Transcript X-ray production

Gamma Camera
Planar nuclear imaging: the anger scintillation camera
 Developed by Hal O. Anger at the Donner Laboratory in
Berkeley, California, in the 1950s.
 A scintillation camera, contains a disk-shaped or sodium
iodide NaI(TI) crystal, typically 0.95 cm (3/8 inch)
thick, optically coupled to a large number of 5.1- to 7.6cm diameter photomultiplier tubes (PMTs).
Gamma Camera
 In most cameras, a preamplifier is connected to the output of each
PMT. Between the patient and the crystal is a collimator, usually
made of lead, that only allows x- or gamma rays approaching from
certain directions to reach the crystal.
PMT
Photomultiplier Tubes (PMTs) perform two functions :1. conversion of ultraviolet and visible light photons into
an electrical signal
2. signal amplification, on the order of millions to billions.
‫أشــعة ـ‬
‫‪X‬‬
‫‪Essential physics‬‬
‫‪of diagnostic‬‬
‫‪radiology‬‬
‫اكتشفت من قبل‪:‬‬
‫‪.‬العالم وليم رونتجن عام ‪1895‬‬
‫وفي عام ‪ 1895‬نشرت أول ورقة علمية عن تطبيقات األشعة‬
‫السينية‬
‫‪Wilhelm Conrad Rontgen‬‬
‫‪1845 - 1923‬‬
‫‪NP 1901‬‬
X-ray production,
x-ray tubes, and generators
• X-rays are produced when highly energetic
electrons interact with matter and convert
their kinetic energy into electromagnetic
radiation.
• x-ray tube insert
• tube housing
X-ray
• collimators
device
• generator
X-ray production
X-ray production
A large voltage is applied between two
electrodes
X-ray production
e anode is positively charged
The cathode is negatively
charged
X-ray production
An x-ray photon with
energy equal to the
kinetic energy lost by the
electron is produced
(conservation of energy).
This radiation is termed
bremsstrahlung, a
German word meaning
"braking radiation."
X-ray production
At relatively "large"
distances from the
nucleus, the
coulombic
attraction force is
weak; these
encounters produce
low x-ray energies
(Fig. electron no. 3).
Factors that affect
x-ray production
• Major factors that affect x-ray production
efficiency include:
1. the atomic number of the target material
2. the kinetic energy of the incident electrons.
• The approximate ratio of collisional energy
loss is expressed as follows:
kinetic energy of the
incident electrons in keV
Atomic number
X-Ray Tubes
• Major components are: the cathode, anode,
rotor/stator, glass (or metal) envelope, and tube
housing.
Anode Configurations
•
a.
b.
•
X-ray tubes have two configurations:
Stationary;
Rotating anode.
Stationary: It consists of a tungsten insert embedded
in a copper block (see Fig. below). The copper serves a
dual role: it supports the tungsten target, and it
removes heat efficiently from the tungsten target.
Anode Configurations
• Rotating anodes are
used
for
most
diagnostic
x-ray
applications,
mainly
because
of
their
greater heat loading and
consequent higher x-ray
output capabilities.
• Electrons impart their
energy on a continuously
rotating
target,
spreading
thermal
energy over a large area
and mass of the anode
disk.
Collimators
• Collimators adjust the size and shape of the x-ray
field emerging from the tube port.
Fluoroscopy
•
•
Fluoroscopy is an imaging procedure that
allows real-time x-ray viewing of the patient
with high temporal resolution.
Before the 1950s, fluoroscopy was performed
in a darkened room with the radiologist viewing
the faint scintillations from a thick
fluorescent screen.
Fluoroscopic
Imaging Components
•
•
The x-ray tube,
filters, and collimation
are similar
technologies to those
used in radiography
and are not discussed
in detail here.
The principal
component of the
imaging chain that
distinguishes
fluoroscopy from
radiography is the
image intensifier.
10 min  18000 images
The Image Intensifier (II)
• There are four principal components of an II:
(a) a vacuum bottle to keep the air out,
(b) an input layer that converts the x-ray signal to
electrons,
(c) electronic lenses that focus the electrons, and
(d) an output phosphor that
converts the accelerated
electrons into visible light.
The optical distributor
• The output window of
the image intensifier,
which is the source of
the optical image, is
also shown (bottom).
Parallel rays of light
enter
the
optical
chamber, are focused
by lenses, and strike
the
video
camera
where an electronicimage is produced.
Conventional Tomography Devices
• Conventional tomography, also called body
tomography or geometric tomography, makes use
of geometric focusing techniques to achieve the
tomographic effect.
Conventional Tomography Devices
• The principles of geometric tomography are
illustrated in Fig. below. The patient is positioned
on the table, and the desired plane in the patient
to be imaged is placed at the pivot point of the
machine.
Conventional Tomography Devices
• The imaging cassette travels in the opposite
direction.
• Tomographic angle is the angle through which the
x-ray tube travels while the x-rays.
Digital Subtraction Angiography
• The most common example of temporal subtraction is
digital subtraction angiography (DSA).
• In DSA, a digital radiographic image of the patient's
anatomy (the "mask") is acquired just before the
injection of contrast agent. A sequence of images is
acquired during and after the contrast agent injection.
• The mask image is subtracted from the images
containing contrast agent.
Detail of the vascular anatomy
and the other anatomic aspects
of the patient (e.g., bones)
Using dual-energy radiography this Figure illustrates:
This patient had a
calcified
granuloma that is
well seen on the
bone-only image.
The soft tissue
image shows the
lung parenchyma
without the
overlaying ribs as
a source of
distraction.
Low-energy
image (56 kVp);
Image shows
the energy
subtraction
image weighted
to present bone
only
high-energy image
(120 kVp, 1 mm
Cu).
The tissueweighted image
Quality Management (QM)
• Quality management and its associated topics,
quality assurance and quality control, are vitally
important.
• Government and accreditation agencies now mandate
procedures to ensure that equipment is functioning
within accepted standards and that is operated
properly.
• I have teach teaching a course in Quality
Assurance/ Quality management since 1999 and have
never required a textbook because I couldn't find
one single book that contained all of the necessary
material. Today there is 100 of textbooks.
Quality Assurance
•
•
Quality Assurance (QA): is an all-encompassing
management program used to insure excellence in
healthcare through the systematic collection and
evaluation data.
The primary objective of the QA program is the
enhancement of patient care; this includes patient
selection parameters and scheduling, management
techniques, departmental policies and procedures,
technical effectiveness and efficiency, in-service
education and image interpretation with timeliness
of reports.
Quality Control
•
Quality Control (QC): is the part of QA program
that deals with techniques used in monitoring and
maintenance of the technical element of the
systems that affect the quality of the image.
• Therefore, QC is the part of the QA program that
deal with instrumentation and equipment.
• QC program includes the following three levels of
testing:
1. Level one: Noninvasive and Simple
2. Level two: Noninvasive and Complex
3. Level three: Invasive and Complex
Quality Control
Noninvasive and Simple evaluations
performed by any technologists.
can
be
Noninvasive and Complex evaluations should
be performed by a technologist trained in
QC procedures.
Invasive and Complex involve some
disassembly of the equipment and
are
normally
performed
by
engineers or medical physicists.
Image Quality
•
Image quality is a generic concept that applies
to all types of images. It applies to medical
images, photography, television images, and
satellite reconnaissance images.
• "Quality" is a subjective notion and is
dependent on the function of the image.
• The principal components of image quality are:
1. Contrast,
2. Spatial resolution,
3. Noise.
Contrast
• What is contrast? Contrast is the difference in the image
gray scale between closely adjacent regions on the image.
• Figure contains two radiographs; the one on the left is
uniformly gray. X-rays were taken, film was exposed, but
the image remains vacant and useless. The chest radiograph
on the right is useful, and is rich with anatomic detail. The
image on the right possesses contrast, the image on the
left has none.
Spatial Resolution
• Spatial resolution is a property that describes
the ability of an imaging system to accurately
depict objects in the two spatial dimensions of
the image.
• Spatial resolution is sometimes referred to
simply as the resolution.
• The classic notion of spatial resolution is the
ability of an image system to distinctly depict
two objects as they become smaller and closer
together.
Noise
• Figure below shows three isometric "images";
each one has similar contrast, but the amount of
noise increases toward the right of the figure.
There are several different sources of noise in an
image.
Magnetic Resonance Imaging (MRI)
 Nuclear magnetic resonance (NMR) is the
spectroscopic study of the magnetic properties of
the nucleus of the atom.
Magnetic field with
neutron & protons
nuclear spin and charge
distribution
 Resonance is an energy coupling that causes the
individual nuclei, when placed in a strong external
magnetic field, to selectively absorb, and later
release, energy unique to those nuclei and their
surrounding environment.
Magnetic Resonance Imaging (MRI)
 NMR start since 1940s as an analytic tool in
chemistry and biochemistry research.
 NMR is not an imaging technique but rather a
method to provide spectroscopic data concerning a
sample placed in the device.
 In the early 1970s, NMR can use to generate images
that display magnetic properties of the proton,
reflecting clinically relevant information.
NMR
mid
1980
MRI
As clinical imaging applications increased
Magnetization Properties
 Magnetism is a fundamental property of matter; it is
generated by moving charges, usually electrons.
 Atoms and molecules have electron orbitals that can
be paired (an even number of electrons cancels the
magnetic field) or unpaired (the magnetic field is
present).
Magnetization Properties
 The magnetic field strength, B, (also called the
magnetic flux density) can be conceptualized as the
number of magnetic lines of force per unit area.
 The SI unit for B is the tesla (T), and as a
benchmark, the earth's magnetic field is about
1/20,000 T..
Magnetization Properties
 Magnetic fields can be induced by a moving charge in
a wire.
 The direction of the magnetic field depends on the
sign and the direction of the charge in the wire, as
described by the "right hand rule": The fingers
point in the direction of the magnetic field when the
thumb points in the direction of a moving positive
charge.
Magnetic Characteristics of the Nucleus
 The nucleus is comprised of protons and neutrons with
characteristics listed in table below.
 The magnetic moment, represented as a vector
indicating magnitude and direction, describes the
magnetic field characteristics of the nucleus.
Magnetic Characteristics
of the Elements
Under the influence of a strong external magnetic field, Bo, however, the spins
are distributed into two energy states: alignment with (parallel to) the applied
field at a low-energy level, and alignment against (antiparallel to) the field at a
slightly higher energy level (see Fig. B).
Suggested reading
1. Axel L, et al. Glossary of MR terms, 3rd ed. Reston, VA:
American College of Radiology, 1995.
2. Brown MA, Smelka RC. MR: basic principles
applications. New Yotk: John Wiley & Sons, 1995.
and
3. Hendrick RE. The AAPM/RSNA physics tutorial for
residents. Basic physics of MR imaging: an introduction.
Radiographies 1994; 14:829-846.
4. NessAiver M. All you really need to know about MRl
physics. Baltimore: Simply Physics, 1997.
5. Plewes DB. The AAPM/RSNA physics tutorial for
residents. Contrast mechanisms in spin-echo MR imaging.
Radiographies 1994; 14: 1389-1404.
Suggested reading
6. Price RR. The AAPM/RSNA physics tutorial for
residents. Contrast mechanisms in gradientecho imaging
and an introduction to fast imaging. Radiographies
1995;15:165-178.
7. Smith H], Ranallo FN. A non-mathematical approach to
basic MR!. Madison, WI: Medical Physics Publishing, 1989.
8. Smith RC, Lange RC. Understanding magnetic resonance
imaging. Boca Raton, FL: CRC Press, 1998.
9. Wherli FW. Fast-scan magnetic resonance: principles and
applications. New York: Raven Press, 1991.
MRI

The protons in a material, with the use of an external uniform
magnetic field and RF energy of specific frequency, are
excited and subsequently produce signals with amplitudes
dependent on relaxation characteristics and spin density, as
previously discussed.

Conventional MRI involves RF excitations combined with
magnetic field gradients to localize the signal from individual
volume elements (voxels) in the patient.
Magnetic Field Gradients
 Magnetic fields are produced in a coil wire
energized with a direct electric current of specific
polarity and amplitude.
 Magnetic field gradients are
obtained by superimposing the
magnetic fields of one or more coils
with a precisely defined geometry.
With appropriate design, the
gradient coils create a magnetic
field that linearly varies in strength
versus distance over a predefined
field of view (FOV).
Magnetic Field Gradients
 Inside the magnet bore, three sets of gradients reside
along the coordinate axes-x, y, and z-and produce a
magnetic field variation determined by the magnitude of
the applied current in each coil set.
Slice select Gradients

The RF antennas that produce the RF pulses do not have the
ability to direct the RF energy. Thus, the slice select gradient
(SSG) determines the slice of tissue to be imaged in the body.
Instrumentation (Magnet)

The magnet is the heart of the MR system.

For any particular magnet type, performance criteria include:
1.
field strength,
2. temporal stability,
3. field homogeneity.
4. These parameters are affected by the magnet design.

Magnet types:
1.
Air core magnets;
2. Solid core magnet;
3. Resistive magnet.
Air Magnet
 1- Air core magnets are made of wire wrapped cylinders of
1m diameter and greater, where the magnetic field is
produced by an electric current in the wires. The main
magnetic field of air core magnets runs parallel to the
long axis of the cylinder.
Solid Magnet
 Solid core magnets are constructed from permanent
magnets, a wire wrapped iron core "electromagnet,“ or a
hybrid combination.
 In these solid core designs, the magnetic field runs
between the poles of the magnet, most often in a vertical
direction.
Resistive electromagnet
 Resistive electromagnets are constructed in either an air
core or solid core configuration.
 Have a vertical magnetic field with contained fringe fields.
 These systems use continuous electric power to produce
the magnetic field, produce a significant amount of heat,
and often require additional cooling subsystems.
 The magnetic field of resistive systems ranges from 0.1 T
to about 0.3 T.
 An advantage of purely resistive system is the ability to
turn off the magnetic field in an emergency. The
disadvantages include high electricity costs and relatively
poor uniformity/homogeneity of the field.
Radio Frequency (RF)
 RF transmitter and receiver body coils are located within
the magnet bore. There are two types of RF coils:
transmit and receive, and receive only.
 Often, transmit and receive functions are separated to
handle the variety of imaging situations that arise, and to
maximize the SNR for an imaging sequence.
MRI

The control interfaces, RF source, detector, and
amplifier, analog to digital converter (digitizer), pulse
programmer, computer system, gradient power supplies,
and image display are crucial components of the MR
system.
Protection

Superconductive magnets produce extensive magnetic fields, and create
potentially hazardous conditions in adjacent areas.

Thus, two requirements must be considered for MR system: protect the
local environment from the magnet system, and protect the magnet
system from the local environment.

Environmental RF noise must be reduced to protect the sensitive
receiver within the magnet from interfering signals. The room containing
the MRI system is typically lined with copper sheet (walls) and mesh
(windows).

Magnetic fields below 0.5 mT are considered safe for the patient
population.

Areas above 1.0 mT require controlled and restricted access with
warning signs.

Disruption of the fringe fields can reduce the homogeneity of the active
imaging volume. Any large metallic object (e.g., elevator, automobile,
etc.) traveling through the fringe field can produce such an effect.
Safety and Bioeffects

In spite of ionizing radiation is not used with MRI, there are
important safety considerations.

These include the presence of strong magnetic fields, RF
energy, time varying magnetic gradient fields, cryogenic
liquids, and noisy operation (gradient coil activation and
deactivation, creating acoustic noise).

Patients with implants, prostheses, aneurysm clips,
pacemakers, heart valves, ete., should be aware of
considerable torque when placed in the magnetic field, which
could cause serious adverse effects.

Even nonmetallic implant materials can lead to significant
heating under rapidly changing gradient fields.
Suggested Reading
1.
NessAiver M. All you really need to know about MR!
physics. Baltimore, MD: Simply Physics, 1997.
2. Price RR. The MPM/RSNA physics tutorial for residents:
MR imaging safety considerations. RadioGraphies
1999;19:1641-1651.
3. Saloner D. The MPM/RSNA physics tutorial for residents.
An introduction to MR angiography. RadioGraphies 1995;
15:453-465.
4. Shellock F, Kanal E. Magnetic resonanceimaging bioefficts,
safety, and patient management, 2nd ed. New York:
Lippincott-Raven, 1996.
5. Smith HJ, Ranallo FN. A non-mathematical approach to
basic MR!. Madison, WI: Medical Physics, 1989.
Ultrasound

Ultrasound is the term that describes sound waves of
frequencies exceeding the range of human hearing and
their propagation in a medium.

Medical diagnostic ultrasound is a modality that uses
ultrasound energy and the acoustic properties of the
body to produce an image from stationary and moving
tissues.

Generation of the sound pulses and detection of the
echoes is accomplished with a transducer, which also
directs the ultrasound pulse along a linear path through
the patient.
Characteristics of sound
Propagation of Sound
Sound is mechanical energy that propagates
through a continuous, elastic medium by the
compression and rarefaction of "particles" that
compose it.
Wavelength, Frequency, and Speed
 Ultrasound represents the frequency range above 20
kHz.
 Medical ultrasound uses frequencies in the range of 2
to 10 MHz, with specialized ultrasound applications up
to 50 MHz.
 The speed of sound is the distance traveled by the
wave per unit time and is equal to the wavelength
divided by the period.

The relationship between speed, wavelength, and
frequency for sound waves is
Wavelength, Frequency, and Speed
 The speed of sound is dependent on the propagation
medium and varies widely in different materials.
 The wave speed is determined by the ratio of the bulk
modulus (B) (a measure of the stiffness of a medium
and its resistance to being compressed), and the
density () of the medium:
 SI units are kg/(m-sec2), kg/m3, and m/sec for B, ,
and c, respectively.
Wavelength, Frequency, and Speed
 A highly compressible medium, such as air, has a low
speed of sound, while a less compressible medium,
such as bone, has a higher speed of sound.
 The ultrasound frequency is unaffected by changes in
sound speed as the acoustic beam propagates through
various media.
Wavelength, Frequency, and Speed
 Example:
A 5-MHz beam travels from soft tissue into fat.
Calculate the wavelength in each medium, and
determine the percent wavelength change.
Answer:
In soft tissue,  = c\f = (1.540 m/sec) /(5x106/sec)
= 3.08 x 10-6 = 0.31 mm
In fat,
= (1.450 m/sec) /(5x106/sec)
= 2.9 x 10-6 = 0.29 mm
Wavelength, Frequency, and Speed
 The resolution of the ultrasound image and the
attenuation of the ultrasound beam energy depend
on the wavelength and frequency.
Wavelength, Frequency, and Speed
small
wavelengt
h
High
frequency
ultrasound
superior
resolution and
image detail
However, the depth of beam
penetration is reduced at
higher frequency.
Wavelength, Frequency, and Speed
longer
wavelengt
h
Lower
frequency
ultrasound
Less
resolution
Wavelength, Frequency, and Speed
 Ultrasound frequencies selected for imaging are
determined by the imaging application.
 For thick body parts (e.g., abdominal imaging), a
lower frequency ultrasound wave is used (3.5 to 5
MHz).
 Most medical imaging applications use frequencies
in the range of 2 to 10 MHz.
Interaction of Ultrasound with matter
 Ultrasound interactions are
acoustic properties of matter.
determined
by
the
 As ultrasound energy propagates through a medium,
interactions that occur include reflection, refraction,
scattering, and absorption.
 Reflection occurs at tissue boundaries where there is
a difference in the acoustic impedance of adjacent
materials. When the incident beam is perpendicular to
the boundary, a portion of the beam (an echo) returns
directly back to the source, and the transmitted
portion of the beam continues in the initial direction.
Interaction of Ultrasound with matter
 Refraction describes the change in direction of the
transmitted ultrasound energy with nonperpendicular
incidence.
 Scattering occurs by reflection or refraction, usually
by small particles within the tissue medium, causes
the beam to diffuse in many directions, and gives rise
to the characteristic texture and gray scale in the
acoustic image.
 Absorption is the process whereby acoustic energy is
converted to heat energy. In this situation, sound
energy is lost and cannot be recovered.
Transducer
 Ultrasound is produced and detected with a
transducer, composed of one or more ceramic
elements with electromechanical properties.
 The ceramic element converts electrical energy into
mechanical energy to produce ultrasound and
mechanical energy into electrical energy for
ultrasound detection.
 Major components include
Transducer
 A piezoelectric material (often a crystal or ceramic) it
converts electrical energy into mechanical (sound) energy.
 Resonance transducers for pulse echo ultrasound imaging,
causing the piezoelectric material vibrate at a natural
resonance frequency.
Image data acquisition
Pressure & blood pressure
 The pressure on a surface is the total force acting on
the surface divided by the surface's area.
Pressure = Force/Area
 Pressure is usually measured in newtons per square
meter (often called pascals) or in pounds per square
inch.
 Pressure is also often measured in millimeters of
mercury (mm HG), a unit that originated from oldfashioned mercury barometers.
 The conversion factor is: 1 mm Hg = 133 pascals =
0.02 pounds per square inch.
Pressure & blood pressure
 Because pressure is commonly measured by its ability
to displace a column of liquid in a manometer,
pressures are often expressed as a depth of a
particular fluid (e.g., inches of water).
 The most
and water;
common
choices
are
mercury
(Hg)
 water is nontoxic and readily available, while
mercury's high density allows for a shorter column
(and so a smaller manometer) to measure a given
pressure
Pressure & blood pressure
 Blood pressure (BP) is the pressure exerted by circulating
blood on the walls of blood vessels, and is one of the principal
vital signs. During each heartbeat, BP varies between a
maximum (systolic) and a minimum (diastolic) pressure.
 The doctor measures the maximum pressure (systolic) and
the lowest pressure (diastolic) made by the beating of the
heart.
 The systolic pressure is the maximum pressure in an artery at
the moment when the heart is beating and pumping blood
through the body.
 The diastolic pressure is the lowest pressure in an artery in
the moments between beats when the heart is resting.
Blood pressure
 A mercury sphygmomanometer is operated by inflating a
rubber cuff placed around a patient's arm until blood flow
stops. The cuff pressure is measured via the mercury
column.
The inflating bulb is used to
inflate the cuff. It contains two
one- way valves. Valve A allows
air to enter the back of the bulb.
When the bulb is squeezed this
valve closes and the air is
propelled through valve B to the
cuff. Valve B stops the air going
back into the bulb.
Blood pressure
 After the cuff has been inflated and the blood pressure taken, the
cufy may be deflated by opening valve C. The reservoir contains the
supply of mercury which rises up the measurement tube. Normally
the apparatus is contained within a box. When opened the graduated
tube becomes vertical, and the mercury reservoir is at the bottom. As
the pressure within the cuff increases the mercury is displaced from
the reservoir into the graduated tube. The two leather discs (D and E)
allow air to pass in and out of the column, but prevent mercury
escaping from the sphygmomanometer.
Blood pressure
 Normal values: In a study of 100 subjects with no known
history of hypertension, an average blood pressure of
112/64 mmHg was found, which is in the normal range
Physics of human body

Magnatisium in medicine (First Medical Uses of
Magnets, generation and safety),

Muscular signals measuring by electromyogram
(EMG),

Heart signals measuring by electrocardiogram
(ECG),

Brain signal measuring by electroencephalogram
(EEG),

Principles of Thermography,

Human Body Dynamics (classical mechanics and
human movement)
Magnatisium in medicine
 The first effects of magnetism were observed
when the smelted iron was brought close to the
iron oxide in the chemical form of FeO.Fe2O3
(Fe3O4), a natural iron ore which came to be known
as lodestone or magnetite.
 The origin of the term ‘‘magnetite’’ is unclear, but
two explanations appear most frequently in the
literature. In one of these, magnetite was named
after the Greek shepherd Magnes, who discovered
it when the nails on the soles of his shoes adhered
to the ore. In the other explanation, magnetite was
named after the ancient county of Magnesia in
Asia Minor, where it was found in abundance.
Magnatisium in medicine
 First Medical Uses of Magnets: Thales of Miletus,
the first Greek speculative scientist and
astronomer was also the first to make a connection
between man and magnet.
 He believed that the soul somehow produced
motion and concluded that, as a magnet also
produces motion in that it moves iron, it must also
possess a soul. It is likely that this belief led to
the many claims throughout history of the
miraculous healing properties of the lodestone.
Hand-held electromagnets used for the removal of 
magnetic objects from the eye.
Magnatisium in medicine
 Removal of an open safety pin from a patient’s
stomach.
Treatment of Nervous Diseases
and Mesmerism
 The first person to mention the topical application
of a magnet in nervous diseases was Aetius of
Amida (550–600), who recommended this approach
primarily for the treatment of hysteria, and also
for gout, spasm, and other painful diseases.
Electrocardiogram (ECG)
 Cardiomagnetism refers to the detection,
analysis and interpretation of the magnetic
fields generated by the electrical activity of the
heart.
 The peak value of the magnetic fields of the
heart, measured near the chest, is more than a
million times smaller than the Earth’s magnetic
field.
Electrocardiogram
 Electrical impulses in the heart originate in the
sinoatrial node and travel through the intimate
conducting system to the heart muscle. The
impulses stimulate the myocardial muscle fibres to
contract and thus induce systole. The electrical
waves can be measured at electrodes placed at
specific points on the skin.
‫لعقدة الجيبية األذينية ‪ Sinoatrial node‬أو ‪ SA node‬هي النسيج‬
‫المولد للنظم الجيبي أي المنظم لنبض القلب‪.‬‬
‫هي مجموعة خاليا تقع في جدار األذين األيمن قرب مدخل الوريد األجوف العلوي‪.‬‬
‫هذه الخاليا هي خاليا عضلية قلبية معدلة ال تتقلص‪ ،‬وإنما تقوم بتوليد الشارة‬
‫المحفزة للقلب بشكل دوري يتراوح ما بين ‪ 120-60‬مرة في الدقيقة بحسب العمر‬
‫أثناء الراحة الجسدية‪.‬‬
Electrocardiogram
 Electrodes on different sides of the heart
measure the activity of different parts of the
heart muscle.
 An ECG displays the voltage between pairs of
these electrodes, and the muscle activity that they
measure, from different directions, can also be
understood as vectors.
Electrocardiogram
 Placement of electrodes: Ten electrodes are
used for a 12-lead ECG. They are labeled and
placed on the patient's body as follows:
Electrocardiogram (ECG)
 A typical ECG tracing of the cardiac cycle (heartbeat)
consists of a P wave, a QRS complex, a T wave, and a
U wave which is normally visible in 50 to 75% of
ECGs. The baseline voltage of the electrocardiogram
is known as the isoelectric line.
Electroencephalogram (EEG)
 Electroencephalography (EEG) is the recording of
electrical activity along the scalp produced by the
firing of neurons within the brain.
 A neuron (also known as a neurone or nerve cell) is an
electrically excitable cell that processes and
transmits information by electrochemical signaling, via
connections with other cells called synapses. Neurons
are the core components of the nervous system, which
includes the brain, spinal cord, and peripheral ganglia.
Electroencephalogram (EEG)
 In clinical contexts, EEG refers to the recording of
the brain's spontaneous electrical activity over a
short period of time, usually 20–40 minutes, as
recorded from multiple electrodes placed on the scalp.
 Neurology, the main diagnostic application of EEG.
 A secondary clinical use of EEG is in the diagnosis of
coma, encephalopathies, and brain death.
 EEG used to be a first-line method for the diagnosis
of tumors, stroke and other focal brain disorders, but
this use has decreased with the advent of anatomical
imaging techniques such as MRI and CT.
Electroencephalogram (EEG)
Wave
discharges
monitored
with
EEG.
Electroencephalogram (EEG)

Neurons, or nerve cells, are electrically active cells which
are primarily responsible for carrying out the brain's
functions. Neurons create action potentials, which are
discrete electrical signals that travel down axons (nerve
fiber is a long, slender projection of a nerve cell).

The neurotransmitter, when combined with the receptor
(protein molecule), typically causes an electrical current
within the dendrite or body of the post-synaptic neuron.
‫ عبارة عن مواد كيميائية موجودة في منطقة‬Neurotransmitters ‫لناقالت العصبية‬
‫ارتباط خلية عصبية بخلية عصبية أخرى وتنظم هذه المواد الكيميائية اإلشارة‬
. ‫العصبية القادمة من الدماغ أو المتجهة إلى الدماغ‬
Electroencephalogram (EEG)
 Thousands of post-synaptic currents from a
single neuron's dendrites and body then sum up to
cause the neuron to generate an action potential
(or not). This neuron then synapses on other
neurons, and so on.
 In the nervous system, a synapse is a structure
that permits a neuron to pass an electrical or
chemical signal to another cell.
Electroencephalogram (EEG)
 The electric potentials generated by single
neurons are far too small to be picked by EEG.
EEG activity therefore always reflects the
summation of the synchronous activity of
thousands or millions of neurons that have similar
spatial orientation, radial to the scalp.
 A routine clinical EEG recording typically lasts
20–30 minutes (plus preparation time) and usually
involves recording from 25 scalp electrodes.
Electroencephalogram (EEG)

Routine EEG is typically used in the following clinical
circumstances:
1.
to distinguish epileptic seizures from other types of spells,
such as psychogenic non-epileptic seizures, syncope
(fainting), sub-cortical movement disorders and migraine
variants.
2. to differentiate "organic" encephalopathy or delirium from
primary psychiatric syndromes such as catatonia
3. to serve as an adjunct test of brain death
4. to prognosticate, in certain instances, in patients with coma
5. to determine whether to wean anti-epileptic medications
‫ الصداع النصفي‬،‫ الصرع‬،‫ الغيبوبة‬، ‫التهاب الدماغ أو هذيان‬
Electroencephalogram (EEG)

In conventional scalp EEG, the recording is obtained by
placing electrodes on the scalp with a conductive gel or
paste, usually after preparing the scalp area by light
abrasion to reduce impedance due to dead skin cells.

Many systems typically use electrodes, each of which is
attached to an individual wire. Some systems use caps or
nets into which electrodes are embedded; this is
particularly common when high-density arrays of electrodes
are needed.

Each electrode is connected to one input of a differential
amplifier (one amplifier per pair of electrodes); a common
system reference electrode is connected to the other input
of each differential amplifier.
Electroencephalogram (EEG)
 These amplifiers amplify the voltage between the
active electrode and the reference (typically
1,000–100,000 times, or 60–100 dB of voltage
gain).
 Most EEG systems these days, however, are
digital, and the amplified signal is digitized via an
analog-to-digital converter, after being passed
through an anti-aliasing filter.
Electromyogram (EMG)
 Muscular signals measuring by electromyogram
(EMG).
 Electromyography (EMG) is a technique for
evaluating and recording the activation signal of
muscles. EMG is performed using an instrument
called an electromyograph, to produce a record
called an electromyogram.
 An electromyograph detects the electrical potential
generated by muscle cells when these cells are both
mechanically active and at rest. The signals can be
analyzed in order to detect medical abnormalities
or analyze the biomechanics of human or animal
movement.
Electromyogram (EMG)
 The electrical source is the muscle membrane
potential. Measured EMG potentials range
between less than 50 μV and up to 20 to 30 mV,
depending on the muscle under observation.
 The first documented experiments dealing with
EMG started with Francesco Redi’s works in 1666.
 Redi discovered a highly specialized muscle of the
electric ray fish (Electric Eel) generated
electricity. By 1773, Walsh had been able to
demonstrate that the Eel fish’s muscle tissue
could generate a spark of electricity.
Electromyogram (EMG)
 The first actual recording of this activity was
made by Marey in 1890, who also introduced the
term electromyography.
 In 1922, Gasser and Erlanger used an oscilloscope
to show the electrical signals from muscles.
Because of the stochastic nature of the
myoelectric signal, only rough information could
be obtained from its observation.
 The capability of detecting electromyographic
signals improved steadily from the 1930s through
the 1950s, and researchers began to use
improved electrodes more widely for the study of
muscles.
Electromyogram (EMG)
 There are many applications for the use of EMG.
EMG is used clinically for the diagnosis of
neurological and neuromuscular problems.
 EMG is also used in many types of research
laboratories,
including
those
involved
in
biomechanics, motor control, neuromuscular
physiology, movement disorders, postural control,
and physical therapy.
Electromyogram (EMG)
 There are two kinds of EMG in widespread use:
surface EMG and needle (intramuscular) EMG.
 To perform intramuscular EMG, a needle
electrode is inserted through the skin into the
muscle tissue.
 A trained professional (most often a physiatrist,
neurologist, or chiropractor) observes the
electrical activity while inserting the electrode.
 The insertional activity provides valuable
information about the state of the muscle and its
innervating nerve.
Electromyogram (EMG)
 Normal muscles at rest make certain, normal
electrical sounds when the needle is inserted into
them. Then the electrical activity when the
muscle is at rest is studied.
 Abnormal spontaneous activity might indicate
some nerve and/or muscle damage. Then the
patient is asked to contract the muscle smoothly.
The shape, size and frequency of the resulting
motor unit potentials is judged.
 Then the electrode is retracted a few
millimeters, and again the activity is analyzed
until at least 10-20 units have been collected.
Electromyogram (EMG)
 A motor unit is defined as one motor neuron and
all of the muscle fibers it innervates.
 EMG is used to diagnose two general categories
of disease: neuropathies and myopathies.
References

M. B. I. Reaz, M. S. Hussain, F. Mohd-Yasin, “Techniques of EMG
Signal Analysis: Detection, Processing, Classification and Applications”,
Biological Procedures Online, vol. 8, issue 1, pp. 11–35, March 2006

Nikias CL, Raghuveer MR. Bispectrum estimation: A digital signal
processing framework. IEEE Proceedings on Communications and
Radar. 1987;75(7):869–891.

Basmajian, JV.; de Luca, CJ. Muscles Alive - The Functions Revealed
by Electromyography. The Williams & Wilkins Company; Baltimore,
1985.

Graupe D, Cline WK. Functional separation of EMG signals via ARMA
identification methods for prosthesis control purposes. IEEE
Transactions on Systems, Man and Cybernetics, 1975;5(2):252-259.

Kleissen RFM, Buurke JH, Harlaar J, Zilvold G. Electromyography in
the biomechanical analysis of human movement and its clinical
application. Gait Posture. 1998;8(2):143–158. doi: 10.1016/S09666362(98)00025-3. [PubMed]
Principles of Thermography,
 Infrared
thermography,
thermal
imaging,
thermographic imaging, or thermal video, is a type
of infrared imaging science.
 Thermographic cameras detect radiation in the
infrared range of the electromagnetic spectrum
(roughly 900–14,000 nanometers or 0.9–14 µm)
and produce images of that radiation, called
thermograms.
Thermogram of a small dog
taken in mid-infrared
Principles of Thermography,
 Since infrared radiation is emitted by all objects
near room temperature, according to the black
body radiation law, thermography makes it
possible to "see" one's environment with or
without visible illumination.
 The amount of radiation emitted by an object
increases
with
temperature,
therefore
thermography allows one to see variations in
temperature (hence the name).
Thermogram of two ostriches
Principles of Thermography,
 The use of thermal imaging has increased
dramatically with governments and airports staff
using the technology to detect suspected swine
flu cases during the 2009 pandemic.
 Other uses include, firefighters use it to see
through smoke, find persons, and localize the
base of a fire.
 Thermal imaging cameras are also installed in
some luxury cars to aid the driver, the first being
the 2000 Cadillac DeVille.
Thermogram of lion
Principles of Thermography,
 It is important to note that thermal imaging
displays the amount of infrared energy emitted,
transmitted, and reflected by an object. Because
of this, it is quite difficult to get an accurate
temperature of an object using this method.
 Thus, Incident Energy = Emitted
Transmitted Energy + Reflected Energy
Energy
+
Principles of Thermography,
 Thermal imaging camera & screen, photographed in an
airport terminal in Greece. Thermal imaging can
detect elevated body temperature, one of the signs of
the virus H1N1 (Swine influenza).
Principles of Thermography,

Advantages of thermography:
1.
It shows a visual picture so temperatures over a large area
can be compared
2. It is capable of catching moving targets in real time
3. It is able to find deteriorating, i.e., higher temperature
components prior to their failure
4. It can be used to measure or observe in areas inaccessible
or hazardous for other methods
5. It is a non-destructive test method
6. It can be used to find defects in shafts, pipes, and other
metal or plastic parts[4]
7. It can be used to see better in dark areas
Physics of human body
 “The human body is a machine whose movements
are directed by the soul,” wrote René Descartes in
the early seventeenth century.
 In pursuit of knowledge, Leonardo da Vinci
dissected the bodies of more than 30 men and
women.
 The advances in the understanding of human body
structure and its relation to movement were soon
followed by the formulation of nature’s laws of
motion.
Human Body Structure
 Humans possess a unique physical structure that
enables them to stand up against the pull of gravity.
 The biggest part of the human body is the trunk;
comprising on the average 43% of total body weight.
Head and neck account for 7% and upper limbs 13% of
the human body by weight. he thighs, lower legs, and
feet constitute the remaining 37% of the total body
weight.
 The frame of the human body is a tree of bones that
are linked together by ligaments in joints called
articulations. There are 206 bones in the human body.
Human Body Structure
 Approximately 700 muscles pull on various parts of the
skeleton. About 40% of the body weight is composed of
muscles.
 These muscles are connected to the bones through
cable-like structures called tendons.
 In the body each long bone is a lever and an associated
joint is a fulcrum.
The types of levers observed
in the human body.
 Neck muscles acting on the
skull, controlling
flexion/extension movements,
constitute a first-class lever
(Fig. a). When the fulcrum lies
between the applied force and
the resistance, as in the case
of a seesaw, the lever is called
a first-class lever.
 In the case shown in the figure
a, the fulcrum is the joint
connecting the atlas, the first
vertebra, to the skull.
The types of levers observed in
the human body.
 Calf muscles that connect the
femur of the thigh to the
calcaneus bone of the ankle
constitute a second-class lever
(Fig. b).
 In the case shown in the figure
b, the fulcrum is at the line of
joints between the phalanges
and the metatarsals of the
feet. The weight of the foot
acts as the resistance.
The types of levers observed
in the human body.
 An example of a third-class
lever in the human body is
shown in Fig. c. In the case
of the biceps muscle of the
arm shown in the figure, the
load is located at the hand
and the fulcrum at the
elbow. When the biceps
contract, they pull the lower
arm closer to the upper arm.
Physics of Radiotherapy
Brachytherapy
External Therapy
LINEAR ACCELERATORS
• Medical linear accelerators (linacs)
are
cyclic
accelerators
which
accelerate electrons to kinetic
energies from 4 MeV to 25 MeV using
non-conservative microwave RF fields
in the frequency range from 103 MHz
to 104 MHz, with the vast majority
running at 2856 MHz
linear accelerator …..
• Various types of linacs are available for
clinical use. Some provide x-rays only in the
low megavoltage range (4 MV or 6 MV)
others provide both x-rays and electrons
at various megavoltage energies. A typical
modern high energy linac will provide two
photon energies (6 MV and 18 MV) and
several electron energies (e.g., 6, 9, 12, 16,
22 MeV)
Components of modern linacs
(1) gantry;
(2) gantry stand or support;
(3) modulator cabinet;
(4) patient support assembly, i.e.,
treatment couch;
(5) control console.
linear accelerator
Linac generations
• - Low energy photons (4-8 MV):
– straight-through beam; fixed flattening filter; external
wedges; symmetric jaws; single transmission ionisation
chamber; isocentric mounting.
• - Medium energy photons (10-15 MV) and electrons:
– bent beam; movable target and flattening filter; scattering
foils; dual transmission ionisation chamber; electron cones.
• - High energy photons (18-25 MV) and electrons:
– dual photon energy and multiple electron energies; achromatic
bending magnet; dual scattering foils or scanned electron
pencil beam; motorized wedge; asymmetric or independent
collimator jaws.
• - High energy photons and electrons:
– computer-controlled operation; dynamic wedge; electronic
portal imaging device; multileaf collimator.
• - High energy photons and electrons:
– photon beam intensity modulation with multileaf collimator; full
dynamic conformal dose delivery with intensity modulated
beams produced with a multileaf collimator.
Dose monitoring system ..
• The primary ionisation chamber measures
monitor units (MU). Typically, the
sensitivity of the chamber electrometer
circuitry is adjusted in such a way that 1
MU corresponds to a dose of 1 cGy
delivered in a water phantom at the depth
of dose maximum on the central beam axis
when irradiated with a 10×10 cm2 field at
an SSD of 100 cm.
linear accelerator
Cobalt -60
Percentage depth dose (PDD)
TAR
The TAR concept works well in isocentric
setups for photon energies of cobalt-60
and below. For megavoltage x rays
produced by high energy linacs, however,
the concept breaks down, because of
difficulties in measuring the “dose to small
mass of water in air” at those energies
(the size of the required buildup cap for
the
ionisation
chamber
becomes
excessively large).
Tissue Air Ratio (TAR)
PDD & TAR
Tissue Phantom Ratio (TPR)
TRS - 398
THE END