Clinical Implementation and Initial Experience With a 1.5 Tesla MR-Linac for MR-Guided Radiation Therapy for Gynecologic Cancer: An R-IDEAL Stage 1 and 2a First in Humans Feasibility Study of New Technology Implementation.

PURPOSE: Magnetic resonance imaging-guided linear accelerator systems (MR-linacs) can facilitate the daily adaptation of radiation therapy plans. Here, we report our early clinical experience using a MR-linac for adaptive radiation therapy of gynecologic malignancies. METHODS AND MATERIALS: Treatments were planned with an Elekta Monaco v5.4.01 and delivered by a 1.5 Tesla Elekta Unity MR-linac. The system offers a choice of daily adaptation based on either position (ATP) or shape (ATS) of the tumor and surrounding normal structures. The ATS approach has the option of manually editing the contours of tumors and surrounding normal structures before the plan is adapted. Here, we documented the duration of each treatment fraction; set-up variability (assessed by isocenter shifts in each plan) between fractions; and, for quality assurance, calculated the percentage of plans meeting the γ-criterion of 3%/3-mm distance to agreement. Deformable accumulated dose calculations were used to compare accumulated versus planned dose for patient treated with exclusively ATP fractions. RESULTS: Of the 10 patients treated with 90 fractions on the MR-linac, most received boost doses to recurrence in nodes or isolated tumors. Each treatment fraction lasted a median 32 minutes; fractions were shorter with ATP than with ATS (30 min vs 42 min, P < .0001). The γ criterion for all fraction plans exceeded >90% (median, 99.9%; range, 92.4%-100%; ie, all plans passed quality assurance testing). The average extent of isocenter shift was <0.5 cm in each axis. The accumulated dose to the gross tumor volume was within 5% of the reference plan for all ATP cases. Accumulated doses for lesions in the pelvic periphery were within <1% of the reference plan as opposed to -1.6% to -4.4% for central pelvic tumors. CONCLUSIONS: The MR-linac is a reliable and clinically feasible tool for treating patients with gynecologic cancer.

Brain stereotactic radiosurgery using MR-guided online adaptive planning for daily setup variation: An end-to-end test.

Online magnetic resonance (MR)-guided radiotherapy is expected to benefit brain stereotactic radiosurgery (SRS) due to superior soft tissue contrast and capability of daily adaptive planning. The purpose of this study was to investigate daily adaptive plan quality with setup variations and to perform an end-to-end test for brain SRS with multiple metastases treated with a 1.5-Tesla MR-Linac (MRL). The RTsafe PseudoPatient Prime brain phantom was used with a delineation insert that includes two predefined structures mimicking gadolinium contrast-enhanced brain lesions. Daily adaptive plans were generated using six preset and six random setup variations. Two adaptive plans per daily MR image were generated using the adapt-to-position (ATP) and adapt-to-shape (ATS) workflows. An adaptive patient plan was generated on a diagnostic MR image with simulated translational and rotational daily setup variation and was compared with the reference plan. All adaptive plans were compared with the reference plan using the target coverage, Paddick conformity index, gradient index (GI), Brain V12 or V20, optimization time and total monitor units. Target doses were measured as an end-to-end test with two ionization chambers inserted into the phantom. With preset translational variations, V12 from the ATS plan was 17% lower than that of the ATP plan. With a larger daily setup variation, GI and V12 of the ATS plan were 10% and 16% lower than those of the ATP plan, respectively. Compared to the ATP plans, the plan quality index of the ATS plans was more consistent with the reference plan, and within 5% in both phantom and patient plans. The differences between the measured and planned target doses were within 1% for both treatment workflows. Treating brain SRS using an MRL is feasible and could achieve satisfactory dosimetric goals. Setup uncertainties could be accounted for using online plan adaptation. The ATS workflow achieved better dosimetric results than the ATP workflow at the cost of longer optimization time.

Online adaptive planning for prostate stereotactic body radiotherapy using a 1.5 Tesla magnetic resonance imaging-guided linear accelerator.

Recent advances in integrating 1.5 Tesla magnetic resonance (MR) imaging with a linear accelerator (MR-Linac) allow MR-guided stereotactic body radiotherapy (SBRT) for prostate cancer. Choosing an optimal strategy for daily online plan adaptation is particularly important for MR-guided radiotherapy. We analyzed deformable dose accumulation on scans from four patients and found that daily anatomy changes had little impact on the delivered dose, with the dose to the prostate within 0.5% and dose to the rectum/bladder mostly less than 0.5 Gy. These findings could help in the choice of an optimal strategy for online plan adaptation for MR-guided prostate SBRT.

Initial Feasibility and Clinical Implementation of Daily MR-Guided Adaptive Head and Neck Cancer Radiation Therapy on a 1.5T MR-Linac System: Prospective R-IDEAL 2a/2b Systematic Clinical Evaluation of Technical Innovation.

PURPOSE: This prospective study is, to our knowledge, the first report of daily adaptive radiation therapy (ART) for head and neck cancer (HNC) using a 1.5T magnetic resonance imaging-linear accelerator (MR-linac) with particular focus on safety and feasibility and dosimetric results of an online rigid registration-based adapt to position (ATP) workflow. METHODS AND MATERIALS: Ten patients with HNC received daily ART on a 1.5T/7MV MR-linac, 6 using ATP only and 4 using ATP with 1 offline adapt-to-shape replan. Setup variability with custom immobilization masks was assessed by calculating the mean systematic error (M), standard deviation of the systematic error (Σ), and standard deviation of the random error (σ) of the isocenter shifts. Quality assurance was performed with a cylindrical diode array using 3%/3 mm γ criteria. Adaptive treatment plans were summed for each patient to compare the delivered dose with the planned dose from the reference plan. The impact of dosimetric variability between adaptive fractions on the summation plan doses was assessed by tracking the number of optimization constraint violations at each individual fraction. RESULTS: The random errors (mm) for the x, y, and z isocenter shifts, respectively, were M = -0.3, 0.7, 0.1; Σ = 3.3, 2.6, 1.4; and σ = 1.7, 2.9, 1.0. The median (range) γ pass rate was 99.9% (90.9%-100%). The differences between the reference and summation plan doses were -0.61% to 1.78% for the clinical target volume and -11.74% to 8.11% for organs at risk (OARs), although an increase greater than 2% in OAR dose only occurred in 3 cases, each for a single OAR. All cases had at least 2 fractions with 1 or more constraint violations. However, in nearly all instances, constraints were still met in the summation plan despite multiple single-fraction violations. CONCLUSIONS: Daily ART on a 1.5T MR-linac using an online ATP workflow is safe and clinically feasible for HNC and results in delivered doses consistent with planned doses.

Hábitos alimentarios y estado nutricional de niños y niñas que asisten a las Escuelas Deportivas Integrales del Instituto Nacional de Deporte, Región de Ñuble / Eating habits and nutritional status of children attending the Integral Sports Schools of the National Sports Institute, Ñuble Region, Chile

RESUMEN La malnutrición por exceso se ha convertido en un problema de salud pública a través de todo el ciclo vital. El objetivo del estudio fue analizar los hábitos alimentarios y el estado nutricional de niños y niñas que asisten a las Escuelas Deportivas Integrales (EDI) del Instituto Nacional de Deporte en la comuna de Chillán. Se realizó evaluación antropométrica y aplicación de encuesta sobre hábitos alimentarios, que permitía medir alimentos consumidos de manera diaria, semanal y mensual de: frutas, verduras, lácteos, agua, carne, pescado, legumbres, golosinas dulces y saladas, productos fritos, comida rápida y embutidos. En los resultados, se confirma una alta prevalencia de malnutrición por exceso (58,7%). Para el cumplimiento de las Guías Alimentarias Basadas en Alimentos (GABAS) para la población chilena, se observó sólo un 59,2% en frutas, 71,4% para verduras, 13,8% en pescado, 39,3% en legumbres y 66,3% en lácteos. Diariamente, más del 65% consume golosinas dulces y/o saladas. Semanalmente, la comida rápida y productos fritos se ingieren en un 66% y 79% respectivamente. Se sugiere la necesidad de realizar intervenciones multidisciplinarias de prevención y promoción de la salud, orientadas a mejorar estilos de vida saludables en la población infantil y así contribuir a disminuir los índices de morbilidad infantil.

ABSTRACT Over nutrition has become a public health problem over the life cycle. The objective of the study was to analyze the eating habits and nutritional status of children attending the Integral Sports Schools (ISS) of the National Sports Institute in Chillán, Chile. An anthropometric evaluation was performed; an eating habits survey, which measured the consumption of fruit, vegetables, dairy products, water, meat, fish, legumes, sweet and salty treats, fried products, junk food, and cold meats on a daily, weekly, and monthly basis was completed. Results confirmed a high prevalence of overnutrition (58.7%). Complying with Food Based Dietary Guidelines for the Chilean Population, values were 59.2% for fruit, 71.4% for vegetables, 13.8% for fish, 39.3% for legumes, and 66.3% for dairy products. More than 65% of the children ate sweet and/or salty treats on a daily basis. Weekly intake of junk food and fried products was 66% and 79%, respectively. Multidisciplinary prevention and health promotion interventions are required to improve healthy lifestyles in children and thus contribute to reducing child morbidity rates.