Components of X ray Tube

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In our previous blog we have discussed about x ray machine working principle. Please check out for the link given below to have better understanding of today’s content.

X ray Machine Working Principle

In today’s blog, we are going to discuss about the components of x ray tube.

The x ray is a important radiography equipment. The invention of x ray machine has created a revolution in the field of diagnostic healthcare. The x ray machine produces the images of inside of our body in black and white. Therefore it is important for every healthcare professional to know in detail about x ray machine.

Let’s get into the topic with a small introduction about X ray.

WHAT IS X RAY?

X rays are almost similar to visible lights. But the only difference is that they have different wavelengths. We can see visible light of higher wavelength, but we cannot see the X ray beams with lower wavelength and high energy. The frequency of X rays is 1020 Hz and wavelength ranges from 10 Picometres to 10 Nanometres.

WHAT ARE THE

COMPONENTS OF X

RAY TUBE?

The x ray tube is a energy converter which converts electrical energy into X ray radiation and  heat. The following are the components of the x ray tube.

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1. Cathode.

2. Anode.

3. Expansion Bellows.

4. Tube Envelope.

5. Tube Housing.

6. Rotor.

7. Induction Slater.

8. Tube Window.

9. Aluminum Filter.

10. Collimator.

CATHODE

Cathode acts as a source of electrons. The electric current is used to heat the cathode filament which in turn accelerates the electrons from the cathode.

ANODE

There are two types of anode used in the x ray tube. One is Stationary anode and other is rotating anode. Rotating anode is used mostly. Anode has two main functions, one is it convert electric energy into X ray radiation and to dissipate the heat created in the process.

Disadvantages of using rotating anode:

Decreased output of X ray beams due to scattering of X ray beams and more absorption of X ray beams by anode target itself.

EXPANSION BELLOWS

Expansion bellows allows oil to expand without increasing pressure on the tube.

TUBE ENVELOPE

The primary function of tube envelope is to use vacuum in the tube. Tube Envelope is usually made up of glass. In some cases it is also made up of ceramic or metal based on the application. In a conventional X ray tube, anode only rotates. In case of dual energy CT’s entire envelope tube rotates, Rotating Envelop Tubes are used. And in addition to that anode is in direct contact with the liquid coolant which results in High heat conduction and increased performance.

Have you ever wondered why vacuum tube is used in X ray production instead of normal air filled tube. The following is the answer.

The presence of gases in the X ray tube would allow electric current to flow through the tube freely instead of flowing only in the electron beam. Thus, inferring in the X ray production and damages the electric circuit.

TUBE HOUSING

The x ray tube housing acts as a shield and absorbs the excess radiation apart from the radiation that pass through the window as a useful X ray beams. The space between the x ray tube housing and inside is filled with oil which creates a electrical insulation and transfers heat from inside to the housing surface.

INDUCTION SLATER

Slater lies at the neck of the tube outside the envelope which provide the magnetic field to provide power to affect the rotation of anode.

ROTOR

The magnetic field produced by induction slater induces the current in the rotor of induction motor which in turn provides power to rotate the anode.

TUBE WINDOW

The x ray tube window is usually made up of beryllium which allows X rays to pass through and has sufficient strength to hold the vacuum required for x ray tube to operate.

ALUMINUM FILTER

The X ray beams produced by x ray machine are used in medical field has wide range of frequencies. X ray beams of unwanted frequencies may cause side effects on the patients if exposed. In order to filter the unwanted frequencies of X ray beam, aluminum filter is used.

COLLIMATOR

Collimator is used to direct the X ray beam from x ray tube to a specific region of interest in a patient’s body. It is used to avoid exposure of radiation to the areas apart from the region of interest.

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Now I hope you have acquired some knowledge about the components of x ray tube. We will discuss in detail about a topic related to Biomedical Engineering  in our next blog.

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Generations of CT Scanners

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X ray Machine Working Principle

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In our previous blogs we have discussed about Capnography and Interpretation of Capnography Waveform. Please check out for the link given below.

Capnography

Interpretation of Capnography Waveform

In today’s blog, we are going to discuss about the x ray machine working principle.

X ray is a radiography equipment which has created a revolution in the field of diagnostic healthcare. It produces the images of inside of our body in black and white. Therefore it is important for every healthcare professional to know in detail about X rays.

Let’s get into the topic.

INTRODUCTION

X Ray was discovered by German physicist Wilhelm Roentgen in 1895. In an eagerness to find out the behaviour of electricity in a vacuum, Roentgen removed the air from the tube which made electrons to move fast. The fast moving electrons hits a anode in the tube and produced a type of light. This is how x ray production took place for the first time. Roentgen noticed that this type of light is not yet discovered and it is called X Ray.

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WHAT IS X RAY?

X rays are almost similar to visible lights. But the only difference is that they have different wavelengths. We can see visible light of higher wavelength, but we cannot see the X ray beams with lower wavelength and high energy. The frequency of X rays is 1020 Hz and wavelength ranges from 10 Picometres to 10 Nanometres.

HOW X RAY BEAMS ARE

PRODUCED?

Let us discuss in detail about the x ray machine working principle. Following is the image of the x ray tube.

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The x ray unit consists of a x ray tube which has hot cathode filament and anode made up of heavy metal placed in a vacuum tube made of glass. The electric current is made to pass through the cathode filament, which in turn heats the cathode filament. The heat activates the electrons from the filaments surface. The positively charged anode draws the activated electrons across the x ray tube from cathode to anode.

Thus the fast moving electrons hits the anode element. Because of the collision of the fast moving electrons, the atoms in the anode loses electrons in the lower orbit. With the lose of electron, the atom becomes unstable. To come back to its normal equilibrium position, the atoms in the anode sends the electrons from higher orbit to fill the vacancy in the lower orbit. As a result X ray beams are produced.

The x ray production takes place from the slanting surface of the anode. Meanwhile along with X ray beam, high amount of heat is also produced. To prevent the anode damage due to excessive heating, a induction motor is used to rotate the anode in order to limit the heating at one particular spot.

A filter is placed near the X ray source which blocks the low energy X rays. So only high energy X rays from the x ray machine passes through the patients to reach the thin sheet of photographic x ray film. X ray beams from the x ray machine pass through the lower density objects such as muscles or flesh whereas in higher density objects like bones, X ray beams are absorbed. The absorbed X ray beams appears as a bright spots on the x ray film. Soft tissue such as skin and organs cannot absorb high energy X ray beams. 

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TUNGSTEN ANODE

MATERIAL

Most x ray tube uses tungsten as an anode material.The x ray production depends upon two factors, atomic number of anode material and energy of electrons. Reason to use tungsten is that it has a high atomic number of 74. As discussed earlier, heat is also produced along with X ray beam. In order to eliminate the effect of high heat, the tungsten element shows maximum strength at high temperatures. It has high melting point and also a low rate of evaporation. The shape of the anode is usually beveled shape discs.

 

Now I hope you have acquired some knowledge about the x ray machine working principle. We will discuss in detail about  x ray tube parts in our next blog.

NOTE: Dear friends!!! ...Please do comment a topic related to Biomedical, so that we can discuss it in future blogs.

Check out for this blog about Computed Tomography

Generations of CT Scanners

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Capnography Waveform Interpretation

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In our previous blog we have seen about capnography, its phases and uses. Please check out for the link below.

CAPNOGRAPHY

Today we are going to see about interpretation of capnography waveform and its indications.

Capnography is a important diagnostic and monitoring equipment used mainly during anesthesia procedure. Failure to used capnography in patients dependent on an artificial airway contributed to more than 70 percent of the ICU related airway deaths.

Therefore it is important for every healthcare professional to know in detail about capnography.

Let’s get into the topic.

WHAT IS

CAPNOGRAPHY?

Capnography is used to measure the amount of carbon dioxide in exhaled air. It is also used in indirect monitoring of carbon dioxide in arterial blood. It has its contribution in the fields of anesthesia and intensive care.

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HOW TO READ

CAPNOGRAPHY

WAVEFORM?

The capnography waveform with a dramatic up sloping plateau phase suggests that the patient has bronchospasm, which means airway is partially blocked or the endotracheal tube has migrated beyond the Carina and into main bronchus.

The capnography waveform with a peaked triangular appearance suggests that there is a significant leak around the tracheal tube or tracheostomy.

Flat capnography waveform indicates that the oesophagus has been mistakenly intubated instead of the trachea, the breathing circuit has become disconnected, the airway has been blocked with secretions.

A top hat appearance of capnography waveform indicates a good unobstructed airway.

COMMON INDICATIONS OF CAPNOGRAM WAVEFORM

APNEA

Apnea means no breath for ten seconds or longer. There is no respiratory effort or respiratory effort without air movement.

Causes of Apnea:

Cardiac arrest, Respiratory arrest, Equipment failure, Displaced airway adjunct.

HYPOVENTILATION

Hypoventilation is a buildup of carbon dioxide as a result of insufficient elimination of the carbon dioxide. Shape of capnogram is normal with rapid increase in phase 2, gradual, smooth and possibly prolonged upslope during phase 3, abrupt descent to baseline during inhalation. Elevated level of above 45 mmHg is seen.

Causes of hypoventilation:

Decrease in respiratory rate, decrease in tidal volume, chest compression during CPR, Obesity hypoventilation.

HYPERVENTILATION

Low carbon dioxide level resulting from excessive elimination through rapid or deep breathing or due to metabolic acidosis. Shape of capnogram is normal with rapid increase in phase 2, gradual, smooth and possibly shortened or peaked upslope during phase 3, abrupt descent to baseline during inhalation. Decreased level of Co2 below 35 mmHg is seen.

Causes of Hyperventilation:

Anxiety/panic disorder, Excessive exercise, Increased respiratory rate, Increased tidal volume.

TACHYPNEA WITH

HYPOCARDIA

Abnormally rapid breathing with reduced Co2. Respiratory rate is rapid and above a rate of 20 breaths per minute. Breathing  pattern is usually regular and occurs at least once in every 3 seconds. Shape of capnogram is normal with rapid increase in phase 2, gradual upslope during phase 3, abrupt descent during phase 0, back to baseline during inhalation.

BRADYPNEA WITH

HYPERCARBIA

Presence of an abnormally high level of carbon dioxide in the circulating blood. Respiratory rate is generally slow and below a rate of 12 breaths per minute, representing bradypnea. As a result of increased levels of exhaled carbon dioxide, capnogram waveform appears enlarged with a rapid increase in phase 2, gradual and smooth upslope during phase 3, abrupt descent during phase 0, back to inhalation. Breathing pattern is usually regular which occurs less than once in every 5 seconds.

HYPOPNEA WITH

BRADYPNEA

Hypopnea is shallow breathing less than 0.5 liters in adult patient. Bradypnea is a low respiratory rate which is less than 12 breaths per minute. The capnogram waveform is abnormal with short, non plateauing waveform and slow respiratory rate followed by a higher concentration of Co2 when a deep breath is taken.

REBREATHING OF CO2

Respiratory rate is generally between 12 and 20 breaths per minute in a adult patient. Breathing pattern usually occurs at every 3 – 5 seconds. Increase or rise in baseline, phase 1 and etco2 value increase with each successive breath or remains same due to hyperventilation.

Now I hope you have acquired some knowledge about capnography. We will discuss in detail about topics related to Biomedical Engineering, Medical Devices, Healthcare in our next blog.

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Capnography

Hi friends!!!

In our previous blog we have seen about Computed Tomography.

Please check out for the link given below.

Generations of CT scanners

COMPUTED TOMOGRAPHY | TECHNOLOGY | ARTIFACTS

Today we are going to see about capnography.

Capnography is a important diagnostic and monitoring equipment used mainly during anesthesia procedure. Failure to used capnography in patients dependent on an artificial airway contributed to more than 70 percent of the ICU related airway deaths.

Therefore it is important for every healthcare professional to know in detail about capnography.

Let’s get into the topic.

WHAT IS CAPNOGRAPHY?

Capnography is used to measure the amount of carbon dioxide in exhaled air. It is also used in indirect monitoring of carbon dioxide in arterial blood. The capnography displays the waveform of expiratory carbon dioxide with time. The capnography waveform provides details about metabolism, circulation and ventilation of patients.  It has its contribution in the fields of anesthesia and intensive care.

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NOTE: Normal value of expired carbon dioxide (Capnometer) is 35 mmHg to 45 mmHg.

WHAT IS CAPNOGRAPHY WAVEFORM?

The following is the normal capnogram waveform.

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The capnography has four phases. The 4 phases of capnography as follows

Phase 1: The phase 1 capnography is a inspiratory baseline, which is due to inspired gas with low levels of carbon dioxide.

Phase 2: Phase 2 is a expiratory upstroke which occurs during expiration of both dead space gas and alveolar gas (CO2 from alveoli reaches the upper airway and mix with the dead space air). Thus CO2 is detected in the exhaled air. The transition from phase 2 to phase 3 is called alpha angle capnography.

Phase 3: The phase 3 capnography is a alveolar plateau, where the last of alveolar gas is exhaled. The alveolar plateau has slightly upward tilt towards the end. The end of phase 3 is the end of exhalation which means end of exhalation has highest amount of CO2, thus it is called as etco2 (Entitled or Expired Carbon dioxide) and displayed in the monitor. The transition from phase 3 capnography to phase 0 is called beta angle. The beta angle is used to access the rebreathing. If the rebreathing occurs the angle is greater than 90 degrees.

Phase 0: Phase 0 is a inspiratory downstroke, that is the beginning of the next inspiration. Oxygen fills the airway and CO2 levels drop back to zero. The return to baseline is called phase 0.

There is a additional phase called Phase 4, which is a terminal upstroke (quick upstroke) which is seen during pregnancy.

WHAT ARE THE 

CHARACTERISTICS OF 

CAPNOGRAPHY 

WAVEFORM?

The capnography monitor (etco2 monitor) displays Capnography waveform which has five important characteristics to look out for.

1. Frequency.

2. Rhythm.

3. Height.

4. Baseline.

5. Shape.

The waveform should return to the baseline, the frequency should match the patient’s respiratory rate. The height of the capnography waveform should be between 35mmHg and 45mmHg, which is the normal etco2 reading.

WHAT ARE THE USES OF 

CAPNOGRAPHY?

1. Capnography is used to diagnose early respiratory depression and airway disorders during sedation, which results in reduction of unknown complications during sedation.

2. Capnography is useful in assessing tracheal tube and tracheostomy patency and position.

3. Capnography is useful in monitoring the adequacy of ventilator support. It provides important information about ventilation status.

4. Capnography provides indications about conditions like Apnea, Hypoventilation, Hyperventilation, asthma, laryngospasm, bronchospasm, rebreathing of CO2.

 

Now I hope you have acquired some knowledge about capnography. We will discuss in detail about interpretation of capnography waveform and its indications in our next blog.

NOTE: Dear friends!!! ...Please do comment a topic related to Biomedical, so that we can discuss it in future blogs.

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COMPUTED TOMOGRAPHY | TECHNOLOGY | ARTIFACTS

Hi friends!!!

In our previous blog we have seen about generations of ct scanners.

Please check out for the link below

Generations of CT scanners

Today’s blog we are going to see about ct technology and artifacts in ct scanners .

Invention of Computed Tomography is a revolution in the healthcare sector. The contribution of Computed Tomography in diagnostic and therapeutic fields in immense. Therefore it is important for every healthcare professional to know in detail about the evolution of CT scanners.

Let’s get into the topic.

INTRODUCTION

Computed Tomography was introduced by G.N. Hounsfield at Central Research Laboratories. The idea of computed tomography raised when G.N. Hounsfield was trying to identify what is inside a box by taking X rays at various angles around a box. Computed Tomography was commercialized in 1972.

WHY COMPUTED

TOMOGRAPHY?

Computed Tomography provides 3 Dimensional cross sectional images of internal organs and structures. Computed Tomography gives three dimensional informational on a single plane. It is used to view images of internal organs, bones, soft tissues and blood vessels. Gives information on the size and location of organs.

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WHAT IS THE

TECHNOLOGY OF

COMPUTED TOMOGRAPHY?

The ct technology is a updated version of X ray technology. In a conventional X ray machine uses a fixed X ray tube that send X ray beams in only one direction whereas in ct scanners, it uses a motorized X ray source that shoots narrow beams of X ray as it rotates around the patient. Special X ray detectors are located exactly opposite to the motorized X ray source. When X ray beams pass through the patient, it is captured by the detectors and send to the processing unit (Computer). The image slices can be displayed individually in a 2 Dimensional form or they can be stacked together to form 3 Dimensional image for examination.

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HOW IMAGES ARE ACQUIRED?

In ct scanners Images are taken in axial or transverse plane perpendicular to long axis of the body. The detectors of ct scanners measure the transmission of a thin beam of X rays through a full scan of the body. The images of the section is taken from different angles and allows to retrieve the information about the third dimension, depth. Visual representation of the raw data obtained is called SINOGRAM. Raw data is processed using reconstruction technique.

Pixel is a mean attenuation coefficient of tissues. Pixel size is based on the matrix size and field of view. It is equal to field of view divided by matrix size. The matrix size is like 128x, 256x. The smaller a pixel size, greater the image spatial resolution. Voxels are 3 Dimensional Pixels and a combination of pixel size and slice thickness, representing a value in a three dimensional space. Closer a part is to the origin of X ray source, smaller the voxel and higher the resolution. Further the part is from the X ray source, larger the voxel size and lower the resolution.

WHAT IS CT NUMBER?

Every region of CT image is expressed in terms of Hounsfield unit (ct number) based on the X ray attenuation. CT numbers are displayed as gray scale pixels on the monitor. White represents the pixels with high ct number (Bone). Shades of gray are assigned to intermediate level of ct number (Soft tissues, fluid and fat). Black region is represented with low ct number (Lungs and air filled organs).

WHAT ARE THE ARTIFACTS

OF COMPUTED 

TOMOGRAPHY?

MOTION ARTIFACT

Motion artifact is due to the voluntary or involuntary movement of patients. Images which appear as blurring, shading, streaking are due to patient movement during image acquisition.

BEAM HARDENING ARTIFACT 

X ray beam has photons of varying energy levels revolving around a mean beam energy level. In beam hardening artifact, low energy X ray beams are attenuated. Because lower energy beams are absorbed more rapidly than higher energy beams. So only high energy X ray beam passes through the patient. It has high mean beam energy level. As a result, the remaining  X ray beam is hardened. It acts similar to a high pass filter.

CUPPING ARTIFACT

The beam hardening artifact produces another type of artifact called cupping artifact. X ray beam passes through the object. If the centre of the object is thickest, then the beam will become harder in the centre than at the periphery. There is a less brighter appearance along the periphery of an object.

STREAKING ARTIFACT

Streaking artifact is a type of beam hardening artifact. In streaking artifact dark streaks can appear between two dense objects in an image. Streaking artifact happens when  a portion of a beam passes through one of the objects at certain tube positions is hardened less than when it passes through both objects at other tube positions. This type of artifacts commonly occur near materials like metals or bony regions of the body.

NOTE: The beam hardening artifact can be reduced using filtration technique. A metallic material is used to pre-harden the beam by filtering out the lower energy beams before it passes out the patient.

Bowtie filter is used to harden the edges of the beam, which will pass through the inner parts of the patient.

PHOTON STARVATION

Photon starvation usually seen in objects with high attenuation. So only insufficient X ray beams reach the detector. As a result during reconstruction process, these regions are magnified leading to the streaks in the image.

The photon starvation can be reduced by using tube current modulation (increased mAs) and adaptive filtration. 

PARTIAL VOLUME EFFECT

Tissues of different absorption are encompassed on the same CT Voxel, producing beam attenuation proportional to average value of these tissues. That is each voxel in an image represents more than one tissue types.

Partial volume effect can be minimized by reduction in the volume of voxel.

RING ARTIFACT

Ring artifact is due to the failure of one or more detector elements in a ct scanners. Most commonly seen in cranial CT images. Ring artifacts are concentric rings superimposed on the tomographic images.

Ring artifact can be corrected by calibration or replacing the concerning detector.

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Now I hope you have acquired some knowledge about ct technology and artifacts in ct scanners . We will discuss about a topic related to Biomedical Engineering, Medical Devices, Healthcare in our next blog.

NOTE: Dear friends!!! ...Please do comment a topic related to Biomedical, so that we can discuss it in future blogs.

Check out for my blog about ultrasound

ULTRASOUND - PART 1

ULTRASOUND - PART 2

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