title: Magnetic resonance imaging (MRI) markers for MRI-guided high-dose-rate brachytherapy: novel marker-flange for cervical cancer and marker catheters for prostate cancer.
abstract: OBJECTIVE
  To present a novel marker-flange, addressing source-reconstruction uncertainties due to the artifacts of a titanium intracavitary applicator used for magnetic resonance imaging (MRI)-guided high-dose-rate (HDR) brachytherapy (BT); and to evaluate 7 different MRI marker agents used for interstitial prostate BT and intracavitary gynecologic HDR BT when treatment plans are guided by MRI.
  
  
  METHODS
  Seven MRI marker agents were analyzed: saline solution, Conray-60, copper sulfate (CuSO4) (1.5 g/L), liquid vitamin E, fish oil, 1% agarose gel (1 g agarose powder per 100 mL distilled water), and a cobalt-chloride complex contrast (C4) (CoCl2/glycine = 4:1). A plastic, ring-shaped marker-flange was designed and tested on both titanium and plastic applicators. Three separate phantoms were designed to test the marker-flange, interstitial catheters for prostate BT, and intracavitary catheters for gynecologic HDR BT. T1- and T2-weighted MRI were analyzed for all markers in each phantom and quantified as percentages compared with a 3% agarose gel background. The geometric accuracy of the MR signal for the marker-flange was measured using an MRI-CT fusion.
  
  
  RESULTS
  The CuSO4 and C4 markers on T1-weighted MRI and saline on T2-weighted MRI showed the highest signals. The marker-flange showed hyper-signals of >500% with CuSO4 and C4 on T1-weighted MRI and of >400% with saline on T2-weighted MRI on titanium applicators. On T1-weighted MRI, the MRI signal inaccuracies of marker-flanges were measured <2 mm, regardless of marker agents, and that of CuSO4 was 0.42 ± 0.14 mm.
  
  
  CONCLUSIONS
  The use of interstitial/intracavitary markers for MRI-guided prostate/gynecologic BT was observed to be feasible, providing accurate source pathway reconstruction. The novel marker-flange can produce extremely intense, accurate signals, demonstrating its feasibility for gynecologic HDR BT.
authors: Department of Radiation Oncology, University of Iowa, Iowa City, Iowa, USA.
authors: Joshua
authors: J
authors: Schindel
authors: Manickam
authors: M
authors: Muruganandham
authors: F Christopher
authors: FC
authors: Pigge
authors: James
authors: J
authors: Anderson
authors: Yusung
authors: Y
authors: Kim
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation / Q000379:methods*; D057785:Catheters; D003035:Cobalt; D019327:Copper Sulfate; D005240:Feasibility Studies; D005260:Female; D057918:Fiducial Markers; D005395:Fish Oils; D006801:Humans; D007482:Iothalamate Meglumine; D053783:Magnetic Resonance Imaging, Interventional / Q000295:instrumentation / Q000379:methods*; D008297:Male; D019047:Phantoms, Imaging; D011471:Prostatic Neoplasms; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012685:Sepharose; D012965:Sodium Chloride; D014025:Titanium; D014057:Tomography, X-Ray Computed / Q000379:methods; D035501:Uncertainty; D002583:Uterine Cervical Neoplasms; D014810:Vitamin E
chemical_list: D005395:Fish Oils; D014810:Vitamin E; D003035:Cobalt; D012965:Sodium Chloride; D012685:Sepharose; D014025:Titanium; C018021:cobaltous chloride; D019327:Copper Sulfate; D007482:Iothalamate Meglumine