O R I G I N A L A R T I C L E Leukocyte Scanning With in ln Is Superior to Magnetic Resonance Imaging in Diagnosis of Clinically Unsuspected Osteomyelitis in Diabetic Foot Ulcers LISA G. NEWMAN, MD JOHN WALLER, MD CHRISTOPHER J. PALESTRO, MD GEORGE HERMANN, MD MICHAEL J. KLEIN, MD MYRON SCHWARTZ, MD ELIZABETH HARRINGTON, MD MARTIN HARRINGTON, MD SHEILA H. ROMAN, MD ALEX STAGNARO-GREEN, MD OBJECTIVE— To compare the accuracies of MRI and leukocyte scanning in diagnosing clinically unsuspected osteomyelitis in diabetic foot ulcers. RESEARCH DESIGN AND METHODS— A prospective study of 16 diabetic foot ulcers in 12 patients, including both ambulatory and hospitalized patients, was performed at a university medical center. Pedal images were obtained by leukocyte scanning with [ m ln]oxyquinoline and MRI. Definitive diagnosis of osteomyelitis then was determined by bone biopsy for culture and histology. RESULTS— Biopsy-proven osteomyelitis was present in 7 (44%) of the 16 foot ulcers. The diagnosis was suspected clinically in 0%. Leukocyte scanning was 100% sensitive, whereas MRI was only 29% sensitive in diagnosing osteomyelitis in diabetic foot ulcers. Specificities were 67 and 78%, respectively. The positive and negative predictive values (70 and 100%, respectively) for the leukocyte scan also were greater than those of MRI (50 and 58%, respectively). CONCLUSIONS — Leukocyte scanning is superior to MRI in detecting clinically unsuspected osteomyelitis in diabetic foot ulcers. FROM THE DEPARTMENT OF MEDICINE, DIVISION OF ENDOCRINOLOGY AND METABOLISM; THE DEPART- MENT OF SURGERY, DIVISION OF ORTHOPEDIC SURGERY AND DIVISION OF VASCULAR SURGERY; THE DEPARTMENT OF PATHOLOGY; THE DEPARTMENT OF NUCLEAR MEDICINE; AND THE DEPARTMENT OF RADIOLOGY, MOUNT SINAI MEDICAL CENTER, NEW YORK, NEW YORK. ADDRESS CORRESPONDENCE AND REPRINT REQUESTS TO LISA G. NEWMAN, MD, DIVISION OF GENERAL MEDICINE, MOUNT SINAI MEDICAL CENTER, 1 GUSTAVE LEVY PLACE, BOX 1087, NEW YORK, NY 10029. RECEIVED FOR PUBLICATION 29 JANUARY 1992 AND ACCEPTED IN REVISED FORM 2 JULY 1992. MRI, MAGNETIC RESONANCE IMAGING; T 1 W 1 , T L WEIGHTED IMAGES; SE, SPIN ECHO; T 2 W I , T2 WEIGHTED IMAGES; TR, REPETITION TIME; TE, ECHO TIME; WBC, WHITE BLOOD CELL. E arly diagnosis of osteomyelitis in di- abetic foot ulcers is important as prompt antibiotic treatment has been shown to decrease the rate of am- putation (1). However, determining this diagnosis is often difficult. We have shown previously that clinical diagnosis frequently is inadequate and fails to de- tect 68% of those with osteomyelitis (2). Of the noninvasive imaging tests, leuko- cyte scans with [ m In]oxyquinoline have been shown to be more sensitive than bone scans or radiographs in diagnosing unsuspected osteomyelitis in diabetic foot ulcers (2,3). Although MRI has been shown to be sensitive -and specific in diagnosing osteomyelitis in severely in- fected diabetic foot ulcers (4,5), it has not been evaluated in clinically unsus- pected osteomyelitis, nor has it been compared with leukocyte scans. We, therefore, compared the sensitivities and specificities of leukocyte scans and MRI for diagnosing clinically unsuspected os- teomyelitis in diabetic foot ulcers and found the leukocyte scan to be superior. RESEARCH DESIGN AND METHODS— Twenty-three patients with diabetes and foot ulcers were eval- uated at Mount Sinai Medical Center from September 1989 to June 1990; 12 patients with 16 foot ulcers were in- cluded in the study. Of the foot ulcers, 94% (15/16) were in outpatients. The in I n leukocyte scan results on 11 ulcers were included in a prior publication (2). Exclusion criteria determined on the ba- sis of possible risks of bone biopsy in- cluded myocardial infarction in the pre- vious 6 mo (n = 1), severe peripheral vascular disease (ankle-brachial index <50%; n = 3), ongoing antibiotic treat- ment for > 7 previous days (n = 4), or patient declining to participate (n = 3). The protocol was approved by the Mount Sinai School of Medicine Institu- tional Review Board and written consent was obtained from participants. The referring physician was asked to render a clinical opinion about DIABETES CARE, VOLUME 15, NUMBER 11, NOVEMBER 1992 1527