Chapter 6 CCD/CMOS

CMOS / CCD CCD

A ____ uses very little power compared to a _____. ____ May use as much as 110 times the power that it does.

semiconductor

A _______ is a solid chemical element or compound that conducts electricity under some conditions but not others, making it a good medium for the control of electrical current.

photosensitive receptor

A ___________ and electronics embedded into a substrate material in a silicon chip make up a CCD.

c. Convert light into x-ray photons

A charged coupled device (CCD) does all of the following except: a. Reduce the size of the projected light image b. Transfer the image to a capacitor c. Convert light into x-ray photons d. Act as receptors via lenses or fiber optics

b. Semiconductor

A solid chemical element or compound doped with impurities that make it highly conductive is known as a. Dopant b. Semiconductor c. Transistor d. Capacitor

d. CMOS

A system that used scintillators that convert x-rays to light, light to electric charge, and store the charge in capacitors is known as the: a. CCD b. ADC c. Image Intensifier d. CMOS

unstructured

An _____ phosphor will produce more light spread when stimulated by x-rays thereby decreasing the efficiency of the detector.

gadolinium sulfur dioxide scintillators

Another way CCDs are used in a whole body scanner, where 12 CCD cameras are coupled to ________ with tapered fiber optics.

100

Because dark noise can be as much as 10,000 electrons/pixel per second, and a 40 degree drop can reduce dark noise by a factor of ____.

5 cm x 5 cm

Because of high cost of a CCD chip, it is not practical to manufacture CCD chips any larger than _______.

electron scanning errors

CCDs are much more compact than TV tubes and CCDs are no susceptible to _____________ the way that TV tubes are.

capacitors

CMOS image sensors convert light into electrons. Electrons are stored in ____ located within each pixel.

CMOS

CMOS or CCD are more susceptible to noise.

needles

CSI _____ focus light onto a very narrow area, reducing light spread and allowing the use of thicker scintillators without losing too much spatial resolution.

temperature rises

Dark current noise happens when the ________ ________ and electrons are moved into the bulk silicon or depletion area and are stored until readout occurs later adding unnecessary information to the image.

complementary metal oxide semiconductor (CMOS)

Developed by NASA, _______ systems use a scintillator that, when struck with x-ray photons, convert x-rays into light photons and store them in capacitors.

size/ light to electrical charge

During the transmission process, the lenses reduce the ____ of the projected visible light image and transfer the image to one or more small capacitors that convert ______ to _______.

detector element (del)

Each pixel or _______ contains three electrodes that hold the electrons in a electrical potential wall.

amplifier

Each pixel or detector elements has its own _____, which is switched on and off by circuitry within the pixel, converting light photons into electrical charges.

N-type P-type

Extra electrons with a negative charge is a ___ transistor and positive charge carries ____ transistors.

dopants

Impurities, also known as _____, are added to semiconductors because the materials semiconductors are made from do not conduct electricity very well by themselves.

scintillation/ lenses or fiber

In a CCD system, x-ray photons interact with a ______ material and the signal is transmitted by _____ or _____ optics to the CCD.

television (TV) pick up tube

In digital flouro, the CCD is a great replacement for the ______ in an image intensifier because the CCD size is closely matched with the output phosphor of an image intensifier.

16 x 12

In general radiography, CCDS may be tiled in a _____ array to a single CCD.

intensity

Its ability to conduct current varies depending on the amount of current or voltage it receives or on the ______ of the radiation by x-rays.

CMOS than CCD CMOS

Light sensitivity of a ____ chip is lower than a ____. This is because ____ pixels are surrounded with transistors and many of the light photons hit the transistors rather than the photo diode.

a. True

Most CMOS detectors use both N-type and P-type transistors to form the electrically controlled gate. a. True b. False

2 to 4 cm

Most chips range from __ to __.

amplifier

Once the readout row is reached, the data are sent sequentially to the sense _____ and are then digitized.

scintillator, light collection components, and noise

Reducing the image size involves several factors that contribute to the quality of the image including _____, _____, and ______.

linear

The CCD readout is ____ and has a greater dynamic range than a TV tube; because over saturation is almost zero, blooming is greatly reduced, shortening recovery time from one image to another.

silicon dioxide/ silicon substrate

The _______ layer is an insulator and the _____ contains the charge storage area.

polysilicon

The _______ layer is coated with a photosensitive material and contains electronic gates.

spectrum sensitivity

The _______ of the CCD must match the spectral output of the phosphor. .

quantum efficiency

The amount of electrons produced relative to the incident light from the scintillator is the ______ of the CCD.

polysilicon layer, silicon dioxide layer, silicon substrate

The chip is made up of a ______ layer, _____ layer, and a _____.

voltage gates/ electrons

The dels are formed by _______ that, at readout, are opened and closed like gates to allow the flow of _____.

lenses, optics, and mirrors

The demagnification uses ____, ____, and ____ to accomplish this.

optics

The design of the _____ is crucial in imaging performance because of the issues that arise with geometric distortion such as light scattering or lens or optic flaws. It is also critical to the quality of the image.

electrostatic forces

The electrons are held by _______ in the array until the charge is read out to from the image.

CCD

The image has to be matched to the size of the ____, which implies that the image must be reduced in size.

c. Silicon dioxide layer

The insulating layer in a CCD chip is the: a. Polygonal layer b. Silicon substrate c. Silicon dioxide layer d. Monosilicon layer

b. Polysilicon layer

The layer in a CCD chip that contains the electron gates is the: a. Silicon dioxide layer b. Polysilicon layer c. Silicon substrate d. All of the above

less

The less sensitive the CCD is to light spectrum of the scintillator the ___ efficient the CCD is

efficient

The more light that is sent to the chip without the creation of noise, the more _____ the system is.

silicon

The most popular semiconductor material is ____ and is the base material or most integrated circuits.

light

The number of electron/hole pairs is related to the amount of ______ that is absorbed.

a. Light absorbed

The number of electron/hole pairs is related to the amount of: a. Light absorbed b. Electric charge c. Incident x-rays d. Reflected light

charge-coupled devices (CCDS)

The oldest indirect conversion digital radiography systems used ________ to acquire the digital image.

light/signal

The quantum efficiency represents the absolute efficiency of the ____ collection and the ____ created in the chip.

modular design demagnification issues/reduced DQE

The strongest advantage of CCDS is their ______, and the greatest disadvantage relates to ____ and ____.

scintillator

The type of _______ and the way it is constructed will determine how much of the incident x-ray photons are absorbed, how much light produced, and wavelength or color of the light.

statistical noise, "dark" current noise, amplification noise

There are several types of noise associated with CCD technology _____, ______, and _____.

electrons

There can be issues with overfill in the dels, which causes excessive _____ to spill out of the del into an adjacent del.

analog-to-digital converter (ADC)

This charge is stored in a sequential pattern and released line by line and sent to an ___________.

"blooming"

This is handled by building overflow drains into the array to reduce or prevent this "_____" effect.

readout row/ "bucket brigade scheme"

To collect the charge on the silicon chips, the voltage sign is changed on the electrodes within each del, moving the electrons by rows down the columns until the _______ is reached. This is known as what?

ADC

Voltage from the amplifier is converted by an ____.

CCD

Which is more expensive to manufacture CCD or CMOS?

b. CMOS

Which of the two technologies, CCDs or CMOS, is more susceptible to noise, has a lower light sensitivity, uses very little power, and is inexpensive to manufacture? a. CCD b. CMOS

CMOS

_____ have been manufactured for a shorter period of time and tend to have lower quality, lower resolutions, and lower sensitivity.

lenses or fiber optics

_____ or _____ are used to focus light onto the CCD chip.

Amplification Noise

______ is common to digital systems. There are no CCDS without this; however the number of defects rises as manufacturing costs decrease. The lower the cost of the CCD, the higher the number of defects.

dark current noise

______ occurs when the CCD chip operates without radiation stimulation.

statistical noise

_______ is noise created by the lack of light photons from the scintillator.

Gadolinium oxysulphide and cesium iodide

________ is considered an unstructured phosphor because of its powder-like grains and ______ is considered a structured phosphor because of its needle like crystals.

Demagnification

________ is the process of reducing the phosphor output image to the size of the active area of the CCD chip.

Incident light

_________ from a scintillator strikes the detector and electron/hole pairs are produced in the silicon.