PET/PET- CT Clinical experience of PET-CT 基本原理 Introduction of PET basic n P n P 核的穩定度 :n/p: ratio force porwer n/p > 1, n p + β - + υ E avg of β - =1/3 E max n/p < 1, E>1.022 MeV p n +β + + υ E avg of β + =1/3 Emax E<1.022 MeV electron capture R : positron range < 1 mm ~ 10 mm 0.511MeV γ-ray 0.511MeV γ-ray 180 ± 0.25 ~ 0.4 C : noncollinearity effect = 0.0022 D (1.5~2.0 mm for 80~90 cm scanner)
R.I. T1/2 (min) E max (MeV) Positron range Production reaction 11 C 20.4 0.96 0.3~5.0 14 7 N (p,α) 11 6C 13 N 15 O 9.96 2.07 1.19 1.72 1.4~5.4 1.5~8.2 16 8 O (p,α) 13 7N 15 7 N (p,n) 15 15 8O 14 7 N (d,n) 15 15 8O 組成 Components of a PET facility 18 8 O (p,n) 18 18 9F 18 F 109.8 0.635 0.2~2.4 10 Ne (d,α) 18 20 10 18 9F 68 Ga 68 1.9 1.9~9.1 Ge 68 Ga 68 Ge 68 Ga 82 Rb 75(Sec Sec) 3.36 2.6~15.6 Sr 82 Rb 82 Sr 82 Rb Components of a PET facility 基本的正子造影團隊應該包括以下幾個單位 : Components of a PET facility 基本的正子造影團隊應該包括以下幾個單位 : i. PET/PET-CT Cyclotron scanner ii. Staff Radiochemistry lab. iii. PET/PET-CT scanner iv. Staff i. PET/PET-CT Cyclotron scanner ii. Staff Radiochemistry lab. iii. PET/PET-CT scanner iv. Staff
ii. Radiochemistry lab. 放射化學實驗室在整個正子造影團隊中的主要工作包括 : 1. 藥物合成 (cold( Lab. hot Lab.). 2. 確保 Q.A. 與 Q.C. 程序. GE PET trace v. staff 典型的 PET center 成員應包括 cyclotron technicians radiochemists radiographers medical physics computing staff. 掃瞄儀 Hard ware & Soft Ware
PET-CT scanner 硬 Hard ware & Sofe 體 ware PET scanner GE DLS SIEMENS Accel ADAC MCD SIEMENS ECAM Plus SIEMENS HR Plus SIEMENS Accel ADAC CPET Old 3D brain PET Dual PET scanner
3 D 快! 儘可能的快! 影像品質 正子核種選擇性 藥物成本與輻射劑量 對臨床的影響 ARTIFACT (density, movement ) 藥物 ( 時間 ) 成本與輻射劑量 對臨床的影響 und Collimator or not? 3D or 2D Coincidence camera or PET scanner AC & NAC CTAC OSEM = Prima? SUV = garbage, but WHY? others
隨機的偶合事件 B (Random coincidences event) electronic Collimator crystal 1a crystal 1b PMT 1b PMT 1a 實際的偶合事件 (True coincidences event) 散射的偶合事件 (Scattered coincidences event) 隨機的偶合事件 A (Random coincidences event) 0.511MeV γ-ray BGO crystal 1b Septa? Collimator? 0.511MeV γ-ray 180 BGO crystal 1a PMT 1a PMT 1b 隨機的耦合事件 B (Random coincidences event) 散射的耦合事件 (Scattered coincidences event) 隨機的耦合事件 A (Random coincidences event) 實際的耦合事件 (True coincidences event)
und Collimator or not? 3D or 2D Coincidence camera or PET scanner AC & NAC CTAC OSEM = Prima? SUV = garbage, but WHY? others 3D acquisition 早期的 PET scanner 為了防止 cross talk 將 septa 視為標準配備, 現有的電腦設備足以分析 3D 造影時的大量資訊, 因此 3D 造影有了顯著發展,3D, 造影時 PET scanner 將 septa 移開, 有利於增加 Z axis 的解析力. SIEMENS PET Scanner 3-D acquisition Accepts caudal/cephalic events 3-4 times higher trues 10% more scatter than 2-D less limits events out of FOV 2-D acquisition Limited to transaxial events Lower trues Less scatter Limits events out of FOV ADAC sys.
und Collimator or not? 3D or 2D Coincidence camera or PET scanner AC & NAC CTAC OSEM = Prima? SUV = garbage, but WHY? others 現在臨床使用晶體特性 晶體 密度 (g/cm3) 有效原子數 潮解性 機械強度 衰變常數 (ns) * 相對發光比 射出波長 折光指數 CdWO 4 7.90 64 沒有 不 ( 易脆 ) 5000 20 480 2.2 Lu 2 SiO 5 (LSO) 7.40 65 沒有 是 40 75 420 1.82 Bi 4 Ge 3 O 12 (BGO ) 7.13 75 沒有 是 300 15 480 2.15 Gd 2 SiO 5 (Ce) (GSO) 6.71 59 沒有 不 ( 易碎 ) 60 30 430 1.85 BaF 2 4.88 50 沒有 是 0.8 12 220 & 310 1.49 NaI(Tl) 3.67 51 有 不 ( 易碎 ) 230 100 410 1.85 * 相對於 1.5 in. NaI(Tl) scatter signals of BGO crystal scatter signals of LSO crystal
block detector coincidence camera system 的 spatial resolution 與 sensitivity 均較低, 用途也多僅限於臨床腫瘤病例後續追蹤的全身掃描檢查. 在均質射源中, 其多孔準直儀幾何效率與準直孔數呈正比, 雖然理論上解析力好壞如下式, 隨孔徑長呈正比 : 但是高能光子會在 septa 發生穿透分率增加 : SIEMENS ECAM PLUS ADAC MCD
crystal PMT crystal PMT dual layer dual layer und Collimator or not? 3D or 2D Coincidence camera or PET scanner AC NAC/CTAC CTAC OSEM = Prima? SUV = garbage, but WHY? others correction for photon attenuation 基本的 PET 影像構成必須包括以下三組資訊 : 1. emission data 2. correction factor (transmission data/blank scan data) 3. 2D/3D 組織 normalization data SIEMENS PET Scanner
Fast & accurate measured AC Ge-68 in coincidence Cs-137 singles 137 Cs 662 kev 68 Ge 511 kev poor statistics (coinc( coinc.) long acq.. times regular replacement 需按時更換 rod source 需經由 segmentation 減少 Tx 處理時間不需額外計算光子能差與衰減 good statistics (x 20, singles) very short acq. times (1 min) no replacement 不需更換 rod source. 不需經過 segmentation. 需額外計算光子能差與衰減
fly-through mode CT bronchoscopy VS PET/CT bronchoscopy copyright 2006 by the Society of Nuclear Medicine. fly-around mode PET/CT VR PET-MR SCANNER Oh!YES!! copyright 2006 by the Society of Nuclear Medicine. copyright 2006 by the Society of Nuclear Medicine.
軟 Hard ware & Sofe 體 ware Accuracy /Sp/Se/PPV/NPV 對臨床的影響
正子藥物 Commonly used radiopharmaceuticals Commonly used radiopharmaceuticals FDG 1. most widely used PET tracer. 2. based on diseased tissue has a different rate of glucose utilization to normal tissue. 3. tumors often exhibit high metabolic rate. 4. FDG is trapped in tissue whereas glucose is not (it s s what different to C-11 C label glucose). 5. usually acquisition post-admin. 40~60 min. 6. normal distribution at first 2 hr.:brain6 brain6% % heart4% bladder 20%. 血漿 細胞 Tumor cell 血漿中 FDG K1 K2 細胞中 FDG Hexokinase K3 FDG / Glucose K4 Glucose-6- Phosphatase 生化代謝後 FDG-6-P Glycolysis FDG / Glucose Normal cell Metabolic rate for glucose: (plasma glu.. Concentration/lumped constant)x[(k1 k3)/(k1+k3)] k3)/(k1+k3)]
F - 1. exchange with hydroxyl ion in hydroxyapatite and rapidly cleared by renal excretion. 2. long history of use in skeletal imaging to investigate focal bone disease. 15 O water 1. extraction fraction of nearly 100% 2. used to image cerebral perfusion examine tumor myocardial perfusion. 3. because of the very short half time, large activities must be handled before admini -stration and high finger dose to staff. 11 C L-MethioineMethioine 1. accumulation it into tumor tissue believed to be due to increased transport of amino acids and incorporation of amino acids into protein fraction, although it is not clear mechanisms. 2. normal uptake is seen in the liver stomach pancreas marrow, sometime may also be seen in gut lacrimal salivary gland and urinary tract. 13 N ammonia 1. rapidly extracted into the myocardium with a 70% extraction fraction (falling to ~35% at high coronary flow)and is trapped by the glutamic acid-glutamate reaction. 2. clinical protocol consist consist of a static scan beginning a few minutes after injection. 3. due to the dependence of trapping on meta -bolism it is seldom used to image cerebral perfusion. 82 Rb 1. used to measure myocardial perfusion. 2. it s s an analogue of potassium, extracted rapidly into the myocardium with a 50-60 60% extraction fraction which falls to 25-30 30% at high flows. 3. repeat studies can be performed in rapid succession. 4. because of the very short half time and generated from 82 Sr, large activities and rapid infusion of the eluate are therefore required, must be handled before admini -stration and high radiation dose to staff.
other radiopharmaceuticals for clinical PET other radiopharmaceuticals for clinical PET C-11 Flumazenil 癲癇病灶定位 C-11 Tyrosine 腫瘤偵檢 ( 腫瘤細胞代謝 ) F-18 FDopa Ga-68 EDTA C-11 Acetate C-11 Palmitate Parkinson's disease 診斷 (dopamine synthesis) BBB 滲透率檢查 心肌缺氧細胞 腫瘤偵檢 ( 缺氧細胞 ) 心肌檢查 ( 脂肪酸代謝 ) N-13 Glutamate C-11 Thymidine F-18 Uracil (FU) Cu-62 PTSM 腫瘤偵檢 ( 腫瘤細胞代謝 ) 腫瘤細胞增生率 ( 腫瘤細胞代謝 ) 化療療效評估 ( 化療藥物 ) Blood flow( 血球標定 ) F-18 Fluoromisonidazole (F-MISO) C-11 aminoisobutyric acid (AIB) 心肌缺氧細胞 腫瘤偵檢 ( 缺氧細胞 ) 腫瘤偵檢 ( 氨基酸合成 ) C-11 aminocyclopentanecarboxylic acid (ACPC) 腫瘤偵檢 ( 氨基酸合成 ) Quality of Item 基於對醫療品質的嚴格要求, 應定期進行系統設備的均勻度測試與校正以確保系統完善, 其中至少應包括 2D 與 3D 之 Tuning 與 calibration 工作, 並依照 Q.A. 與 Q.C. 工作流程, 區分介入性與非介入性品管工作, 指派專人或依合約進行專業保養. 品管 Daily? monthly? and How??
電腦斷層品管 QC of PET&CT
正子斷層品管 QC of PET&CT check for the result of blank scan
1/10 Peak of each crystal distribution block histogram position profile PMT energy histogram
bucky singles reference bucky Voltage Timing histogram 設備穩定度 整體效度 / 信度 其他 Devil is hiding in the detail 對臨床的影響
SUV = garbage Standard Uptake Value but WHY? SUV = K(Bq/cc) Dose(Bq) /cc) Wt (Bq) 1000 Wt(kg) 1000(cc/kg) K: : 每單位組織中的造影劑活性 Wt: : 受檢者體重 1000: : 每公斤水 1000c.c.( 人體密度換算約略值 ) Dose: : 注射劑量
Mr. 差不多 禁食未達 4~6 小時以上或 DM 之受檢者 還有 SUV = garbage, but WHY? others DM 或是過早進行檢查之受檢者腦部
其他 Devil is hiding in the detail 攝取分佈 血漿 細胞 Tumor cell 血漿中 FDG K1 K2 細胞中 FDG Hexokinase K3 FDG / Glucose K4 Glucose-6- Phosphatase 生化代謝後 FDG-6-P Glycolysis FDG / Glucose Normal cell Metabolic rate for glucose: (plasma glu.. Concentration/lumped constant)x[(k1 k3)/(k1+k3)] k3)/(k1+k3)]
Uptake 其間受到視覺刺激之受檢者 聲帶 顏面肌肉過度攝取之受檢者 Rb-82 myocardial perfusion http:// www.emory.edu Rb- 82 myocardial perfusion scan
造影技術 Position 禁食與游離脂肪酸多寡均可能對 FDG hwart scan 產生影響 改變姿勢對於假影產生的影響 Delay view 與改變姿勢對於影像偵檢的影響
由於影像重組方式造成的限制, 在進行胸頸部區域造影時可以以耳朵上緣作為起始點, 避免因雜訊遺漏病灶, 同樣的平常進行區段造影時亦需避免將主要目標置於 FOV 的上下緣 造影技術 Truncated
造影技術 Breathing GATED IEEE Transactions on Nuclear Science, 44(6):2473 2476, 1997 (a) without respiratory gating, and (b) with gating technology (a) without respiratory gating, and (b) with gating technology
NIPPON ACTA RADIOLOGICA 2002 ; 62 : 252-257 257 Fig. Efficacy of data acquisition with respiratory gating for lung cancer A: No gate. Note a tumor change the shape as oval (arrow). SUV of the tumor is 10.3 B: Under gate. A shape of the tumor shows spherical. SUV of the tumor is 14.9 造影技術 Auto ma? 重組方式 parameter
3D vs. 2D Ex: subset-9 9 with different filter volume I 2 S 8 G V 8 不同的造影方式與重組條件將影響影像結果 I 2 S 8 G V 4 I 6 S 8 G V 6 THINI2S8GV 6 I 2 S 8 G V 6 THINI2S8GV 4
重組方式 processing OSEM 在高 count rate 時的假影 fly-through mode CT bronchoscopy VS PET/CT bronchoscopy copyright 2006 by the Society of Nuclear Medicine. AC- NAC mode 對於靈敏度的影響 (A,C,E) Standard 2D PET/CT tomographs show with highly FDG-avid malignant subcarinal/paratracheal mass that extends along right tracheal sidewall and right bronchus. (B) CT virtual bronchoscopy illustrating that tracheal sidewall and carina appear normal, without indication of large tumors that abut central airways. (D) PET/CT virtual bronchoscopy showing abnormal F-18 FDG
其他因素 Site planning 真理並不難, 困難的是, 假象往往披著似是而非的外衣, 而我們總是自以為無所不能 ~ 知識份子的謙卑 Thank for your attention camus.wu@msa.hinet.net
Oh! Quiz 1 Oh! Quiz 2 如我們所知互毀輻射具有 Positron range 與 non collinearity 的特性, 以下何者為非 : i. 此特性限制了 PET/PET-CT scanner 的發展. ii.positron range 與正電子本身所帶動能有關. iii. 互毀輻射的發生位置即為其原始遭遇負電子之位置. 如我們所知 PET/PET-CT scanner 的硬體特性, 足以影響 工作人員與受檢者接受之輻射劑量 影像品質 檢查時間 藥物成本 可使用之正子核種 等, 若您是工作人員或者是家屬, 下列哪一個項目可以協助您減低劑量 : i. 舒適高雅燈光美氣氛佳的環境. ii. 各式各樣的文宣廣告. iii. 使用性能良好符合需求的 PET/PET-CT scanner. Oh! Quiz 如我們所知正子造影影像品質在重組時會受到 重組條件 設備特性 給予劑量 疾病特性 等諸多條件影響, 即使 OSEM 不是最完美的重組模組, 但仍為目前臨床廣泛使用, 請問當您走進一間正子造影的造影室, 正巧碰到同仁在重組影像時, 您覺得目前他最可能使用的重組模組為 : i.fbp. ii.osem. iii.ramla. 3 Oh! Quiz 4 如我們所知 SUV 是最常見的輔助判讀的半定量工具, 當然它也極易受到如 攝取分佈 造影流程 疾病特性 等因素影像, 但是比起 較不客觀的視覺直接判讀 與 過於繁瑣但是屬於絕對定量的 Kinetic analysis, 它仍不啻為一個有效可靠的半定量工具, 請問當您需要使用這一類輔助工具時, 由方便到不便, 就方便性上三者的排列應為 : i. 視覺判讀 SUV Kinetic analysis. ii. SUV 視覺判讀 Kinetic analysis. iii. 視覺判讀 Kinetic analysis SUV SUV.
Oh! Quiz 5 其他影響正子造影的因素還包括 攝取分佈 造影技術 ( 如 position 輔助裝置等 ) 設備周遭環境 等, 某日, 某正子中心的造影結果被認定不符需求, 下列哪一項是您不需去考慮的部分 : i. 設備狀態 : 品管記錄 溫濕度情形 處理參數等. ii. 攝取分佈 : 正子藥物品管紀錄 檢查準備流程 疾病特性 受檢者病史等. iii. 造影技術 : 輔助裝置狀況 造影時擺位 掃瞄區域等. iv. 受檢者為健保病人或自費病人.