title: Assessment of osteosarcoma response to preoperative chemotherapy using dynamic FLASH gadolinium-DTPA-enhanced magnetic resonance mapping.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee 38101.
authors.forename: S L
authors.initials: SL
authors.lastname: Hanna
authors.forename: D M
authors.initials: DM
authors.lastname: Parham
authors.forename: D L
authors.initials: DL
authors.lastname: Fairclough
authors.forename: W H
authors.initials: WH
authors.lastname: Meyer
authors.forename: A H
authors.initials: AH
authors.lastname: Le
authors.forename: B D
authors.initials: BD
authors.lastname: Fletcher
mesh_terms: D000293:Adolescent; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D001859:Bone Neoplasms / Q000175:diagnosis* / Q000188:drug therapy / Q000473:pathology; D017024:Chemotherapy, Adjuvant; D002648:Child; D003287:Contrast Media; D004317:Doxorubicin / Q000008:administration & dosage; D005260:Female; D005682:Gadolinium; D019786:Gadolinium DTPA; D006801:Humans; D007069:Ifosfamide / Q000008:administration & dosage; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage; D009336:Necrosis; D009942:Organometallic Compounds; D012516:Osteosarcoma / Q000175:diagnosis* / Q000188:drug therapy / Q000473:pathology; D004369:Pentetic Acid; D011300:Preoperative Care
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; D004369:Pentetic Acid; D004317:Doxorubicin; D005682:Gadolinium; D019786:Gadolinium DTPA; D007069:Ifosfamide; D008727:Methotrexate