ct的質(zhì)量控制ppt課件(2)(參考版)
2025-01-22 02:00本頁(yè)面
【正文】 。 optimize 知曉，理解和優(yōu)化 CTDImax , CTDIvol, DLP, and E ? Reference doses had positive effect in UK, used as part of the ACR accreditation process in the US 在英國(guó)，參考劑量具有積極的效果；在美國(guó)，它被應(yīng)用于認(rèn)證過(guò)程 ? Use effective dose to assess relative risk 應(yīng)用有效劑量評(píng)估風(fēng)險(xiǎn) Summary 總述 ? CT: large percentage of the medical collective dose to population CT: 對(duì)人群使用醫(yī)療檢查劑量的高百分比 ? Prudent response: Apply ALARA principles 審慎響應(yīng)：使用 ALARA原則 ? CT Automatic Exposure Control a long overdue product is now available on new scanners makes dose calculations more difficult. CT dose worthy of closer attention CT自動(dòng)曝光控制 —一個(gè)姍姍來(lái)遲的、應(yīng)用于新掃描儀的產(chǎn)品 —使得劑量計(jì)算更困難。T ? CTDIw I PITCH = table index per rotation total nominal scan width CTDIvol = 1 ? CTDIw pitch estimate of average patient dose 平均病人劑量的估算值 measurement from one axial scan 來(lái)自軸向掃描的測(cè)量值 When a patient asks … ―What is my dose‖ they typically mean ―What is my risk‖ 當(dāng)病人說(shuō)“我的劑量是多少？”時(shí)， 其實(shí)他們?cè)趩?wèn)“我承受了多大風(fēng)險(xiǎn)？” ? Biological injury includes 生物傷害包括 ? deterministic 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 effectiv
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