OMFPR 5: Intraoral Radiography - Digital, Extraoral 2D Imaging, Cephalometric Radiograph Waters View

X-rays

Patient

Receptor

Image detection

Interpretation

Radiographic imaging chain

Digital

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

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

In terms of spatial distribution of pixels

In terms of different shades of gray of each of the pixels

Digital images are discrete and numeric in which two ways?

Pixel

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

0-255

Pixels are usually expressed in what range of values?

Pixel

Basic unit

1

Each pixel contains _ shade of gray.

Digital image

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

Digital direct

Digital indirect

Indirect/hybrid

Types of digital image acquisition

Charged coupled device (CCD)

Complementary metal oxide semiconductors (CMOS)

Flat panel detectors

Types of direct digital receptors

Photostimulable phosphors (PSP)

Wireless

Types of indirect digital receptors

Silicon

CCD/CMOS are _______ based semiconductors.

X-rays

Signal charge

Electronic amplifier

Readout

Digital data

CCD/CMOS steps in image acquisition

Image histogram

Map with distribution of light and dark colors

True

T/F: PSP imaging plates are 100% reusable.

True

T/F: PSP imaging plates are the same size as film.

False; one of biggest advantages

T/F: A drawback of using PSP imaging plates is that they are thin.

No

Do PSP imaging plates use wires?

Laser scanning

Erase

Hygienic protection

Acquisition

PSP cycle (indirect)

Photostimulable phosphor (PSP) imaging plate

Europium doped barium flurohalide

Absorb and store energy from x-rays

What do PSPs do?

Stimulated by another light of appropriate wavelength

PSPs release energy when...

Imaging plate (Europium doped barium flurohalide) -> latent image -> laser scanning read row by row -> electrical signal

Describe PSP laser scanning.

Expose for 2 min

Light source should be close and intense

Recommend using view box

Laser erases the images in some type of systems

Ghost images appear if incomplete

Describe erasing imaging plates (PSPs).

Sizes 0-4

Provide protection from light and cross contamination

Disposable

Describe PSP barrier envelopes.

Direct and fast -- endodontics + urgent care diagnosis!

High spatial resolution

Benefits of CCD/CMOS

CCD/CMOS

High spatial resolution = CCD/CMOS or PSP?

Film-like / no cable

Larger active surface area

Larger exposure latitude

Economical

Benefits of PSP

Indirect

Plate handling

Lower spatial resolution

Downsides of PSP

Spatial resolution

Contrast resolution (bit depth + dynamic range)

Sensitivity

Detector latitude

Noise

Physical characteristics

Spatial resolution

Capacity to distinguish fine detail in an image

Minimum pixel size

Spatial resolution is defined and limited by...

Pixel size

What controls spatial resolution?

Line pairs per mm

At least 2 pixels required to resolve a line pair

Spatial resolution is measured in units of...

> 20 lp/mm

Maximum spatial resolution for film

25 lp/mm

Maximum spatial resolution for CCD/CMOS

> 7 lp/mm

Maximum spatial resolution for PSP

6

Human eye can distinguish _ lp/mm without benefit of magnification.

True

T/F: No significant differences exist among modalities in SR for common diagnostic tasks.

Contrast resolution

Ability to distinguish different densities in the radiographic image

Pixel size

Shades of gray distribution

Spatial resolution = ?

Contrast resolution = ?

Contrast resolution

Different densities/shades of gray stored in a radiographic image

8, 10, 12, 16

Contrast resolution can be how many bits?

256 (2^8) to 65,536 (2^16)

Contrast resolution can be how many different densities?

Noise, computer display

In practice, contrast resolution is limited by _____ and _______ _______.

Detector latitude

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

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

Desirable detector latitude

Detector sensitivity

Ability to respond to small amounts of radiation

Detector efficiency, pixel size, system noise

Components of detector sensitivity

Detective quantum energy (DQE)

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

Less radiation needed to achieve identical image quality

What do high DQE values indicate?

Optimizing contrast

Reducing noise

Removing technical artifacts

Goal of digital image processing is to improve image quality by...

False; cannot be influenced because it is dependent on technical variables of the detector (e.g. pixel size)

T/F: Spatial resolution is influenced by processing software.

Tape (slow but cheap)

Hard drive

Magneto-optical

Writable CD/DVD

Digital storage options

False

T/F: Patients should bring hard copies of their radiographs.

CCD

PSP

Digital receptor for digital panoramic imaging

CCD

Sirona introduced first digital ceph unit: ___ based

Almost instant image availability

Rapid storage and retrieval

Dose reduction

Ability to process images after they are recorded

Ability to transfer images from one location to another rapidly (teleradiology)

Ability to duplicate without loss of image quality

Better patient communication

Advantages of digital imaging

50-70% alcohol

E-speed film has a __% dose reduction with PSP and __% reduction with solid state sensors.

2-8

Dose reductions are _-_ fold.

High initial costs

Sensor placement (inflexible, cable)

Image quality (noise, CCD, storage)

Evolving technology

Disadvantages of digital imaging

Anywhere film would be used

Teleradiology

Integration into electronic record

Patient education

Clinical applications of digital imaging

Extraoral imaging

Both the x-ray source and the image receptor are outside the patient's mouth

Phosphor

________ layer in the screen absorbs x-ray photons and emits visible light (blue or green).

Using intensifying screen film compared to intraoral film

What allows a significant reduction in patient exposure?

Panoramic

Lateral ceph

Postero-anterior skull

Towne

Waters

Submental vertex

Sinuses

What are Waters x-rays used for?

Cephalometric analysis - orthodontics

Survey of skull and facial bones: trauma, disease, developmental abnormality

Assessment of nasopharyngeal soft tissues, paranasal sinuses (sleep apnea)

Lateral ceph applications

Assess symmetry

Evaluate skull for disease, trauma and developmental abnormalities

Assess frontal and ethmoid sinuses, nasal fossa and orbits

PA ceph applications

Panoramic

Lateral ceph

PA ceph

Which x-rays are mainly used?

Maxillary sinuses

Waters projection is for evaluation of mainly the __________ sinuses.