Environmental costs of investigations

Hello

Can anyone point me in the direction of a resource which provides numbers for the environmental costs of investigations such as x-rays and ultrasound scans. I'm trying to demonstrate the environmental costs of a patient pathway and the financial/social/environmental savings of cutting out the unnecessary appointments and investigations. I've been using the SDUs carbon hotspots for the appointment data but cannot find anything on the environmental costs of x-rays and ultrasounds. 

Thanks in advance

Millie