【正文】 rministic effects (skin burns, cataract formation) 確定效應(yīng)（皮膚灼傷，白內(nèi)障形成） ? stochastic effects (cancer induction, geic effects) 隨機(jī)效應(yīng)（癌癥的誘發(fā)，遺傳效應(yīng)） ? Risk estimates are derived from 風(fēng)險(xiǎn)評(píng)估來(lái)源于 ? atomic bomb survivor data, other exposed groups 原子彈生存者的數(shù)據(jù)，其它暴露人群 ? Risk estimates are dependent on 風(fēng)險(xiǎn)評(píng)估有賴于 ? an dose and type, age, gender, reproductive status 器官劑量和類型，年齡，性別，生殖狀態(tài) ? an doses depend on patient size 器官劑量有賴于病人的身高與體重 Risk ? Biological Injury 風(fēng)險(xiǎn) =生物傷害 What‘s the dose from an abdominal CT scan? 腹部 CT掃描的劑量？ Radiation Absorbed Dose (rad) Energy (100 ergs) Mass (1 gram) = What‘s the dose from an abdominal CT scan? 腹部 CT掃描的劑量？ ? Intuitively, we understand that the biologic risk from 20 CT slices is greater than from 10 CT slices. 直覺(jué)上，我們認(rèn)為 20層 CT掃描的危害大于 10層掃描 ? If the average dose is 2 rad for 10 slices, what is the dose for 20 slices? 如果 10層 CT掃描的劑量是 2 rad， 20層的劑量是多少哪？ MSADw = 2 rad ten 1cm slices MSADw STILL = 2 rad twenty 1cm slices So how do we represent the greater biologic risk? 因此，我們?nèi)绾蚊枋鲚^嚴(yán)重的生物風(fēng)險(xiǎn)哪？ Integral dose 累計(jì)計(jì)量 ? Average dose ? slices = integral dose 平均計(jì)量乘以層數(shù)等于累計(jì)計(jì)量 ? But, dose and integral dose have same units (leads to confusion) and is not specific enough (doesn‘t reflect the difference between 1 or 10 mm slices) 但是，劑量和累計(jì)劑量具有相同的單位，而且并不明確 ? Better concept …. 更好的概念 … Dose Length Product (DLP) 劑量長(zhǎng)度積 ? Represents integrated dose in terms of total scan length ( slices ? slice width) 代表了總掃描路徑中的累計(jì)劑量（層數(shù)乘以層厚） ? Related to energy imparted but more intuitive than using energy units (Joules) 涉及應(yīng)用的能量，但與使用能量單位相比更直觀 ? Required in Europe, migrating to US 歐洲要求使用，后被美國(guó)采用 ? DLP = CTDIvol (mGy) ? scan length (cm) So, DLP represent the greater biologic risk! 所以， DLP代表了更高的生物風(fēng)險(xiǎn)！ DLP = 20 rad?cm DLP = 40 rad?cm CTDIvol = 2 rad ten 1cm slices CTDIvol STILL = 2 rad twenty 1cm slices SI units (1 rad = 10 mGy) 國(guó)際單位 (1 rad = 10 mGy) DLP: 20 mGy ? 20 cm = 400 mGy?cm DLP gives an indication of the overall ―risk‖ DLP表明了總的風(fēng)險(xiǎn) DLP can ? from ? scan length or ? CTDI (primarily mAs, kVp, detector mode) ? CTDIvol (scan overlap or gap, . pitch) Need to pay attention to all three! 需特別注意這三個(gè)值（ scan length ， CTDI 和 CTDIvol ）！ What‘s the dose (risk)? 劑量（風(fēng)險(xiǎn)）是多少？ ? Radiation detriment better expressed by Effective Dose (E 輻射損害的較好表達(dá)為有效劑量 ? a single dose parameter which reflects the risk of a nonuniform exposure in terms of a wholebody exposure 就整個(gè)軀體的而言，單個(gè)劑量參數(shù)反映了非均勻暴露的風(fēng)險(xiǎn) ? Published values of effective dose per DLP provides a quick estimate of effective dose 已出版的每 DLP的有效劑量值提供了一個(gè)快速估算途徑 ICRP 60 Weighting Values 國(guó)際輻射防護(hù)委員會(huì)的 60加權(quán)值 Gonads RBM, colon, lung, stomach Bladder, breast, liver Esophagus, thyroid Skin, bone surface Remainder ? Typical effective dose values 典型的有效劑量 Head CT 頭 CT 1 2 mSv (100 200 mrem) Chest CT 胸 CT 5 7 mSv (500 700 mrem) Abdomen CT 腹部 CT 5 7 mSv (500 700 mrem) Pelvis CT 骨盆 CT 3 4 mSv (300 400 mrem) Abdomen amp。 7 T) FDA使用定積分極限（ 177。 pelvis CT 8 11 mSv (800 1100 mrem) 腹部和骨盆 CT Average . background radiation 平均本底輻射 ? mSv (360 mrem) Effective dose values (cont.) 典型的有效劑量 Stereo chest xray mSv (10 mrem) 立體胸部 X線 Low dose chest CT mSv (70 mrem) 低劑量胸部 CT Mammogram mSv (180 mrem) 乳腺 CTC (5 mm) mSv (550 mrem) CTC (5 mm) Double contrast BE mSv (750 mrem) 增強(qiáng)對(duì)比 BE CTC ( mm) mSv (980 mrem) CTC ( mm) CT liver perfusion 15 mSv (1500 mrem)