ONLINE Physics Review Sheet

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Transcript of ONLINE Physics Review Sheet

ULTRASOUND

C = f ( )

Velocity of Sound.

C = 154000 cm/sec in soft tissue 1.54 mm/usec

dB = 10 Log Io / I

Relative Intensity in decibels

dB = ( f) (x)

attenuation of ultrasound = 0 .5 1 for soft tissue

attenuation coefficient dB/Mhz-cm f - frequency x - distance

z = pc

Acoustical Impedance = physical density of material c = speed of sound in the material

TRANSDUCER (PZT) t = 1/2 Transducer thickness fr = c / Resonant Frequency

(FR) x (N) X 2D = 154000

Frame Rate and Number of Scan Line Relationship N = Number of Scan Lines D = Depth FR = Frame Rate

f=

(2 f v cos ) / c DOPPLER SHIFT f transducer frequency c speed of sound (1540 m/se in soft tissue) Doppler angle ( 0 o and 180 o US beam parallel to blood flow max shift) 90 o US beam perpendicular to blood flow no Doppler shift)

RADIATION SAFETYDOSE LIMITS (MPD- Maximum Permissible Dose) OCCUPATIONAL WORKER Total Body (effective dose equivalent) Annual 50 mSv Eye (dose equivalent) Annual 150 mSv Extremities (dose equivalent) Annual 500 mSv Other Organs (dose equivalent) Annual 500 mSv Gestation Monthly FETUS 5.0 mSv 0.5 mSv 0.5 rem 0.05 rem 0.1 rem 0.5 rem 0.1 rem

5.0 rem 15.0 rem 50.0 rem 50.0 rem

MEMBER GENERAL PUBLIC Continuous Annual 1 mSv Infrequent Annual 5 mSv New Installations Annual 1 mSv

Equivalent Dose (H) = D Wr D- Radiation dose Wr - quality factor of radiation Effective Dose Equivalent = WT HT (Used when only part of body is irradiated) WT = weighting factor tissue sensitivity HT = dose W Gonads = 0.25, W Thyroid = 0.03, W Lung = 0.12 W Breast = 0.15 W Other = 0.3 FLUOROSCOPY ( ABS- automatic brightness control) Units without ABS = 5 R/min Units with ABS = 10 R/min Units with ABS w high 'R' mode Operating in high 'R' mode = 20 R/min MAMMOGRAPHY: AGD Average Glandular Dose Maximum per film = 300 mrem/film Typical per film = 100 mrem/film BACKGROUND (typical) INTERNAL DOSE CALCULATION Cosmic 30 mrem/yr Terrestrial 30 mrem/yr D = 1.44 Teff A S Internal 40 mrem/yr A = accumulated activity Radon 200 mrem/yr S = ( ) Radon = 20 rem/year bronchial epithelium = Eq dose constant Some regions 600 -1000 mre/yr = Absorbed fraction Increased chromosome aberrations, no inc in ca = 1 for < 1 for SCATTER FROM X-RAY UNITS 0.1 % (1/1000) of primary @ 1 m 1 mR / slice CT @ tableside

Genetically Significant Dose (GSD) From Background radiation = 100 mrem/year From Diagnostic X-ray exams = 20 mrem/year

UNITSRoentgen: Unit of Radiation exposure, measure of the amount of ionization produced in a quantity of air only defined for photons (x-rays, gamma rays up to 3 Mev) 1 R = 2.58 x 10 -4 coulombs/kgm of air Rad: Unit of Absorbed dose (D), energy absorbed per gram of material 1 rad = 100 ergs/gram 100 rads = 1 Gray = 1 joule/kilogram To convert Roentgens into rads we use the 'f' factor D (rads) = R x f f (soft tissue) ~ 1.0, f (Bone) ~ 2.5, f (air) = .87 Rem: Unit of Dose Equivalent (H) , energy absorbed per gram of material x Q.F. Q.F. Quality factor, used to equilibrate equal biological effect H = D (wR) wR - weighting factor same as Q.F> rem = rad X Q.F. 100 rem = 1 Sievert Q.F. for high LET radiations ( , , n etc) > 1 typical (3 -20) Rem: Also unit of Effective Dose (HE) takes into account the detriment (cancer genetic effects etc) of the radiation damage to particular tissues/organs HE = HT x wT HT - equivalent dose to each organ wT - weighting factor of organ based upon detriment of radiation Energy of all electromagnetic radiation E = h H = Planck's constant = frequency E = 12.4 / E in keV and in Angstroms Rest Energy of particles E = moc2 E (electrons) = 0.511 meV E (protons) = 931 meV

RADIOACTIVE DECAYActivity (A) : rate of radioactive decay A = N = (0.693 N) / T1/2 Where: = units dps

decay constant (fractional number of radioactive atoms that decay per unit time) N = number of radioactive atoms present

Curie: Unit of Radioactive Activity, number of disintegrations occurring per unit time 1 Ci = 3.7 x 1010 disintegrations per second 1 Bq = 1 dps N = No e t

Exponential Decay

T1/2 = Half Life: time required for one half the radioactive atoms to decay T1/2 = 0.693 / = 0.693 / T1/2 1/ Teff = 1/ T bio + 1 / T phy Effective Half Life Taverage = 1.44Teff Mean Life

Mo - Generator Contamination Limits 0.15 uCiMo/ mCiTc Misadministration (medical event) Dx: + or - 50% Activity, wrong route, wrong patient, wrong agent reportable - patient must also receive > 5 rem total body or >30 rem to any one organ

RADIATION SAFETY (MISC)Medical Dx = 50-75 mrem/year Airflight: 0.5 mR/hr Various Dose Levels CT Scan Multi slice exam Chest X-ray Mammography 1 film Maximum 1 film Abdomen Film GI Series Nuclear Med Exams Max organ dose Dental 3 - 5 rads per slice + 20% 20 mrads 100 mrads 300 mrads 300 mrads 5 - 20 rads < 1 rad whole body 1-4 rads organ 100 mrem/film Bkg = 100 mrem/year 1 cGy = 1 rad

BREAST FEEDING CESSATION I-131 (NaI) any use - Discontinue Tl-201 (TlCl) 3 mCi Cardiac 3 weeks Ga 67 6- 10 mCi tumor scans 4 weeks Tc-99m 5-25 mCi general rule - 24 hrs Tc-99m 10 mCi DTPA - 17 hrs Tc-99m 5 mCi Sulfur colloid - 15 hrs I-123 >50 uCi Tyroid Imag - 5 days < 50 uCi - 3 days

Doubling Dose: 100 rem (dose required to double the natural mutation rate) Sterility 600 rads men 15 rads may produce temporary sterility in men 400 rads women

Cancer Risks Risk of developing non fatal cancer ~2X greater than Ca death Ca Deaths: 800/100,000 per 10 rads at high dose and high dose rates rate patient exposure may fall here 400/100,000 per 10 rads at low dose rate what radiation workers receive 800 extra Ca deaths if 100,000 people are exposed to 10 rads one time total body Dx Radiology 400 extra Ca deaths/100,000 at 10 rads for LOW DOSE - LOW DOSE RATE Leukemia: 110 Thyroid 300 children induction Thyroid 150 adult induction Breast 70 all ages Breast 295 age 15 Digestive 170 Lung 190 IF population is exposed to 0.1 rem/year continuous the risk for Ca death is 560 Ca deaths / 100, 000 FETAL EFFECTS GESTATION 0 -10 days 2 -8 weeks organogenesis 8 - 25 weeks >25 weeks EFFECT pre implantation death (SA, local -reabsorption,all or nothing doses low as 5 rem cause death) growth retardation, cataracts, embryonic malformations mental retardation most within 8-15 wk increase childhood cancer and leukemia

RADIATION AREA: Area where dose rate >5 mRem/hr HIGH RADIATION AREA: Area where dose rate > 100 mRem/hr CONTROLLED AREA: operator has control of who enters this area, if dose rate>2mR/hr area MUST be controlled FILM BADGE MONITORING: must monitor person if they are likely to receive 1/10 the MPD (Max Perm Dose)

PACS DIGITAL PACS - Picture Archiving and Communication System DICOM - Digital Imaging and Communications in Medicine (standard) LAN - Local Area Network (general within the Hospital) WAN - Wide Area Network ( includes facilities outside the hospital can use the internet)The Internet is a large WAN

NETWORK LAYERSApplication - Program used on computer for specific application (MS-Word) Transport - may use TCP - Transmission Control Protocol Network - may use IP internet Protocol - computers are assigned aa specific IP address (XXX.XXX.XXX.XXX) or obtain one dynamically Host Name - the DNS (Domain name Server (system) can assign a name to a specific IP address (ie downstate.edu) URL - Universal Resourse Locator - helps to located another computer Consists of protocol type and URL (www.http//downstate.edu) ETHERNET - combines TCP/IP and DATA Link Data Link - describes the type of packets (data elements) to be sent Physical - physical wiring coaxiale cable, fiber cables, twisted pair etc. Also includes Routers switches hubs - devices used to separate parts of large network to small Branches, tries to limit congestion increased efficiency Of physical network

COMMUNICATION PROTOCOLS TCP/IP , FTP - File transfer Protocol, SMTP - Simple Mail Transfer Protocol, TELNET - Telecommunications network Transfer speeds Twisted Pair (Cat 5 wires) - 10 , 100, 1000 Mb/sec Ethernet Optical Fiber - 1G - 10G FDDI - Fiber Distributed data Interface 100 Mb ATM - Asynchronous Transfer Mode typical 154 Mb/sec can combine 600 Mb/sec Modem - 56 kb/sec ISDN - 128 kb/sec DSL - can go up to 1.54 Mb/sec need several lines Cable Modem - download rates up to 10 Mb/sec Upload 10X slower T1 - 1.54Mb/sec T3 - 50 Mbits/ec

PACS DIGITAL Digital Modalities CT - 512 x 512 x 2 B = 0.5MB/image MRI - 256 x 256 x 2B = 0.13 MB/image US - 512 x 512 x1B = 0.25 MB/image FILM DIGITIZERS - 2K x 2K x 2B =8 MB/image CR - 2000 x 2000 x 2B = 8MB/image DR - Digital Radiography CCD - CsI - 2000x2000 x 2B = 8 MB/image TFT - CsI-Si - 2000 x 2000 x 2B = 8 MB/image TFT - Se 2000 x2000 x2B = 8 MB/image CR and DR require a processing (table look up) of Image. Both systems produce wide latitude images Need to 'convert' into film like image STORAGE RAM - Radom Access Memory - 1 GB Floppy Disk - 1.44 MB ZIP Disk - 100 MB, 250, 100 MB Hard Disk - 10 - 100 GB CD - 650 MB DVD - 6 GB WORM - write once read many times MOD - Magneto Optical Disks - 10 GB RAID - Redundant Array of Independent Disks 100s GB One fails can still recover data Digital Tape - 40-100 GB per tape Jukebox - Mechanical device holding Many tapes, MOD, CD, DVD's Compression Lossless - typical 3:1 Lossey - images degrades as reduction increases Image Formats JPEG TIFF - tagged image file format Bit mapped GIFF

SHADES OF GRAY 1 bit - 21 = 2 shades of gray 2 bit - 22 = 4 " 8 bits - 28 = 256 " 10 10 bits - 2 = 1024 " 16 bits - 216 = 64,000 "

SMPTE - digital test pattern for calibrating monitors and workstations

CTCT # = 1000 ( ux - uwater) uwater where ux = linear attenuation coefficient of material

10 CT #'s = 1.0 % contrast (% co