Radiology Question:

During residency: This varies from program to program depending on the number of sites covered and number of residents. At McMaster, we do call roughly 1 in 7 or 8 (averages out to 3-4 calls per month). We cover two sites on each call shift. Our hospitals have established a contrast policy whereby residents do not need to travel between sites, in order to cover contrast-enhanced examinations.
As a staff radiologist: Your call frequency will depend on the number of radiologists in your practice, as well as the imaging modalities and technologist/imaging hours your hospital offers. As a rough estimate, it there are 4 radiologists in your group, you will be on-call 1 in 4; if there are 13 of you, then it's 1 in 13, etc. This may change if you have specialized skills, such as in interventional radiology. The other determinant of call depends on whether you are working at an academic centre (with resident and fellow call-coverage) or a community setting. For the latter, another factor which influences the busyness of your call is whether or not your centre provides 24/7 CT, US or MRI imaging.