䜟䜜䜟䜜䛿➨4❶䛻䛚䛔䛶䝃䜲䝜䜾䝷䝮䝕䞊䝍䜢ᚲせ䛸䛧䛺䛔㧗⥺㔞CT⏬ീ䛛䜙ప⥺㔞⏬ീ
䜢䝅䝭䝳䝺䞊䝅䝵䞁䛩䜛ᢏ⾡䜢㛤Ⓨ䛧䛯䠊➨5❶䛷䛿䠈2✀㢮䛾䝣䜯䞁䝖䝮⏬ീ䛻㐺⏝䛧⏬㉁䜢ホ౯ 䛩䜛䛣䛸䛷༑ศ䛺⢭ᗘ䛷䝅䝭䝳䝺䞊䝅䝵䞁䛩䜛䛣䛸䛜ྍ⬟䛷䛒䜛䛣䛸䠈䜎䛯ᇶ‽䝣䜯䞁䝖䝮䛻䜘䜚Ỵᐃ䛧 䛯䝟䝷䝯䞊䝍䜢௵ព䛾⏬ീ䛻㐺⏝䛩䜛䛣䛸䛜ྍ⬟䛷䛒䜛䛣䛸䜢☜ㄆ䛧䛯䠊䛧䛛䛧䛺䛜䜙䠈ಶ䚻䛾ᝈ⪅
䛾᭱㐺⥺㔞䛾Ỵᐃ䜢┠ⓗ䛸䛧䛯ホ౯䛻ᮏᡭἲ䛻䜘䛳䛶సᡂ䛥䜜䜛䝅䝭䝳䝺䞊䝅䝵䞁⏬ീ䛜⏝ྍ
⬟䛛䛹䛖䛛䛻䛴䛔䛶䛿䠈⮫ᗋ⏬ീ䜈䛾㐺⏝⤖ᯝ䜢ホ౯䛩䜛ᚲせ䛜䛒䜛䠊
䝣䜯䞁䝖䝮⏬ീ䛻䜘䜛᳨ウ䛷䛒䜜䜀䠈MTF 䜔 NPS 䛻䜘䜛ゎീᗘ≉ᛶ䠈䝜䜲䝈≉ᛶ䛾ẚ㍑䛜ྍ
⬟䛷䛒䜚䠈ᐇ㝿䛻䛥䜎䛦䜎䛺᮲௳䛷ᙳ䛧䛯ᐇ㝿䛾⏬ീ䛸䝅䝭䝳䝺䞊䝅䝵䞁⏬ീ䜢ẚ㍑䛩䜛䛣䛸䛜ྍ
⬟䛷䛒䜛䠊䛧䛛䛧䛺䛜䜙䠈⮫ᗋ⏬ീ䜈㐺⏝䛧䛯⏬ീ䛾ホ౯䛷䛿䠈⮫ᗋ⏬ീ䛻䛚䛔䛶 MTF 䜔 NPS 䜢⡆౽䛻ィ 䛩䜛ᡭἲ䛜䛺䛔䛣䛸䠈䜎䛯䝅䝭䝳䝺䞊䝅䝵䞁⏬ീ䛸ẚ㍑䛩䜛䛯䜑䛾ྠ୍ᝈ⪅䛻ᑐ䛧䛶
ู⥺㔞䛷ᙳ䛥䜜䛯⏬ീ䛿ᚓ䜙䜜䛺䛔䛣䛸䛛䜙䠈ẚ㍑䛿ᐜ᫆䛷䛿䛺䛔䠊Žabić 䜙䛾◊✲䛷䛿㛤Ⓨ
䛧䛯ᡭἲ䛾ホ౯䜢䠈⏕䛝䛯ື≀䛾88 mAs䛾CT⏬ീ䜘䜚䝅䝭䝳䝺䞊䝅䝵䞁䛧䛯11 mAs䛾CT⏬
ീ䛸䠈ᐇ㝿䛻11 mAs䛷ᙳ䛥䜜䛯CT⏬ീ䛾ẚ㍑䛾どぬホ౯䛻䜘䜚⾜䛳䛶䛔䜛 [9]䠊䜎䛯⮫ᗋ⏬
ീ䜢⏝䛔䛶ప⥺㔞⏬ീ䜢సᡂ䛧䛯ሗ࿌䛿䛔䛟䛴䛛䛒䜛䛜 [7, 8]䠈䝅䝭䝳䝺䞊䝅䝵䞁⏬ീ䛸ᐇ㝿䛾ప
⥺㔞䛾⮫ᗋ⏬ീ䜢䜒䛱䛔䛶ྠ➼䛾⏬㉁䛜ᚓ䜙䜜䛶䛔䜛䛛䜢ホ౯䛧䛶䛔䜛◊✲䛿䜟䜜䜟䜜䛜▱䜛
⠊ᅖ䛷䛿☜ㄆ䛷䛝䛺䛛䛳䛯䠊
䛣䛾䜘䛖䛻䠈ྠ୍ᝈ⪅䛷⥺㔞䜢ኚ䛥䛫䛯ሙྜ䛾⮫ᗋ⏬ീ䜢ᚓ䜛䛣䛸䛿䠈୍⯡䛻䛿㠀ᖖ䛻ᅔ㞴 䛷䛒䜚䠈◊✲┠ⓗ䛷䛭䛾䜘䛖䛺⏬ീ䜢ᚓ䜛䛣䛸䛿チ䛥䜜䛺䛔䠊䛧䛛䛧䛺䛜䜙䠈ᐇ㝿䛾⮫ᗋ䛻䛚䛔䛶䛿䠈
ึᅇ䛾⢭ᰝ䛾 CT ᳨ᰝ䛷䛿䠈㏻ᖖ⥺㔞䛷ᙳ䜢⾜䛖䛜䠈䛭䛾ᚋ䛾䝣䜷䝻䞊䜰䝑䝥䛾᳨ᰝ䛷䛿䠈⥺
㔞䜢ᖜ䛻㍍ῶ䛧䛶᳨ᰝ䜢⾜䛖ሙྜ䛜䛒䜛䠊䛣䛾ሙྜ䠈㏻ᖖ⥺㔞䛷䛾ᙳ䛸ప⥺㔞䛷䛾ᙳ䛾㛫 䛻ᩘ㐌㛫䛛䜙ᩘ䞄᭶䛾䜲䞁䝍䞊䝞䝹䛜⏕䛨䜛䛯䜑䠈䛭䛾㛫䛻ᝈ⪅䛾≧ែ䛜ኚ䛩䜛ྍ⬟ᛶ䛜㧗䛔 䛾䛷䠈ཝᐦ䛺ព䛷䛾ẚ㍑ホ౯䛸䛿䛔䛘䛺䛔䛜䠈䝅䝭䝳䝺䞊䝅䝵䞁ᡭἲ䛾⮫ᗋ⏬ീ䛻䛚䛡䜛᭷⏝
ᛶ䜢᳨ド䛩䜛᪉ἲ䛸䛧䛶䛿᭱䜒ಙ㢗ᗘ䛜㧗䛔䛸⪃䛘䜙䜜䜛䠊
➨6❶㻌 ప⥺㔞CT⏬ീ䝅䝭䝳䝺䞊䝅䝵䞁ᢏ⾡䛾⮫ᗋ⏬ീ䜈䛾ᛂ⏝
᧰᧴
6.2㻌 ᪉ἲ
6.2.1㻌 ⏝⨨䛚䜘䜃㐺⏝
๓㏙䛾䜘䛖䛻䠈ᮏᡭἲ䛻䛚䛡䜛䝅䝭䝳䝺䞊䝅䝵䞁⏬ീ䛾᭷⏝ᛶ䜢᳨ド䛩䜛䛯䜑䛻㏻ᖖデ⒪䛻䛚 䛔䛶䠈ྠ୍ᝈ⪅䛻ᑐ䛧䛶⥺㔞䜢ኚ䛥䛫䛶 CT᳨ᰝ䛜⾜䜟䜜䛯䜢⏝䛔䛯䠊䛣䜜䜙䛾䛿⤒
⓶⫵⏕᳨䜢ཷ䛡䛯ᝈ⪅䛾༢⣧CT⏬ീ䛷䛒䜛䠊᭱ึ䛾⢭ᰝ䛷䛿ᝈ⪅䛾య᱁䛻ྜ䜟䛫䛯㏻ᖖ䛾⥺
㔞䛷 CT ᳨ᰝ䛜⾜䜟䜜䠈䛭䛾⤖ᯝ䠈⢭ᰝ䛜ᚲせ䛺ኚ䛜᳨ฟ䛥䜜䠈⤒⓶⫵⏕᳨䛜⾜䜟䜜䛯
䛷䛒䜛䠊ᮏ㝔䛷䛿䛣䛾䜘䛖䛺ᝈ⪅䛻䛴䛔䛶䛿䠈⏕᳨ᚋ䠈Ẽ⬚䛺䛹䛾䝸䝇䜽䛾☜ㄆ䛾䛯䜑ప⥺㔞 (50
mAs) 䛷CT ᳨ᰝ䛜⾜䜟䜜䛶䛔䜛䠊⏝⨨䛿➨5 ❶䛾䝣䜯䞁䝖䝮ᐇ㦂䛷⏝䛧䛯 CT⨨䛸ྠ
୍䛾64ิ䝬䝹䝏䝇䝷䜲䝇CT (Brilliance䠗 Philips㻌 Healthcare䠈Cleveland䠈OH) 䛷䛒䜚䠈䛣䛾
⨨䛻䜘䜚ᙳ䛥䜜䛯⮫ᗋ⏬ീ䜢⏝䛧䛯䠊⮫ᗋ⏬ീ䛾ᵓᡂ䛿ᶆ‽䛾䝣䜱䝹䝍 (type C) 䜢⏝䛔 䛯 FBP䜰䝹䝂䝸䝈䝮䛻䜘䜚⾜䜟䜜䛯䠊⟶㟁ᅽ䠈䝇䝷䜲䝇ཌ䠈DFOV 䛿䛭䜜䛮䜜120 kV䠈5.0 mm䠈
250 mm䛷䛒䛳䛯䠊䝅䝭䝳䝺䞊䝅䝵䞁䛻⏝䛩䜛䝜䜲䝈䝰䝕䝹䛸ᵓᡂ䝣䜱䝹䝍䛿ྠ䛨ᙳ᮲௳䛷ᚓ
䜙䜜䛯ACR䝣䜯䞁䝖䝮⏬ീ䜢ᇶ‽䝣䜯䞁䝖䝮䛸䛧䛶Ỵᐃ䛧䛯䠊䝇䝷䜲䝇ᯛᩘ䛿䛻䜘䜚␗䛺䜚䠈䛭䛾
⠊ᅖ䛿 51-151 ᯛ䛷䛒䛳䛯䠊ᑐ㇟䛸䛧䛯䛩䜉䛶䛾䛿␗䛺䜛 2 ✀㢮䛾⥺㔞䛷ᙳ䛥䜜䛶䛔䛯䠊
䛭䛾䛖䛱䛾ప⥺㔞䛿䛩䜉䛶50 mAs䛷䛒䜚䠈㧗⥺㔞䛿䝇䝷䜲䝇䠈䛷␗䛺䜚105-339 mAs䛷䛒 䛳䛯䠊ᮏᐇ㦂䛷䛿䛣䜜䜙䛾⤒⓶⫵⏕᳨๓ᚋ䛷ᙳ䛥䜜䛯CT⏬ീ䠈䜎䛯䛿⤒⓶⫵⏕᳨ᚋ䛻ᙳ䛥 䜜䛯ప⥺㔞⏬ീ䛸䛭䛾ᚋ䛾⤒㐣ほᐹ䛷ᙳ䛥䜜䛯㧗⥺㔞䛾⏬ീ䜢⏝䛧䠈䛭䜜䛮䜜䛾㧗⥺㔞⏬
ീ䛛䜙50 mAs䛾ప⥺㔞⏬ീ䜢䝅䝭䝳䝺䞊䝅䝵䞁䛧ẚ㍑ホ౯䜢⾜䛳䛯䠊䛩䜉䛶䛾䛻䛴䛔䛶䠈㧗
⥺㔞䛸ప⥺㔞䛾2ᅇ䛾 CT᳨ᰝ䛾㛫㝸䛿6᪥䛛䜙415᪥䛷䠈䜎䛯䠈⤒⓶⫵⏕᳨ᚋ䛻ᙳ䛥䜜䛯 ప⥺㔞⏬ീ䛿䛩䜉䛶㣗ᚋ䛻ᙳ䛥䜜䛯䠊୍⯡ⓗ䛻㧗⥺㔞⏬ീ⢭ᰝ䛾ᙳ䛻䛿㐀ᙳ⏝䛾
ྍ⬟ᛶ䜢⪃៖䛧䛶⤯㣗≧ែ䛷᳨ᰝ䛜⾜䜟䜜䜛ሙྜ䛜ከ䛔䛾䛷䠈㧗⥺㔞⏬ീ䛸ప⥺㔞⏬ീ䛷䛿 ᝈ⪅䛾⨨䜔᮲௳䛜␗䛺䜛䠊䛺䛚䠈ᮏ◊✲䛷⏝䛔䛯䛩䜉䛶䛾⮫ᗋ⏬ീ䛾⏝䛻䛴䛔䛶䛿䠈⇃ᮏ
Ꮫ䛾⌮ጤဨ䛻䜘䛳䛶ᢎㄆ䜢ཷ䛡䛶䛔䜛䠊
6.2.2㻌 ⮫ᗋ⏬ീ䛾䝅䝭䝳䝺䞊䝅䝵䞁ప⥺㔞⏬ീ䛾ホ౯
5䛭䜜䛮䜜䛾㧗⥺㔞⏬ീ䛛䜙50 mAs䛾ప⥺㔞⏬ീ䜢䝅䝭䝳䝺䞊䝅䝵䞁䛧䠈ᐇ㝿䛻50 mAs 䛷ᙳ䛥䜜䛯⏬ീ䛸ẚ㍑䛩䜛䛣䛸䛷ホ౯䜢⾜䛳䛯䠊ᙳ᪥䜔ᝈ⪅䛾≧ἣ䛜␗䛺䜛䛯䜑䠈༢⣧䛻ྠ
䛨䝇䝷䜲䝇䛷ẚ㍑䛩䜛䛣䛸䛿䛷䛝䛺䛔䠊䛭䛾䛯䜑䠈Fig. 6.1 䛻♧䛩䜘䛖䛻⓶ୗ⬡⫫䠈⫢⮚䠈ᕥᚰᐊ䠈
ୗ⾜ື⬦䠈⭁⮚䛭䜜䛮䜜䛾⮚ჾෆ䛻ROI䜢䛸䜚䠈SD䜢ẚ㍑䛩䜛䛣䛸䛷ホ౯䜢⾜䛳䛯䠊
➨6❶㻌 ప⥺㔞CT⏬ീ䝅䝭䝳䝺䞊䝅䝵䞁ᢏ⾡䛾⮫ᗋ⏬ീ䜈䛾ᛂ⏝
᧰᧵
Fig. 6.1 ROIs for SD measurement. They are within 䐟LV, 䐠fat, 䐡liver, 䐢spleen, and 䐣 aorta.
➨6❶㻌 ప⥺㔞CT⏬ീ䝅䝭䝳䝺䞊䝅䝵䞁ᢏ⾡䛾⮫ᗋ⏬ീ䜈䛾ᛂ⏝
᧱᧬