title: Assessment of renal function after conformal radiotherapy and intensity-modulated radiotherapy by functional 1H-MRI and 23Na-MRI.
abstract: OBJECTIVE
  Adjuvant radiochemotherapy (RCHT) improves survival of patients with locally advanced gastric cancer. Conventional three-dimensional conformal radiotherapy (3D-CRT) results in ablative doses to a significant amount of the left kidney, while image-guided intensity-modulated radiotherapy (IG-IMRT) provides excellent target coverage with improved kidney sparing. Few long-term results on IMRT for gastric cancer, however, have been published. Functional magnetic resonance imaging (fMRI) at 3.0 T including blood oxygenation-level dependent (BOLD) imaging, diffusion-weighted imaging (DWI) and, for the first time, (23)Na imaging was used to evaluate renal status after radiotherapy with 3D-CRT or IG-IMRT.
  
  
  METHODS
  Four disease-free patients (2 after 3D-CRT and 2 after IMRT; FU for all patients > 5 years) were included in this feasibility study. Morphological sequences, axial DWI images, 2D-gradient echo (GRE)-BOLD images, and (23)Na images were acquired. Mean values/standard deviations for ((23)Na), the apparent diffusion coefficient (ADC), and R2* values were calculated for the upper/middle/lower parts of both kidneys. Corticomedullary (23)Na-concentration gradients were determined.
  
  
  RESULTS
  Surprisingly, IG-IMRT patients showed no morphological alterations and no statistically significant differences of ADC and R2* values in all renal parts. Values for mean corticomedullary (23)Na-concentration matched those for healthy volunteers. Results were similar in 3D-CRT patients, except for the cranial part of the left kidney. This was atrophic and presented significantly reduced functional parameters (p = 0.001-p = 0.033). Reduced ADC values indicated reduced cell density and reduced extracellular space. Cortical and medullary R2* values of the left cranial kidney in the 3D-CRT group were higher, indicating more deoxygenated hemoglobin due to reduced blood flow/oxygenation. ((23)Na) of the renal cranial parts in the 3D-CRT group was significantly reduced, while the expected corticomedullary (23)Na-concentration gradient was partially conserved.
  
  
  CONCLUSIONS
  Functional MRI can assess postradiotherapeutic renal changes. As expected, marked morphological/functional effects were observed in high-dose areas (3D-CRT), while, unexpectedly, no alteration in kidney function was observed in IG-IMRT patients, supporting the hypothesis that reducing total/fractional dose to the renal parenchyma by IMRT is clinically beneficial.
authors.affiliation: Institute of Clinical Radiology and Nuclear Medicine, Medical Faculty Mannheim, Heidelberg University, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany. Stefan.Haneder@umm.de
authors.forename: S
authors.initials: S
authors.lastname: Haneder
authors.forename: H J
authors.initials: HJ
authors.lastname: Michaely
authors.forename: S O
authors.initials: SO
authors.lastname: Schoenberg
authors.forename: S
authors.initials: S
authors.lastname: Konstandin
authors.forename: L R
authors.initials: LR
authors.lastname: Schad
authors.forename: K
authors.initials: K
authors.lastname: Siebenlist
authors.forename: H
authors.initials: H
authors.lastname: Wertz
authors.forename: F
authors.initials: F
authors.lastname: Wenz
authors.forename: F
authors.initials: F
authors.lastname: Lohr
authors.forename: J
authors.initials: J
authors.lastname: Boda-Heggemann
mesh_terms: D000368:Aged; D059186:Chemoradiotherapy, Adjuvant; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D018572:Disease-Free Survival; D005240:Feasibility Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007668:Kidney / Q000528:radiation effects*; D007677:Kidney Function Tests; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D010100:Oxygen / Q000097:blood*; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000175:diagnosis*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal; D050397:Radiotherapy, Intensity-Modulated; D013274:Stomach Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*
chemical_list: D010100:Oxygen