title: Reusable heat-sensitive phantom for precise estimation of thermal profile in hyperthermia application.
abstract: OBJECTIVE
  The emergence of thermal modalities has promoted the use of heat-sensitive phantoms for calibration, measurement, and verification purposes. However, development of durable phantoms with high precision ability to represent the temperature distribution remains a challenge. This study aims to introduce a reusable phantom that provides an accurate assessment of the heated region in various thermal modalities.
  
  
  METHODS
  The phantom contains a thermochromic dye that is transparent blue at room temperature and becomes colourless after exceeding a threshold temperature. In order to determine the threshold temperature of the phantom, spectrophotometry analysis was performed. The various thermal (specific heat, thermal conductivity, melting point and latent heat of melting) and acoustic (sound speed, attenuation) properties of this phantom were measured and compared with those of the reference phantom without dye. The application of this phantom for radio-frequency and magnetic resonance guided focused ultrasound modalities was also examined.
  
  
  RESULTS
  The spectrophotometry analysis showed a threshold temperature of 50 ± 3 °C for this phantom. The results also demonstrated a 6 °C difference between the onset and ending temperatures of the discolouration process. Moreover, the starting temperature of colouration during cooling was found to be 4 °C lower than the ending temperature of discolouration. The sound speed, attenuation, specific heat, thermal conductivity and melting point of the heat-sensitive phantom were statistically equal to those of the reference phantom; however, the latent heat, and onset temperature of the melting of the heat-sensitive phantom were decreased by addition of the dye.
  
  
  CONCLUSIONS
  The developed phantom is applicable for accurate evaluation of temperature variations in various thermal modalities.
authors.affiliation: Department of Biomedical Imaging, Faculty of Medicine, University of Malaya , Kuala Lumpur .
authors.forename: Ali
authors.initials: A
authors.lastname: Dabbagh
authors.forename: Basri Johan Jeet
authors.initials: BJ
authors.lastname: Abdullah
authors.forename: Noor Hayaty
authors.initials: NH
authors.lastname: Abu Kasim
authors.forename: Chanthiriga
authors.initials: C
authors.lastname: Ramasindarum
mesh_terms: D000162:Acoustics; D000180:Acrylic Resins; D004396:Coloring Agents / Q000528:radiation effects; D005029:Ethylenediamines / Q000528:radiation effects; D005782:Gels / Q000528:radiation effects; D057086:High-Intensity Focused Ultrasound Ablation; D006358:Hot Temperature; D006979:Hyperthermia, Induced / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging; D019047:Phantoms, Imaging; D013814:Thermal Conductivity; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D004396:Coloring Agents; D005029:Ethylenediamines; D005782:Gels; D000099166:Polyacrylamides