title: Evaluation of the visibility of a new thinner ¹²⁵I radioactive source for permanent prostate brachytherapy.
abstract: OBJECTIVE
  The ¹²⁵I source currently used for prostate brachytherapy at St. James's Institute of Oncology is a standard size seed (≈4.5mm in length and 0.8mm in diameter). A new, thinner seed is under evaluation. This is designed to be implanted using narrower needles, potentially reducing edema and improving the dose distribution. This study investigated the visibility of the thinner source on multimodality images and compared it with that of standard size seeds.
  
  
  METHODS
  Images of dummy seeds of both thinner and standard size models were taken using ultrasound, fluoroscopy, computed tomography (CT), and magnetic resonance (MR) imaging. The ultrasound, fluoroscopy, and CT images were acquired with the seeds inserted into phantoms positioned in a water tank. The MR images were acquired using phantoms containing single seeds. The images were analyzed visually and quantitatively. The resolution of closely spaced seeds on CT images was investigated.
  
  
  RESULTS
  The visibility of both seeds was similar on ultrasound, fluoroscopy, and MR images. On CT images, the thinner seeds give reduced artifacts and better resolution.
  
  
  CONCLUSIONS
  The use of the thinner seed would have minimal effect on ultrasound and fluoroscopy imaging during treatment. However on CT images, the use of the thinner seeds may improve seed identification for post-treatment dosimetry. Further study is required into the suitability of MR images alone for post-treatment dosimetry.
authors.affiliation: Medical Physics and Engineering, St James's Institute of Oncology, St James's Hospital, Leeds, UK.
authors.forename: Gemma
authors.initials: G
authors.lastname: Roberts
authors.forename: Bashar
authors.initials: B
authors.lastname: Al-Qaisieh
authors.forename: Peter
authors.initials: P
authors.lastname: Bownes
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D019047:Phantoms, Imaging; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals