Magnetic Resonance Image-Guided Radiotherapy (MRIgRT): A 4.5-Year Clinical Experience.

AIMS: Magnetic resonance image-guided radiotherapy (MRIgRT) has been clinically implemented since 2014. This technology offers improved soft-tissue visualisation, daily imaging, and intra-fraction real-time imaging without added radiation exposure, and the opportunity for adaptive radiotherapy (ART) to adjust for anatomical changes. Here we share the longest single-institution experience with MRIgRT, focusing on trends and changes in use over the past 4.5 years. MATERIALS AND METHODS: We analysed clinical information, including patient demographics, treatment dates, disease sites, dose/fractionation, and clinical trial enrolment for all patients treated at our institution using MRIgRT on a commercially available, integrated 0.35 T MRI, tri-cobalt-60 device from 2014 to 2018. For each patient, factors including disease site, clinical rationale for MRIgRT use, use of ART, and proportion of fractions adapted were summated and compared between individual years of use (2014-2018) to identify shifts in institutional practice patterns. RESULTS: Six hundred and forty-two patients were treated with 666 unique treatment courses using MRIgRT at our institution between 2014 and 2018. Breast cancer was the most common disease, with use of cine MRI gating being a particularly important indication, followed by abdominal sites, where the need for cine gating and use of ART drove MRIgRT use. One hundred and ninety patients were treated using ART in 1550 fractions, 67.6% (1050) of which were adapted. ART was primarily used in cancers of the abdomen. Over time, breast and gastrointestinal cancers became increasingly dominant for MRIgRT use, hypofractionated treatment courses became more popular, and gastrointestinal cancers became the principal focus of ART. DISCUSSION: MRIgRT is widely applicable within the field of radiation oncology and new clinical uses continue to emerge. At our institution to date, applications such as ART for gastrointestinal cancers and accelerated partial breast irradiation (APBI) for breast cancer have become dominant indications, although this is likely to continue to evolve.

An automated method for adaptive radiation therapy for prostate cancer patients using continuous fiducial-based tracking.

Electromagnetic tracking technology is primarily used for continuous prostate localization during radiotherapy, but offers potential value for evaluation of dosimetric coverage and adequacy of treatment for dynamic targets. We developed a highly automated method for daily computation of cumulative dosimetric effects of intra- and inter-fraction target motion for prostate cancer patients using fiducial-based electromagnetic tracking. A computer program utilizing real-time tracking data was written to (1) prospectively determine appropriate rotational/translational motion limits for patients treated with continuous isocenter localization; (2) retrospectively analyze dosimetric target coverage after daily treatment, and (3) visualize three-dimensional rotations and translations of the prostate with respect to the planned target volume and dose matrix. We present phantom testing and a patient case to validate and demonstrate the utility of this application. Gamma analysis of planar dose computed by our application demonstrated accuracy within 1%/1 mm. Dose computation of a patient treatment revealed high variation in minimum dose to the prostate (D(min)) over 40 fractions and a drop in the D(min) of approximately 8% between a 5 mm and a 3 mm PTV margin plan. The infrastructure has been created for patient-specific treatment evaluation using continuous tracking data. This application can be used to increase confidence in treatment delivery to targets influenced by motion.

Long-term follow-up of upper extremity implanted venous access devices in oncology patients.

PURPOSE: To evaluate function and assess incidence of complications relating to upper extremity implanted venous access devices placed in oncology patients primarily for chemotherapy. MATERIALS AND METHODS: The authors retrospectively evaluated the clinical course of 205 upper extremity implanted venous access devices placed with fluoroscopic and sonographic guidance in 204 patients during a 2-year period. All patients had a diagnosis of malignancy for which chemotherapy was planned. Follow-up data were collected by patient examination, direct evaluation of device function, as well as chart review and review of relevant imaging procedures. A modified technique for device placement is described. RESULTS: The devices were placed successfully on the initial attempt in all cases. Clinical follow-up was obtained for 195 devices (95.1%) for a total device service period of 33,619 days (mean service interval = 169 days). Seventy-eight devices (40%) had service intervals greater than 180 days. Thirty-seven devices (19% of total devices) led to 39 complications (0.116 event/100 days). No immediate procedural complications were incurred. Eight complications occurred after 180 days of port service. Nineteen devices (9.7% of total devices followed) required removal as a result of complication. Common complications included port malfunction requiring urokinase to clear (n = 10; 0.030 event/100 days), ipsilateral upper extremity deep venous thrombosis (n = 9; 0.027), and local infection (n = 7, 0.021). A comparison of these results relative to other published series of similar devices placed for mixed indications is presented. CONCLUSIONS: Implanted venous access devices are an effective means of long-term venous access in oncology patients. Complication rates in this large series compared favorably to other published radiologic and surgical series. Analysis of complications in a subgroup of extended use implanted venous access devices (greater than 180 days follow-up) showed no statistically significant (P < .05) difference from the larger group of devices.