***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: This paper presents a new method for deformable model-based segmentation of lumen and thrombus in abdominal aortic aneurysms from  computed tomography ( CT ) angiography ( CTA ) scans .  First the lumen is segmented based on two positions indicated by the user , and subsequently the result ing surface is used to initialize the automated thrombus segmentation method . For the lumen , the image-derived deformation term is based on a simple grey level model ( two thresholds ) . For the more complex problem of thrombus segmentation , a grey level modeling approach with a nonparametric pattern classification technique is used , namely k-nearest neighbors . The intensity profile sample d along the surface normal is used as classification feature . Manual segmentations are used for training the classifier : sample s are collected inside , outside , and at the given boundary positions . The deformation is steered by the most likely class corresponding to the intensity profile at each vertex on the surface . A parameter optimization study is conducted , followed by experiments to assess the overall segmentation quality and the robustness of results against variation in user input . Results obtained in a study of 17 patients show that the agreement with respect to manual segmentations is comparable to previous values reported in the literature , with considerable less user interaction Screening for abdominal aortic aneurysm ( AAA ) is commonly restricted to men . Recent studies have indicated a possible increase in deaths due to ruptured AAA in women , and a higher rate of rupture in women than in men . The present report details results from a r and omized controlled trial that assessed the effects of screening women for AAA BACKGROUND Opposing views have been published on the importance of ultrasound screening for abdominal aortic aneurysms . The Multicentre Aneurysm Screening Study was design ed to assess whether or not such screening is beneficial . METHODS A population -based sample of men ( n=67800 ) aged 65 - 74 years was enrolled , and each individual r and omly allocated to either receive an invitation for an abdominal ultrasound scan ( invited group , n=33839 ) or not ( control group , n=33961 ) . Men in whom abdominal aortic aneurysms ( > or =3 cm in diameter ) were detected were followed-up with repeat ultrasound scans for a mean of 4.1 years . Surgery was considered on specific criteria ( diameter > or = 5.5 cm , expansion > or = 1 cm per year , symptoms ) . Mortality data were obtained from the Office of National Statistics , and an intention-to-treat analysis was based on cause of death . Quality of life was assessed with four st and ardised scales . The primary outcome measure was mortality related to abdominal aortic aneurysm . FINDINGS 27147 of 33839 ( 80 % ) men in the invited group accepted the invitation to screening , and 1333 aneurysms were detected . There were 65 aneurysm-related deaths ( absolute risk 0.19 % ) in the invited group , and 113 ( 0.33 % ) in the control group ( risk reduction 42 % , 95 % CI 22 - 58 ; p=0.0002 ) , with a 53 % reduction ( 95 % CI 30 - 64 ) in those who attended screening . 30-day mortality was 6 % ( 24 of 414 ) after elective surgery for an aneurysm , and 37 % ( 30 of 81 ) after emergency surgery . INTERPRETATION Our results provide reliable evidence of benefit from screening for abdominal aortic aneurysms Abdominal aortic aneurysm ( AAA ) meets the criteria as a possible target for early detection by screening or case-finding , although the effectiveness of such an intervention has not yet been demonstrated . The purpose of this study was to estimate the increase in cost-effectiveness that would result from selectively screening individuals based on their risk of AAA . Data from a hospital-based case-control study involving 78 men with AAA ( unruptured ) and 99 male controls were used to derive a risk function based on age , cigarette smoking , high blood pressure , history of heart disease , body mass index and serum high-density lipoprotein , using logistic regression analysis . For each of the control subjects ( assumed to be a representative sample of the general population of elderly men ) , the risk of AAA was estimated and multiplied by the expectation of life to give a measure of the potential benefit of screening . The proportion of the total potential benefit that would be obtained by screening only those with a given level of risk was estimated , and this was related to the proportion of the population screened . In order to obtain 80 % of the total potential benefit among men , we found that it would be necessary to examine 52 % of the elderly male population if using a risk function based on age alone ; 35 % would have to be screened if age and smoking were included ; and 17 % would require screening if all the risk factors were included . Selective screening for AAA appears to be a promising strategy , but a prospect i ve study is required to demonstrate that the predictions are valid OBJECTIVE We compared long-term health-related quality -of-life outcome after r and omization to immediate elective repair or imaging surveillance , and in relation to time of elective repair , in patients with small asymptomatic abdominal aortic aneurysm ( AAA ) . METHODS This r and omized clinical trial was carried out in 16 Veterans Affairs medical centers . Study subjects were patients at good surgical risk , aged 50 to 79 years , with AAAs 4.0 to 5.4 cm in diameter . Interventions included immediate open surgical AAA repair or imaging surveillance every 6 months with repair reserved for AAAs that became symptomatic or enlarged to 5.5 cm . Main outcome measures considered were SF-36 health status question naire , prevalence of impotence , and maximum activity level , which were determined at r and omization and at all follow-up visits . RESULTS Eleven hundred thirty-six patients were r and omized and followed up for 3.5 to 8 years ( mean , 4.9 years ) . The two r and omized groups did not differ significantly for most SF-36 scales at most times , but the immediate repair group scored higher overall in general health ( P < .0001 ) , which was particularly evident in the first 2 years after r and omization , and slightly lower in vitality ( P < .05 ) . The baseline value of one SF-36 scale , physical functioning , was an independent predictor of mortality . Overall , more patients became impotent after r and omization to immediate repair compared with surveillance ( P < .03 ) , but this difference did not become apparent until more than 1 year after r and omization . Maximum activity level did not differ significantly between the two r and omized groups , but decline over time was significantly greater in the immediate repair group ( P < .02 ) . CONCLUSIONS For most quality -of-life measures and times there was no difference between r and omized groups . Immediate repair result ed in a higher prevalence of impotence more than 1 year after r and omization , but was also associated with improved perception of general health in the first 2 years OBJECTIVES to analyse the hospital costs and benefits of screening  older males for abdominal aortic aneurysm ( AAA ) . MATERIAL S AND METHODS in 1994 a hospital-based screening trial of 12 658 65 - 73-year-old males was started . AAA > 5 cm were referred for surgery . The remaining AAA were offered annual scans . Those with aortic ectasia were rescreened at 5 yearly intervals . AAA-operations and hospital AAA-related deaths were research ed . The costs of screening , surveillance , and treatment  were also registered . RESULTS the attendance rate was 76 % ; of whom 191 ( 4.0 % ) had AAA . Mean observation time was 5.13 years . Sixty in the screened and 41 in the control group were operated ( p=0.06 ) , of which 7 and 27 respectively were operated as an emergency ( p<0.001 ) , and 6 and 19 respectively died due to AAA ( p=0.009 ) . The costs per scan were 83.50 DKK , 81 400 DKK per emergency operation ( 71 485 DKK after screening ) , and 117 000 DKK per emergency operation . The cost per prevented hospital death was 67 855 DKK , equivalent to approximately life year saved approx . 7540 DKK ( GBP1=12 DKK ) . CONCLUSION screening appears to reduce hospital AAA mortality and to be cost-effective OBJECTIVE To describe the potential psychological consequences of screening for abdominal aortic aneurysms ( AAAs ) . METHODS The participants were prospect ively and r and omly sample d from a r and omised screening trial for AAA and asked to complete a vali date d generic and global anonymous quality of life ( QL ) question naire by self- assessment ( ScreenQL ) . Material case-control study : ScreenQL was completed once by 168 ( 48 % ) of 350 non-responders to screening  , 271 ( 81 % ) of 335 attenders before screening , 286 ( 85 % ) of 335 attenders after screening , 127 ( 85 % ) of 149 with a small AAA diagnosed at screening , and 231 ( 66 % ) of 350 who were r and omised not to be offered screening for AAA ( controls ) . Prospect i ve study ( paired data ): 127 men having a small AAA diagnosed . Twenty-nine ( 81 % ) of 36 men operated after initial conservative treatment . RESULTS Initially , the QL score was 5 % lower among men with a small AAA compared to the controls ( p<0.05 ) , mainly because of poorer health perception . The QL score declined significantly further to 7 % below control values during the period of conservative treatment . This impairment was mainly due to a 21 % and 15 % reduction in scores relating to health perception and psychosomatic distress , respectively . However , all scores improved to control levels in patients operated on . The QL of attending men for screening was significantly lower than that of the controls and the attenders after the screening . No differences were noticed concerning the non-attenders . CONCLUSION The offer of screening causes transient psychological stress in subjects found not to have AAA . However , diagnosis of an AAA seems to impair QL permanently and progressively in conservatively treated cases . This impairment seems reversible by operation . Nevertheless , the impairment seems considerable , and must be considered in the management of AAA and in the final evaluation of screening for AAA OBJECTIVE To assess whether screening for abdominal aortic aneurysms in men reduces mortality . DESIGN Population based r and omised controlled trial of ultrasound screening , with intention to treat analysis of age st and ardised mortality . SETTING Community based screening programme in Western Australia . PARTICIPANTS 41,000 men aged 65 - 83 years r and omised to intervention and control groups . INTERVENTION Invitation to ultrasound screening . MAIN OUTCOME MEASURE Deaths from abdominal aortic aneurysm in the five years after the start of screening . RESULTS The corrected response to invitation to screening was 70 % . The crude prevalence was 7.2 % for aortic diameter > or = 30 mm and 0.5 % for diameter > or = 55 mm . Twice as many men in the intervention group than in the control group underwent elective surgery for abdominal aortic aneurysm ( 107 v 54 , P = 0.002 , chi2 test ) . Between scheduled screening and the end of follow up 18 men in the intervention group and 25 in the control group died from abdominal aortic aneurysm , yielding a mortality ratio of 0.61 ( 95 % confidence interval 0.33 to 1.11 ) . Any benefit was almost entirely in men aged between 65 and 75 years , where the ratio was reduced to 0.19 ( 0.04 to 0.89 ) . CONCLUSIONS At a whole population level screening for abdominal aortic aneurysms was not effective in men aged 65 - 83 years and did not reduce overall death rates . The success of screening depends on choice of target age group and the exclusion of ineligible men . It is also important to assess the current rate of elective surgery for abdominal aortic aneurysm as in some communities this may already approach a level that reduces the potential benefit of population based screening PURPOSE Over the past 20 years , there have been numerous advances in our ability to detect and to treat abdominal aortic aneurysms ( AAAs ) . We hypothesized that these advances would lead to ( 1 ) an increase in the rate of elective repair and a decrease in the incidence of ruptured AAA ( rAAA ) and ( 2 ) a decrease in operative deaths for both elective AAA ( eAAA ) and rAAA . METHODS To test these hypotheses , we investigated the incidence and outcomes of  eAAA and rAAA surgery between 1979 and 1997 , using the National Hospital Discharge Survey .  This data set is a r and omized , stratified sample representing discharges from the nation 's acute care , nonfederally funded hospitals . Codes from the International Classification of Diseases , Ninth Revision were used to identify our study population . RESULTS Over the past 19 years , there has been no change in the incidence rate of eAAA repair ( range , 44.1 - 77.9 per 100,000 ) . Moreover , the incidence of rAAAs presenting to the nation 's hospitals has not changed ( range , 6.6 - 16.3 per 100,000 ) . There has been no consistent improvement over time in operative deaths 
    Output:
    
Questions asked : Is population -based AAA screening effective in improving health outcomes in asymptomatic population s?Is AAA screening acceptable to the population ?
SUMMARY OF FINDINGS  Population -based ultrasound screening  is effective in men aged 65 to 74 years , particularly in those with a history of smoking .
Screening reduces the incidence of AAA ruptures , and decreases rates of emergency surgical repair for AAA and AAA-attributable mortality .
Acceptance rates decline with increasing age and are lower for women .
Low acceptance rates may affect the effectiveness of a screening program .
A one-time screen is sufficient for a population -based screening program with regard to initial negative scans and development of large AAAs .
There is no difference between early elective surgical repair and surveillance for small aneurysms ( 4.0 - 5.4 cm ) .
Repeated surveillance of small aneurysms is recommended .
There is evidence suggesting that screening women for AAA should be considered with respect to mortality and case fatality rates in Ontario .
There is a small risk of physical harm from screening .
There is little evidence of severe psychological harms associated with screening .
Based on this review , the Medical Advisory Secretariat concluded that there is sufficient evidence to determine that AAA screening using ultrasound is effective and reduces negative health outcomes associated with the condition .
Moreover , screening for AAA is cost-effective , comparing favorably for the cost of per life year gained for screening programs for cervical cancer , hypertension , and breast cancer that are in practice in Ontario , with a high degree of compliance , and can be undertaken with a minimal effort at fewer than 10 minutes to screen each patient .
Overall , the clinical utility of an invitation to use ultrasound screening to identify AAA in men aged 65 to 74 is effective at reducing AAA-attributable mortality .