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A feasibility study on monitoring the evolution of apparent diffusion coefficient decrease during thermal ablation
Author(s) -
Plata Juan C.,
Holbrook Andrew B.,
Marx Michael,
Salgaonkar Vasant,
Jones Peter,
PascalTenorio Aurea,
Bouley Donna,
Diederich Chris,
Sommer Graham,
Pauly Kim Butts
Publication year - 2015
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4928155
Subject(s) - effective diffusion coefficient , nuclear medicine , hyperthermia , receiver operating characteristic , ablation , imaging phantom , confidence interval , ultrasound , thermal ablation , materials science , prostate , medicine , biomedical engineering , nuclear magnetic resonance , radiology , magnetic resonance imaging , physics , cardiology , cancer
Purpose: Evaluate whether a decrease in apparent diffusion coefficient (ADC), associated with loss of tissue viability (LOTV), can be observed during the course of thermal ablation of the prostate. Methods: Thermal ablation was performed in a healthy in vivo canine prostate model ( N = 2, ages: 5 yr healthy, mixed breed, weights: 13–14 kg) using a transurethral high‐intensity ultrasound catheter and was monitored using a strategy that interleaves diffusion weighted images and gradient‐echo images. The two sequences were used to measure ADC and changes in temperature during the treatment. Changes in temperature were used to compute expected changes in ADC. The difference between expected and measured ADC, ADC DIFF , was analyzed in regions ranging from moderate hyperthermia to heat fixation. A receiver operator characteristic (ROC) curve analysis was used to select a threshold of detection of LOTV. Time of threshold activation, t LOTV , was compared with time to reach CEM 43 = 240, t DOSE . Results: The observed relationship between temperature and ADC in vivo (2.2%/ °C, 1.94%–2.47%/ °C 95% confidence interval) was not significantly different than the previously reported value of 2.4%/ °C in phantom. ADC DIFF changes after correction for temperature showed a mean decrease of 25% in ADC 60 min post‐treatment in regions where sufficient thermal dose (CEM 43 > 240) was achieved. Following our ROC analysis, a threshold of 2.25% decrease in ADC DIFF for three consecutive time points was chosen as an indicator of LOTV. The ADC DIFF was found to decrease quickly (1–2 min) after reaching CEM 43 = 240 in regions associated with heat fixation and more slowly (10–20 min) in regions that received slower heating. Conclusions: Simultaneous monitoring of ADC and temperature during treatment might allow for a more complete tissue viability assessment of ablative thermal treatments in the prostate. ADC DIFF decreases during the course of treatment may be interpreted as loss of tissue viability.