ct的質(zhì)量控制ppt課件(2)-在線瀏覽
2025-03-08 02:00本頁(yè)面
【正文】 ? Table Motion and Alignment Lights 床位移和光定位 ? Quarterly 每季 ? Weekly if used for therapy planning 對(duì)于治療方案，可每周進(jìn)行 ? Full Physics Evaluation 全部評(píng)估 ? Annually 每年 ? Following major service 大修后 Essential QC Activities 基本質(zhì)控 ? Determine doses from scanner 確定掃描劑量 ? Working with physician colleagues determine appropriate imaging protocols 與臨床人員協(xié)調(diào)確定適當(dāng)?shù)墓ぷ鞣桨? ? Insure that water has a appropriate CT number 確定水測(cè)試時(shí)獲得適當(dāng)?shù)?CT值 ? Accurate 精度 ? No artifacts 無(wú)偽影 ? Uniform 均一 ? Appropriate noise 噪聲適當(dāng) Essential QC Activities 基本質(zhì)控 ? Insure that the monitors and film printers work correctly 確認(rèn)監(jiān)視器和底片打印機(jī)工作正常 ? Insure that positioning lights and table motion are correct 確認(rèn)定位光和掃描床定位正確 ? Determine doses from scanner 確定掃描劑量 ? CT Dose Fundamentals 基本原則 ? CT Dose Terminology 術(shù)語(yǔ) ? CT Dose Variations – Equipment 劑量變化 —設(shè)備 ? CT Dose Variations – Exams 劑量變化 —測(cè)試 ? CT Dose Optimization 劑量?jī)?yōu)化 CT Dose Evaluation CT計(jì)量評(píng)估 X Z Y CT Coordinates CT 坐標(biāo) Ideal World …. 理想狀態(tài) … ? Radiation delivered only to the imaged volume 輻射僅涵蓋成像部分 5 mm 0 + 5 mm Peak dose = “dose” Real World …. 現(xiàn)實(shí)情況 … ? Radiation distribution crosses the imaged volume 輻射跨越成像區(qū)域 5 mm 0 + 5 mm Peak dose “Tails” of dose distribution 劑量分布尾跡 Computed Tomography Dose Index ( CTDI ) CT劑量指數(shù)（ CTDI） ? Integral under ONE radiation dose profile 在單一劑量曲線下積分 ? Dose profile has very long ―tails‖ 劑量曲線有很長(zhǎng)的尾跡 ? FDA uses finite integration limits (177。 7 T ） ? Typically measured with TLD (laborious) 典型測(cè)量使用 TLD ? Underestimates tail dose for slices 7 mm 低估了尾跡劑量，層厚在 7mm之內(nèi) ? Ion chamber method integrates over 100 mm 電離室法積分 100mm ? CTDI100 CTDI100 ? single convenient measurement 單一實(shí)用的測(cè)試 CTDI = Integral under the radiation dose profile along the zaxis from a single axial scan of width nT. CTDI=沿 Z軸的輻射劑量曲線積分，寬度為 nT的單一軸向掃描 nT “nominal beam width” = “total nominal scan width” Z radiation dose profile 輻射劑量曲線 CTDI100 MSAD CTDIw CTDIvol DLP Effective Dose CT Dosimetry CT 劑量 100 mm Ionization Chamber 100 mm電離室 ? CTDI measurements are usually made using a 100 mm ionization chamber CTDI測(cè)量通常使用 100mm電離室進(jìn)行 ? Therefore the CTDI is defined for use with this chamber 因此，這一電離室被確定為 CTDI測(cè)試的使用工具 CTDI measurements CTDI測(cè)量 ? In phantoms 在模體中 ? Polymethyl methacrylate (acrylic) 丙烯酸 ? 32 cm diameter, ? 16 cm length (body) 頭部模體 ? 16 cm diameter, ? 14 cm length (head) 體部模體 ? At least five 1 cm holes for exposure measurements throughout FOV 至少五個(gè) 1cm測(cè)試空，暴露于全部視場(chǎng)中 ? In air 在空氣中 ? at isocenter (center of rotation) 等量點(diǎn) CTDI Phantoms CTDI模體 Typical FOV dose distributions (%) 典型視場(chǎng)劑量分布 (%) 100 100 100 100 50 Body 32 cm 100 100 100 100 100 Head 16 cm CTDIW = 83 CTDIW = 100 CTDIW CTDIW Weighted average of center and periphery doses 中心和外圍劑量的加權(quán)平均 = 2/3 CTDI100 (edge) + 1/3 CTDI100 (center) Real World …. 現(xiàn)實(shí)情況 … ? Radiation distribution crosses the imaged volume 輻射跨越成像區(qū)域 5 mm 0 + 5 mm Peak dose “Tails” of dose distribution 劑量分布尾跡 Real World …. 現(xiàn)實(shí)情況 … ? Radiation distribution crosses the imaged volume 輻射跨越成像區(qū)域 5 mm 0 + 5 mm A x ial Po s iti on (m m)Exposure (mR)0200400600800100012001400 8 0 6 0 4 0 2 0 0 20 40 60 80S i n g l e s c a n p r o f i l e M u l t i p l e s c a n p r o f i l e : 3 m m x 3 m m , 4 0 s c a n s P o s i t i o n i n s
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