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Файл:English Guide for Bio-Medical Engineers. Учебное пособие
.pdf
8.2.2 Write out the international words and translate them.
rotational frequency magnetic resonance water protons spectrum liquids
magnetic field macromolecules dipolar coupling interaction incoherent
8.2.3 Complete each sentence with a word or phrase from the box:
1) In ... ... imaging of molecular solutions, two types of water molecules are found.
2) Free water protons have faster average ... ... and hence less fixed water molecules.
3) Most free ... ... have resonance frequency lying narrowly around the normal
proton resonance frequency of 63 MHz (at 1.5 teslas).
4) Hydration water molecules are slowed down by ... with solute molecules.
5) In free ... protons exhibit translational and rotational motions.
6) The moving dipoles disturb the surrounding ... ... on long enough time-scales and
the average field caused by the motion of protons is zero.
7) Protons bound to ..., such as proteins, tend to have a fixed orientation.
8) A spatial pattern in the magnetic field gives rise to a residual ... ... for the protons
experiencing the magnetic field.
9) The wide frequency distribution appears as a broad ... that may be several kHz
wide.
10) Due to exchange mechanisms the (...) spins bound to the macromolecules
continually switch places with (coherent) spins in the bulk media and establish a dynamic
equilibrium.
8.2.4 Make up the plan to the text and retell according to it.
Text C. 8.3 MRI versus CT
8.3.1 Read and translate text A:
The use of X-rays, a type of ionizing radiation, by computed tomography (CT)
scanner, to acquire images, make computed tomography a good tool for examining tissues
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composed of elements of a higher atomic number than the tissue surrounding them, such
as bone and calcifications (calcium based) within the body (carbon based flesh), or of
structures (vessels, bowel). MRI, on the other hand, uses non-ionizing radio frequency
(RF) signals to acquire its images and is best suited for soft tissue (although MRI can also
be used to acquire images of bones, teeth and even fossils).
CT scans use ionizing radiation (X-rays) to produce images, which can damage
DNA and subsequently cause cancer. There is a small increased risk of cancer with CT
scans. It is estimated that 0.4 % of current cancers in the United States are due to CTs
performed in the past and that this may increase to as high as 1.5–2 % with 2007 rates of
CT usage. Unlike CT, MRI does not use ionizing radiation, though it is associated with
other risks.
Contrast in CT images is generated purely by X-ray attenuation, while a variety of
properties may be used to generate contrast in MR images. By variation of scanning
parameters, tissue contrast can be altered to enhance different features in an image (see
applications for more details). Both CT and MR images may be enhanced by the use of
contrast agents. Contrast agents for CT contain elements of a high atomic number, relative
to tissue, such as iodine or barium, while contrast agents for MRI have paramagnetic
properties, such as gadolinium and manganese, used to alter tissue relaxation times.
Commonly used MRI contrast agents may be contraindicated in persons with significant
permanent or transient kidney dysfunction.
CT and MRI scanners are able to generate multiple two-dimensional cross-sections
(tomographs, or "slices") of tissue and three-dimensional reconstructions. MRI can
generate cross-sectional images in any plane (including oblique planes). In the past, CT
was limited to acquiring images in the axial plane (or near axial). The scans used to be
called Computed Axial Tomography scans (CAT scans). However, the development of
multi-detector CT scanners with near-isotropic resolution, allows the CT scanner to
produce data that can be retrospectively reconstructed in any plane with minimal loss of
image quality. For purposes of tumor detection and identification in the brain, MRI is
generally superior. However, in the case of solid tumors of the abdomen and chest, CT is
often preferred as it suffers less from motion artifacts. Furthermore, CT usually is more
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widely available, faster, and less expensive. However, CT has the disadvantage of
to acquire
to make computed tomography
calcification
on the other hand
to be suited for
to increase
to be associated with
to be altered
to enhance features
cross-section
three-dimensional
oblique plane
axial plane
abdomen
to undergo the exam
hazard
с другой стороны
приобретать
удовлетворять требованиям
сделать компьютерную томографию
накопление солей кальция
связанный с чем-либо
увеличивать
поперечное сечение
трёхмерный
приобретать свойства
наклонная плоскость
быть изменённым
пройти обследование
риск, опасность
блуждающий нерв
петля
exposing the patient to harmful ionizing radiation.
MRI is also best suited for cases when a patient is to undergo the exam several times
successively in the short term, because, unlike CT, it does not expose the patient to the
hazards of ionizing radiation. However MRI is usually contraindicated if the patient has
any type of medical implant, such as vagus nerve stimulators, implantable cardioverterdefibrillators, loop recorders, insulin pumps, cochlear implants, deep brain stimulators,
etc.; metallic foreign bodies such as shrapnel or shell fragments; or metallic implants such
as surgical prostheses. These devices can malfunction or heat up during a scan, and as
such, for patients having them, CT scans are considered the safer option.
8.3.2 Match the words and word-combinations in the right hand column with the
words and word-combinations in the left hand column:
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vagus nerve
loop
malfunction
неисправность
брюшная полость
осевая плоскость
8.3.3 Complete each sentence with a word or phrase from the box:
cause increased associated X-ray attenuation two-dimensional
contrast agents cross-sectional features undergo the exam
disadvantage malfunction radio frequency expensive dysfunction
1) MRI uses non-ionizing ... ... (RF) signals to acquire its images and is best suited
for soft tissue.
2) CT scans use ionizing radiation (X-rays) to produce images, which can damage
DNA and subsequently ... cancer.
3) There is a small ... risk of cancer with CT scans.
4) MRI does not use ionizing radiation, though it is ... with other risks.
5) Contrast in CT images is generated purely by ... ..., while a variety of properties
may be used to generate contrast in MR images.
different ... in an image.
significant permanent or transient kidney ....
three-dimensional reconstructions.
successively in the short term.
6) By variation of scanning parameters, tissue contrast can be altered to enhance
7) CT and MR images may be enhanced by the use of ... ... .
8) Commonly used MRI contrast agents may be contraindicated in persons with
9) CT and MRI scanners are able to generate multiple ... cross-sections of tissue and
10) MRI can generate ... images in any plane (including oblique planes).
11) CT usually is more widely available, faster, and less ... .
12) CT has the ... of exposing the patient to harmful ionizing radiation.
13) MRI is also best suited for cases when a patient is to ... ... ... several times
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14) These devices can ... or heat up during a scan.
8.3.4 Speak up on the difference in CT and MRI application.
Text D. 8.4 MRI signs
8.4.1 Read and translate text D:
Magnetic field
Some types of medical implants are generally considered contraindications for MRI
examinations, while others may be acceptable for patients under high specific MRI
conditions. Patients are therefore always asked for complete information about all implants
before entering the room for an MRI scan. Several deaths have been reported in patients
with pacemakers who have undergone MRI scanning without appropriate precautions. To
reduce such risks, implants are increasingly being developed to make them able to be
safely scanned, and specialized protocols have been developed to permit the safe scanning
of selected implants and pacing devices. Cardiovascular stents are considered safe,
however.
Ferromagnetic foreign bodies such as shell fragments, or metallic implants such as
surgical prostheses and ferromagnetic aneurysm clips are also potential risks. Interaction
of the magnetic and radio frequency fields with such objects can lead to trauma due to
movement of the object in the magnetic field or thermal injury from radio-frequency
induction heating of the object.
Titanium and its alloys are safe from movement from the magnetic field.
In the United States a classification system for implants and ancillary clinical
devices has been developed by ASTM International and is now the standard supported by
the US Food and Drug Administration:
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Figure 11 – MR Safe sign
MR-Safe — The device or implant is completely non-magnetic, non-electrically
conductive, and non-RF reactive, eliminating all of the primary potential threats during an
MRI procedure.
Figure 12 – MR Conditional sign
MR-Conditional — A device or implant that may contain magnetic, electrically
conductive or RF-reactive components that is safe for operations in proximity to the MRI,
provided the conditions for safe operation are defined and observed (such as 'tested safe to
1.5 teslas' or 'safe in magnetic fields below 500 gauss in strength).
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contraindication
acceptable
complete
precautions
приемлемый
полный
меры предосторожности
противопоказание
Figure 13 – MR Unsafe sign
MR-Unsafe — Nearly self-explanatory, this category is reserved for objects that are
significantly ferromagnetic and pose a clear and direct threat to persons and equipment
within the magnet room.
The very high strength of the magnetic field can also cause "missile-effect"
accidents, where ferromagnetic objects are attracted to the center of the magnet, and there
have been incidences of injury and death. To reduce the risks of projectile accidents,
ferromagnetic objects and devices are typically prohibited in proximity to the MRI scanner
and patients undergoing MRI examinations are required to remove all metallic objects,
often by changing into a gown or scrubs and ferromagnetic detection devices are used by
some sites.
There is no evidence for biological harm from even very powerful static magnetic
fields.
8.4.2 Match the words and word-combinations in the right hand column with the
words and word-combinations in the left hand column:
67
to permit
clips
alloy
ancillary
incidence
injury
proximity
evidence
разрешать
сплав
вспомогательный
зажимы
сфера действия
сходство
наглядность, очевидность
повреждение, травма
8.4.3 Make up the MRI signs table.
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9 Unit 9. Methods of Ocular Observation
Text A. 9.1 Variations in methods
9.1.1 Read and translate text A:
Observation by optical section
If media, especially that of the cornea, are opaque, optical section images are often
impossible depending on severity. In these cases, direct diffuse illumination may be used
to advantage. For this, the slit is opened very wide and a diffuse, attenuated survey
illumination is produced by inserting a ground glass screen or diffuser in the illuminating
path. "Wide beam" illumination is the direct diffuse, indirect, retro-, scattering sclerocorneal illumination.
Direct diffuse illumination
If media, especially that of the cornea, are opaque, optical section images are often
impossible depending on severity. In these cases, direct diffuse illumination may be used
to advantage. For this, the slit is opened very wide and a diffuse, attenuated survey
illumination is produced by inserting a ground glass screen or diffuser in the illuminating
path. "Wide beam" illumination is the only type that has the light source set wide open. Its
main purpose is to illuminate as much of the eye and its adnexa at once for general
observation.
Indirect illumination
With this method, light enters the eye through a narrow to medium slit (2 to 4 mm)
to one side of the area to be examined. The axes of illuminating and viewing path do not
intersect at the point of image focus, to achieve this; the illuminating prism is decentered
by rotating it about its vertical axis off the normal position. In this way, reflected, indirect
light illuminates the area of the anterior chamber or cornea to be examined. The observed
corneal area then lies between the incident light section through the cornea and the
irradiated area of the iris. Observation is thus against a comparatively dark background.
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Retro-illumination
inserting image focus sufficient impossible crystalline lens
incident light cornea a glance medium slit "Wide beam"
In certain cases, illumination by optical section does not yield sufficient information
or is impossible. This is the case, for example, when larger, extensive zones or spaces of
the ocular media are opaque. Then the scattered light that is not very bright normally is
absorbed. A similar situation arises when areas behind the crystalline lens are to be
observed. In this case the observation beam must pass a number of interfaces that may
reflect and attenuate the light.
Scattering sclero-corneal illumination
With this type of illumination, a wide light beam is directed onto the limbal region
of the cornea at an extremely low angle of incidence and with a laterally de-centered
illuminating prism. Adjustment must allow the light beam to transmit through the corneal
parenchymal layers according to the principle of total reflection allowing the interface
with the cornea to be brightly illuminated. The magnification should be selected so that the
entire cornea can be seen at a glance.
9.1.2 Write out the international words and translate them.
9.1.3 Complete each sentence with a word or phrase from the box:
1) If media are opaque, optical section images are often ... depending on severity.
2) The slit is opened very wide and a diffuse, attenuated survey illumination is
produced by ... a ground glass screen or diffuser in the illuminating path.
3) ... illumination is the only type that has the light source set wide open.
4) Light enters the eye through a narrow to ... ... (2 to 4 mm) to one side of the area
to be examined.
5) The axes of illuminating and viewing path do not intersect at the point of ... ... .
6) The observed corneal area then lies between the ... ... section through the cornea
and the irradiated area of the iris.
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