RESUMEN
Phenomenon: Mental shortcuts are commonly used in medical education to facilitate the learning and application of a large volume of information. However, the use of demographic identifiers such as race, ethnicity, region, and descent from one of these groups as mental shortcuts in association with disease can perpetuate misconceptions about the construction of these identities and reinforce stereotypes. The United States Medical Licensing Exam (USMLE) Step 1 is a major driver of pre-clinical undergraduate medical education that requires memorization of a large volume of information and application of this information to clinical vignettes. This study assesses how demographic identifiers have been used in a nearly universally used study resource for this exam. Approach: The authors analyzed First Aid for the USMLE Step 1 2020, Thirtieth Edition, a resource that contains "high yield facts" and was built and maintained based on experiences with the USMLE Step 1 for references to race, ethnicity, region, and descent from one of these groups and the distribution of skin tones used in photos. These findings were subsequently compared to the changes made in the 2021 edition of the resource. Findings: The authors found 50 references in the 2020 edition to race, ethnicity, region, and descent from one of these groups, all in relation to disease. More than half of these references had an associated heritable component. Black or African American race was disproportionately represented, comprising more than half of all racial associations (13/24). Additionally, light skin tone was used in 170/204 photos (84.2%) in the 2020 edition. In the 2021 edition, only 12/209 photos (5.7%) were new or changed. Insights: These findings highlight the trend to associate race with disease while also furthering the misconception that there are innate, heritable differences between socially constructed groups and establishing light skin tone as the norm. While some favorable changes were made to the 2021 text, further work within this resource and across medical education is required to avoid further misuse of race and challenge existing implicit biases.
RESUMEN
IntraVoxel Incoherent Motion (IVIM) is a magnetic resonance imaging (MRI) technique capable of measuring perfusion-related parameters. In this manuscript, we show that the mono-exponential model commonly used to process IVIM data might be challenged, especially at short diffusion times. Eleven rat datasets were acquired at 7T using a diffusion-weighted pulsed gradient spin echo sequence with b-values ranging from 7 to 2500 s/mm2 at three diffusion times. The IVIM signals, obtained by removing the diffusion component from the raw MR signal, were fitted to the standard mono-exponential model, a bi-exponential model and the Kennan model. The Akaike information criterion used to find the best model to fit the data demonstrates that, at short diffusion times, the bi-exponential IVIM model is most appropriate. The results obtained by comparing the experimental data to a dictionary of numerical simulations of the IVIM signal in microvascular networks support the hypothesis that such a bi-exponential behavior can be explained by considering the contribution of two vascular pools: capillaries and somewhat larger vessels.