埼玉医科大学雑誌 第33巻 第2号 (2006年4月) 19-23頁 ◇論文(図表を含む全文)は，PDFファイルとなっています．
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湯浅 昌之，小澤 栄人，平敷 淳子
Evaluation of Adrenal Adenoma: Correlation between Pre Contrast CT Value and the Signal Intensity Loss on Dual Chemical Shift MRI
Purpose: The aim of our study is to assess pre-contrast CT value and signal intensity loss of adrenal adenoma on dual phase chemical shift MRI. Materials and Methods: From May 1997 to December 2004, 52 patients with adrenal adenoma were examined with pre-contrast CT and dual chemical shift MRI. Eleven of 52 were proven by surgery and the rest did not show any change for 12 months period. All patients were studied with CT (GE Hispeed Advantage SG, SP LightSpeed Qx/i-α) and 1.5 T MRI units (Magnetom Quantum and Sonata, Siemens, Germany) with a body-coil. CT was scanned with slice thickness of 3 mm, 5 mm or 10 mm, and pitch of 1. In additional to the MR routine sequences such as FLASH and HASTE, dual chemical shift sequence was scanned (TR/TE/FA＝140/2.3 and 5.2/90). Hounsfield units (HU) on pre contrast CT, signal intensity ratio (SIR), and signal noise ratio (SNR) on MRI were measured. Signal intensities were measured quantitatively in opposed-phase (OP), in-phase (IP) and background noise (N). SIRs (OP/IP) and SNRs (OP-N)/(IP-N)) were calculated as well as mean and standard deviation. Using JMP (commercial analysis software), correlation analysis was performed between HU and the parameters of SIR and SNR with linear regression method. Results: The mean and SD of CT value, SNR and SIR was 12.6±15.04, SNR＝0.51±0.28, SIR＝0.47±0.30, respectively. Correlation coefficient between CT value and SNR was 0.78(p＜0.001), and between CT vale and SIR was 0.76(p＜0.001). Discussion and conclusion: SNR and SIR of in-phase and opposed-phase study is an established method for assessing of fat and water components in the adrenal adenoma. However, CT value also has the power for the evaluation of fat element. In this study the CT vs. SIR and the CT vs. SNR were correlated well. These results suggest that CT value may show the amount of fat element in adrenal nodule. In conclusion, pre-contrast CT value could suggest a good index of a lipid component of an adrenal adenoma. The signal intensity ratios are the reliable evaluation method for diagnosis adrenal adenomas.