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  1. Nationwide Evaluation of X-Ray Trends (NEXT)

NEXT Data Summaries

Each year the NEXT survey program selects a particular radiological examination for study and collects radiation exposure data from a nationally representative sample of U.S. clinical facilities. Surveys are repeated periodically to track trends as technology and clinical practices change. Since 1973, NEXT has been conducting surveys on examinations related to the adult chest, abdomen, lumbosacral (LS) spine, upper gastrointestinal fluoroscopy, mammography, computed tomography, dental radiography, and pediatric chest radiography. The following is a breakdown by year of the NEXT surveys that have been performed and the corresponding number of facilities surveyed:

Next Surveys Performed

Survey YearSurvey TypeNumber of Facilities Surveyed
1984Adult Chest429
1986Adult Chest (Private Practice)137
1987Abdomen and Lumbosacral (LS) Spine (Hospitals)496
1989Abdomen and LS Spine (Private Practice)374
1990Computed Tomography264
1991Upper GI Fluoroscopy373
1993Dental Radiography322
1994Adult Chest314
1995Abdomen and LS Spine240 Abdomen / 320 LS Spine
1996Upper GI Fluoroscopy344
1998Pediatric Chest397
1999Dental Radiography342
2000Computed Tomography265
2001Adult Chest220
2002Abdomen and LS Spine*200
2003Upper GI Fluoroscopy*

*As of 8/03       

The NEXT surveys today capture comprehensive data on radiation exposure and image quality associated with the practice of medical diagnostic radiology. Among the data obtained are the evaluations of film processing quality, the integrity of the film processing darkroom environment, x-ray film-image quality, and information about the facility's general practice.

The following are data summary tables for the NEXT exams that have been performed:

Adult Chest Exam

Number of Facilities220314137429
Entrance Air Kerma (mGy)
Clinical kVp10910187104
Exposure Time (ms)29316422
Percent Using Grids93793271
Phantom Film Optical Density1.641.671.421.43

Abdomen Exams

Number of Facilities*200240374496
Entrance Air Kerma (mGy)2.732.823.393.23
Clinical kVp75767875
Exposure Time (ms)306145371247
Phantom Film OD1.831.741.731.80
Half-Value Layer (mm Al)


Lumbosacral Spine Exams

Number of Facilities*200320374496
Entrance Air Kerma (mGy)
Clinical kVp78788077
Exposure Time (ms)351145371247
Phantom Film Optical Density1.411.321.261.15
Half Value Layer (mm Al)

*As of 8/03

Fluoroscopy- Upper GI Exam and Special Topics

Number of Facilities3212552320
TypeUpper GICardiac Catch LabsMobile C-Arm UnitsUpper GI
Entrance Air Kerma Rate (mGy/min)45382243
Clinical kVp998278102
Tube Current (mA)
Air Kerma Rate with  contrast* (mGy/min)67714165
Maximum Air Kerma Rate (mGy/min)70744467

*Copper is used to simulate the presence of barium contrast

Pediatric Chest Exam

Number of Facilities397
Entrance Air Kerma (mGy).051
Clinical kVp71
Exposure Time (ms)12
Percent Using Grids9.0
Phantom Film Optical Density1.73
Patient Restraint Method Most Frequent UsedAdult
Percent AP / Percent PA40/60

Dental (Intraoral) Exam

Number of Facilities342320
Entrance Air Kerma (mGy)1.601.90
Clinical kVp7172
Percent Manual Film Processing10.029.0
Phantom Film Optical Density1.491.48
Percent using D-speed Film6590

Computed Tomography

Head Exam (axial scanning)

MSAD (mGy)50.345.9
Effective Dose (mSv)1.2--

Body Exams (helical scanning) - Effective Dose (mSv)


Darkroom Fog and Film Processing

Darkroom fog is a measure of optical density on clinical radiographs that results from ambient light conditions in the darkroom.  Darkroom fog can result from light leaks, improper safelight conditions from the use of inappropriate bulbs or damaged filters, and from inadvertent exposure during film storage or handling.

The quality of film processing is evaluated by a procedure known as the "Sensitometric Technique for the Evaluation of Processing" or STEP. This test utilizes a selected control batch of radiographic film with a pre-determined sensitometric curve when processed according to film manufacturer recommendations. The control film is flashed by a sensitometer and then processed the same way as film is processed normally at the facility. A comparison is made of the optical densities obtained at the facility with what should be obtained were the control film processed as required by the film manufacturer. Any deviation of the control film optical density produced at the facility from what should be obtained were the facility processing according to the "gold standard" determines the extent of under- or over-processing of the film by the facility. The resulting processing speed value is then determined, with a speed range of 80 to 120 considered acceptable for standard cycle processing. Under processing, which corresponds to a processor speed value of below 80, is an inefficiency that maybe inappropriately compensated with increased radiation exposure to patients.

The following is an overall survey comparison of Film Processing and Darkroom Fog:

YearSurvey TypeNMean Processing SpeedPercent (%) of Under-processing**Darkroom Fog (OD)
1984Chest (Hospitals)4089618.9N/A
1986Chest (Private Practice)998640.4N/A
1987Abdomen/LS Spine (Hospitals)2618837.2N/A
1989Abdomen/LS Spine (Private Practice)3018941.9N/A
1994Chest (Hospitals)1341154.50.09
1994Chest (Private Practice)14810715.50.11
1995Abdomen/LS spine (Hospitals)141987.20.09
1995Abdomen/LS Spine (Private Practice)17892270.12
1995Abdomen/LS Spine (Chiropractic)628737.10.09
1998Pediatric Chest3801005.60.13
2002Abdomen/LS Spine (Hospitals)411074.20.09
2002Abdomen/LS Spine (Private Practice)901046.70.14
2002Abdomen/LS Spine (Chiropractic)151025.30.07

*Results are from MQSA inspections
**The range of acceptable processing speed is 80 to 120 (standard cycle), and 100-130 (extended cycle)

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