Table 4 Estimated difference in percent medicare visits for MRI exams for physicians Post/Pre Onsite MRI acquisition relative to physicians without onsite MRI, 2007–2009 cohorts
∆MRIs as % Visits | Model 1 | Model 2 | Model 3 | Model 4 | ||||
|---|---|---|---|---|---|---|---|---|
| Â | Coeffi-cient | p-value | Coeffi-cient | p-value | Coeffi-cient | p-value | Coeffi-cient | p-value |
Onsite MRI | −0.330 | 0.486 | −0.139 | 0.753 | −0.237 | 0.507 | −0.468 | 0.161 |
MRI Year | Â | Â | Â | Â | Â | Â | Â | Â |
 2007 | Reference | -- | Reference | -- | Reference | -- | Reference | -- |
 2008 | 1.569 | 0.063 | 1.570 | 0.068 | 0.817 | 0.125 | 2.175 | 0.038 |
 2009 | 0.424 | 0.454 | 0.567 | 0.323 | 0.227 | 0.533 | 1.157 | 0.067 |
Number of providers | Â | Â | Â | Â | Â | Â | Â | Â |
 1-2 | -- | -- | Reference | -- | Reference | -- | Reference | -- |
 3-5 | -- | -- | −1.930 | 0.088 | −1.121 | 0.398 | −1.086 | 0.448 |
 6-10 | -- | -- | −2.199 | 0.037 | −2.142 | 0.076 | −1.892 | 0.095 |
 >10 | -- | -- | −2.395 | 0.023 | −2.015 | 0.072 | −1.907 | 0.083 |
Practice Payer Mix (%) | Â | Â | Â | Â | Â | Â | Â | Â |
 Medicare | -- | -- | -- | -- | 0.0734 | 0.006 | 0.0926 | 0.010 |
 Private Insurance | -- | -- | -- | -- | 0.0660 | 0.004 | 0.0644 | 0.006 |
 Workers’ Comp | -- | -- | -- | -- | 0.0289 | 0.511 | 0.0442 | 0.353 |
 Other | -- | -- | -- | -- | Reference | -- | Reference | -- |
Area Characteristics | Â | Â | Â | Â | Â | Â | Â | Â |
 ∆Per cap inc ($1000s) | -- | -- | -- | -- | -- | -- | 0.072 | 0.278 |
 ∆Pop age 65+ (%) | -- | -- | -- | -- | -- | -- | 0.516 | 0.198 |
 ∆Unemployment (%) | -- | -- | -- | -- | -- | -- | −0.246 | 0.216 |
 ∆MDs/1000 Pop | -- | -- | -- | -- | -- | -- | −1.215 | 0.418 |
F-Statistic (p-value) | 1.37 | 0.266 | 1.81 | 0.125 | 2.80 | 0.013 | 2.93 | 0.007 |