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An Amateur's View of MQSA. Victor E. Anderson, C.H.P. Radiologic Health Branch California Department of Health Services. The Circle Problem. Inspectors are required by eye to determine if a part is “out of round”, e.g., not a circle. Not a hard process, unless you define “roundness.”.

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an amateur s view of mqsa

An Amateur's View of MQSA

Victor E. Anderson, C.H.P.

Radiologic Health Branch

California Department of Health Services

the circle problem
The Circle Problem
  • Inspectors are required by eye to determine if a part is “out of round”, e.g., not a circle.
  • Not a hard process, unless you define “roundness.”
mammography
Mammography
  • Similar problem:
    • Is it a cancer or ?
  • Some Factors
    • Quality of image
    • Skill of interpreter
    • Size of tumor mass
    • Physical/Psychological
problem
Problem
  • Screening test.
    • Not expected to detect every tumor
  • When does the interpreter and system fail?
    • Easy answer: does it meet MQSA Standards?
  • What about false negatives and positives?
facility failure
Facility Failure
  • How bad is bad?
  • Or “How many cancers went undetected that should have been seen?”
  • Two interrelated areas:
    • Physical factors (“Physics”)
    • Ability of the Interpreter
review actions
Review Actions
  • How far back in time does the problem go?
    • Previous inspections
    • Clinical Image Reviews
  • MQSA records
    • Image Quality
    • Interpreter skill (Additional Mammography Review)
how many
How Many?
  • Typically 30 additional cases.
  • Breast Cancer Rate
    • Various with age
    • About 0.008 on the average per screening
  • Out of 1,000 cases, eight may have detectable cancer!
rates and sampling
Rates and Sampling
  • Mammography facilities see lots of patients.
  • As much as 20 per day per machine.
  • About 100 per week per machine.
  • A ten machine facility could find about eight cases per week.
  • What is bad?
false negatives
False Negatives
  • Indications are that
    • For every eight
    • About two will be missed.
  • Given a poorly performing facility
    • How many films to review?
    • How bad is bad?
how far back
How Far Back?
  • Ideally no further than last inspection.
  • Indicators
    • Daily checks
    • Physics reports
    • Referrals
    • CIR
    • AMR
one testing solution
One Testing Solution
  • Make a time estimate.
  • Using average rates, determine number of cases seen.
  • Total number of films.
  • How big a sample?
sample size
Sample Size
  • Mil spec tables or AQL
    • Period of potential sub standard performance is 10 weeks.
    • Four machine facility.
    • 4,000 patients.
    • AQL table indicates 200 samples with an acceptance level of one false negative.
    • And a rejection level of two false negatives.
issues
Issues
  • Cost of sample size.
  • What is at stake?
  • Rational assurance that proper screening occurred.
  • Follow up
conclusions
Conclusions
  • MQSA provides good QA/QC
  • Need Sampling scheme to follow up.
  • Provide rational basis for extent of a problem with respect to time.
  • How many patients to notify?
  • Aid in corrective actions.
references
References
  • False-negative breast screening assessment: what lessons can we learn?, Burrell HC, Evans AJ, Wilson AR, Pinder SE., Clin Radiol 2001 May;56(5):385-8
  • Comparison of full-field digital mammography with screen-film mammography for cancer detection: results of 4,945 paired examinations., Lewin JM, Hendrick RE, D'Orsi CJ, Isaacs PK, Moss LJ, Karellas A, Sisney GA, Kuni CC, Cutter GR., Radiology 2001 Mar;218(3):873-80
  • The evaluation of false negative mammography from malignant and benign breast lesions., Wang J, Shih TT, Hsu JC, Li YW., Clin Imaging 2000 Mar-Apr;24(2):96-103
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