Alzheimer's Disease

Alzheimer's disease is a progressive neurologic disease of the brain leading to the irreversible loss of neurons and the loss of intellectual abilities, including memory and reasoning, which become severe enough to impede social or occupational functioning. Alzheimer's disease is also known as simply Alzheimer's, and Senile Dementia of the Alzheimer Type (SDAT) .

Osteoporosis

The bones of people with osteoporosis become thin and weak. The word "osteo" comes from the Greek osteon meaning "bone", while "porosis" comes from the Greek poros meaning "hole, passage". According to Medilexicon's medical dictionary, osteoporosis is a "reduction in the quantity of bone or atrophy of skeletal tissue; an age-related disorder characterized by decreased bone mass and loss of normal skeletal microarchitecture, leading to increased susceptibility to fractures."

Pixel Count (Resolution)

Differences in cameras is responsible for differences in pixel count. With resolution ranging from 512 x 512 to 1024 x 1024, not all cameras are equal. The pixel count of a CCD camera in an OEC 9800, for example, is 980 x 980, 768 x 494 in a Quantum or 1024 x 1024 in a Pulsera or Ziehm Vision.

X-Ray TV Camera

Initial C-arms made by market leader OEC, the OEC 9000 and OEC 9400, both used analog (Vidicon) cameras. Other vendors such as Philips and Siemens and Ziehm used CCD cameras. Today almost all C-arms have CCD cameras. These high-quality lens' provide more light to the camera. Ziehm introduced a spectrally responsive CCD camera that translate to a more sensitive camera requiring less dose.

Collimation

OEMs differ on methods of collimation. Types used include: translucent blades, solid tungsten shutters, full lead shutters.  The translucent blades with tapered edges permit soft tissue visualization around long bone or spine and aids in placement of needle and screw alignment. Nearly all C-arms have both iris and parallel shutter positions and ratation indicators.

Anode Heat Capacity and Cooling

Heat capacity and dissipation are limiting factors in heat management. Higher heat capacity in the housing generally translates to the ability to do many high dose procedures back to back. As many practices schedule high patient volume on specific days of the week, this is an important consideration. Also important is the anode cooling rate.

Anode Tubes

The combination of power (kW), anode angle and focal spot size dictate the use of stationary or rotating anodes. Mobile C-arm fluoroscopic applications are sufficiently handled by a stationary anode and 0.6mm focal spot. The use of 0.3mm focal spot mandates the use of a rotating anode.  

Focal Spot Fluoro

Focal spot size, measured in mm. directs image quality to a large extent. The smaller the focal spot, the better the image resolution. However, it is important to consider the image matrix of the system. For example, a 1k x 1k matrix with 0.3mm focal spot will produce approximately the same resolution as a 0.6mm focal spot at object-to-image distances of 40cm or less. Therefore, in C-arm imaging with 1k x 1k matrix, the performance of a 0.6mm is equal to a 0.3mm.

Image Intensifier

The standard image intensifier is 9"/6". Most systems built after mid-90s have tri-mode IIs with 9"/6"/4.5" IIs.  When considering field of view, it can be said that the smalles, 4.5" is not clinically necessary and not worth the trade-off of higher dose. Manufacturers use technical aspects of the camera and lens assembly in order to more efficiently provide an image, some resulting in comparatively lower dose in the 4.5 field of view.

Digital Cine

8 to 15 frames per second (f/s) is considered sufficient for vascular procedures. Some cases of neurovascular or cardiac nature may require 30 f/s. In general, however, lap chole, ERCP and other general surgery applications are well served by slower acquisition speeds.

Pulsed Fluoro Rates

The best specifications for superior pulsed fluoro rates would be those that gave a wide range of pulse rate selections. Ideally, rates should exceed 8 pps because that is the rate at which an image starts to appear continuous to the naked eye. There are significant differences in pulse rates between various C-arms.

For vascular, cardiac, bolus chase application 15 and 30 pps rates are  used to acquire cine. These applications are almost always options to standard C-arms.

Pulsed Fluoroscopy

The primary purpose of pulsed fluoro is for dose reduction. The secondary purpose is reduction of blurring while imaging moving anatomy. Some systems allow pulse mode to be used with higher mA values to improve image quality.

Digital Radiology

DR mode is commonly know as Snapshot or One-Shot mode. It is a single, brief exposure made at higher than normal mA to capture a higher quality single image.

Deep Oblique Views

Higher mA output provides better visualization of dense anatomy by reducing noise in the image, given appropriate penetration by kV output.  Maximum mA values by themselves can be misleading. Maximum wattage values allow calculation of maximum mA at a given kV. Knowing the maximum kV output for fluoroscopy mode is essential for ensuring adequate penetration of dense anatomy such as deep oblique views and lateral views of the lumbar spine.

High Level Fluoro

High Level Fluoro technique used for when higher power is needed in dense anatomy (obese patients) typically does not exceed 1 - 1.2 kW. For example, 80 kV @ 12.5 mA. This is important as federal limit on HLF (high level fluoro) dose rate is 20R/min. HLF is designed to run higher level fluoroscopy to improve anatomical visualiztion while decreasing patient dose. Some systems like the Ziehm Quantum, when using a 30 ms. pulse width, actual dose mA to the patient is reduced by a factor of nearly one-third.

Real-time Fluoroscopy

 Mobile C-arms use standard real-time fluoroscopy. Generally fluoro techniques are usually 1.5 mA @ 60-100 kV  (.06 kW - .5 kW). This it can be concluded that most surgical imaging is accomplished at power outputs of less than 2 kW.  Standard C-arms, beginning with the OEC 9000, BV 25, and Ziehm 7000 series architectures have generators exceeding 2.5 kW and are thus sufficient for many procedures.


See HIGH LEVEL FLUORO

Depth of C

The depth of the C (or free space), is an important consideration. The higher the free space, the more likely the user will be able to position the C around larger patients and tables. Also, more working space will be available for the physician. The OEC 9800 Super C is an example of a C-arm with extra large depth. 

Generator Power

Nearly all c-arms have high-frequency generators, however, over the years the power ratings have increased from system to system. Generally speaking, the more powerful the general, the better penetration that can be achieved.