5- 2D digital imaging

definition of digital image

• relating to/using calculation by numerical methods or by discrete units

• relating to/using data in the form of numerical digits

definition of pixel

• matrix/picture element of a digital array which identifies a gray level at that point

• basic unit of a 2D digital image

3 types of digital image acquisition

1. digital direct

2. digital indirect

3. indirect/hybrid

2 types of direct digital receptors

1. charged coupled device (CCD)

2. complementary metal oxide semiconductors (CMOs)

ones we use in clinic at Tufts

1 type of indirect digital receptor

photostimulable phosphors (PSP)

5 advantages of PSP imaging plates

1. 100% re-usable

2. same size as film

3. flexible + thin

4. no wires

5. used w/ existing x-ray equipment

2 advantages of using CCD/CMOs

1. direct + fast: for endo + urgent diagnosis

2. high spatial resolution

5 disadvantages of using CCD/CMOs

1. sensor dimensions

2. cable

3. smaller active surface area

4. small exposure latitude

5. expensive

spatial resolution of a digital image is determined by

minimum pixel size

what do the numbers above each column represent

# of line pairs (1 black + 1 white) → at least 2 pixels are required to resolve a line pair

definition of contrast resolution

ability to distinguish different densities in the radiographic image

definition of detector latitude

ability of a detector to capture a range of x-ray exposures

definition of detector sensitivity

ability to respond to small amounts of radiation

definition of detective quantum efficiency (DQE)

• efficiency of a detector in converting incident x-ray energy into an image signal

• high DQE indicates less radiation needed to achieve optimal image quality

T/F: spatial resolution cannot be influenced by processing software because it is dependent on technical variables of the detector (pixel size)

true

5 advantages of digital imaging

1. instant image availability

2. rapid storage + retrieval

3. dose reduction

4. ability to transfer images from one location to another

5. ability to duplicate w/o loss of image quality

5 disadvantages of digital imaging

1. high initial costs

2. sensor placement

3. image quality

4. evolving technology

5. difficult to learn for non-tech savy people

water projection is used for what

evaluating maxillary sinuses