The proton has a positive charge that moves with it and turns on itself, which is called spin. In doing so, each proton generates an electric current accompanied by a small magnetic field (like a magnet). When the patient is introduced in a powerful magnet, the protons lines up with the magnet’s magnetic field of the equipment (longitudinal magnetization). The protons move around major axis of the external magnetic field (precession movement), besides the spin¹.

Energy in pulses of radiofrequency is applied that is absorbed by the protons, provided that it presents a suitable frequency, which is equal to the precession frequency. The precession frequency is calculated with the Larmor equation:

ω₀ = γB₀

Where ω_0, is the precession frequency. γ, is the radius of magnetic rotation that varies for different materials, and B₀, the strength of the external magnetic field¹.

By sending radiofrequency pulses, with the same precession frequency calculated with the Larmor equation, we are transferring energy to the protons (resonance phenomenon). In this way, the nuclei capture this energy by changing its orientation and magnetic vector, so that the longitudinal magnetization decreases and a transverse magnetization appears. Finally, the radiofrequency is suppressed, the nuclei tend to return to their base state (relaxation) and release energy, in the form of an oscillating electrical signal (echo), which we detect. This released energy, which is also a radiofrequency pulse, is called a signal and is measured at times T1 and T2².

The relaxation times (T1 and T2), are fundamentally times that measure the speed of recovery of the resonant nuclei when subjected or disturbed by the appropriate radiofrequency waves.

T1: It is the parameter that measures the longitudinal return of the protons for their alignment with the external magnetic field after the radiofrequency pulse is interrupted (longitudinal relaxation)².

T2: It is the parameter that measures the time it takes the transverse magnetization to decrease and disappear (transversal relaxation).

In general, T1 is longer than T2 and, for example, water and tissues with a high liquid content have longer relaxation times than fat.

The radiofrequency pulses are differentiated by the amount of energy they transfer to the protons, causing more or less relaxation. An MRI sequence usually consists of several radiofrequency pulses that may be different from each other. The difference between some images depends on the type of radiofrequency pulses used and the time between them¹.

The MR images can be enhanced in T1 or in T2. The images in T1 allow to clearly distinguish anatomical structures and have less sensitivity to pathological changes. However, in T2 the anatomical structures are not represented with such sensitivity, but the sensitivity is greater in the face of pathological changes³.

The receiver of the MRI equipment captures the longitudinal and transverse relaxation of the protons. The information obtained directly from the relaxation of the protons is called raw data matrix or space k, which is nothing more than a grid of points that must be transformed using the Fourier equation to obtain an interpretable image: ¹

J= -K (T/x)

The image is created using a computer.

Bibliographic references:

1. Novelline, R. (2000). Squire Fundamentos de Radiología. Barcelona: Masson
2. Hore, P.J. (2000). Resonancia Magnética Nuclear. Buenos Aires: Eudeba.
3. Cobeñas R, Aguilar M, Aranguren J, Gallo J, Espil G, Kozima S. Cefalea… ¿y algo más? Neuroimágenes en el estudio de la cefalea. Revista Argentina de Radiología. 2016;80(3):192-203. (Imagen 2).

Figure – available via license: CC BY-NC-ND 4.0

Manuela Castañeda Taborda

Isabel María Taboada Berlanga

Alba Cordero González

Carolina Valero Solera

There are many advantages of using MRI instead of ultrasound. Among them, the MRI improves the spatial resolution, allows the observation of both cerebral hemispheres at the same time and the direct development of the cerebral cortex and does not generate confusing shadows.

One of the applications of MRI is the monitoring and detection of possible congenital anomalies in the myelination of the fetus. Myelination is a good indicator of the degree of cerebral maturation.

Firstly, regarding the normal myelination process, it is estimated that it begins around the fourth month of gestation and does not end until the child is two years old. The normal direction of the process in the brain is from the back to the front, from caudal to cranial and from the central zone to the peripheral zone.

Myelination appears in each zone at different times of fetal development. Thus, a myelination sequence is created in which myelin is first generated in the sensory fibers and the proximal zone of the SN. Secondly, the myelination occurs in the motor fibers and the distal zone of the SN.

In the progress of myelination, a shortening of the signal is observed both in T1 (due to an increase in cholesterol and glycolipids) and in T2 (due to an increase in water due to the increase in lipids). These shortenings are visible with a hyper signal in T1 and a hyposignal in T2.

These changes can be observed in the white matter and present the following sequence:

• At 20 weeks: posterior part of the brainstem
• At 27 weeks: vermis, middle cerebellar peduncles and central basal ganglia
• At 33 weeks: posterior limb of the internal capsule
• End of gestation: radiated crown of the thalamus

Agenesis of the corpus callosum

The corpus callosum is a structure that connects the two cerebral hemispheres. It may present agenesis of the corpus callosum (ACC), a congenital defect in which the corpus callosum is partially or totally absent.

Prenatal diagnosis is difficult due to the limitations of ultrasound so the clinical suspicion of agenesis of the corpus callosum is obtained by indirect sonographic signs. An MRI will be performed to check if the apparent agenesis of the corpus callosum is isolated or there are associated anomalies.

The prognosis depends on the degree and severity of the malformations that accompany this anomaly, such as cortical alterations, heterotopia, Dandy-Walker malformation, schizencephaly and encephalocele.

ACC induces specific anatomical effects such as the formation of Pbrost fibers on the lateral ventricles. The nerves cannot cross the midline because the callosal commisure does not form and are oriented according to the ventral-dorsal axis.

Other consequences are the radial arrangement of medial sulci and convolutions of the cerebral hemispheres, inverted cingulum convolutions and characteristic anomalies of the lateral ventricles.

“(A) Sagital SSFSE T2; (B) Axial SSFSE T2; (C) Axial SSFESE T2. EG 27, 2s agenesis of genu and 2/3 anterior parts of corpus callosum (white arrow). Anterior-inferior fusion of both frontal lobes (arrow’s head) and absence of frontal horns (arrow). Dysplastic multicystic left kidney (curved arrow). (D) Coronal SSFSE T2; (E) Axial SSFSE T2; (F) Axial SSFSE T2 21, 4s. Semilobar holoprosencephaly with thalamic (curved arrow) and frontal lobes (arrow’s head) fusion. Formation of the temporal and occipital horns (white arrow). Rudimentary falx cerebri (arrow)” ².

References:

1. es [Internet]. H.I.U. Niño Jesús. Madrid: Miguel A. López Pino; 2015 [updated 28 Feb 2018; cited 20 Dic 2018]. Available from: https://seram.es/images/site/02-rm_en_la_valoraci%C3%B3n_de_la_maduraci%C3%B3n_de_la_mielina.pdf

2. Recio Rodríguez M., Martínez de Vega Fernández V., Martínez Ten P., Pérez Pedregosa J., Martín Fernández-Mayoralas D., Jiménez de la Peña M. RM fetal en las anomalías del SNC. Aspectos de interés para el obstetra. R.A.R. [Internet]. 2010 [cited 20 Dic 2018]; 74 (4): 385-396 Available from: https://isradiology.org/gorad/docs/2011/rar_6_espl.pdfç

3. Images taken from M. Recio et al, 2010.

4. Gonçalvez-Ferreira T., Sousa-Guarda C., Oliveira-Monteiro J.P., Carmo-Fonseca M.J., Filipe-Saraiva P., Goulão-Constâncio A. Agenesia del cuerpo calloso. Neurol [Internet]. 2003 [cited 22 Dic 2018]; 36 (8): 701-706. Available from: https://www.sld.cu/galerias/pdf/sitios/rehabilitacion-logo/agenesia_cuerpo_calloso.pdf

Andrea Sánchez Alonso

Marta Presentación Rodríguez Rodríguez

Eva Zhang Huang

Indications^[1]

With more precision, the clinical indications registered are the following:

1. For ocular biometry for calculation of the power the intraocular lens
2. Cases with media haze in which the posterior segment cannot be evaluated clinically
   • Cornea: corneal scar, hazy cornea, corneal edema, and others
   • Anterior chamber: hyphema, severe anterior segment inflammation with exudates
   • Dense cataract
   • Pupillary membrane, posterior synechia
   • Retrolental membrane, posterior capsular opacity
   • Vitreous hemorrhage, severe vitreous membranes/exudates
3. To determine the nature of ocular mass, optic disc lesion
4. To differentiate retinal detachment (RD) of rhegmatogenous etiology from an exudative retinal detachment, and also to differentiate RD from retinoschisis
5. To detect and localize intraocular foreign bodies
6. To evaluate orbital lesions
7. To evaluate Retina, choroid, sclera in various conditions including inflammatory diseases

Physical mechanism

At one end of the ultrasound probe there is a piezoelectric crystal, usually a quartz, which is a material that, when subjected to electric current, is capable of elastically deforming its structure; as a consequence a mechanical vibration is produced, from which a sound wave is generated. More specifically, a longitudinal ultrasound wave is generated (inaudible frequency above 20kHz) and it propagates through the medium and, when it impacts an anatomical structure, returns back. The probe therefore also has an antenna capable of capturing the reflected wave and converting it into an image through a transducer.

Methodologies

In ophthalmological diagnostics two different ultrasound methods can be used; however they are usually associated to obtain a more complete anatomical information that has a great diagnostic value.

• A-Scan (amplitude scan): produces a one-dimensional graphic image, where each echo is represented as a deflection of the baseline proportional to its intensity. It is very useful in tissue diagnosis (since it allows to differentiate between normal and abnormal tissue) and for biometrics (since it allows to calculate the length of the eyeball and the power of IOLs, ie the intraocular lenses used in cataract surgery).
• B-scan (brightness scan): produces a two-dimensional image, allowing to visualize the axial, longitudinal and transversal planes of the eyeball. The image obtained is very similar to an anatomical section and therefore is useful for a structural diagnosis. The echoes are represented sequentially along a line depending on their distance from the source. The intensity is represented in grayscale: the white corresponds to the maximum intensity (hyperechoic structure), while the black to the absence of echoes (anechoic structure).

Examination technique and probes used ^[2]

The patient, after being thoroughly informed of the procedure, is laid down on a reclining bed and is put at ease. Being a contact method, a gel is applied on the eyelid or on the sclera that can allow the correct passage of waves.

The most commonly used in clinical practice is the 12 MHz probe which, thanks to its very high sensitivity, allows an evaluation of the vitreous body and the retina, a discrimination between choroidal tumors and an investigation of the orbit pathologies.

The 20 MHz probe is particularly indicated for the diagnosis of retinal and choroidal diseases.

The 35 MHz probe is instead suitable for viewing the entire anterior segment with the contact ultrabiomicroscopy technique.

The 50 MHz probe allows a very high resolution of the iris-corneal angle and specific structures of the anterior segment.

Bibliography

[1] https://eyewiki.aao.org/Echography_(ultrasound)

[2] https://medmedicine.it/articoli/oftalmologia/ecografia-oculare

Photo: https://www.sonomojo.org/keeping-an-eye-on-intracranial-pressure-detecting-elevated-icp-using-ocular-ultrasound/

Luca di Gregorio e Mario Di Croce

ERASMUS students

It uses the Doppler effect, which was discovered by Christian Andreas Doppler, an Austrian physicist of the 17th century. The fact is that when an object is removed from a person or approached to her (or in this case, to a transducer), the sound emitted varies its frequency. There are three types of ultrasound scanner:

• Continuous Doppler Ultrasound Scanner (or with a continuous wave): the transmission of sound and the reception of information occurs at the same time in the transducer. It is used to detect simpler changes in the Doppler frequency, without identifying any directional changes thereof. It’s the most sensible one.

• Pulsed Doppler Ultrasound Scanner. It is used to obtain information on the distance and direction of the information collected by the transducer, but with the inconvenience of the aliasing or overlap -effect that causes continuous signals indistinguishable when digitalized to form an image-

• Colour Doppler Ultrasound Scanner represents the distance between the transducer and the vessel with different colours, mainly red and blue. The lower colour intensity, the slower and the more stable is the blood flow.

Doppler ultrasound scan is a type of ultrasound scan that studies the flow of blood passing through the arteries and veins, and allows us to know its quantity, velocity and consistency in a particular moment¹. The physical foundations of this technique are as follows: when the blood is reflected in the vessels, the ultrasound will be different according to the direction and velocity of the blood. The frequency will increase the lower the distance between the transducer and the vessel is.

This device has a variety of uses, such as diagnosis of arterial occlusions, vascular diseases such as peripheral arterial disease or peripheral venous insufficiency, aneurysms or arterial stenosis, presence of blood clots² and even prenatal diagnosis of possible fetal pathologies such as neural tube defects, spina bifida, cleft lip, multiple pregnancies, etc³. It is less invasive than other diagnostic tests such as arteriography. It also avoids the risk of using X-rays in certain patients.

An additional utility of the Doppler Ultrasound Scanner is that it can be used in oncology for the detection of malignant neoplasms with rapid growth and high rate of vascularization. For example, it allows us to differentiate a pancreatic pseudocyst from a pseudoaneurysm.

Tumors release an essential angiogenic substance for its growth and dissemination. The new vessels created are an aberration -with little smooth muscle in the middle layer- and they can form “lakes” or vascular sinuses without smooth muscle. The presence of arteriovenous fistulas is usually common, as indicative of high vascular proliferation. Tumors are usually detected using a Continuous Doppler Ultrasound Scanner as it is the existing ultrasonic probe most sensible. Breast tumors, liver tumors, renal tumors, uterine tumors, etc…, can be detected. At the same time, it can rule out the presence of a tumor (low vascularization, normal flow, absence of vascular anomalies)⁴.

BIBLlOGRAPHY

1. A-Z E, auxilios P, médicas P, Embarazo P, embarazada Q, anticonceptivos M et al. Cómo se hace la ecografía-doppler [Internet]. Webconsultas.com. 2018 [cited 28 December 2018]. Available from: https://www.webconsultas.com/pruebas-medicas/como-se-hace-la-ecografia-doppler-13671

2. Ecografía Doppler: ¿Para qué se usa? [Internet]. Mayo Clinic. 2018 [cited 28 December 2018]. Available from: https://www.mayoclinic.org/es-es/doppler-ultrasound/expert-answers/faq-

3. Técnicas de Diagnóstico Prenatal | La genética al alcance de todos, Genética, herencia, malformaciones congénitas, enfermedades hereditarias, genes, aborto [Internet]. info. 2018 [cited 28 December 2018]. Available from: https://lagenetica.info/es/el-diagnostico-prenatal/tecnicas-de-diagnostico-prenatal/

4. Taylor, K., Burns, P. and Wells, P. (1999). DOPPLER Aplicaciones Clínicas de la Ecografía Doppler. Madrid: Marban, pp.Capítulo 2 (páginas 29-35); Capítulo 17 (páginas 361-369).

 Indalecio Andrés García Santos

Katja Ljubic Bambill

Cristina Cañete Santiago

They are longitudinal mechanical waves with a frequency higher than 20 KHz, undetectable by our ear. They need a medium to propagate¹.

Ultrasounds are generated by a device called transducer, which contains one or more crystals with piezoelectric properties. This means that, by compressing them, a difference of electric potential on their surface is generated. However, in the transducer crystals the inverse piezoelectric effect is produced, so, when we apply an alternating electrical voltage, they experience oscillations in mechanical strain and contract and expand rapidly, generating ultrasounds. In that way, the crystals transform the electrical energy that is supplied to them into ultrasounds².

To make a diagnosis using this method, the ultrasound machine must be used. This machine is composed by: a transducer, a computer, a monitor, a storage unit, a keyboard and controls¹. The transducer emits the ultrasounds and receives echoes from them. The computer processes and transforms the electrical signals that it receives from the transducer into images. Besides, the controls modify the characteristics of the emitted ultrasounds, for example: the frequency.

By applying the transducer over the patient’s surface, the ultrasounds travel through tissues, interacting with them. Depending on the differences of the physical properties (mainly the density) between the tissues the waves penetrate, they will be reflected in a different proportion, returning the echoes to the transducer. This fact is due to the difference in acoustic impedance (resistance to propagation of sound waves through tissues), which depends on the density of the tissues and the speed of propagation of the wave. In this way, the greater the difference is, the greater the reflection of the ultrasound will be. Because the difference in acoustic impedance between the air and the skin is very big, a high reflection will be experienced and waves won’t be able to penetrate into the body. Consequently, an ultrasound transmission gel is applied over the patient’s skin².

Image taken from: https://commons.wikimedia.org/wiki/File:Echographe_(Toshiba_Aplio).jpg

Nevertheless, when the sound wave passes through the tissue, it is attenuated (its energy decreases) because of the absorption, reflection and divergence. The absorption depends on the frequency, so that the higher the frequency is, the more ultrasounds will be absorbed by the tissues and the less they will penetrate. In addition, the increase in frequency allows us to obtain higher resolution ultrasound images, unlike the lower frequency ones².

Finally, the transducer will transmit the sound energy of the echo as an electrical signal that is received by the computer, which “draws” the image attending the amplitude and position of the echoes.

The ultrasound machine has three different ways to represent the image:

• A-Mode: it uses a single ultrasound beam and it represents the information in a graphic based on the distance (time) and the amplitude of the echo.
• B-Mode: it uses multiple ultrasound beams to get 2D images. The echoes are represented in a grey scale.
• M-Mode: it uses a single ultrasound beam to get one-dimensional moving images.³

In conclusion, the fact that the ultrasounds are used to obtain ultrasound images makes that this non-invasive diagnostic method does not produce adverse biological effects.

References:

1. Barceló e I. Iriarte. Ecografía musculoesquelética. Atlas ilustrado. 1ª edición. Madrid. Panamericana; 2015
2. Nilam J. Soni, MD; Robert Arntfield, MD y Pierre Kory, MD. Ecografía a pie de cama. Fundamentos de la ecografía clínica. 1ª edición. Barcelona. Elsevier; 2015.
3. Díez Bru. Principios básicos de la ecografía. Artículo de revisión. Madrid. 1992

https://ddd.uab.cat/pub/clivetpeqani/11307064v12n3/11307064v12n3p138.pdf

Authors:

Luisa María Benítez Cejas (2º Medicine)

Alejandro Antonio Jiménez Prados (2º Medicine)

Kamal Hammu Mohamed (2º Medicine)

All this procedure is explained through the interaction of the radiation on the tissues.  The emitted radiation are the x-rays, which will traverse the patient and they will provide an image of their inside once they traverse the different tissues. This beam of electromagnetic radiation can be absorbed or scattered in its trajectory, resulting a decrease in the original intensity of the X-rays and the atoms of the substance where the beam of radiation is incident. There are several factors which determine that this radiation would be more or less absorbed and/or scattered: the atomic number of the irradiated atom, the thickness of the traversed material, the density of the given material (in our case body tissue) and the energy that the radiation beam has (wavelength of incident radiation). This is going to provoke that the initial radiation, while it traverses each part of our body (each tissue with different characteristics), the intensity of the final radiation would be different from the initial one and different depending on the traversed materials or tissues. This means that in the plate of the radiography different contrasts are seen in the grayscale obtaining radiopacity depending on the final intensity that reaches each point of it after crossing the human body. These possible results are known as radiological densities, and they are going to allow us to identify the nature of each structure in the radiography.

This effect of absorption, dispersion and penetration causes that in the human body we can find 5 fundamental densities, with which we will be able to interpret an x-ray. Of these densities, four belong to the human economy, and only one of them is external in nature.

Air Density:

It is the density of less absorption, because when the X-rays pass through the tissues with this density there is no resistance that opposes them; So all the radiation will be reflected in the radiographic plate. This density is easily identified as being black. It will occur in lungs or digestive tract, among others.

Density Fat:

Tissues with this density absorb a minimum of radiation, but somewhat higher than air. For this reason it is visualized as a faint whitish gray color. It is characteristic of fat or muscles, being able to find it also surrounding the abdomen and intra-abdominal structures.

Water Density:

The tissues which exhibit the characteristics of this density have a high aqueous content. The amount of absorbed X-rays is greater than in the two previous densities. This is why gray films are displayed on the radiographs. They own soft tissue such as muscles, intestine with own content or blood vessels.

Density Calcium (or bone):

In this case there is great absorption because the X-rays find great resistance to their passage. That is why little radiation from the incident will reach the plate and we will see that white tissue. It is the proper density of the bones. However, it can also occur in some calcified cartilages, vascular calcifications or lithiasis.                      [Hueso (calcio): bone (calcium);

                                                                                                   Aire: air; Metal: metal; grasa: fat;

                                                                                                   Tejidos blandos (agua): soft                

                                                                                                   tissues (water)].

Metal Density:

It naturally does not exist in the body. These materials will absorb even more radiation than those with calcium or bone density. On the plate you will see a very intense white color. This density can be easily observed in the presence of surgical material, pacemakers (as can be seen in the photograph), prostheses, oral or intravenous contrasts, or pellets.

Bibliography:

1. https://es.slideshare.net/medicinacusiiztacala/radiologia-basica
2. https://diagnographic.com/densidades-radiologicas-basicas/
3. Some information obtained in the theoretical classes of the subject “Medical Image and Instrumentation” of the faculty of Medicine of Granada in the course 2016/17 and given by the professors: María Isabel Núñez López, Juan Villalba Moreno, Francisco Ramírez Garrido, José Maximiliano Garófano López y Francisco Artacho Cordón.

Made by:

Simón García Maldonado.

Alicia García Martínez.

Alba Mª Moreno del Salto.

DICOM format (Digital Imaging and Communications in Medicine) is a network communication protocol, based on patterns, which includes managing, storing, printing and transmission of medical images. It responds to the need to communicate different devices and adopting a common working protocol.

HISTORY

As a result of the digitalization of radiological images, a computer image viewing format called DICOM 1.0 is invented. This concept appears in 1985 thanks to the work done by American College of Radiology. It developed into DICOM 2.0 in 1988. In 1993, the Electronic Communications Committee designs DICOM 3.0, and in 1995 HL7 is integrated into DICOM, which means a maximum synchronization of the clinic information.

STRUCTURE

DICOM general structure is composed of a “headboard” and the data set.

The “headboard” helps to set the image on a particular context, because it contains information about the patient, the scanning type, and the radiological image, and it classifies all the data in tags. In other words, it allows the correct image identification and the link with the patient.

The data set contains the medical image and all the information in 3D format, which becomes important to future reconstructions. The image is organized in different data elements, which are

written following an only pattern: the transfer syntax.

DICOM SERVICES

DICOM offers a range of possibilities. Many of these tools are:

Verification service: it allows to check the connection between the different associated devices.

DICOM store: it allows the transfer of images to PACS or work stations. PACS is a storage element that saves all images in a database and shares them on the network.

DICOM worklist: it allows the access to the “patient appointments list”.

DICOM storage commitment: it allows the verification of the requested storage.

DICOM print: it allows the image printing.

DICOM query/retrieve: it eases the image searching and the image recovering.

Media storage: it allows the file transmission without using the network, thanks to external storage devices (CD/DVD).

Modality Performed Procedure Step: it allows to know the image status (completed, disrupted, in process, etc.)

DICOM CONECTIVITY

There are many conditions that allow the connection between two devices in order to share DICOM files: getting an accordance statement, defining the service, searching the service in statements and taking into account the Service Query attributes, the transfer syntax and the private attributes.

Each element of the network is called node and the communication between the nodes should have been previously defined thanks to a connectivity table.

CONCLUSION

DICOM has meant an extraordinary medical service improvement, as well as a great evolution of health community. It is a huge impact in health science, because DICOM integrates many electronic functions that offer choices and opportunities such as viewing a radiological image in another geographical place in real time. That is, definitely, an essential improvement in medical computing development.

BIBLIOGRAPHY

 ¹Dahilys González López, Liset M. Álvarez Barreras, Adrián Fernández Orozco. ”Implementación de estándares DICOM SR y HL7 CDA para la creación y edición de informes de estudios imagenológicos”. ”SciELO” [Internet]. 2014 [cited 18 january 2017]; 6(1):1. Available in: <https://scielo.sld.cu/scielo.php?script=sci_arttext&pid=S1684-18592014000100008>

 ²DICOM Official Webpage [Internet]. Rosslyn: DICOM; 2013 [updated september 2016; cited 16 january 2017]. Available in: <https://dicom.nema.org/>

Carmen García Cerdán

Antonio José Pérez Villaescusa

Maite Valentina Serrano Pérez  

The production of X-rays can be by:
Production of slowed down radiation or Bremsstrahlung. When an electron with a given charge, coming from the outside, passes near the nucleus of an atom, the nuclear electric field decelerates to the electron, changing the direction of the same. This slowing down of the electron causes that part of the energy that had the charge of the electron to leave in the form of an electromagnetic wave. This is known as a radioactive collision: “The charged particle deviates from its trajectory in its interaction with the atomic nuclei of the medium and as a result EM radiation (photons) are produced” [2]. The radiations that are produced are of different wavelengths, they are emitted in the form of a continuous spectrum, due to the different speed of the electrons when hitting .
Characteristic radiation. Orbital electronic transmission. When an electron, from outside, strikes an electron from one of the orbital layers of the atom (usually in the K-layer), the electron of that layer is expelled from the orbital, leaving its place vacant. This is called an inelastic collision: The particle collides with the atoms in the medium and produces ionizations (they pull electrons from the atom) . This vacant place is occupied by an electron from the upper layers. The passage of an electron from an outer layer to an inner one causes the emission of photons. This emission is called characteristic because the photons are characteristic of the material where the electronic transmission of the orbital has taken place [3].
For the production of X-rays, we need electrons that interact with matter and thus produce radiation. For this, a vacuum glass tube is used in which are found two electrodes with potential difference at their ends, where the electrons will accelerate. At one end we have a tungsten filament called a cathode, which produces electrons by passing electric current through a filament. These electrons are going to hit a high Z material, which is in the filament at the other end of the tube called the anode. At the anode there is a white dot that usually has a slope of 45 °. The tube has a window for the passage of the X-rays that occur as a result of the collision of the electrons of the cathode with the anode.

[1] Mejía N, Mendoza Y, Ramírez W, Sosa E, Zerpa L, Peña, D. Rayos x. Producción de Rayos x. 2014. Available from: https://rayosxuptm.blogspot.com.es/2014/04/produccion-de-rayos-x.html.

[2] Tidito, Imagen Diagnóstica y Enfermería. Producción de Rayos X, agosto 2012. Available from: https://www.needgoo.com/produccion-de-rayos-x/.

[3] Haz de Rayos X y formación de la imagen. El haz de Rayos X. Available from: https://fisicaradiologica.wikispaces.com/HAZ+DE+RAYOS+X+Y+FORMACION+DE+LA+IMAGEN.

[4] Tidito, Imagen Diagnóstica y Enfermería. Producción de Rayos X, agosto 2012. Available from: https://www.needgoo.com/produccion-de-rayos-x/.
Giorgia Menin
Rafael M. Palacios López

Download (PDF, 1.69MB)

Download (PDF, 579KB)