title: High-frequency jet ventilation for complete target immobilization and reduction of planning target volume in stereotactic high single-dose irradiation of stage I non-small cell lung cancer and lung metastases.
abstract: OBJECTIVE
  To demonstrate the feasibility of complete target immobilization by means of high-frequency jet ventilation (HFJV); and to show that the saving of planning target volume (PTV) on the stereotactic body radiation therapy (SBRT) under HFJV, compared with SBRT with respiratory motion, can be predicted with reliable accuracy by computed tomography (CT) scans at peak inspiration phase.
  
  
  METHODS
  A comparison regarding different methods for defining the PTV was carried out in 22 patients with tumors that clearly moved with respiration. A movement span of the gross tumor volume (GTV) was defined by fusing respiration-correlated CT scans. The PTV enclosed the GTV positions with a safety margin throughout the breathing cycle. To create a PTV from CT scans acquired under HFJV, the same margins were drawn around the immobilized target. In addition, peak inspiration phase CT images (PIP-CTs) were used to approximate a target immobilized by HFJV.
  
  
  RESULTS
  The resulting HFJV-PTVs were between 11.6% and 45.4% smaller than the baseline values calculated as respiration-correlated CT-PTVs (median volume reduction, 25.4%). Tentative planning by means of PIP-CT PTVs predicted that in 19 of 22 patients, use of HFJV would lead to a reduction in volume of >or=20%. Using this threshold yielded a positive predictive value of 0.89, as well as a sensitivity of 0.94 and a specificity of 0.5.
  
  
  CONCLUSIONS
  In all patients, SBRT under HFJV provided a reliable immobilization of the GTVs and achieved a reduction in PTVs, regardless of patient compliance. Tentative planning facilitated the selection of patients who could better undergo radiation in respiratory standstill, both with greater accuracy and lung protection.
authors.affiliation: Department of Radiotherapy, St Marien-Krankenhaus, Siegen, Germany. p.h.fritz@t-online.de
authors.forename: Peter
authors.initials: P
authors.lastname: Fritz
authors.forename: Hans-Jörg
authors.initials: HJ
authors.lastname: Kraus
authors.forename: Werner
authors.initials: W
authors.lastname: Mühlnickel
authors.forename: Volker
authors.initials: V
authors.lastname: Sassmann
authors.forename: Werner
authors.initials: W
authors.lastname: Hering
authors.forename: Konstantin
authors.initials: K
authors.lastname: Strauch
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D005240:Feasibility Studies; D005260:Female; D006611:High-Frequency Jet Ventilation / Q000379:methods*; D006801:Humans; D007103:Immobilization / Q000379:methods*; D001239:Inhalation; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy* / Q000556:secondary; D008297:Male; D008875:Middle Aged; D009068:Movement; D018579:Patient Selection; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012119:Respiration; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden