MODALITY EXPLORATION AND RADIATION THERAPY

magnetic resonance imaging

a radiologic examination that involves the USE of STRONG MAGNETS, RADIOFREQUENCY, and COMPUTER to create an IMAGE of the INTERNAL STRUCTURES of the BODY

magnetic resonance imaging

also known as NUCLEAR MAGNETIC RESONANCE

magnetic resonance imaging

discovered simultaneously in 1947

magnetic resonance imaging

discovered by:

* Felix Bloch
* Edward Mills Purcell

Felix Bloch

discovered MRI

Edward Mills Purcell

discovered MRI

Raymond Damadian

provided and IMPETUS to the DEVELOPMENT of ACTUAL CLINICAL IMAGING using STRONG MAGNETIC FIELDS by suggesting that RADIO WAVE SIGNAL RELAXATION TIMES of DIFFERENT TISSUES might be indicative of TUMOR MALIGNANCY

1971

the year Damadian provided the impetus to the development of actual clinical imaging using strong magnetic fields

Paul Lauterbur

provided the FIRST 2D MR IMAGE of CHEMICAL SAMPLE

1972

the year Lauterbur provided the first 2D MR image

MRI COMPONENTS

* primary magnets
* gradient magnets
* radiofrequency coils
* computer system

MRI IMAGE FORMATION

1. LARGE MAGNETS produces a STRONG MAGNETIC FIELD around the BODY
2. NUCLEI in the body PRECESS at the LARMOR FREQUENCY
3. GRADIENT COILS vary the MAGNETIC FIELD across the body
4. a SLICE OF THE BODY is SPECIFIED by the MAGNETIC FIELD VARIATION along the Z-AXIS
5. GRADIENT COILS also vary MAGNETIC FIELD along the X AND Y DIRECTION to select a TINY VOLUME
6. the MAGNETIC FIELD in that VOLUME is set so that ONLY THE NUCLEI IN THAT VOLUME are at RESONANT LARMOR FREQUENCY
7. the procedure that follows will IDENTIFY THE TISSUE TYPE IN THAT VOLUME
8. this SMALL VOLUME will form ONE PIXEL of the FINAL IMAGE
9. during the SCAN, many SMALL VOLUMES will be SCANNED
10. NUCLEI in the VOLUME PRECESS at the SPECIFIED LARMOR FREQUENCY
11. a PULSE of RADIO PHOTON is TRANSMITTED into the BODY
12. NUCLEI absorb ENERGY and RESONANT, they FLIP BACK to their NORMAL ENERGY STATE
13. after a period of time, the NUCLEI RELAX: FLIP BACK to their NORMAL ENERGY STATE
14. when they RELAX, they emit a RADIO PHOTON
15. the EMITTED RADIO PHOTONS from the SIGNAL received by the RF COILS
16. the MEAN TIME that elapses BETWEEN SWITCHING OFF the TRANSMITTED RF PULSES and RECEIVING a SIGNAL from RELAXING NUCLEI is the RELAXATION TIME
17. the TISSUE TYPE at the SPECIFIED VOLUME is identified from the RELAXATION TIME

large magnets

produces a STRONG MAGNETIC FIELD around the BODY

nuclei in the body

PRECESS at the LARMOR FREQUENCY

gradient coils

vary the MAGNETIC FIELD across the body

slice of the body

SPECIFIED by the MAGNETIC FIELD VARIATION along the Z-AXIS

gradient coils

also vary MAGNETIC FIELD along the X AND Y DIRECTION to select a TINY VOLUME

magnetic field at that volume

set so that ONLY THE NUCLEI IN THAT VOLUME are at RESONANT LARMOR FREQUENCY

pulse of radio photon

TRANSMITTED into the BODY

nuclei

absorb ENERGY and RESONANT, they FLIP BACK to their NORMAL ENERGY STATE

mean time

elapses BETWEEN SWITCHING OFF the TRANSMITTED RF PULSES

relaxation time

RECEIVING a SIGNAL from RELAXING NUCLEI

tissue type at specified volume

identified from the RELAXATION TIME

precession

SLOW MOVEMENT of the AXIS of a SPINNING BODY around another axis due to a TORQUE acting to CHANGE the DIRECTION of the FIRST AXIS

larmor frequency

precessional frequency

larmor frequency

RATE of PRECESSION of the MAGNETIC MOMENT of the PROTON around the EXTERNAL MAGNETIC FIELD

fourier transform

MATHEMATICAL TECHNIQUE that allows an MRI SIGNAL to be DECOMPOSED into a SUM of SINE WAVES of DIFFERENT FREQUENCIES, and AMPLITUDES

nuclear medicine

specialized area of radiology that USES VERY SMALL AMOUNTS OF RADIOACTIVE MATERIALS, or RADIOPHARMACEUTICALS, to examine organ function and structure

THREE STAGE PROCESS OF RADIONUCLIDE IMAGING

* introduction of suitable radionuclides into the patient
* the concentration of radionuclides in the specific organ
* scanning of the organ using an appropriate scanner

COMMON WAYS ON HOW TO PRODUCE ARTIFICIAL RADIONUCLIDE

* irradiating materials in a nuclear reactor
* using technetium generator
* using a medical cyclotron

nuclear reactor

produces and controls the release of energy from splitting the atoms of certain elements

nuclear reactor generator

the energy released is used as heat to make steam to generate electricity

technetium-99 generator

colloquially a technetium cow or moly cow

technetium-99 generator

device used to extract the metastable isotope 99mTc of technetium from a decaying sample of molybdenum-99

cyclotron

an apparatus in which charged atomic and subatomic particles are accelerated by an alternating electric field while following an outward spiral or circular path in a magnetic field

gamma camera

developed by Hal Oscar Anger (1958)

gamma camera

Specialized type of scintillation counter where the position as well as the count of the scintillations within a thin NaI crystal (or multiple crystals) are obtained using a number of photomultipliers.

gamma camera

also called as scintillation camera or Anger camera

gamma camera

device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy

scintillation

process or state of emitting flashes of light.

scintillation

A small flash of visible or ultraviolet light emitted by fluorescence in a phosphor when struck by a charged particle or high-energy photon.

Gamma Camera System Components

* collimator
* scintillation crystal
* array of photomultiplier tube
* preamplifiers
* pulse height analyzer
* digital correction circuitry
* cathode ray tube
* control console
* computer
* picture archiving communication system

pulse height analyzer

instrument that records or counts an electrical pulse if its amplitude falls within specified limits: used in nuclear physics research for the determination of energy spectra of nuclear radiations

pulse height analyzer (basic principle)

to discard signals from background and scattered radiation and/or radiation interfering isotopes so that the only primary photons known to come from the photopeak of the isotope being image and recorded

pulse height analyzer

discriminates between events occurring in the crystal that will be displayed or stored in the computer and events that will be re

collimator

made from lead

collimator

Maintains the quality of the image

Collimator consisting of a series of holes in a lead plate

be used to select the direction of the rays falling on the crystal.

4 Types of Collimator

* parallel-hole collimator
* pin-hole collimator
* diverging collimator
* converging collimator

ultrasonography

diagnostic medical procedure that uses sound waves to produce images on a screen, which allows medical providers to view internal structures of the body

air

340 m/s

lung

650 m/s

fat

1460 m/s

pure water

1500 m/s

salt water

1530 m/s

kidney

1560 m/s

blood

1570 m/s

muscle

1580 m/s

bone

3000 m/s

echogenicity

echogeneity

echogenicity

ability to bounce an echo

Types of Echo

* hyperechoic
* hypoechoic
* anechoic

transducer

device that produces sound waves that bounce off body tissues and make echoes

transducer

receives the echoes and sends them to a computer that uses them to create a picture called a sonogram

piezoelectric effect

ability of certain materials to generate an electric charge in response to applied mechanical stress

piezein

to squeeze or press

piezo

push

piezoelectric effect

converts kinetic or mechanical energy, due to crystal deformation, into electrical energy (how transducers receive sound waves)

inverse piezoelectric effect

(reverse) application of an electric field to a crystal causes realignment of the internal dipole structure. This realignment results in crystal lengthening or contraction, converting electrical energy into kinetic or mechanical energy (how ultrasound transducers produce sound waves)

ultrasound gel

conductive medium that creates a bond between the skin and the ultrasound transduce

ultrasound gel

ultrasound sound waves have a hard time traveling through air, so the gel prevents any extra air space between the probe and your skin in order to create a clear image

transducer damping

a material (damping element, damping material) bonded to the back of the piezoelectric element of a transducer to limit the duration of vibration

Ultrasound Strengths

* inexpensive
* quick
* mobile
* non-invasive
* can depict free fluid and aneurysms (acute aneurysms)
* can differentiate between solid and fluid structures
* can depict flow and motion
* good for shallow structures

Ultrasound Weaknesses

* operator dependent
* images may be hard to interpret
* suffers from image artifacts
* may be prone to giving “false positives”
* not good for deep structures
* cannot penetrate through bone or air

interventional radiography

Began in 1930s with angiography

Mason Jones

early 1960s) pioneered transbrachial selective coronary angiography

Melvin Judkins

introduced coronary angiography

Charles Dotter

introduced visceral angiography

angiography

the opacification of vessels through injection of contrast media.

Imaging Procedures in IR Suite

* angiography
* aortography
* arteriography
* cardiac catherization
* myelography
* venography

Interventional Procedures in IR Suite

* Stent placement
* embolization
* intravascular stent
* thrombolysis
* balloon angioplasty
* atherectomy
* electrophysiology

atherectomy

minimally invasive endovascular surgery technique for removing atherosclerosis from blood vessels within the body

atherectomy

an alternative to angioplasty for the treatment of peripheral artery disease, but the studies that exist are not adequate to determine if it is superior to angioplasty

stent

tiny tube that your doctor can insert into a blocked passageway to keep it open. The stent restores the flow of blood or other fluids, depending on where it's placed

stent

made of either metal or plastic.

stent grafts

larger stents used for larger arteries

electrophysiology

branch of physiology that pertains broadly to the flow of ions (ion current) in biological tissues and, in particular, to the electrical recording techniques that enable the measurement of this flow.

balloon angioplasty

the surgical widening of a blocked or narrowed blood vessel, especially a coronary artery, by means of a balloon catheter

embolization

the artificial or natural formation or development of an embolus

Sven Ivar Seldinger

described a method of arterial access in which catheter was used (1953)

Seldinger needle

18 gauge hollow needle with stylet

guidewires

Allows safe introduction of the catheter into the vessel

guidewires

Fabricated of stainless steel and contain an inner core wire that is tapered at the end to a soft flexible tip

conventional guidewires

145 cm long

cathethers

Categorized in French (Fr) sizes;

3 Fr

equal to 1 mm in diameter

H1 or headhunter tip

used for femoral approach to the brachiocephalic vessels

H1 or headhunter tip

designed by Vincent Hick

Simmons catheter

highly curved designed for cerebral angiography