The ability of dynamic, gadolinium-enhanced magnetic resonance (MR) imaging to allow prediction of histologic responses to initial chemotherapy was evaluated in 20 patients with osteosarcoma (n = 12), Ewing sarcoma (n = 4), rhabdomyosarcoma (n = 3), or synovial sarcoma (n = 1). Tumor signal intensity was measured on fast low-angle shot (FLASH) gradient-echo images obtained at 15-second intervals before and 3 or more minutes after manual intravenous injection of gadopentetate dimeglumine. Signal intensity was plotted against time, and slopes were calculated for the percentage increase in signal intensity per minute. Slopes and changes in maximum tumor size during and after chemotherapy were correlated with histologic evaluations of tumor response. Eleven of the 20 tumors met histologic criteria for response. Histologic response was moderately correlated with slopes obtained during chemotherapy (rs [Spearman rank correlation] = .53, P = .02) but not with changes in tumor size (rs = .02, P = .94). Tumor slopes obtained after chemotherapy were highly correlated with histologic findings (rs = .65, P = .007); the correlation with changes in tumor size increased but remained nonsignificant (rs = .41, P = .11).

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Hematopoietic activity induced by growth factors can produce changes in bone marrow SI that may simulate bone marrow involvement by musculoskeletal tumors.

Magnetic resonance imaging (MRI) is a sensitive method for the diagnosis of bone marrow abnormalities, but its usefulness in detecting active disseminated cancer in this tissue in treated patients has not been determined. We therefore examined 14 children who had been treated for disseminated bone marrow involvement by neuroblastoma (n = 6), lymphoma (n = 3), Ewing's sarcoma (n = 3), osteosarcoma (n = 1), and leukemia (n = 1). MRI studies were performed at 21 marrow sites to evaluate residual or recurrent tumor and were correlated with histologic material from the same site. T1- and T2-weighted sequences were employed in 21 and 14 studies, respectively; short tau inversion recovery (STIR) in 18; and static gadolinium diethylene triamine pentaacetic acid (Gd-DPTA)-enhanced. T1-weighted sequences in 13. All MRI studies showed an altered bone marrow signal. Technetium 99m methylene diphosphonate (99mTc-MDP) bone scintigraphy was also performed (19 studies). On histologic examination, 7 marrow specimens contained tumor, and 14 did not. Of the 7 tumor-positive lesions, all T1-weighted, 4 of 6 T2-weighted, and all 6 STIR sequences showed abnormal signal; all 5 Gd-DTPA-enhanced. T1-weighted sequences showed enhancement of the lesion. However, abnormal signals were also observed on all T1-weighted, 6 of 8 T2-weighted, 11 of 12 STIR, and 5 of 8 Gd-DTPA-enhanced, T1-weighted images of the tumor-negative sites. In this clinical setting, MRI did not consistently differentiate changes associated with treatment from malignant disease.