Magnetic resonance imaging guidance for laser photothermal therapy

Abstract

Temperature distribution is a crucial factor in determining the outcome of laser phototherapy in cancer treatment. Magnetic resonance imaging MRI is an ideal method for 3-D noninvasive temperature measurement. A 7.1-T MRI was used to determine laser-induced high thermal gradient temperature distribution of target tissue with high spatial resolution. Using a proton density phase shift method, thermal mapping is validated for in vivo thermal measurement with light-absorbing enhancement dye. Tissue-simulating phantom gels, biological tissues, and tumor-bearing animals were used in the experiments. An 805-nm laser was used to irradiate the samples, with laser power in the range of 1 to 3 W. A clear temperature distribution matrix within the target and surrounding tissue was obtained with a specially developed processing algorithm. The temperature mapping showed that the selective laser photothermal effect could result in temperature elevation in a range of 10 to 45°C. The temperature resolution of the measurement was about 0.37°C with 0.4-mm spatial resolution. The results of this study provide in vivo thermal information and future reference for optimizing laser dosage and dye concentration in cancer treatment.

Assessment of thermal effects of interstitial laser phototherapy on mammary tumors using proton resonance frequency method

“…A fast low angle shot (FLASH) gradient-echo pulse sequence was used for optimal temporal resolution and reliability. [38][39][40] The echo time (TE) and repetition time were set at 4 and 200 ms, respectively. Ten 1-mm slices were partitioned along the length of the active cylindrical tip, as shown in Fig.…”

Interstitial photoacoustic technique and computational simulation for temperature distribution and tissue optical properties in interstitial laser photothermal interaction

“…And temperature measurement based on water proton resonance frequency (PRF) in MRT has been used for interstitial laser therapy. 15,16 MRT provided noninvasive three-dimensional temperature distribution with high sensitivity. However, it had relatively low temporal resolution and its cost and complexity severely limited its practical applications.…”

“…Current noninvasive methods to measure tissue temperature include infrared thermography, [11][12][13] ultrasound thermograph, 14 and magnetic resonance thermometry (MRT). [15][16][17] Infrared thermography could provide sensitive and real-time detection. However, it can only measure surface temperature.…”

Diffuse optical tomography to monitor the photocoagulation front during interstitial photothermal therapy: Numerical simulations and measurements in tissue-simulating phantoms

“…Options for focal therapy include high-intensity focused ultrasound (HIFU) [8][9][10], cryotherapy [11][12][13], radiofrequency ablation [6,14], and photothermal therapy (PTT) [15,16]. Regardless of treatment modality, successful focal therapy requires tailoring the treatment delivery to the individual patient using realtime monitoring of the treatment progression.…”