Alexander Henry Thieme

Magnetic resonance thermometry: Methodology, pitfalls and practical solutions

Abstract Clinically established thermal therapies such as thermoablative approaches or adjuvant hyperthermia treatment rely on accurate thermal dose information for the evaluation and adaptation of the thermal therapy. Intratumoural temperature measurements have been correlated successfully with clinical end points. Magnetic resonance imaging is the most suitable technique for non-invasive thermometry avoiding complications related to invasive temperature measurements. Since the advent of MR thermometry two decades ago, numerous MR thermometry techniques have been developed, continuously increasing accuracy and robustness for in vivo applications. While this progress was primarily focused on relative temperature mapping, current and future efforts will likely close the gap towards quantitative temperature readings. These efforts are essential to benchmark thermal therapy efficiency, to understand temperature-related biophysical and physiological processes and to use these insights to set new landmarks for diagnostic and therapeutic applications. With that in mind, this review summarises and discusses advances in MR thermometry, providing practical considerations, pitfalls and technical obstacles constraining temperature measurement accuracy, spatial and temporal resolution in vivo. Established approaches and current trends in thermal therapy hardware are surveyed with respect to potential benefits for MR thermometry.

Role of Dose intensification for Salvage Radiation Therapy after Radical Prostatectomy

For primary radiation therapy (RT) of prostate cancer, dose intensification is established as standard of care. Less is known on the role of dose intensification in the postprostatectomy setting for salvage RT. Thus, we aimed to identify and summarize the existing literature. In retrospective analyses, dose-intensified salvage RT showed a superior biochemical control compared to standard dose salvage radiation with favorable acute and late gastrointestinal and genitourinary toxicity rates, especially when modern radiation techniques such as intensity modulated RT were applied. We identified one randomized phase III trial addressing the potential benefits of dose-intensified salvage RT (SAKK 09/10). Recently, acute gastrointestinal and genitourinary toxicities and early quality of life data of this trial were reported, and no significant difference in acute toxicities between both treatment arms were found; however, a significant worsening of genitourinary quality of life was noted in the dose-intensified treatment arm. Whereas dose-intensified salvage RT appears to be feasible and well tolerated, the improved biochemical control rates using dose intensified RT as suggested by retrospective analyses have yet to be validated by prospective trials.

A novel voxel based homogeneity index: Rationale and clinical implications for whole-brain radiation therapy

PURPOSE OR OBJECTIVE A homogeneity index (HI) measures the uniformity of a dose distribution within a given target volume. Traditional HIs only use a limited number of dose-volume histogram data-points for calculation. A voxel-based homogeneity index (VHI) is proposed which utilizes the entire information of the three-dimensional dose distribution. We compared the VHI with existing HIs and analyzed if VHI results were associated with treatment outcomes in patients who underwent therapeutic WBRT. MATERIAL AND METHODS The VHI analyzes deviations from the prescribed dose in each voxel of the target volume. We retrospectively analyzed WBRT treatment plans. Overall survival (OS), CNS progression-free-survival (CNS PFS) and hazard rates were compared for tertile-split levels of the VHI using the Kaplan-Meier methods and multivariable Cox-regression analysis. RESULTS WBRT treatment plans (n = 770) were used for HIs comparison. OS and CNS PFS were assessed for 430 patients. The VHI showed a higher sensitivity for dose inhomogeneities. Lower OS and CNS PFS were observed for higher levels of VHIUnderdosage, particularly in patients with good performance status (KPS >70%) (OS: Log-rank P = .007, HR = 1.37 95%CI [1.09, 1.72]). CONCLUSION Higher sensitivity and feasibility to assess treatment plan quality using the VHI were demonstrated. First clinical implications were found in terms of compromised OS/CNS PFS for WBRT with radiation underdosage.

EP-1925: Online open source software to assess adverse events of patients undergoing radiochemotherapy

We used the “Static sequential with verification and confirmation” method to perform the checklist. This method uses both initial configuration and mutual redundancy; the treatment planner writes down and calls the values on the checklist and the physician confirms that those values match the treatment intent. As part of a department practice quality improvement (PQI) project, we used a series of Plan, Do, Study, Act (PSDA) quality improvement cycles, and assessed the effectiveness of the safety checklist and the success of the project implementation. During each plan reviewed by the physician, we tracked two metrics: 1) Effectiveness of the checklist to catch a deviation and 2) Compliance of the physician to the checklist process. Additionally, we used a survey to assess communication dynamics between physician and planner.