Week 1 Concepts of Sectional Imaging- Grp 2 answers Flashcards
Sagittal Plane
The vertical plane that goes through the body, dividing it into right and left portions.
Coronal Plane
The vertical plane that goes through the body, dividing it into anterior(ventral) and posterior(dorsal) portions. Slice from the front to back.
Axial(Transverse Plane)
The horizontal plane that passes through the body, dividing it into superior and inferior portions.
Oblique Plane
The plane that passes diagonally between the axes of two other planes. This can combine sagittal and axial planes or another two planes. The kidney is an example of an oblique plane within the alignment of the human body.
Briefly describe how to orient yourself when viewing an axial cross-sectional image.
When viewing an axial cross-sectional image it is important to alway do it the same way every time. The patient position for this is the supine position which means the patient will be laying on their back. Then the cross-sectional image is taken from the feet up. Images are then viewed as if the patient were standing in front of them. This means that the right side of the image will be seen as the viewers left side.
Explain what is meant by “decreasing the slice thickness” when setting up to image a segment of the body
When an image is created a number is associated with each section of the image, this is known as slice allocation. This is used to know where the orientation is within the anatomical structure and how much anatomy is in the image. Decreasing the slice thickness refers to an increase in images taken within a portion of the anatomical structure. This means that the more numbers that are on the images the thinner the slice thickness.
Explain the basic concepts of how a CT unit produces an image.
CT unit image production steps:
X-Ray
Digital number
Gray scale assignment
Matrix plotting and image production
A CT unit produces an image by using x-rays, and detectors. The detector is on the opposite side of the x-ray source and it calculates the amount of x rays that are penetrate through the anatomic structure. It also measures the intensity/number of x-ray waves that hit the detector. After the intensity is measured, it is going to be assigned a gray scale. The gray scale is then used to plot on a matrix, which will create the image.
Axial CT scan
Images taken one at a time
The machine takes one image and then the patient is moved through machine for each new picture
Provides excellent detail in images
Axial is the longer CT scan
Needs multiple breath holds to capture images with patient comfort.
Explain the importance of technical factor manipulation when considering patient dose versus image quality with CT
When considering technical factor manipulation and patient radiation dose versus image quality with CT, there are a few components associated with it:
Sectional anatomy being covered
Slice thickness
Exposure time
Intensity of photon beam
Use of Intravenous Contrast
Axial versus Helical
Intravenous Contrast: A medium such as Iodine may sometimes be used when imaging parts of the anatomy such as the chest, abdomen, pelvis and sometimes brain. This increases visibility of vascular tissues within the anatomy.
Axial (1 image at a time): The benefit of this way of imaging is that if done correctly it provides a more detailed image and you are able to see specific structures within the image produced. It does however take a significant amount of time to complete which increases radiation exposure time to the patient. There is room for error due to possible patient movement and breaths being taken between each image taken.
Helical (Volume images): This way of imaging is a much faster process and can be completed in a patient’s single breath. This is achieved because multiple images are taken at once which also allows for more anatomy able to be covered.The issue with this is that because of the motion associated with helical imaging detail can be lost and the image is not as clear.
Helical CT scan
Takes multiple images
Patient is moved through the beam of x-ray photons
The detectors analyze and capture information in a circular manner around the patient.
The detector moves with the x-ray beams to produce images.
This process collects data 360 degrees around the patient.
The images are less detailed because there is motion in the image collection process.
Scan can be done in a single breath hold for patient
Explain the basic concepts of how an MRI unit produces an image
An MRI unit produces an image by using a high strength magnet that creates a pull on hydrogen atoms.The protons in the body are essentially forced to align with the magnetic field that is being produced. A radiofrequency current is used to stimulate the protons causing them to spin, and they spin at a particular rate depending on the strength of the magnet. The radio waves are used to move the hydrogen atoms out of their position, and when the radiofrequency source is turned off the atoms return to their original alignment which causes a signal to be emitted that is used to create the MRI images.The MRI images are collected in all planes sagittal, coronal, axial, and oblique.
It is the signal that is emitted when the atoms return to their original position that creates the image and is seen on the screen itself. Abnormalities in the patient can be emphasized for the image by emitting different frequencies.
Explain how MRI will produce images of the same anatomy with vastly different scales of contrast.
MRI images use gray scaling to produce a visual image. Hence where the contrast ranges from lightest to darkest using white to black to produce an image. With this, the MRI measures the signal intensity of adjacent tissues and when compared allows you to see contrast. Along with precession analogy a signal is produced from a proton. Intensity of the signal then gives it a gray scale value.
Different types of tissues such as fat and water will have different relaxation times. This allows for fat and water to be differentiated. Using pulse sequencing the signal from fat can be highly reduced. This allows for other tissues to be enhanced. MRI methods used to adjust contrast scaling include T1 and T2 weighted sequences which will allow for different tissues to be highlighted.
Contrast dye can also be used to enhance imagery. Gadolinium will help with tissue, organs and blood vessels to enhance an MRI scan due to the magnetic properties.
Explain the basic concepts of how an Diagnostic Medical Sonography unit produces an image.
Ultrasound images are produced by using a transducer. The transducer is composed of crystals that are embedded into it, that create and collects the signal with sound waves. The sound waves pass from the transducer to the body of the individual. The sound waves ability to pass through the tissue is enhanced by using a water based gel that acts as a carrier for the sound waves, the waves bounce off structures in the body and the intensity of this wave or echo is what is collected by the transducer, which creates the image. The moving of the transducer is what determines what plane the image is going to be seen in.
Explain the basic concept of how a Nuclear Medicine unit produces an image
Nuclear medicine relies on the detection of gamma ray emissions to visualize and assess the physiological functions of organs and tissues within the body. MRI uses strong magnetic fields and radiofrequency energy to capture images, while CT relies on radiation for imaging. Both methods have the ability to create images in both 2D and 3D formats.
Describe the different types of DMS transducers that can be used to visualize anatomy.
There are four types of DMS transducers used in sonography that are designed to enhance specific imaging.
Superficial- These are passed over the surface of the body for internal imaging.
Endocavity- Can be inserted from an external orifice of the body and inserted up to a couple inches. This allows for a closer imaging than from the surface of the body. Example insertion point would be the rectum or vaginal canal.
Endoscopic- Designed for narrower external oracifes of the body with the flexibility to insert further than the endocavity transducer. This also allows for a closer imaging than from the surface of the body. Example insertion point would be into the urethra to the bladder or down the throat into the stomach.
Endovascular- Inserted into a vessel and as an example can be manipulated to the heart for imaging.
Describe how the color scale is used in PET scanning
The color scale in a PET scan is used to signify the intensity of the image. It helps to visualize the different activity levels of the metabolic activity within different organs and tissues. It is also crucial to getting a clear image.
Cancer with show up as bright spots.
A blue-green color indicates that there is low metabolic activity
A yellow-orange color indicates that there is a moderate level of metabolic activity
A red color indicates that there is a high level of metabolic activity
Explain the basic concepts of how a PET scanner produces an image.
PET or Positron Emission Tomography scanners are used to visualize and measure metabolic processes in the body.
The image is produced by the following steps that take place:
The first step is an admission of a radioactive tracer, it is designed to to target specific tissues and organs based on their individual metabolic activity.
Positron Annihilation- When a positron meets an electron they undergo annihilation which produces two gamma rays.
Gamma Ray Detection- Detectors in the PET scanner detect gamma Rays, then they make a ring around the patient to capture the image.
Image Reconstruction- A three-dimensional image is produced that can be assessed to determine if their is any abnormalities, for example, a tumor.
