We retrospectively reviewed head MR images in a group of 330 adult patients (1 97 women and 1 33 men 20-88 years old) to establish the normal MR appearance of the clivus on

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Analysis of the focal− spot size is important for the quality control (QC)program concerning a clinica ！ X − ray fi ］ m systeIn ． It is especially important in magni 丘cation radiography ． In this sしudy the focal − spot size of a microfocus X − ray tube (Toshiba， DRX − 89H)was studied using a slit foca［spot camera (Nuclear Associates ， Roeck) ．The focal − spot was examined visually ． Its length was O． 115 mm ， and its width was O． 183 mrn ， according to the measurements obtained by the slit images、 That results were not suMcient for NEMA and IEC standards ． The grid bias voltage affected the focal − spot size of the three ・ conductor terminal X − ray tube ． Therefore ， we measured lt according to changes in the automatic control and the manual control of the grid bias voltage which improved (minimized ＞ the focal spot ． That obtained the best grid bias voltages to correspond with the tUbe VOltageS 、 We imprOVed the fOCal − SpOt Size ， tO O， 113 mm in length and O． 165 nlm ill width ， 〔364)