title: Evaluation of field-in-field technique for total body irradiation.
abstract: OBJECTIVE
  To evaluate the clinical use of a field-in-field (FIF) technique for total body irradiation (TBI) using a treatment-planning system (TPS) and to verify TPS results with in vivo dose measurements using metal-oxide-semiconductor field-effect transistor (MOSFET) detectors.
  
  
  METHODS
  Clinical and dosimetric data of 10 patients treated with TBI were assessed. Certain radiation parameters were measured using homogenous and regular phantoms at an extended distance of 380 cm, and the results were compared with data from a conventional standard distance of 100 cm. Additionally, dosimetric validation of TPS doses was performed with a Rando phantom using manual calculations. A three-dimensional computed tomography plan was generated involving 18-MV photon beams with a TPS for both open-field and FIF techniques. The midline doses were measured at the head, neck, lung, umbilicus, and pelvis for both open-field and FIF techniques.
  
  
  RESULTS
  All patients received planned TBI using the FIF technique with 18-MV photon energies and 2 Gy b.i.d. on 3 consecutive days. The difference in tissue maximum ratios between the extended and conventional distances was <2%. The mean deviation of manual calculations compared with TPS data was +1.6% (range, 0.1-2.4%). A homogenous dose distribution was obtained with 18-MV photon beams using the FIF technique. The mean lung dose for the FIF technique was 79.2% (9.2 Gy; range, 8.8-9.7 Gy) of the prescribed dose. The MOSFET readings and TPS doses in the body were similar (percentage difference range, -0.5% to 2.5%) and slightly higher in the shoulder and lung (percentage difference range, 4.0-5.5%).
  
  
  CONCLUSIONS
  The FIF technique used for TBI provides homogenous dose distribution and is feasible, simple, and spares time compared with more-complex techniques. The TPS doses were similar to the midline doses obtained from MOSFET readings.
authors.affiliation: Department of Radiation Oncology, Baskent University Faculty of Medicine, Adana, Turkey. hcemonal@hotmail.com
authors.forename: Cem
authors.initials: C
authors.lastname: Onal
authors.forename: Aydan
authors.initials: A
authors.lastname: Sonmez
authors.forename: Gungor
authors.initials: G
authors.lastname: Arslan
authors.forename: Serhat
authors.initials: S
authors.lastname: Sonmez
authors.forename: Esma
authors.initials: E
authors.lastname: Efe
authors.forename: Ezgi
authors.initials: E
authors.lastname: Oymak
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005240:Feasibility Studies; D005260:Female; D006257:Head / Q000000981:diagnostic imaging / Q000528:radiation effects; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000000981:diagnostic imaging / Q000528:radiation effects; D058958:Organs at Risk / Q000528:radiation effects; D010388:Pelvis / Q000000981:diagnostic imaging / Q000528:radiation effects; D019047:Phantoms, Imaging; D011874:Radiometry / Q000295:instrumentation / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D012666:Semiconductors / Q000295:instrumentation; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014472:Umbilicus / Q000000981:diagnostic imaging / Q000528:radiation effects; D014916:Whole-Body Irradiation / Q000379:methods*; D055815:Young Adult