Metrology

The Welsh abdominal aortic aneurysm screening programme (WAAASP) in UK invites all men aged 65 to have an abdominal ultrasound scan performed at one visit to a screening centre.
The programme employs technicians that only perform this type of scan. There are normally 3 or 4 technicians at each screening centre, there are 3 separate screening technician teams, one each for North Wales, South West and South East Wales. All the teams move around different centres within each region.
The measurement value used to determine whether an aneurysm is present or not is 3cm.
3cm or above on the scan means that you have an aneurysm and that you will have regular scans from then on, or referral to a vascular surgeon if the aneurysm is 5.5cm or larger.
Under 3cm means no further scans are required.
Using appropriate vocabulary and terminology, describe what type of variations in measurements may occur when using ultrasound scans to screen a population for abdominal aortic aneurysms and how these variations may be predicted and dealt with. (70% x total marks)
Discuss the implications of the programme on individuals having the scan. (30% x total marks)

The essay should be around 2000 words
No less than 20 references
Figures may be included (up to a maximum of 5) with a descriptive title and legend.
Please cite all sources and produce a reference list in Harvard style.