°í, ±âÁ¸ÀÇ T1 À̿ϰ R1 = 1- exp ()À¸·Î, Áï Ernst angle cos = exp ()°úÀÇ °ü°è¼ºÀ¸·Î T1°­Á¶¿µ»ó¿¡¼­ WM°ú GMÀÇ SNR°ú CNRÀÇ Á¤±Ô¼º °ËÁ¤°ú ºñ¸ð¼ö °ËÁ¤ÀÎ Kruskal-wallis ºÐ¼®À¸·Î ÀûÁ¤ÀÇ ¼÷ÀÓ°¢À» ¾Ë¾Æº¸°íÀÚ ÇÏ¿´´Ù.

°á °ú: WM¿Í GMÀÇ ½ÅÈ£°­µµ¿Í ¹è°æÀâÀ½ ½ÅÈ£°­µµ¸¦ ÀÌ¿ëÇÏ¿© SNR¸¦ ±¸ÇÑ °á°ú WMÀÇ SNR´Â ¼÷ÀÓ°¢ 50º¸´Ù 130¿¡¼­ 1.6¹è Á¤µµ Áõ°¡ÇÏ¿´°í, GMÀÇ SNR´Â ¾à 1.9¹è Á¤µµ ³ô°Ô ³ªÅ¸³µ´Ù. µÎ Á¶Á÷ÀÇ SNRÀº T1 À̿ϰ°ú µ¿ÀÏÇÑ ¾ç»óÀ» º¸¿©ÁÖ°í ÀÖ´Ù. R1 = 1- exp ()À¸·Î ºÐ¼®ÇÑ SNRÀÇ ½ÅÈ£Áõ°¡°¡ µÐÈ­µÇ´Â ±âÁ¡ÀÌ WMÀº 120ÀÇ ¼÷ÀÓ°¢¿¡¼­, GMÀº 110 ÀÌÈÄ·Î ³ªÅ¸³ª µÎ Á¶Á÷¿¡¼­ ´Ù¸£°Ô ³ªÅ¸³ª´Â °ÍÀ» ¾Ë ¼ö ÀÖ¾ú´Ù. WM°ú GMÀÇ SNR´Â 130ÀÇ ¼÷ÀÓ°¢¿¡¼­ ³ô¾ÒÁö¸¸ CNR¿¡ À־´Â 80¿¡¼­ ÃÖ°í ³ô°Ô ³ªÅ¸³µÀ¸¸ç, 80 ÀüÈÄÀÇ ¼÷ÀÓ°¢¿¡¼­´Â °¨¼ÒÇÏ¿´´Ù.

°á·Ð: 3.0T MRÀÇ SE T1°­Á¶¿µ»ó ±â¹ý¿¡¼­ ¼÷ÀÓ°¢ÀÇ Áõ°¡¿¡ µû¶ó SNR´Â Áõ°¡ÇÏ¿´Áö¸¸ CNR´Â ÀÌÀü±îÁöÀÇ ÀÓ»ó¿¡¼­ »ç¿ëÇÏ´Â ¼÷ÀÓ°¢ÀÌ 90 º¸´Ù ÀûÀº 80¿¡¼­ CNRÀÌ ÃÖ°í·Î ³ªÅ¸³ª Åë»óÀûÀ¸·Î »ç¿ëÇÏ´Â ¼÷ÀÓ°¢º¸´Ù 10 ³·Àº RF pulse duration time »ç¿ëÇÔÀ¸·Î½á 3T¿¡¼­ ¹®Á¦·Î Á¦±âµÈ SARµµ ÁÙÀÏ ¼ö ÀÖ¾ú´Ù. ¾ÕÀ¸·Î 3.0T MRÀÇ SE T1°­Á¶¿µ»ó ±â¹ý¿¡¼­ ÀûÁ¤ ¼÷ÀÓ°¢À» »ç¿ëÇÔÀ¸·Î¼­ CNRÀ» ³ôÀÏ ¼ö ÀÖÀ» °ÍÀ¸·Î ±â´ëµÇ¾îÁø´Ù.

Purpose: This study presents the optimization of flip angle (FA) to obtain higher contrast to noise ratio (CNR) and lower specific absorption rate (SAR).

Materials and Methods : T1-weighted images of the cerebrum of brain were obtained from 50 to 130 FA with 10 interval. Signal to noise ratios (SNRs) were calculated for white matter (WM), gray matter (GM), and background noise. The proper FA was analyzed by T-test statistics and Kruskal-wallis analysis using R1 = 1- exp () and Ernst angle cos = exp ().

Results: The SNR of WM at 130 FA is approximately 1.6 times higher than the SNR of WM at 50. The SNR of GM at 130 FA is approximately 1.9 times higher than the SNR of GM at 50. Although the SNRs of WM and GM showed similar trends with the change of FA values, the slowdown point of decrease after linear fitting were different. While the SNR of WM started decreasing at 120 FA, the SNR of GM started decreasing at less than 110. The highest SNRs of WM and GM were obtained at 130 FA. The highest CNRs, however, were obtained at 80 FA.

Conclusion: Although SNR increased with the change of FA values from 50 to 130 at 3T SE T1WI, CNR was higher at 80 FA than at the usually used 90 FA. In addition, the SAR was decreased by using smaller FA. The CNR can be increased by using this optimized FA at 3T MR SE T1WI.

Ű¿öµå

½ºÇÉ¿¡ÄÚ; T1°­Á¶¿µ»ó; ¼÷ÀÓ°¢; ½ÅÈ£´ë ÀâÀ½ºñ; ´ëÁ¶µµ ÀâÀ½ºñ
spin echo; T1-weighted image; flip angle; signal to noise ratio; contrast to noise ratio
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