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 attenuation coefficient dB/Mhz-cm

for soft tissue f - frequency x - distance

z = pc Acoustical Impedancephysical density of materialc = speed of sound in the material

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

(FR) x (N) X 2D = 154000 Frame Rate and Number of Scan Line RelationshipN = Number of Scan LinesD = DepthFR = Frame Rate

f = (2 f v cos c DOPPLER SHIFTf transducer frequencyc 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 SAFETY

DOSE LIMITS (MPD- Maximum Permissible Dose) OCCUPATIONAL WORKER

Total Body (effective dose equivalent) Annual 50 mSv 5.0 remEye (dose equivalent) Annual 150 mSv 15.0 remExtremities (dose equivalent) Annual 500 mSv 50.0 remOther Organs (dose equivalent) Annual 500 mSv 50.0 rem

FETUSGestation 5.0 mSv 0.5 remMonthly 0.5 mSv 0.05 rem

MEMBER GENERAL PUBLICContinuous Annual 1 mSv 0.1 remInfrequent Annual 5 mSv 0.5 rem

New Installations Annual 1 mSv 0.1 rem

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) SCATTER FROM X-RAY UNITS

Units without ABS = 5 R/min 0.1 % (1/1000) of primary @ 1 m Units with ABS = 10 R/min 1 mR / slice CT @ tablesideUnits with ABS w high 'R' mode Operating in high 'R' mode = 20 R/min

MAMMOGRAPHY: AGD Average Glandular DoseMaximum per film = 300 mrem/filmTypical per film = 100 mrem/film

BACKGROUND (typical) INTERNAL DOSE CALCULATIONCosmic 30 mrem/yrTerrestrial 30 mrem/yr D = 1.44 Teff A SInternal 40 mrem/yr A = accumulated activity Radon 200 mrem/yr S = Radon = 20 rem/year bronchial epithelium Eq dose constantSome regions 600 -1000 mre/yr Absorbed fraction Increased chromosome aberrations, no inc in ca 1 for

1 for

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

UNITS

Roentgen: 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 material1 rad = 100 ergs/gram 100 rads = 1 Gray = 1 joule/kilogram

To convert Roentgens into rads we use the 'f' factorD (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 radiationE = h

H = Planck's constantfrequency

E = 12.4 / E in keV and in Angstroms

Rest Energy of particlesE = moc2

E (electrons) = 0.511 meVE (protons) = 931 meV

RADIOACTIVE DECAY

Activity (A) : rate of radioactive decay

A = N = (0.693 N) / T1/2 units dps

Where: 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 agentreportable - patient must also receive > 5 rem total body or >30 rem to any one organ

RADIATION SAFETY (MISC)

Medical Dx = 50-75 mrem/year Bkg = 100 mrem/year 1 cGy = 1 radAirflight: 0.5 mR/hr

Various Dose Levels BREAST FEEDING CESSATION

CT Scan 3 - 5 rads per slice I-131 (NaI) any use - Discontinue Multi slice exam + 20% Tl-201 (TlCl) 3 mCi Cardiac - 3 weeks

Chest X-ray 20 mrads Ga 67 6- 10 mCi tumor scans - 4 weeksMammography 1 film 100 mrads Tc-99m 5-25 mCi general rule - 24 hrs Maximum 1 film 300 mrads Tc-99m 10 mCi DTPA - 17 hrsAbdomen Film 300 mrads Tc-99m 5 mCi Sulfur colloid - 15 hrsGI Series 5 - 20 rads I-123 >50 uCi Tyroid Imag - 5 daysNuclear Med Exams < 1 rad whole body < 50 uCi - 3 days

Max organ dose 1-4 rads organDental 100 mrem/film

Doubling Dose: 100 rem (dose required to double the natural mutation rate)

Sterility 600 rads men 15 rads may produce temporary sterility in men400 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 receive800 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: 110Thyroid 300 children inductionThyroid 150 adult inductionBreast 70 all agesBreast 295 age 15Digestive 170Lung 190

IF population is exposed to 0.1 rem/year continuous the risk for Ca death is560 Ca deaths / 100, 000

FETAL EFFECTSGESTATION EFFECT0 -10 days pre implantation death (SA, local -reabsorption,all or

nothing doses low as 5 rem cause death)2 -8 weeks organogenesis growth retardation, cataracts, embryonic malformations8 - 25 weeks mental retardation most within 8-15 wk>25 weeks increase childhood cancer and leukemia

RADIATION AREA: Area where dose rate >5 mRem/hrHIGH RADIATION AREA: Area where dose rate > 100 mRem/hrCONTROLLED AREA: operator has control of who enters this area, if dose rate>2mR/hr area MUST be controlledFILM 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 SystemDICOM - 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 ProtocolNetwork - may use IP internet Protocol - computers are assigned aa specific IP address

(XXX.XXX.XXX.XXX) or obtain one dynamicallyHost 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 smallBranches, tries to limit congestion increased efficiencyOf physical network

COMMUNICATION PROTOCOLSTCP/IP , FTP - File transfer Protocol, SMTP - Simple Mail Transfer Protocol, TELNET - Telecommunications network

Transfer speedsTwisted Pair (Cat 5 wires) - 10 , 100, 1000 Mb/sec EthernetOptical Fiber - 1G - 10GFDDI - Fiber Distributed data Interface 100 MbATM - Asynchronous Transfer Mode -

typical 154 Mb/sec can combine 600 Mb/secModem - 56 kb/secISDN - 128 kb/secDSL - can go up to 1.54 Mb/sec need several linesCable Modem - download rates up to 10 Mb/sec

Upload 10X slowerT1 - 1.54Mb/secT3 - 50 Mbits/ec

PACS DIGITAL Digital Modalities SHADES OF GRAY

CT - 512 x 512 x 2 B = 0.5MB/image 1 bit - 21 = 2 shades of grayMRI - 256 x 256 x 2B = 0.13 MB/image 2 bit - 22 = 4 "US - 512 x 512 x1B = 0.25 MB/imageFILM DIGITIZERS - 2K x 2K x 2B =8 MB/imageCR - 2000 x 2000 x 2B = 8MB/image 8 bits - 28 = 256 "DR - Digital Radiography 10 bits - 210 = 1024 "

CCD - CsI - 2000x2000 x 2B = 8 MB/image 16 bits - 216 = 64,000 "TFT - CsI-Si - 2000 x 2000 x 2B = 8 MB/imageTFT - Se 2000 x2000 x2B = 8 MB/image

CR and DR require a processing (table look up) ofImage. Both systems produce wide latitude images

Need to 'convert' into film like image

STORAGERAM - Radom Access Memory - 1 GBFloppy Disk - 1.44 MBZIP Disk - 100 MB, 250, 100 MBHard Disk - 10 - 100 GBCD - 650 MBDVD - 6 GBWORM - write once read many timesMOD - Magneto Optical Disks - 10 GBRAID - Redundant Array of Independent Disks 100s GB

One fails can still recover dataDigital Tape - 40-100 GB per tapeJukebox - Mechanical device holding

Many tapes, MOD, CD, DVD's

CompressionLossless - typical 3:1Lossey - images degrades as reduction increases

Image FormatsJPEGTIFF - tagged image file formatBit mappedGIFF

SMPTE - digital test pattern for calibrating monitors and workstations

CT

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

uwater

10 CT #'s = 1.0 % contrast (% contrast of u, since we use high kVp

we estimate most interactions are Compton, since Compton depends only on density we sometimes say 1 % change in density)

ResolutionSpatial Resolution ~ FOV / Matrix

Head ~ 250 mm / 512 = 0.5 mm = 1 lp/mmBody ~ 350 mm / 512 = 0.7 mm = 0.7 lp/mm

Factors affecting spatial resolutionPixel size - want small pixel size = FOV / Matrix

Hence small FOV large matrix Focal spot size - want small focal spotDetector size - want small detectorsDetector spacing - want detectors close togetherNumber of Projections - want a lot of projections viewsRecon. Alogorithm - sharp, edge enhancement, bonePatient motion - want short scan time

Contrast Resolution ~ 0.3 % or 3 CT #'s Spatial Resolution ~ 0.5 mm Head scans 1.0 mm Body Scans

CT Noise This is major factor limiting low contrast detectability (density resolution)

[ k . ] 1/ 2 where: h = slice thickness [ h w3 D ] D = patient exposure

D mAs, kVp 2-3

k = patient attenuation (thickness)w = pixel size

INTERACTIONS

PHOTOELECTRIC EFFECT

E pe = E - E BE

E = Energy of incident photonE pe Energy of photelectronBE = Binding Energy of electron

E c x-ray = BE

E c x-ray = Energy of the characteristic x-ray

pe = linear PE attenuation coefficient - fractional number of photons attenuated per cm by the photoelectric effect

pe Z3 Z - atomic number - physical density E - photon energy

COMPTON SCATTERING

E comp el = E - E scat

E = Energy of incident photonE scat Energy of scattered photonE comp el - Energy of

Compton (recoil) electron

Enax(Recoil e) = (E E in MeV

comp = linear PE attenuation coefficient - fractional number of photons attenuated per cm by the photoelectric effect

comp - physical density comp decrease in increasing E

FILM SCREEN

BASIC

X-ray Production targetmAs) (kVp)2.5 bremstralung (spectrum)Al filter used to reduce low energy photons Intensity decreases, Eaver increasesHU (Heat Units) = (kVp ) (mA) (sec) (N) N - number of exposures

P (Penumbra) = FS (Mag-1) FS focal spot size

Mag = SID / SOD SID - Source Image Distance SOD - Source Object Distance

FILM

OD (Optical Density) = Log ( Io / I t) Io - incident light It - transmitted lightOD = 1.0 (10% of light transmitted) OD = 2 (1% of light transmitted)

Gradient - average slope of H&D curve Gamma max slope of H&D curve

Speed 1/ E (R) required to produce on OD of 1.0 + Base Fog level

SCREENSCaWO4 - old type screens LaOBr, GdSO4 rare earths - better 'K' edge-increased

Absorption eff and conversion effResolution = 5 lp/mm Mammo 10 lp/mm

Thicker screens poorer resolutionNoise increases when using screens with HIGHER CONVERSION EFF or

HIGHER speed filmNoise Stays same when using screen with HIGHER or LOWER ABSORPTION EFF

Intensification Factor = mAs (Exposure) without screens / mAs with screens

GRIDSGrid Ratio = H /d H - height of lead strips d- space between lead strips

Higher grid ratio more scatter reduction, higher contrast, increase pt doseMore sensitive to lateral decentering, angluation, wrong distance

Bucky - moving grid to eliminate grid linesBucky Factor = mAs (Exposure) with grid / mAs without grid Typical 5:1 (portables and mammo) to 12: 1 chest abdomens etc

MAMMOGRAPHY

Film Screen Use: Single screen (no parallelax ) single emulsion film (no crossover) for high spatial resolution >10 lp/mmHigh contrast film

X-Ray Tube : Mo / Mo Anode/Filter combo for good energy spectrum use Characteristic X-ray of MoMo Filter passes Mo C x-ray,

Sometimes use Mo/Rh and Rh/Rh for increase energy use for dense breast reduces pt exposure

Focal Spot Size - 0.3 mm normal 0.1 mm for mag Mag - typical 2X no change in patient dose when grid is removed

Grid : 5:1 with . 100 lines/inch

Patient Dose; AGD (average glandular Dose) Max (FDA limit) 300 mrem/ film 100 mrem/film Typical

Risk: 200 Ca Deaths / 100,000 per 10 rem 400 Ca produced /100,000 per 10 rem6 Ca Deaths/100,000 per 10 rem for female age 55 300 Ca Deaths/100,000 @ age 15

Qualifications: ABR, & 60 CME last 3 yrs & 240 patients last 6 Mo

Reports: lay language to patient within 30 days, negative study to referring MD within 30 days Positive findings ASAP (3days)

Recalls - should be about 10%

MQSA (FDA/ACR) QATECHNOLOGIST PHYSICIST

Processor - daily AEC - annualPhantom scoring - weekly kVp - annualRepeat analysis - quarterly Output and HVL - annual (>800mR/sec)Fixer retention - quarterly Radiation Pt Dose - annualDarkroom fog - semi annual Screen Uniformity - annualCompression device - semiannual Artifacts- annualScreen film contact - semiannual Auto decompression - annual

MRI

SPIN ECHO

Sequence Weighting flip) TR (msec) TE (msec) Bright Tissue

Spin Echo T1 90 short 500 short (est) 20 Short T1 T2 90 Long 2500 Long 100 Long T2 PD 90 Long 2500 Short(est) 20 Large PD

Gradient T1 45 - 60 short 250 short (est) 10 Short T1 T2* 5 - 20 Long 300 Long 40 Long T2* PD 5 - 20 Long 300 Short(est) 10 Large PD

T2*/T1 5 - 20 Short 30 Short 10 LongT2 -ShortT1

Tissue T1 (1.5T) T2 Coils Use

CSF 2000 200 Shim UniformityGray Matter 900 100 Gradients localizationWhite Matter 800 90 RF Transmit RFLiver 500 40 Surface Receive & inc SNRFat 250 80 (small FOV, closer)

SNR f( Bo) TR ST Nphase NEX

(BW)1/2 TEf( Bo) - increase in Bo increases signal no direct proportionNphase - number of phase encoding stepsST - slice thicknessNEX - number of excitations

(BW)1/2 - bandwidth (range of frequencies) of receiver

SAR – Specific Absorption Rate Watts/kgm – used to estimate heating (1o C limit)SAR = 4 W/kgm for 15 min body 3W/kgm for 10 min head