"has been gradually implemented" is correct and usable in written English.
You could use it to describe a process that's been happening over a long period of time, such as: The new health and safety regulations have been gradually implemented over the past five years.
The Dutch screening program for breast cancer has been gradually implemented in the North Netherlands since 1991.
Since its publication in 2001, the ICF has been gradually implemented in a variety of settings and sectors.
13 14 Since then organised screening has been gradually implemented, with all women aged 50-69 inviteveryery two years.
In more recent years (from 2003 onwards), chromoendoscopy has been gradually implemented where pancolonic dye spray was used to highlight abnormal mucosa for targeted biopsy.
The international guidelines of IPF and IIP in 2000 and 2002 recommended that NSIP should be separated from IPF, which has been gradually implemented into the clinical practice during the 2000s.
Second, extensive prehospital field-triaging using ECG telemedicine has been gradually implemented in order to identify patients with ST segment elevation myocardial infarction (STEMI) in the ambulance enabling swift transportation to invasive heart centres.
In recent decades, TMD systems have been gradually implemented to control train-induced structural vibration.
EHR system functional requirements and standards have been used successfully in the past to specify system behavior, the criteria of which have been gradually implemented in EHR systems through certification programs and other national health IT strategies.
The research was released as debate continues over the standards, which have been gradually implemented since the fall of 2012 and require schools to serve more fresh fruit, vegetables, and whole grains and to limit calories, fat, and sodium in their federally subsidized meals.
Since their introduction into the European market in 2002, DES have been gradually implemented in clinical practice in Italy, mainly by hospitals in the north of the country.
The reduction in median LOS from 6 days to 3 days in the national cohort indicates that fast-track programs had been gradually implemented during the entire study period, but we have no information about which fast-track components were involved and when.
