Intra-luminal thermometry: is tissue type assignment a necessity for thermal analysis?

Area of Science:

• Oncology
• Medical Physics
• Radiotherapy

Background:

• Interstitial thermometry typically differentiates tumor from normal tissue.
• Pelvic tumor thermometry often uses intra-luminal tracks.
• The relevance of tissue discrimination for deep regional hyperthermia dosimetry using intra-luminal and adjacent thermometry is unclear.

Purpose of the Study:

• To analyze temperature data to determine if differentiating between normal and tumor tissue is relevant for deep regional hyperthermia thermal dosimetry.
• To assess the clinical relevance of temperature differences between tumor and normal tissues in the lower pelvis.

Main Methods:

• Seventy-five patients with locally advanced cervical carcinoma were included.
• 100 hyperthermia treatments were analyzed from patients treated with radiotherapy +/- chemotherapy.
• Tissue type was defined using CT scans, and temperature maps were analyzed for insertion length and slope changes.

Main Results:

• Average T50 (median temperature) for bladder tumor and normal tissue were 40.9°C +/- 0.9°C and 40.8°C +/- 0.9°C, respectively.
• Average T50 for vagina tumor and normal tissue were 39.7°C +/- 0.9°C and 40.1°C +/- 0.9°C, respectively.
• Significant temperature differences were found between bladder tumor/normal tissue and vagina tumor/normal tissue (p=0.0001), but not for rectal tissue.

Conclusions:

• The cause of observed temperature differences between tumor and normal tissues is unknown.
• The small temperature differences and potential inaccuracy in tissue assignment suggest a lack of clinical relevance.
• Current findings do not support the need to differentiate between normal and tumor tissue in intra-luminal thermometry for this patient group.