OMFPR 5 - Intraoral Radiography (Dr. Campos)

1. X-rays generated by an x-ray tube

2. Detector absorbs the energy from the x-rays

3. Energy is transformed into electrical charges

4. Electrical charges are recorded, digitized and quantified into a gray scale

5. Post processing software - clinically meaningful image

Put the following steps in order for the radiographic imaging digitial chain:

- Detector absorbs the energy from the x-rays

- Post processing software - clinically meaningful image

- Energy is transformed into electrical charges

- X-rays generated by an x-ray tube

- Electrical charges are recorded, digitized and quantified into a gray scale

1. X-rays

2. Patient

3. Receptor

4. Image Detection

5. Interpretation

Put the following steps in order for the radiographic imaging chain:

- X-rays

- Interpretation

- Patient

- Image Detection

- Receptor

Digital

Define the following:

- Of, relating to, or using calculation by numerical methods or by discrete units...

- Of, or relating to data in the form of numerical digits

- Spatial distribution of pixels

- Different shades of gray of each of the pixels

Digital images are discrete and numeric in 2 ways, they are:

pixel

Define the following:

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

true

t/f: pixels can be processed and manipulated

True

T/F: Pixels are usually expressed in 0-255 values

1

every pixel in picture contains how many colors?

Black

A pixel is the basic unit of any digital photograph. What color is the value of 0?

White

A pixel is the basic unit of any digital photograph. What color is the value of 255?

0-255 (2^8)

what is the optimal range for pixel bit depth?

Digital image

Define the following:

Large collection of pixels organized in a matrix of rows and columns

digital direct

ID the method of digital image acquisition:

- sensor -> computer image

digital indirect

ID the method of digital image acquisition:

-sensor -> scanner -> computer image

indirect/hybrid

ID the method of digital image acquisition:

- film -> developer -> scanner -> computer

Direct

The charged coupled device (CCD) is an example of a __________ receptor

Direct

The complimentary metal oxide semiconductor (CMOS) is an example of a __________ receptor

Direct

The flat panel detectors is an example of a __________ receptor

Indirect

The photostimulable phosphors (PSP) is an example of a __________ receptor

Indirect

Are wireless receptors direct or indirect?

Digital direct

What type of digital receptors do we use at Tufts?

CCD/CMOS sensors

What type of sensor is silicon based semiconductor?

A covalent bond between Si atoms is broken, releasing an electron, creating an electron-hole pair. The freed electron is then collected and stored in a pixel's electron well.

In CCD/CMOS detectors, what happens when an X-ray photon strikes the silicon-based semiconductor?

1. X-rays

2. Signal charge

3. Electronic amplifier

4. Readout

5. Digital data

What is the correct steps of CCD /CMOS-steps in image acquisition?

- Electronic amplifier

- X-rays

- Signal charge

- Digital data

- Readout

It shows the distribution of pixel intensities to evaluate contrast and exposure and it can be manipulated

Why is an image histogram useful in digital radiography?

PSP imaging plates

What sensor has the following advantages?

- 100% re-usable

- Same size as film

- Flexible

- Thin

- No wires

- Used with existing x-ray equipment

- Hygienic protection

- Acquisition

- Laser scanning

- Erase

What are the four steps of the PSP imaging plate cycle?

PSP sensor (photostimulable phosphor)

What has the following characteristics:

- Europium doped barium flurohalide

- Absorb and store energy from x-rays

- Release this energy when stimulated by another light of appropriate wavelength

Europium-doped Barium Fluorohalide

In PSP plates, what material stores the latent image after X-ray exposure?

Releases stored energy from the plate as visible light

What does laser scanning do in the PSP system?

It is converted into electrical signals for image formation

What happens to the light signal captured by the photomultiplier in PSP systems?

2 minutes

How long should PSP imaging plates typically be exposed to light to erase residual images?

Close and intense

What type of light conditions are recommended for erasing PSP plates?

True

T/F: Using a view box when erasing PSP plates provides a uniform, intense light source

Lasers

In some PSP systems, how are the plates erased automatically?

Ghost images appear

What happens if erasure of a PSP plate is incomplete?

Barrier envelopes

What has the following characteristics:

- Sizes 0, 1, 2, 3, 4

- Provide protection from light and cross contamination

- Disposable

CCD/CMOS sensors

What type of sensor is best for endodontics and urgent care diagnosis due to being direct and fast?

CCD/CMOS sensors

What type of sensor has high spatial resolution?

CCD/CMOS sensors

What type of sensor has bulky sensor dimensions and a cable?

CCD/CMOS sensors

What type of sensor has a small active surface area?

CCD/CMOS sensors

What type of sensor has a small exposure latitude?

CCD/CMOS sensors

What type of sensor is comparably expensive?

PSP sensors

What type of sensor is 100% re-usable?

PSP sensors

What type of sensor is wireless?

PSP sensors

What type of sensor is used with existing x-ray equipment?

PSP sensors

What type of sensor is sensitive to handling, bending, and dust?

PSP sensors

What type of sensor is thin, flexible, and has no wires?

PSP sensors

What type of sensor has low spatial resolution?

PSP sensors

What type of sensor has a large active surface area?

PSP sensors

What type of sensor has a large exposure latitude?

PSP sensors

What type of sensor is comparably more economical?

spatial resolution

Define the following:

The capacity to distinguish fine detail in an image

Minimum pixel size

What is spatial resolution defined and limited by?

true

t/f: scatter of x-rays within a detector can influence spatial resolution

false, increase in quantity of radiation (kVp) will not improve max spatial resolution

T/F: Increase in quantity of radiation (kVp) will improve maximum spatial resolution

thickness of phosphor material

what can help improve the spatial resolution when using a PSP sensor?

pixel size

what is the only factor that determines spatial resolution?

decrease

increased pixel size will ______ spatial resolution

increase

decreased pixel size will ______ spatial resolution

Line pairs per mm (at least 2 pixels required to resolve a line pair)

what is spatial resolution measured in units of?

CCD/CMOS sensors

between film, CCD/CMOS, and PSP, which one will produce the best spacial resolution?

PSP sensors

between film, CCD/CMOS, and PSP, which one will produce the worst spatial resolution?

>20 lp/mm

Maximum spatial resolution for film:

25 lp/mm

Maximum spatial resolution for CCD/CMOS sensors:

>7 lp/mm

Maximum spatial resolution for PSP sensors:

6 lp/mm

The human eye can distinguish ___ lp/mm without the assistance of magnification

contrast resolution

Define the following:

Ability to distinguish different densities in the radiographic image

Contrast resolution

What deals with the following characteristics?

- Attenuation characteristics of tissues imaged

- Capacity of detector/receptor to distinguish these differences

- Ability of the computer display to portray the differences

- Ability of observer to recognize those differences

pixel size

spatial resolution is dependent upon:

bit depth

contrast resolution is dependent upon

high

images with high bit depth will have _____ contrast resolution

low

images with low bit depth will have _____ contrast resolution

Bit depth (8, 10, 12, 16 bits)

Define the following:

Different densities/shades of gray stored in a radiographic image

Noise, computer display

In practice, what is contrast resolution limited by?

detector latitude

Define the following:

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

- Desirable: Ability to record a wide range of tissue densities from gingiva-enamel

detector sensitivity

Define the following:

- Detector ability to respond to small amounts of radiation

- Detector efficiency, pixel size, system noise

detective quantum efficiency (DQE)

Define the following:

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

high

_____ DQE values indicate that less radiation needed to achieve identical image quality

low

_____ DQE values indicate that more radiation needed to achieve identical image quality

digital image processing

Define the following:

Any operation that acts to improve, correct, analyze, or in some way change a digital image

- Optimize contrast

- Reduce noise

- Remove technical artifacts

What are the 3 ways we can improve image quality in digital image processing?

C) Spatial resolution (e.g. pixel size)

Which of the following cannot be manipulated during digital image processing?

A) Contrast

B) Brightness

C) Spatial resolution

D) Edge enhancement

Brightness/contrast

What physical characteristics are these images showing?

Edge enhancement

What physical characteristics are these images showing?

Magnification

What physical characteristics is this image showing?

Inversion

What physical characteristics is this image showing?

Linear measurement

What physical characteristics is this image showing?

Areas of bone loss (black) and bone deposition (white) over time

In digital subtraction radiography, what does the subtraction image (Image C) reveal?

Panoramic (1-5 MB vs intra-oral is 180kB-250kB)

What has a larger image file: intra-oral or panoramic?

Digital Imaging and Communications in Medicine (DICOM)

what systems compatibility is required for viewing/saving digital radiographs?

Digital storage options

What type of storage are the following examples:

- Tape (slow but cheap)

- Hard drive

- Magneto-Optical (up to 4.6 GB)

- Writable CD/DVD

Hard copy

What type of storage are the following examples:

- Thermal printout (poor)

- Laser gray scale

- Dye sublimation

- Dry "xerox" process

- Standard printers in high resolution mode with photographic paper

Digital panoramic imaging

What type of storage are the following examples:

- Digital Receptor (CCD, PSP)

- Mounted on Pan Machine

- Imaging geometry same

- Display on high resolution monitor

Digital Cephalometry

What type of storage are the following examples:

- Sirona introduced first digital ceph unit: CCD based

- PSP

Digital imaging

All of the following are advantages of what?

- Almost instant image availability

- Rapid storage and retrieval

- Dose reduction

- Ability to process images after they are recorded- contrast, magnification

- Ability to transfer images from one location to another rapidly (Teleradiology)

- Ability to duplicate without loss of image quality

- Better patient communication

50%

Compared to E-speed film, using a PSP sensor will reduce radiation dose by ____%

70%

Compared to E-speed film, using a CCD/CMOS sensor will reduce radiation dose by ___%

2-8 fold

Compared to conventional film, digital radiography can reduce patient radiation dose by approximately what fold?

Digital imaging

All of the following are advantages of what?

- High initial costs

- Sensor placement (Inflexible/rigid, Cable)

- Image quality (noise, exposure latitude, hard copies not good on screen, storage requirements)

- Evolving technology

- Unfamililiarity

- Learning curve for staff

- Integration