Soheil L. Hanna

Magnetic resonance imaging of disseminated bone marrow disease in patients treated for malignancy

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), Ewings 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 GdDTPA-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.

Assessment of osteosarcoma response to preoperative chemotherapy using dynamic FLASH gadolinium DTPA-enhanced magnetic resonance mapping

RATIONALE AND OBJECTIVES.To improve the accuracy of magnetic resonance imaging (MRI) in evaluating the response of osteosarcomas to preoperative chemotherapy, the authors developed a technique of mapping tumor necrosis and viability by quantitating slope values of gadolinium-DTPA (Gd-DTPA) uptake on dynamic fast low-angle shot (FLASH) images. METHODS.Dynamic contrast-enhanced FLASH imaging of a single representative plane was performed on six osteosarcomas. Tumors were mapped by dividing resultant images into contiguous regions of interest and deriving slopes representing percentage increase in signal intensity (SI) per minute over the baseline for each region. The results were compared with estimations of viable tumor volume on subtracted Gd-DTPA–enhanced T1-weighted images and histologic maps of necrotic and viable tumor. RESULTS.Dynamic FLASH estimations of percent tumor necrosis using a critical slope value of 45% per minute correctly predicted histologic response to chemotherapy in all six patients. Comparison of dynamic FLASH and histologic maps showed a high degree of correlation. Static enhanced T1- weighted images overestimated the amount of residual viable tumor. CONCLUSIONS.Dynamic FLASH Gd-DTPA–enhanced mapping is a potentially useful noninvasive method of quantitating tumor response to chemotherapy.

Changes in MR signal intensity and contrast enhancement of therapeutically irradiated soft tissue

Increased MR signal intensity was observed on T2-weighted, STIR, and Gadolinium-DTPA-enhanced T1-weighted images of subcutaneous and muscular soft tissue in 9 of 10 children treated with combination chemotherapy and radiation therapy (RT) for malignancy in the pelvis or an extremity. Total radiation doses ranged from 59.5 to 65 Gy. Eight of the patients with these changes received hyperfractionated RT (seven for Ewing sarcoma and one for perineal rhabdomyosarcoma); one was treated for pelvic hemangiopericytoma with once-daily fractions. Evidence of soft tissue damage became apparent as early as the sixth week of RT and was seen for up to 69 wk post-RT. There was no clear MR evidence of RT-induced soft tissue damage in one patient, who underwent hyperfractionated RT for pelvic rhabdomyosarcoma. Other MR findings in this group included evidence of bladder wall thickening in three of the seven patients given pelvic RT and increased T1-weighted signal of irradiated marrow in nine patients. All patients had clinical evidence of skin, soft tissue, or epithelial radiation effects. Increased MR signal intensity secondary to RT-induced damage can be differentiated from widespread tumor by geometric borders that conform to the margins of the radiation field.

Subtraction technique for contrast-enhanced MR images of musculoskeletal tumors

Vascularized malignant tissue, fat and hemorrhage may have similar intensities on Gd-DTPA-enhanced, T1-weighted MRI performed to evaluate musculoskeletal tumors. We describe a simple, rapid post-processing subtraction technique which resulted in improved definition of these tissues in 33 of 42 examinations. While the subtraction process is susceptible to complex patient motion, the improved contrast can be obtained without modifying standard pulse sequences.

MR imaging findings in recurrent primary osseous Ewing sarcoma

The objective of this study was to determine the value of magnetic resonance (MR) imaging in diagnosing local recurrence of Ewing sarcoma. We retrospectively reviewed radiographs, Tc99m-methylene diphosphonate (MDP) skeletal scintigraphy, computed tomography scans, and MR studies of 11 patients who had local recurrences of osseous Ewing sarcoma following initial responses to chemotherapy and local radiation. The MR images were compared to those of a control group of nine patients who had no evidence of relapse. T1- and T2-weighted MR images identified 9 of the 11 recurrences. Computed tomography was diagnostic in 4 of 6 cases evaluated, Tc99m-MDP bone scintigraphy in 4 of 11 cases, and plain radiographs in 2 of 10. MR findings at relapse included changes in signal intensity, increased extent of abnormal marrow signal on T1- and T2-weighted images, and identification of a new soft tissue mass. These findings suggest that MR imaging is valuable in the routine follow-up of primary osseous Ewing sarcoma.

Increased confidence of diagnosis of Ewing sarcoma using T2-weighted MR images☆

To assess whether magnetic resonance imaging could assist in diagnosing Ewing sarcoma, we retrospectively analyzed T1- and T2-weighted images of 24 consecutive solitary lytic bone lesions, including 18 cases of histologically proven Ewing sarcoma, and six aggressive-appearing benign lesions including eosinophilic granuloma and osteomyelitis (3 cases each). Images were obtained using a (1.0T) Siemens GBSII system. No signal intensity differences were noted among the various lesions on T1-weighted images. The observed differences in T2-weighted marrow signal intensities were scored on a 5-point scale (5 = water, 3 = fat, and 1 = muscle) and then histologically correlated. Sixteen of 18 Ewing sarcomas showed homogeneous T2-weighted signal isointense with fat and two were heterogeneous. Signals for all 6 benign lesions were homogeneous and more intense than fat on T2-weighted images. All Ewing sarcomas had associated soft tissue masses whereas, only one benign lesion, an eosinophilic granuloma had a small soft tissue component. In our patient population, a homogeneous intramedullary T2-weighted signal isointense with fat, and the presence of an associated soft tissue mass helped differentiate Ewing sarcoma from benign lytic lesions. The reproducibility of these results requires testing in larger series of patients using a variety of MR imaging equipment of differing field strengths.

Childhood chondrosarcoma: MR imaging with Gadolinium-DTPA

The radiologic, CT, MR, and histological features of a case of chondrosarcoma of the femur presenting in childhood are reported. This case emphasizes the use of correlative imaging in establishing the diagnosis as well as the value of MR supplemented by Gadolinium-DTPA enhancement in disclosing abundant necrosis within the tumor.

Muscle Edema Associated with Musculoskeletal Neoplasms and Radiation Therapy

The exceptional tissue contrast provided by magnetic resonance imaging (MRI) permits the observation of physiologic and pathologic changes within skeletal muscle. As described in the previous chapters, even physiologic events such as exercise may alter the signal intensity of muscle on MR images,1 and the effects of minor trauma2 and inflammation3 are readily visualized. These alterations in contrast can possibly be attributed to changes in the interstitial water content of skeletal muscle and alterations in the physical state of water,4 which modify T1 and T2 relaxation times.5,6 As a result, radiologists involved in oncologic MRI are now observing muscle abnormalities that were previously undetectable by other imaging modalities. In this chapter, we will discuss the MRI findings accompanying pathophysiologic changes in muscle in patients with tumors or tumor-like lesions of the musculoskeletal system and the effects of radiation therapy.