title: T2*-weighted image/T2-weighted image fusion in postimplant dosimetry of prostate brachytherapy.
abstract: Computed tomography (CT)/magnetic resonance imaging (MRI) fusion is considered to be the best method for postimplant dosimetry of permanent prostate brachytherapy; however, it is inconvenient and costly. In T2*-weighted image (T2*-WI), seeds can be easily detected without the use of an intravenous contrast material. We present a novel method for postimplant dosimetry using T2*-WI/T2-weighted image (T2-WI) fusion. We compared the outcomes of T2*-WI/T2-WI fusion-based and CT/T2-WI fusion-based postimplant dosimetry. Between April 2008 and July 2009, 50 consecutive prostate cancer patients underwent brachytherapy. All the patients were treated with 144 Gy of brachytherapy alone. Dose-volume histogram (DVH) parameters (prostate D90, prostate V100, prostate V150, urethral D10, and rectal D2cc) were prospectively compared between T2*-WI/T2-WI fusion-based and CT/T2-WI fusion-based dosimetry. All the DVH parameters estimated by T2*-WI/T2-WI fusion-based dosimetry strongly correlated to those estimated by CT/T2-WI fusion-based dosimetry (0.77 ≤ R ≤ 0.91). No significant difference was observed in these parameters between the two methods, except for prostate V150 (p = 0.04). These results show that T2*-WI/T2-WI fusion-based dosimetry is comparable or superior to MRI-based dosimetry as previously reported, because no intravenous contrast material is required. For some patients, rather large differences were observed in the value between the 2 methods. We thought these large differences were a result of seed miscounts in T2*-WI and shifts in fusion. Improving the image quality of T2*-WI and the image acquisition speed of T2*-WI and T2-WI may decrease seed miscounts and fusion shifts. Therefore, in the future, T2*-WI/T2-WI fusion may be more useful for postimplant dosimetry of prostate brachytherapy.
authors.affiliation: Department of Radiology, Japanese Red Cross Society Himeji Hospital, Japan. n-katayama@bea.hi-ho.ne.jp
authors.forename: Norihisa
authors.initials: N
authors.lastname: Katayama
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Takemoto
authors.forename: Kotaro
authors.initials: K
authors.lastname: Yoshio
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Katsui
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Uesugi
authors.forename: Yasutomo
authors.initials: Y
authors.lastname: Nasu
authors.forename: Toshi
authors.initials: T
authors.lastname: Matsushita
authors.forename: Mitsumasa
authors.initials: M
authors.lastname: Kaji
authors.forename: Hiromi
authors.initials: H
authors.lastname: Kumon
authors.forename: Susumu
authors.initials: S
authors.lastname: Kanazawa
mesh_terms: D001918:Brachytherapy; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000627:therapeutic use; D008279:Magnetic Resonance Imaging; D008297:Male; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed
chemical_list: D007457:Iodine Radioisotopes