For every 25th consecutive Yottalook query from August 1, 2007 to August 24, 2007, the time of search, IP address, and other data were downloaded for retrospective analysis. Institutional review board (IRB) approval was not required according to our local IRB.
Two authors (RES, MJS) sorted the terms into predefined categories including 11 radiology subspecialties (musculoskeletal, pulmonary, gastrointestinal, genitourinary, neuroradiology, vascular and interventional, nuclear, ultrasonography, pediatrics, breast, and cardiac) and three other categories (general radiology, other medical conditions, and other queries). Radiology subspecialty allocation was determined through consensus using criteria defined by the American Board of Radiology in its Diagnostic Radiology Study Guide.10
Reviewers utilized radiology texts and Medline searches of the primary medical literature to assist in categorization of searches. Search terms that met criteria for inclusion in more than one radiology subspecialty were classified into multiple subspecialties.
Radiology subspecialties were defined as follows: Musculoskeletal radiology included all imaging modalities related to normal physiology or pathology of the musculoskeletal system, including disorders of the bone marrow. Pulmonary radiology included diseases of the lungs, pleura, mediastinum, and all of its structures excluding the heart and great vessels. Gastrointestinal radiology included imaging of the esophagus, stomach, small and large intestines, biliary tract, liver, spleen, pancreas, peritoneal cavity, and abdominal wall. Genitourinary radiology included searches of the kidneys, adrenal glands, ureter, bladder, urethra, and the male and female genital systems. Neuroradiology was defined as imaging related to the skull, sinuses, mastoids, spine, head and neck, thyroid, parathyroid, and pituitary glands. Vascular and interventional radiology included all imaging of the arteries, veins, and lymphatic structures. Nuclear imaging included all static and dynamic imaging using radiopharmaceuticals. Ultrasonography included use of the modality to investigate the head and neck, thorax, abdomen, pelvis, extremities, breast, scrotum, vascular system, uterus, and fetus. The pediatric category included all imaging of infants and children. Breast radiology included all modalities for diagnosing breast disease. Cardiac was defined as the evaluation of the heart and the great vessels.
The category of general radiology included searches that were radiologic in nature but did not fit into established radiology subspecialties. Terms that did not fit into a specific subspecialty and were medical rather than radiological in nature were classified as other medical topics. Terms not fitting into any of the above-described categories were classified as other queries. The inclusion of specific imaging modalities in search queries was also noted.
International WHOIS databases were used to determine the search origin of queries from their Internet protocol (IP) address. This location was also used to categorize queries into geographical regions using accepted classification systems. Geographic regions included Africa, Asia, Europe, North America, Oceania, and South America. Radiology subspecialty categorization and imaging modality categorization were analyzed by region. After the search origin location was identified, the time of the search was converted to that region’s local standard time to analyze searches by time of day.
Search terms were analyzed using standard medical references to check for misspellings. The presence of abbreviations and the language of the search were also noted for each search term.
Data analysis was performed using Microsoft Excel and accepted methods for calculating 95% confidence intervals for proportions with nominal data. Statistical differences were considered significant at the 95% level.