Detectors can be divided into two major categories: imaging detectors (such as photographic plates and X-ray film (photographic film), now mostly replaced by various digitizing devices like image plates or flat panel detectors) and dose measurement devices (such as ionization chambers, Geiger counters, and dosimeters used to measure the local radiation exposure, dose, and/or dose rate, for example, for verifying that radiation protection equipment and procedures are effective on an ongoing basis).

Projectional radiography relies on the characteristics of X-ray radiation (quantity and quality of the beam) and knowledge of how it interacts with human tissue to create diagnostic images.

X-rays are a form of ionizing radiation, meaning it has sufficient energy to potentially remove electrons from an atom, thus giving it a charge and making it an ion.

Areas on the image receptor that receive the most radiation (portions of the remnant beam experiencing the least attenuation) will be more heavily exposed, and therefore will be processed as being darker.

Conversely, areas on the image receptor that receive the least radiation (portions of the remnant beam experience the most attenuation) will be less exposed and will be processed as being lighter.

Contrast is determined by the kilovoltage (kV; energy/quality/penetrability) of the x-ray beam and the tissue composition of the body part being radiographed.

abdomen or chest), lower contrast is preferable in order to accurately demonstrate all of the soft tissue tones in these areas.

Geometric unsharpness increases proportionally to the focal spot size, as well as the estimated radiographic magnification factor (ERMF).

[9] In addition to using an anti-scatter grid, increasing the ODD alone can improve image contrast by decreasing the amount of scattered radiation that reaches the receptor.

Often a tube with a molybdenum anode is used with about 30 000 volts (30 kV), giving a range of X-ray energies of about 15-30 keV.

Conditions commonly identified by chest radiography include pneumonia, pneumothorax, interstitial lung disease, heart failure, bone fracture and hiatal hernia.

Chest radiographs are also used to screen for job-related lung disease in industries such as mining where workers are exposed to dust.

Unless a fractured rib is suspected of being displaced, and therefore likely to cause damage to the lungs and other tissue structures, an X-ray of the chest is not necessary as it will not alter patient management.

Computed tomography provides an overall better surgical strategy planning, and possibly less unnecessary laparotomies.

[14] The standard abdominal X-ray protocol is usually a single anteroposterior projection in supine position.

In case of trauma, the standard UK protocol is to have a CT scan of the skull instead of projectional radiography.

[15] These include: The body has to be rotated about 30 to 45 degrees towards the shoulder to be imaged, and the standing or sitting patient lets the arm hang.

This method reveals:[17] The lateral contour of the shoulder should be positioned in front of the film in a way that the longitudinal axis of the scapula continues parallel to the path of the rays.

[15] A projectional radiograph of an extremity confers an effective dose of approximately 0.001 mSv, comparable to a background radiation equivalent time of 3 hours.

In projectional radiography, general disease mimics include jewelry, clothes and skin folds.