Statistical Analysis of Ultrasonic Scattered Echoes Enables the Non-invasive Measurement of Temperature Elevations inside Tumor Tissue during Oncological Hyperthermia

Non-invasive monitoring of temperature elevations inside tumor tissue is imperative for the oncological thermotherapy known as hyperthermia. In the present study, two cancer patients, one with a developing right renal cell carcinoma and the other with pseudomyxoma peritonei, underwent hyperthermia. The two patients were irradiated with radiofrequency current for 40 min during hyperthermia. We report the results of our clinical trial study in which the temperature increases inside the tumor tissues of patients with right renal cell carcinoma and pseudomyxoma peritonei induced by radiofrequency current irradiation for 40 min could be detected by statistical analysis of ultrasonic scattered echoes. The Nakagami shape parameter m varies depending on the temperature of the medium. We calculated the Nakagami shape parameter m by statistical analysis of the ultrasonic echoes scattered from the tumor tissues. The temperature elevations inside the tumor tissues were expressed as increases in brightness on 2-D hot-scale maps of the specific parameter α_mod, indicating the absolute values of the percentage changes in m values. In the α_mod map for each tumor tissue, the brightness clearly increased with treatment time. In quantitative analysis, the mean values of α_mod were calculated. The mean value of α_mod for the right renal cell carcinoma increased to 1.35 dB with increasing treatment time, and the mean value of α_mod for pseudomyxoma peritonei increased to 1.74 with treatment time. The increase in both α_mod brightness and the mean value of α_mod implied temperature elevations inside the tumor tissues induced by the radiofrequency current; thus, the acoustic method is promising for monitoring temperature elevations inside tumor tissues during hyperthermia.

Multiple Breath-hold Volumetric Modulated Arc Therapy Under Fluoroscopic Image Guidance with an Implanted Fiducial Marker: An Advanced Technique

An advanced technique for multiple breath-hold volumetric modulated arc therapy (VMAT) has been proposed under fluoroscopic image guidance with a fiducial marker implanted close to a tumor. The marker coordinates on a digitally reconstructed radiography image at a gantry start angle, under a planned breath-hold condition, were transferred to the fluoroscopic image window. Then, a reference lateral line passing through the planned breath-hold marker position was drawn on the fluoroscopic image. Additional lateral lines were further added on both sides of the reference line with a distance of 3 mm as a tolerance limit for the breath-hold beam delivery. Subsequently, the patient was asked to breathe in slowly under fluoroscopy. Immediately after the marker position on the fluoroscopic image moved inside the tolerance range, the patient was asked to hold the breath and the VMAT beam was delivered. During the beam delivery, the breath-hold status was continuously monitored by checking if the deviation of the marker position exceeded the tolerance limit. As long as the marker stayed within the tolerance range, a segmented VMAT delivery continued for a preset period of 15 to 30 seconds depending on the breath-hold capability of each patient. As soon as each segmented delivery was completed, the beam interrupt button was pushed; subsequently, the patient was asked for free breathing. This procedure was repeated until all the segmented VMAT beams were delivered. A lung tumor case is reported here as an initial study. The proposed technique may be clinically advantageous for treating respiratory moving tumors including lung tumor, liver cancer, and other abdominal cancers.