Past paper Qs Flashcards
How does the X-ray spectrum vary with Kv and Ma changes. what is the characteristic peak of tungston.
Increases in Kv shift the peak to the right and increase area under the graph. Increases quality and quantity of the beam. If the max Kv includes the characteristic X-ray energy then that will be emitted. For tungston that is 60 and 70KeV.
Ma will increase only area under graph. i.e. quantity
How do you increase X-ray tube efficiency
Increase the voltage
Define absorbed dose, Equivalent Dose and Effective dose. Under what conditions would they be the same for the same exposure?
Absorbed - Energy deposited by ionising radiation
Equivalent - Includes a weighting factor to take into account the type of radiation and it’s ionising effect.
Effective - From equivalent takes into account the sensitivity of that type of tissue to radiation.
The same if radiation weighting factor = 1 (X-rays) and the entire body is uniformly irradiated.
Summerise the main functions of a pacemaker
Why is carbon not used for MRI but Hydrogen is?
It does not provide as good a nuclear magnetic resonance signal as hydrogen. because it has an even number of protons and neutrons.
How do you change a spin echo pulse sequence to a gradient echo pulse sequence?
Which are the two main categories of non-ionising radiation sources in healthcare. and which one has heating as it’s main health effect?
Radiofrequency radiation - MRI
Optical Radiation - UV. Main effect is heating
Which are the three main health effects in the optical radiaition spectrum between 200-700nm.
Photochemical effects
Thermal effects
Photomechanical
Distinguish between stochastic and deterministic effects of ionising radiation
Stochastic -
Deterministic -
Explain how these principles of stochastic and deterministic radiation lead to the two principles of ionising radiatino protection
As low as reasonably Practicable.
Threshold of what exposures should not be more than
Summerize with a diagram the main parts of an image intensifier and an X-ray tube
kjb
Cacculate the spatial resolution of a CT scanner if the diameter of teh scanning field is….
,,,,
Explain briefly blood pressure measurement
blah blah
Describe the characteristics of laser radiation that differentiate it from other non-ionising EMF radiations
- It uses visible light
2.
3.
Describe the need of a common image format in PACS systems
5
Identify an application where the hydrogen nucleus is not used for MRI
duh duh duhhhh
Summerise the main sources of noise in ECG and briefly explain the main methods of minimising / eliminating them
many things
Describe the major processes performed on a digital image during segmentation. Include pre-processing through object discrimination and morphological processing.
Pre-processing - Histogram equilisation
Object discrimination - Binary contrast enhancement
This produces an object with rough edges ill define and noisey.
Binary morphological processing. Erosion and dilation filters are used either in opening or closing ways. These smooth contours and removes either bright pixels or dark pixel areas respectively.
Outline an example of a simple brightness / texture feature and of a shape feature which might be appropriate in identifying stained circular cells on histology slides
Mean brightness feature can help identify whether a pixels belong to an object or not.
Texture analysis can be completed by Fourier analysis. Completed in small sections this can help identify the object outlines according to local variance in spatial frequencies.
Various shape parameters can be used to identify a shape once it’s boundaries have been identified. icluding the objects area. In this case roundness: the ratiio of the object area to the area of it’s convex hull, close to 1 in circular objects.
How might the features of of circular shape and edges be used in finally classifying the segmented objects.
Brightness/ Tesxture: Objects with similar brightness levels or texture patterns may belong to the same class.
Shape: Circular cells in histology slides can be identified based on their roundness
Classification: Cells may be classified based on a combination of brightness texture and shape. Neural networks and fuzzy logic can be employed to classify objects based on multiple features.
Image data is often resampled or remapped prior to processing it further. Why and how is this done and what precautions should be taken to minimise errors and aretefacts?
Resampling and mapping is done for various reasons including correcting distortions alterting perspective or adjusting resolution. This process invovles repositioning pixels within an image according to mathematical transformations.
How its done:
Completed using affine transforms for translationg rotation and caling to reposition pixels without introducing curvature.
Warping: Non-linear transformations for complex distortions (barrel) involving polynomial equations with higher powers.
Control points: Selected points in the image define areas of pixels and their positions in the transformed image.
- Precautions: Low-pass filtering for down-sampling: This avoids aliasing artefacts when reucing resolution.
Pixel interpolation for Up-sampling: During up-sampling, where the output resolution is higher than the input, pixel interpolation techniques are used to estimate pixel values between already known values. Nearest neighbour or bilinear or higher order interpolation. Avoids pixelation.
Image processing may be classified into point local and global processes explain these and give practical examples
Pixel point
Briefly describe Image re-sampling prior to spatial transformation
Spatial transformations include enlarging and distorting images and moving them in space. There is an issue with resampling as the new position is not an exact pixel shift. With rotations, the pixels will be in slightly more offset positions. Resampling is required on the original image to ensure that when you move something, you don’t result in issues with sharp edges. For example, scaling down - resampling is important to do before reducing the size as you might lose data. You begin by smoothing the image to avoid moire fringes / sampling errors.
What is the equation to find max frame rate in ultrasound.
f = C / 2DN
