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MEDICAL PHYSICS: Imaging with X-Rays by emperorhassy

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MEDICAL PHYSICS: Imaging with X-Rays
<p class="MsoNormal"><span style="font-size: 1.714rem; font-weight: bold;">PRODUCTION OF X-RAYS</span><br></p><p class="MsoNormal"><span lang="">X-rays are ionizing electromagnetic radiations
(photons) with short wavelengths (of about 10<sup>-8</sup> to 10<sup>-12</sup> m)
and correspondingly high photon energies (of about 100 eV to 1 MeV). Diagnostic
X-rays give best result at energies of about 30 keV, and are produced by
bombarding a tungsten anode with electrons accelerated through potential
differences of 60 to 125 kV.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">X-rays are produced when electrons are rapidly
decelerated as they strike the anode, It becomes very hot, so the usual material
is tungsten which has a very high melting point. The electrons also disturb
(excite) tungsten atoms which then emit more high-frequency photons at
particular wavelengths. These photons add a line spectrum of K and L lines to the
continuous spectrum produced decelerating electrons.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">The spectra show that the distribution of
photon energies depend on the target anode and the tube voltage and current.</span></p><p class="MsoNormal" style="text-align: center; "><img src="https://res.cloudinary.com/drrz8xekm/image/upload/v1562079039/igfvbnuivktgoeycwm16.jpg" data-filename="igfvbnuivktgoeycwm16" style="width: 527.5px;"><span lang=""><o:p><br></o:p></span></p><p class="MsoNormal" style="text-align: center; "><a href="https://pixabay.com/photos/x-ray-examination-hospital-2117685/" target="_blank"><span style="font-size: 12px;">X-ray examination.</span></a></p><p class="MsoNormal" style="text-align: center; "><a href="https://pixabay.com/photos/x-ray-examination-hospital-2117685/" target="_blank"><span style="font-size: 12px;"> Pixabay</span></a><span lang=""><o:p><br></o:p></span></p><h3><span lang="">Tube voltage<o:p></o:p></span></h3><p class="MsoNormal"><span lang="">The higher the potential difference through
which the electrons move, the more kinetic energy E<sub>k</sub> they gain, and
so the higher the frequency f of the X-ray photons produced:<o:p></o:p></span></p><p class="MsoNormal"><span lang="">Maximum energy of photon hf = E<sub>k</sub> =
eV<o:p></o:p></span></p><p class="MsoNormal"><span lang="">Where h is the Planck constant, e is the
electronic charge and V is the accelerating voltage. Most electrons lose energy
in heating the anode, and only a few have this maximum energy.<o:p></o:p></span></p><h3><span lang="">Tube current<o:p></o:p></span></h3><p class="MsoNormal"><span lang="">Increasing the tube current, which means
increasing the number of electrons moving from cathode to anode, increases the
number of X-ray photons produced:<o:p></o:p></span></p><p class="MsoNormal"><span lang="">i.e the beam intensity is directly
proportional to the tube current<o:p></o:p></span></p><h3><span lang="">Target anode material<o:p></o:p></span></h3><p class="MsoNormal"><span lang="">Increasing the proton number Z of the anode
material increases the likelihood that electrons produce X-ray photons:<o:p></o:p></span></p><p class="MsoNormal"><span lang="">Output beam intensity is directly proportional
to Z, the proton number.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">A change in Z also changes the frequency (energy)
of the line spectra, which are characteristic of the target atoms.<o:p></o:p></span></p><h2><span lang="">RADIOGRAPHY: HOW X-RAYS PRODUCE IMAGES<o:p></o:p></span></h2><p class="MsoNormal"><span lang="">X-rays interact with matter in various ways.
In all of them, the material removes photons (absorbs energy) from the direct
beam and so causes <b>attenuation</b>,
meaning that the energy of the beam is diminished.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">Radiography, the term given to producing images
with X-rays, relies on the fact that different types of tissue cause differing attenuations.
An X-ray image is really a shadowgraph and the darkest shadows are cast by the
strongest absorbers (attenuators) of the X-rays. There are four main processes
that can reduce the intensity of an X-ray beam:<o:p></o:p></span></p><p class="MsoListParagraphCxSpFirst" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span lang="" style="font-family:Symbol;mso-fareast-font-family:Symbol;mso-bidi-font-family:
Symbol">·<span style="font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; font-size: 7pt; line-height: normal; font-family: &quot;Times New Roman&quot;;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><!--[endif]--><b>Simple scattering</b><span lang=""> occurs when X-ray photons
bounce elastically off the nuclei of atoms. They do not lose energy but change
direction so that they do not reach the detector.<o:p></o:p></span></p><p class="MsoListParagraphCxSpMiddle" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span lang="" style="font-family:Symbol;mso-fareast-font-family:Symbol;mso-bidi-font-family:
Symbol">·<span style="font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; font-size: 7pt; line-height: normal; font-family: &quot;Times New Roman&quot;;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><!--[endif]--><span lang="">A photon may instead ionize an
atom, transferring all or most of its energy in doing so. This is essentially
the photoelectric effect in which the photon energy liberates an electron from
an atom. X-rays have high energy and tend to knock out inner orbital electrons
in this ionizing process. (Ions usually result from loss of outer orbital
electrons.)<o:p></o:p></span></p><p class="MsoListParagraphCxSpMiddle" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span lang="" style="font-family:Symbol;mso-fareast-font-family:Symbol;mso-bidi-font-family:
Symbol">·<span style="font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; font-size: 7pt; line-height: normal; font-family: &quot;Times New Roman&quot;;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><!--[endif]--><span lang="">Sometimes a photon will collide
with an outer electron in an atom. The photon acts as a particle with a
particular momentum, which it shares with the electron. The photon goes off at
an angle after losing energy to the electron. This process is called the <b>Compton effect</b>.<o:p></o:p></span></p><p class="MsoListParagraphCxSpLast" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span lang="" style="font-family:Symbol;mso-fareast-font-family:Symbol;mso-bidi-font-family:
Symbol">·<span style="font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; font-size: 7pt; line-height: normal; font-family: &quot;Times New Roman&quot;;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
</span></span><!--[endif]--><span lang="">A photon with very high energy
that travels very close to the nucleus of an atom may disappear completely. Its
energy is enough to produce a pair of particles – an electron and a positive
electron (a positron). The photon’s energy has been converted to matter in a
process called <b>pair production</b>. The
energy has to be high enough to satisfy Einstein’s relationship E = mc<sup>2</sup>,
where m is the sum of the masses of the two particles produced.<o:p></o:p></span></p><h3><span lang="">Measuring the total attenuation<o:p></o:p></span></h3><p class="MsoNormal"><span lang="">Each of the four processes produces attenuation
which depends on the mass of matter interacted with, and this is measured in
terms of the <b>mass attenuation
coefficient</b>, </span><span lang="">μ</span><sub><span lang="">m</span></sub><span lang="">.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">As a general rule, attenuation gets less as
photon energy increases, so the higher the X-ray energy, the more the photons
penetrate matter. In diagnostic radiography, an optimum photon energy of about
30 keV produces the best contrast between different types of tissue. This is
because at 30 keV energy the main attenuation process is the photoelectric
effect, with absorption proportional to the cube of the proton number Z. This
means that bones, which are mainly calcium with Z = 20, produce significantly
more attenuation per unit mass than soft tissue (mostly water with hydrogen: Z =
1 and oxygen: Z = 16).</span></p><p class="MsoNormal" style="text-align: center; "><img src="https://res.cloudinary.com/drrz8xekm/image/upload/v1562079364/mfs4io0s7rhhljsmu3ej.png" data-filename="mfs4io0s7rhhljsmu3ej" style="width: 527.5px;"><span lang=""><o:p><br></o:p></span></p><p class="MsoNormal" style="text-align: center; "><a href="https://commons.wikimedia.org/wiki/File:X-Ray.png" target="_blank"><span style="font-size: 12px;">X-Ray. </span></a></p><p class="MsoNormal" style="text-align: center; "><a href="https://commons.wikimedia.org/wiki/File:X-Ray.png" target="_blank"><span style="font-size: 12px;">BruceBlaus - Own work, CC BY-SA 4.0</span></a><span lang=""><o:p><br></o:p></span></p><h2><span lang="">HOMOGENEOUS BEAMS<o:p></o:p></span></h2><p class="MsoNormal"><span lang="">It is not easy to obtain an intense beam of
X-rays containing photons of just one energy a – &nbsp;<b>homogeneous</b>
or <b>monoenergetic</b> beam. A near-monoenergetic
beam can be obtained by <b>filtering</b>
it: the beam passes through a metal sheet which absorbs some X-ray photons,
more of the low-energy photons than the high-energy ones. This means that when
an X-ray beam is filtered, the beam becomes more penetrating.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">In the ideal case, a near-monoenergetic beam
is attenuated in matter to give the percentage transmission curve. The shape of
the graph is familiar: it is an exponential fall. This is because each small
distance </span><span lang="">Δx</span><span lang=""> in the material produces a small
attenuation -</span><span lang=""> Δ</span><span lang="">I, which is
proportional both to </span><span lang="">Δx</span><span lang=""> and to the beam
intensity <i>I</i>:<o:p></o:p></span></p><h4 align="center" style="text-align:center"><span lang="">-</span><span lang="">ΔI = μIΔx&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; [1]</span><span lang=""><o:p></o:p></span></h4><p class="MsoNormal"><span lang="">μ</span><span lang=""> is a constant for a
given X-ray wavelength in a given attenuating material, and is called the <b>linear attenuation coefficient</b>.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">In any situation where the change in a quantity
is proportional to the (varying) quantity itself, the result is an exponential
change. We can rewrite equation [1] as:<o:p></o:p></span></p><h4 align="center" style="text-align:center"><span lang="">ΔI/I = -μΔx</span><span lang=""><o:p></o:p></span></h4><p class="MsoNormal"><span lang="">or, in calculus notation:<o:p></o:p></span></p><h4 align="center" style="text-align:center"><span lang="">dI/I = -μdx&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; [2]</span><span lang=""><o:p></o:p></span></h4><p class="MsoNormal"><span lang="">where integrating equation [2] gives:<o:p></o:p></span></p><h4 align="center" style="text-align:center"><span lang="">ln I = -</span><span lang="">μ</span><span lang="">x + C&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; [3]<o:p></o:p></span></h4><p class="MsoNormal"><span lang="">where I is the intensity at a depth of
penetration <i>x</i>. C is a constant which
we can identify by the fact that when <i>x</i>
is zero, the beam has its starting unattenuated value I<sub>0</sub>, so:<o:p></o:p></span></p><h4 align="center" style="text-align:center"><span lang="">ln I<sub>0 </sub>= C<o:p></o:p></span></h4><p class="MsoNormal"><span lang="">Putting this value for C in equation 3 gives:<o:p></o:p></span></p><h4 align="center" style="text-align:center"><span lang="">ln I – ln I<sub>0</sub>
= -</span><span lang=""> μ</span><span lang="">x<o:p></o:p></span></h4><p class="MsoNormal"><span lang="">or<o:p></o:p></span></p><h4 align="center" style="text-align:center"><span lang="">ln I/I<sub>0</sub> = -</span><span lang=""> μ</span><span lang="">x<o:p></o:p></span></h4><p class="MsoNormal"><span lang="">which we can write as:<o:p></o:p></span></p><h4 align="center" style="text-align:center"><span lang="">I/I<sub>0</sub> = e<sup>-</sup></span><sup><span lang="">μ</span><span lang="">x</span></sup><span lang="">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; [4]<o:p></o:p></span></h4><p class="MsoNormal"><span lang="">&nbsp;</span></p><p class="MsoNormal"><span lang="">Note that filtering the beam makes it <b>harder</b>, that is, more penetrating. For
a filtered, monoenergetic beam we can define a <b>half-value thickness</b> (compare <i>half-life</i>
in radioactivity) which is the thickness of a material that cuts the X-ray intensity
by a half. We can use equation [4] to state the half-value thickness x<sub>1/2</sub>
in terms of the linear attenuation coefficient </span><span lang="">μ</span><span lang=""> as follows:<o:p></o:p></span></p><h4 align="center" style="text-align:center"><span lang="">I = ½ I<sub>0</sub><o:p></o:p></span></h4><p class="MsoNormal"><span lang="">so:<o:p></o:p></span></p><h4 align="center" style="text-align:center"><span lang="">e<sup>-</sup></span><sup><span lang="">μ</span><span lang="">x1/2</span></sup><span lang=""> = ½ <o:p></o:p></span></h4><p class="MsoNormal"><span lang="">or:<o:p></o:p></span></p><h4 align="center" style="text-align:center"><span lang="">e</span><sup><span lang="">μ</span><span lang="">x1/2</span></sup><span lang=""> = 2<o:p></o:p></span></h4><p class="MsoNormal"><span lang="">giving:<o:p></o:p></span></p><h4 align="center" style="text-align:center"><span lang="">x<sub>½</sub> = ln2/</span><span lang="">μ</span><span lang="">&nbsp; <o:p></o:p></span></h4><h3><span lang="">The inverse square law<o:p></o:p></span></h3><p class="MsoNormal"><span lang="">As with light., in a vacuum the energy of X-rays
spreads out from the source according to the inverse square law. This means that
the intensity decreases as 1/r<sup>2</sup> where r is the distance from the
source.<o:p></o:p></span></p><h2><span lang="">X-RAY IMAGE QUALITY<o:p></o:p></span></h2><p class="MsoNormal"><span lang="">The X-ray image or shadowgraph is usually
produced on special photographic film. The sharpness of the image is affected by
the size of the X-ray source, known as the focal spot, and the scattering
effect as photons pass through the object.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">A point source produces perfectly sharp
shadows. But X-rays originate in a small spot of finite size on the tungsten
anode. And so the shadow contains an edge effect – a <b>penumbra</b>. The penumbra can be reduced by placing the film as close
to the object (part of the patient) as possible.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">Photons scattered by nuclei in the object
carry no information and merely blur the final image, reducing contrast between
the darker and lighter areas. To minimize this effect, a filter grid is used.
Only unscattered photons can reach the film.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">Clearer pictures would be produced if higher energy
(harder) beams were used and the exposure time increased. But this would increase
the risk of damage to the patient because atoms in living cells would be
ionized, and that increases the risk of cancer.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">Improvements in detection systems allow better
images with quite low beam intensities. For example, a fluorescent (phosphor-coated)
screen placed in front of and behind light-sensitive film will absorb X-rays
and re-emit the energy as light in a pattern matching the X-ray image. In the
arrangement of the phosphors and light sensitive film; the film is much more
sensitive than ordinary X-ray film, so images can be produced using low-intensity X-ray beams.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">When an X-ray image of the digestive system is
required, the patient swallows a harmless suspension of barium sulphate (a ‘barium
meal’). This enhances image contrast since barium atoms have a high <i>Z</i> value. Similarly, harmless high-<i>Z</i> dyes can be injected into blood. <o:p></o:p></span></p><h2><span lang="">COMPUTERIZED TOMOGRAPHY (CT)<o:p></o:p></span></h2><p class="MsoNormal"><span lang="">This technique for X-ray imaging was developed
in the 1970s, and is a great improvement on traditional X-ray imaging techniques.
A narrow beam of X-rays is rotated around the patient and after passing through
the body is detected electronically. The body is surrounded by several hundred
photon detectors, whose outputs are fed to a computer. This analyses the data
and forms an image of a narrow slice of the body on a monitor screen: a <b>CT scan</b>. This method produces images
with good resolution and does so very quickly – so that changes in ‘real time’
can be observed. The technique is particularly useful for diagnosing damage
(e.g. lesions) in the brain, where exploratory surgery is not usually possible.</span></p><p class="MsoNormal" style="text-align: center; "><img src="https://res.cloudinary.com/drrz8xekm/image/upload/v1562079722/fichjfnrwqdzxxbohtq1.jpg" data-filename="fichjfnrwqdzxxbohtq1" style="width: 527.5px;"><span lang=""><o:p><br></o:p></span></p><p class="MsoNormal" style="text-align: center; "><a href="https://commons.wikimedia.org/wiki/File:UPMCEast_CTscan.jpg" target="_blank"><span style="font-size: 12px;">GE LightSpeed CT scanner at Open House, Monroeville, Pennsylvania. </span></a></p><p class="MsoNormal" style="text-align: center; "><span style="font-size: 12px;"><a href="https://commons.wikimedia.org/wiki/File:UPMCEast_CTscan.jpg" target="_blank">Daveynin from United States, CC BY 2.0</a></span><span lang=""><o:p><br></o:p></span></p><h2><span lang="">MAGNETIC RESONANCE IMAGING (MRI)<o:p></o:p></span></h2><p class="MsoNormal"><span lang="">This technique gives images of tissues deep in
the body by using radio waves and a rather obscure property of nuclei, their <b>nuclear magnetic resonance</b>, or <b>NMR</b>. The process is now generally called
magnetic resonance imaging. MRI, and targets the hydrogen nuclei which form such
a large component of living tissue.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">The nucleus of an atom spins. It is also charged,
and a spinning charge generates a magnetic field. Just as one magnet becomes
aligned in the presence of another (e.g. compass needle in the Earth’s magnetic
field), so hydrogen atoms are aligned in a magnetic field. The field has to be
very strong, and a hydrogen nucleus can align itself in one of two ways, which
correspond to two different quantized energy states.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">The magnetic field of the nucleus is along its
axis of spin. When an external field is applied, the spin axis itself rotates
in an effect known as <b>precession</b>.
The earth’s axis, for example, precesses in a period of 23,000 years or so
about a line perpendicular to the plane of its orbit. The rate of precession of
the hydrogen nucleus, the <b>Larmor</b> <b>precession</b>, is a lot quicker; in a
field of strength 1.5 Tesla, the frequency is about 63.8 MHz, which is in the
radio frequency (RF) range at 42.57 MHz. When an extra, weaker magnetic field
is applied which is made to oscillate at this frequency, the direction of the
nucleus’ magnetic axis reverses. Most of the nuclei align in the direction of
the field, but some align in the opposite direction, giving rise to two
different quantized energy states.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">The frequency of the applied RF signal is
chosen to match the precession frequency of the hydrogen nuclei so that <b>resonance</b> can occur. The magnetic
component of the electromagnetic wave supplies the energy to cause the reversal
of the spin alignment of many nuclei. The energy taken from the radio wave depends
on the number and distribution of the nuclei in the sample: molecules of biological
tissue contain plenty of hydrogen nuclei in water and carbohydrates. In simple <b>absorption</b> MRI this loss is measured
and used to build up the image.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">A better method is to send the RF signal as a
short <b>pulse</b>. This realigns the
nuclei as before, but after a time the nuclei return to the normal arrangements
of their alignment in the steady magnetic field. The effect due to the pulse
decays in a way similar to the decay of charge in a capacitor or of radioactive
nuclei. This is characterized by a time constant called the <b>relaxation time</b>, typically about 1
second. As the precession rearrangements decay, the nuclei emit a radio signal
at the same frequency as the original pulse. The character of the signal is
decided by the number and distribution of the hydrogen nuclei in the tissue and
is used to create the final image. The relaxation time depends on the molecule
of which the hydrogen is a part – in water the relaxation time is longer than
in more complex molecules, for example. This means that the decay signal is
complex and carries information about the different molecules in the tissue – hence
providing contrast. By changing the timing of the pulses, the signal can be
better matched to the relaxation times of the different components of the
tissue. In practice, the pulsing is repeated many times, and in more complex
ways, so building more detail in the final image. Further improvement is
produced by injecting chemicals with magnetic properties that enhance contrast.</span></p><p class="MsoNormal" style="text-align: center; "><img src="https://res.cloudinary.com/drrz8xekm/image/upload/v1562080314/ari1jwtxonsoko5hf3bo.jpg" data-filename="ari1jwtxonsoko5hf3bo" style="width: 514px;"><span lang=""><o:p><br></o:p></span></p><p class="MsoNormal" style="text-align: center; "><a href="https://commons.wikimedia.org/wiki/File:Mra1.jpg" target="_blank"><span style="font-size: 12px;">Magnetic resonance angiography. </span></a></p><p class="MsoNormal" style="text-align: center; "><a href="https://commons.wikimedia.org/wiki/File:Mra1.jpg" target="_blank"><span style="font-size: 12px;">Ofirglazer at English Wikipedia, CC BY-SA 3.0</span></a><span lang=""><o:p><br></o:p></span></p><p class="MsoNormal"><span lang="">MRI can produce images of slices of tissue.
This is done by making the steady magnetic field graded in strength from strong
to weak. The strength of this field decides the resonance frequency of the
precession of the nuclei, so by choosing the appropriate frequency, the system
can target a slice of the tissue that has that particular field strength.<o:p></o:p></span></p><p class="MsoNormal"><span lang="">Magnetic resonance imaging needs expensive
equipment, but it is a particularly useful technology for probing delicate
areas of the body such as the brain. This is because the energy carried by the radio
signal is very small and at a frequency far from the frequencies at which
molecules of the body vibrate, so it does no damage. Lower frequencies (such as
those in microwave ovens) might provide information – but at the expense of
cooked tissue!<o:p></o:p></span></p><h2><span lang="">Thanks for reading.</span></h2><p>





















































































































































</p><h2><span lang="">REFERENCES</span></h2><p><a href="https://www.medicalnewstoday.com/articles/146309.php">https://www.medicalnewstoday.com/articles/146309.php</a><a href="https://www.medicalnewstoday.com/articles/146309.php" target="_blank"></a></p><p><a href="https://www.webmd.com/a-to-z-guides/what-is-a-mri" target="_blank">https://www.webmd.com/a-to-z-guides/what-is-a-mri</a><br></p><p><a href="https://www.nibib.nih.gov/science-education/science-topics/magnetic-resonance-imaging-mri" target="_blank">https://www.nibib.nih.gov/science-education/science-topics/magnetic-resonance-imaging-mri</a><br></p><p><a href="https://www.sciencedirect.com/topics/neuroscience/radiography" target="_blank">https://www.sciencedirect.com/topics/neuroscience/radiography</a><br></p><p><a href="https://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm175028.htm" target="_blank">https://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm175028.htm</a><br></p><p><a href="https://www.sor.org/about-radiography/what-radiography-who-are-radiographers" target="_blank">https://www.sor.org/about-radiography/what-radiography-who-are-radiographers</a><br></p><p><a href="https://www.sciencedirect.com/topics/neuroscience/x-ray-imaging" target="_blank">https://www.sciencedirect.com/topics/neuroscience/x-ray-imaging</a><br></p><p><a href="https://www.fda.gov/radiation-emittingproducts/radiationemittingproductsandprocedures/medicalimaging/medicalx-rays/default.htm" target="_blank">https://www.fda.gov/radiation-emittingproducts/radiationemittingproductsandprocedures/medicalimaging/medicalx-rays/default.htm</a><br></p><p><a href="https://www.nibib.nih.gov/science-education/science-topics/x-rays" target="_blank">https://www.nibib.nih.gov/science-education/science-topics/x-rays</a><br></p><p><a href="https://www.radiologyinfo.org/en/info.cfm?pg=chestrad" target="_blank">https://www.radiologyinfo.org/en/info.cfm?pg=chestrad</a><br></p><p><a href="https://en.wikipedia.org/wiki/Magnetic_resonance_imaging" target="_blank">https://en.wikipedia.org/wiki/Magnetic_resonance_imaging</a><br></p><p><a href="https://en.wikipedia.org/wiki/CT_scan" target="_blank">https://en.wikipedia.org/wiki/CT_scan</a><br></p><p><a href="https://en.wikipedia.org/wiki/Radiography" target="_blank">https://en.wikipedia.org/wiki/Radiography</a><br></p><p><a href="https://en.wikipedia.org/wiki/X-ray" target="_blank">https://en.wikipedia.org/wiki/X-ray</a></p><h2><span lang=""><o:p></o:p></span></h2>
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@utopian-io ·
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@agmoore2 ·
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This reads like a course in imaging.  It's about x-rays and so much more.  It has practical applications...who among us has not had an MRI or a CT scan?  So, of course it's nice to know how these processes work.  But more than that, you explain the properties of photons and the behavior of x-ray beams.  I'll be back to read more and understand more, because it's all fascinating.  I'll skip the math, though.  Too late for me to learn calculus :)
A really thorough, interesting blog. 
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