title: Clinical use of the Utrecht applicator for combined intracavitary/interstitial brachytherapy treatment in locally advanced cervical cancer.
abstract: OBJECTIVE
  The aims of this study were to investigate the benefit of the Utrecht interstitial CT/MR applicator for combined intracavitary/interstitial (IC/IS) approach, using magnetic resonance imaging-guided brachytherapy, over the intracavitary approach alone in patients with locally advanced cervical cancer and to analyze the clinical use of needles.
  
  
  METHODS
  This study includes the first 20 patients treated with the new applicator. Brachytherapy consisted of two pulsed dose rate applications, and the second application was performed with the IC/IS approach. The number of needles, chosen guiding holes through the ovoids, and insertion depths were based on the dose distribution and dosimetric shortcomings of the first application (IC alone). We investigated the dosimetric gain by comparing the clinical interstitial optimized plan (IC/IS(clinical)) with an additionally generated optimized plan without needle use (IC(study)). Furthermore, we studied the relation of the inserted needles and their source loading patterns with the high-risk clinical target volume (HR-CTV).
  
  
  RESULTS
  A total of 54 needles (range, 1-6 per application) were applied with an average depth of 25 mm. The chosen needle positions corresponded with the location of the HR-CTV extensions. The total and individual needle treatment times per application were on average 19% (range, 4-35%) and 7% (range, 2-14%) of the implant treatment time, respectively. The total (external-beam radiotherapy + brachytherapy) D90 HR-CTV for the IC(study) and the IC/IS(clinical) were on average 79.5 (SD 7.4) Gy(α/β10) and 83.9 (SD 6.7) Gy(α/β10), respectively, with an average gain of 4.4 (SD 2.3) Gy(α/β10) for the second application.
  
  
  CONCLUSIONS
  Needle placement was feasible in all patients and resulted in a gain in dose and better coverage of HR-CTV. Defining the location of HR-CTV protrusions and analyzing the associated needles has given us deeper understanding of the possibilities in magnetic resonance imaging-guided (pre)treatment planning with the IC/IS Utrecht applicator.
authors.affiliation: Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands. c.nomden@umcutrecht.nl
authors.forename: Christel N
authors.initials: CN
authors.lastname: Nomden
authors.forename: Astrid A C
authors.initials: AA
authors.lastname: de Leeuw
authors.forename: Marinus A
authors.initials: MA
authors.lastname: Moerland
authors.forename: Judith M
authors.initials: JM
authors.lastname: Roesink
authors.forename: Robbert J H A
authors.initials: RJ
authors.lastname: Tersteeg
authors.forename: Ina Maria
authors.initials: IM
authors.lastname: Jürgenliemk-Schulz
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D012809:Colon, Sigmoid; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D009367:Neoplasm Staging; D058958:Organs at Risk; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D012007:Rectum; D013997:Time Factors; D047368:Tumor Burden; D001743:Urinary Bladder; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*