I had an issue when printing forms with checkboxes where the checkbox marks would not print. This looks like an issue with the background images.

Original Form:
Click image for larger version. 

Name:	ExtJS-Checkbox-Original-CSS.PNG 
Views:	193 
Size:	4.3 KB 
ID:	24816

Form when printed:
Click image for larger version. 

Name:	ExtJS-Checkbox-Before-CSS.PNG 
Views:	223 
Size:	13.2 KB 
ID:	24817

My work around was to use the following print-media CSS:
        .x-form-checkbox {
            display: none;
        }
        .x-form-cb-checked .x-form-cb-label:before {
          content: '☑';
          font-size: 18px;
          line-height: 0.8;
        }

        
        .x-form-cb-label:before {
          content: '☐';
          font-size: 18px;
          line-height: 0.8;
        }
With the CSS hack above the form now looked like this when printed:
Click image for larger version. 

Name:	ExtJS-Checkbox-After-CSS.PNG 
Views:	198 
Size:	15.4 KB 
ID:	24818

I'd say radioboxes would be able to modified in the same way.