XDR Clarity Sensor Exposure Guidelines

Use XDR’s recommended exposure times as a guide for the specific anatomic area and according to the patient size ensures the adequate dose of radiation to fully penetrated all of the tissue being imaged before reaches the sensor to produce a diagnostic-quality radiograph.  

Understand your X-ray machine

There are four factors that determines the strength of your X-ray beam:

• kVp/kV: The kilovolt describes the energy level of the X-ray beam. On AC machines it is shown as peak kilo voltage, because the AC machines’ output is a range of energies; on DC machines this is at a consistent. The main difference between a DC vs AC X-ray machine is the DC’s consistent output of X-ray energies, therefore, the DC machine doesn’t produce soft X-rays like the AC machines and is healthier for the patient. This kV value is usually fixed on most X-ray machines, some machines will vary the kV dependent on the specific anatomic area. Dense tissue will require a higher kV, and a lower kV will increase the image contrast.
• mA: The milliamp determines how many X-ray photons are generated at the anode of the X-ray machine. This is usually fixed for most machines. Dense tissue will require a higher mA. Some older X-ray machines will vary the mA on their presets.

• Exposure Time: Controls how long X-ray photons are produced. Denser anatomic areas will require a longer exposure time compared to a less dense area to produce a diagnostic X-ray.  Most modern X-ray machines give exposure time in second or milliseconds in decimals, some older X-ray machines will give exposure time in fractions of a second (i.e.1/2 sec, 1/10 sec, 1/60 sec); there are some that use pulses, like the Gendex 770 – a pulse is 1/60 second, it is equal to .016 sec. 

• Distance: X radiation strength decreases as the square of the distance between the end of the cone and the subject; therefore, it is crucial when using any aiming device to slide the aiming ring as close to the skin of the patient as possible, this also applies to “Snap-a-Ray” type holders. 

XDR Clarity sensor exposure ranges

DC/Wall Units 60- 70 kVp and 4-10 mA

Portable Handheld Units 60-70 kVp and 1.7-3 mA

Portable handheld X-ray machines have gained popularity lately, the main difference is the lower mA output at around 2 mA compared to the wall mounted units at 6-10 mA; to compensate for this difference in the number of X-ray photons produced, a longer exposure time is required for the same image quality relative to a wall mounted unit. 

To optimize the image quality of the X-ray, the clinician is responsible for selecting the appropriate kV, mA, and exposure time relative to the specific anatomic area to be imaged. 

A step-by-step approach to adjusting exposure times

1. Start Low:  Begin with the lower range of recommended exposure time settings for the desired anatomic area you are imaging.
2. Check the XDR Exposure Meter after the initial image:  See where the black pointer shows on the exposure meter.   
   
3. Adjust: Increase or decrease the exposure time as needed. Remember, there's no "one size fits all" exposure time, as patient size and anatomic densities vary. The provided exposure times are a starting point for average-sized patients with full dentition.  
4. Target the Green:  Aim to get the black pointer minimally into the green zone on the XDR exposure meter. This unique XDR sensor feature helps ensure optimal exposure and resultant image quality.  
5. ALARA:  By following this process, you're also adhering to ALARA principles (As Low As Reasonably Achievable), minimizing excess patient radiation exposure.

The effect of X-ray exposure time on radiographic image quality

The following examples illustrate the impact of exposure time on image quality.

Under-Exposure

Insufficient exposure time leads to grainy image, making it challenging to visualize anatomic details.

Exposure time is LOW

• Cause: Insufficient exposure time leads to fewer X-ray photons reaching the receptor.
• Effect: The image appears to lack contrast or washed out, often vertical lines are present, with poor delineation of anatomic details resulting in an undiagnostic radiograph

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Over-Exposure

Excessive exposure time results in a muddy looking dark image, obscuring critical information and reducing diagnostic accuracy. Cervical burnout will often be present on an over-exposed image.

Exposure time is HIGH

• Cause: Excessive exposure time results in too many X-ray photons hitting the receptor.
• Effect: The image appears too dark, with reduced contrast and potential loss of detail. This can also lead to unnecessary radiation exposure for the patient.

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Optimal Exposure

A properly exposed image will exhibit fine anatomic detail and dynamic range, the exposure meter will indicate a reading within the green zone.

Exposure time is GOOD

• Cause: Appropriate exposure time provides enough X-ray photons to reach the receptor and produce a well-exposed image.
• Effect:  The resultant image has good density, dynamic range, and contrast, allowing for a diagnostic radiograph delineating normal anatomical structures and potential pathologies.