Variability In Direction Research Articles

Optimal Setup and Parameters of Diffusion-Weighted Magnetic Resonance Imaging for Translational Evaluation of a Tumor Progression Model for Soft Tissue Sarcomas

PurposeDefining a microscopic tumor infiltration boundary is critical to the success of radiation therapy. Currently, radiation oncologists use margins to geometrically expand the visible tumor for radiation treatment planning in soft tissue sarcomas (STS). Image-based models of tumor progression would be critical to personalize treatment radiation field to the pattern of sarcoma spread. Evaluation of these models is necessary to demonstrate feasibility in the clinical setting. This study presents an imaging protocol for the preclinical evaluation of a tumor progression model in extremity STS. MethodsWe recruited seven healthy volunteers and acquired diffusion-weighted MRI (DW-MRI) images of the thigh on an MRI scanner used for imaging cancer patients in a radiation oncology department. We developed a protocol, which includes positioning the patient, configuring the RF coils, and setting the diffusion-weighted MRI sequence parameters. To find the optimal parameter configuration, the image signal-to-noise ratio (SNR) and the directional variability (DV) of the principal eigenvector of the diffusion tensor were calculated. ResultsThe mean SNR across all trials and 12 thigh muscles was 41 with a range of 12 to 72. The mean DV was 13° and ranged from 11° to 23°. The longest scan time was 22 min 58 s and the shortest 11 min 46 s. For the high-resolution image with a voxel volume of 1.3×1.3×6 mm3 and 38 slices, the optimal parameters were found to be a repetition time of 8000 ms, 12 signal averages, and 6 gradient directions. This configuration resulted in a scan time of 11 min 46 s, an SNR of 34, and a DV of 13°. ConclusionsA DW-MRI scan duration acceptable for imaging cancer patients was achieved with an image quality suitable for reproducible modeling of tumor infiltration. The developed protocol can be used for preclinical evaluation in STS patients.

A tiered approach to optimize pediatric laparoscopic appendectomy outcomes

Background/PurposeSurgical management of appendicitis accounts for ~30% of total expenditure in the practice of pediatric surgery and is associated with high cost variation. We hypothesize that incorporating single-incision laparoscopy (SILS) and the resultant by-product dual-incision laparoscopy (DILS) into a historically three-incision laparoscopic (TILS) appendectomy practice affords equal outcomes at lower cost. MethodsAppendectomies performed at a large-volume tertiary care children's hospital from 1/2015–12/2017 were retrospectively reviewed. Appendectomy technique and appendicitis severity were stratified against operative and admission direct variable (DV) costs. Secondary outcomes included perioperative time course and 30-day postoperative outcomes. ResultsA total of 970 appendectomies were analyzed during the study period (61% acute, 39% complex appendicitis). SILS and DILS had significantly lower mean DV costs and OR times compared to TILS for both acute and complex appendicitis while maintaining equivalent outcomes. ConclusionsSILS and DILS appendectomy techniques can be incorporated into pediatric surgical practice at lower cost than TILS appendectomy while maintaining equivalent outcomes. Further, the introduction of a tiered approach to laparoscopic appendectomy, in which all cases are started as SILS with additional incisions added based on operative difficulty, is estimated to save $74,580 annually in operative DV costs at a pediatric surgical center averaging 314 laparoscopic appendectomies per year. Type of StudyTreatment Study. Level of EvidenceLevel III.