Stereotactic body radiotherapy of central lung tumours using a 1.5 T MR-linac: First clinical experiences.

Background: MRI-guidance may aid better discrimination between Organs at Risk (OARs) and target volumes in proximity of the mediastinum. We report the first clinical experiences with Stereotactic Body Radiotherapy (SBRT) of (ultra)central lung tumours on a 1.5 T MR-linac. Materials and Methods: Patients with an (ultra)central lung tumour were selected for MR-linac based SBRT treatment. A T2-weighted 3D sequence MRI acquired during free breathing was used for daily plan adaption. Prior to each fraction, contours of Internal Target Volume (ITV) and OARs were deformably propagated and amended by a radiation oncologist. Inter-fractional changes in volumes and coverage of target volumes as well as doses in OARs were evaluated in offline and online treatment plans. Results: Ten patients were treated and completed 60 Gy in 8 or 12 fractions. In total 104 fractions were delivered. The median time in the treatment room was 41 min with a median beam-on time of 8.9 min. No grade ≥3 acute toxicity was observed. In two patients, the ITV significantly decreased during treatment (58 % and 37 %, respectively) due to tumour shrinkage. In the other patients, 81 % of online ITVs were within ±15 % of the volume of fraction 1. Comparison with the pre-treatment plan showed that ITV coverage of the online plan was similar in 52 % and improved in 34 % of cases. Adaptation to meet OAR constraints, led to decreased ITV coverage in 14 %. Conclusions: We describe the workflow for MR-guided Radiotherapy and the feasibility of using 1.5 T MR-linac for SBRT of (ultra) central lung tumours.

Optimizing treatment of brain metastases in an era of novel systemic treatments: a single center consecutive series.

BACKGROUND: The multidisciplinary management of patients with brain metastases consists of surgical resection, radiation treatment and systemic treatment. Tailoring and timing these treatment modalities is challenging. This study presents real-world data from consecutively treated patients and assesses the impact of all treatment strategies and their relation with survival. The aim is to provide new insights to improve multidisciplinary decisions towards individualized treatment strategies in patients with brain metastases. METHODS: A retrospective consecutive cohort study was performed. Patients with brain metastases were included between June 2018 and May 2020. Brain metastases of small cell lung carcinoma were excluded. Overall survival was analyzed in multivariable models. RESULTS: 676 patients were included in the study, 596 (88%) received radiotherapy, 41 (6%) awaited the effect of newly started or switched systemic treatment and 39 (6%) received best supportive care. Overall survival in the stereotactic radiotherapy group was 14 months (IQR 5-32) and 32 months (IQR 11-43) in patients who started or switched systemic treatment and initially did not receive radiotherapy. In patients with brain metastases without options for local or systemic treatment best supportive care was provided, these patients had an overall survival of 0 months (IQR 0-1). Options for systemic treatment, Karnofsky Performance Score ≥ 70 and breast cancer were prognostic for a longer overall survival, while progressive extracranial metastases and whole-brain-radiotherapy were prognostic for shorter overall survival. CONCLUSIONS: Assessing prognosis in light of systemic treatment options is crucial after the diagnosis of brain metastasis for the consideration of radiotherapy versus best supportive care.

Performance analysis of a dedicated breast MR-HIFU system for tumor ablation in breast cancer patients.

MR-guided HIFU ablation is a promising technique for the non-invasive treatment of breast cancer. A phase I study was performed to assess the safety and treatment accuracy and precision of MR-HIFU ablation in breast cancer patients (n=10) using a newly developed MR-HIFU platform dedicated to applications in the breast. In this paper a technical analysis of the performance of the dedicated breast MR-HIFU system during breast tumors ablation is described. The main points of investigation were the spatial targeting accuracy and precision of the system and the performance of real-time respiration-corrected MR thermometry.The mean targeting accuracy was in the range of 2.4-2.6 mm, whereas the mean targeting precision was in the range of 1.5-1.8 mm. To correct for respiration-induced magnetic field fluctuations during MR temperature mapping a look-up-table (LUT)-based correction method was used. An optimized procedural sedation protocol in combination with the LUT-based correction method allowed for precise MR thermometry during the ablation procedure (temperature standard deviation <3 °C). No unwanted heating in the near field (i.e. skin) nor in the far field (pectoral muscle) was detected.The newly developed dedicated breast MR-HIFU system allows for safe, accurate and precise ablation of breast tumors.

3-T breast magnetic resonance imaging in patients with suspicious microcalcifications on mammography.

OBJECTIVE: To investigate the diagnostic value of 3-Tesla (T) breast MRI in patients presenting with microcalcifications on mammography. METHODS: Between January 2006 and May 2009, 123 patients with mammographically detected BI-RADS 3­5 microcalcifications underwent 3-T breast MRI before undergoing breast biopsy. All MRIs of the histopathologically confirmed index lesions were reviewed by two breast radiologists. The detection rate of invasive carcinoma and ductal carcinoma in situ (DCIS) was evaluated, as well as the added diagnostic value of MRI over mammography and breast ultrasound. RESULTS: At pathology, 40/123 (33%) lesions proved malignant; 28 (70%) DCIS and 12 (30%) invasive carcinoma. Both observers detected all invasive malignancies at MRI, as well as 79% (observer 1) and 86% (observer 2) of in situ lesions. MRI in addition to conventional imaging led to a significant increase in area under the receiver operating characteristic (ROC) curve from 0.67 (95% CI 0.56­0.79) to 0.79 (95% CI 0.70­0.88, observer 1) and to 0.80 (95% CI 0.71­0.89, observer 2), respectively. CONCLUSIONS: 3-T breast MRI was shown to add significant value to conventional imaging in patients presenting with suspicious microcalcifications on mammography. KEY POINTS: • 3-T MRI is increasingly used for breast imaging in clinical practice. • On 3-T breast MRI up to 86% of DCIS lesions are detected. • 3-T MRI increases the diagnostic value in patients with mammographically detected microcalcifications.

Effect of stenting on cerebral CT perfusion in symptomatic and asymptomatic patients with carotid artery stenosis.

BACKGROUND AND PURPOSE: The introduction of CAS has led to increased treatment of both symptomatic and asymptomatic patients with internal carotid stenosis. This study was performed to compare the effect of stent placement on cerebral perfusion in symptomatic and asymptomatic patients using CT perfusion. MATERIALS AND METHODS: We included 45 patients with carotid artery stenosis of ≥70% who underwent arterial stent placement. Thirty-one patients were treated because of symptoms; 14 asymptomatic patients were treated before coronary artery bypass grafting. Patients underwent CTP before and after stent placement. We calculated MTT, CBV, and CBF, and derived relative numbers that compared treated with untreated hemispheres: ratios of CBV and CBF and difference in MTT. We compared the effect of carotid stent placement on cerebral perfusion in symptomatic and asymptomatic patients. RESULTS: All perfusion parameters changed significantly after treatment in symptomatic patients: rCBF increased from 0.81 to 0.93 (P < .001), rCBV decreased from 1.02 to 0.95 (P < .05), and dMTT decreased from 1.29 to 0.14 (P < .001). In asymptomatic patients only, rCBF changed significantly with an increase from 0.92 to 1.03 (P < .05). When we compared symptomatic and asymptomatic patients before treatment, rCBF in symptomatic patients was significantly lower. The decrease of rCBV after treatment in symptomatic patients resulted in a significantly lower value than in asymptomatic patients. CONCLUSIONS: Carotid artery stent placement improves blood flow in the affected hemisphere in symptomatic and asymptomatic patients. CBF before treatment is more strongly impaired in patients with symptomatic carotid stenosis. Compensatory hyperemia on the symptomatic side before treatment (rCBV > 1) turns into hypoxemia after treatment, suggesting impaired autoregulation in these patients.