1 X Aluminum filter Thickness of aluminium filter

1. X 光機與其他設備 Aluminum filter Thickness of aluminium filter (absorb low level x-ray) =70 k. Vp -- at least 1. 5 cm Long & short wavelengths Short wavelengths >70 k. Vp -- more than 2. 5 cm Enlargement of detail Long wavelength Aluminum filter Collimator lead Short wavelength low energy Long wavelength Low frequency high energy Short wavelength High frequency

1. X 光機與其他設備 ü計時器timer：最好要能精確到 1/20秒， 最長不應超過5秒。 固定 k. VP 調整 時間 k. V m. A Control Panel Upper Lower molar anterior Upper premolar Lower premolar Upper molar Lower anterior Control Panel

1. X 光機與其他設備 ü應儘可能選用高速底片，以期用最少的X光照射。 Use a “fast” speed film : F speed instead of D speed film 50% Less Radiation Intraoral film Speed of film 大 小 粒子 最小 感光 最慢 Detail 最好 粒子 最大 感光 最快 Detail 最差

1. X 光機與其他設備 ü牙科口外片使用增感屏，以期用最少的X光照射。 Panoramic Cassette Front Intensifying Screen Back Cephalometric Cassette Back Intensifying Screen Front Panoramic Front Extraoral film Front Intensifying Screen Back Intensifying Unexposed Screen film Indirect-action, screen film Calcium tungsate screen 螢光 Photoelastic effect UV Rare earth screen

1. X 光機與其他設備 自動洗片機 顯影 清水 定影 5 min later 自動洗片機 溫度 Rollers 溫度越高— 洗片時間越短 Roller film transporter Developer component Power Drive Off 開關 Fixer component Film lead slot Water component Drying chamber Film slot Processor housing Replenisher pump Replenisher solution

1. X 光機與其他設備 ü使用牙科X-ray數位化，以降低radiation dose (up to 80%)。 Image detectors (Digital) Direct Indirect Intraoral Laser scanner Extraoral

1. X 光機與其他設備 Air Techniques 牙科數位影像系統 Air Techniques

1. X 光機與其他設備 Cone Beam CT Comparison of absorbed dose of radiation Absorbed dose of radiation ( Sv) Protocol Panoramic Lateral cephalogram TMJ (per cut) Implant/tomogram Submental vertex Complete mouth series Total dose Conventional X-ray Medical CT 2. 9 -9. 6 12 1. 9 -2. 0 22. 1 -52 48 33 -84 119. 9 -207. 6 New. Tom 9000 Not available 300 -2426 Low quality 36. 9 -50. 3 This type of cone beam CT (New. Tom 9000) can produce an image with significantly less radiation than traditional CT because it uses an image intensifier; this is particularly important for children. The absorbed dose from a full volume scan is 36. 9 to 50. 3 Sv (Am J Orthod Dentofacial Orthop 2007; 132: 7 -14)

3. 人員防護 ü安全規定： 安全標準。 Current Guidelines International Commission on Radiological Protection (ICRP, Pub 26) 1. No practice unless a positive net benefit 2. As low as reasonably achievable (ALARA) 3. Not exceed recommended dose limits 1. Patients 2. Radiation workers 3. General public

1. Patients 2. Radiation workers 3. General public 1. Exam associated with illness 2. Periodic health checks 3. Exam for occupational, medico-legal, insurance 4. Medical research Classified workers Non-classified workers 1. No set dose limits 2. IRB approval Not receiving radiation dose as a patient or radiation worker 3. Child avoided ICRP annual dose limits Classified workers Nonclassified workers General public 1 m Sv 13 m. Sv in any consecutive 3 months

3. 人員防護 Radiation absorbed dose Amount of energy absorbed from the radiation beam per unit mass (joules/kg) 1 Gray (Gy) =100 rads (1 c. Gy = 1 rad) Equivalent dose = radiation absorbed x quality factor (Sievert, Sv) X-rays, particles Q=1 Tissues Fast neutrons & protons Q=10 particles Q=20 Effect dose = equivalent dose x weighting factor (Sievert, Sv) Weighting factor

結 論 Typical Doses during Radiographic Examinations Effective Dose (m. Sv) 0 2 4 6 8 10 Web et al. Background radiation levels and medical exposure in Australia, Radiation Protection in Australia, 1999; 15(2): 25 -32 12

結 X-ray Exam 論 Effective dose (m. Sv)

結 論 % Relative Dose % Improve in Radiation Relative Dosage for Intra-Oral Radiography (1919 -2005) 100 80 60 40 20 0 1919 1925 1941 1955 1981 1991 2005 Time frame (Year) Since 1919 a reduction in the dosage of ionizing radiation needed to produce an intraoral x-ray image is 2 orders of magnitude (Oral Surg Oral Med Oral Pathol Oral Radiol 2005; 100: 395 -6)