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A novel approach for the definition of small-field sizes using the concept of superellipse
Ignasi Méndez Carot, Božidar Casar, 2021, izvirni znanstveni članek

Povzetek: In radiotherapy, field sizes are defined in terms of the dimensions of the irradiation area. However, geometric square fields result in irradiation areas with rounded corners, which become almost elliptical for small fields. Superellipses are a family of curves encompassing shapes lying between ellipses and rectangles. The purpose of this work was to analyze the advantages and disadvantages of a novel approach that describes small-field sizes with superellipses. Square fields with nominal side lengths ranging from 0.5 to 10 cm were irradiated with two different linacs using 6 and 10 MV photon beams with and without flattening filters. Field size dimensions and output factors were measured by employing radiochromic films and the software. An alternative definition of equivalent square small-field size based on the superellipse (Sse) was introduced. The degree n of the superellipse for 10 cm nominal fields measured between 14.8 % 1.0 to 27.7 % 1.9. However, it decreased with the field size, down to between 2.26 % 0.10 and 2.64 % 0.15 for 0.5 cm nominal side lengths. A relation between the degree n and the equivalent square small-field size (Sclin) as defined by Cranmer-Sargison et al. [%A methodological approach to reporting corrected small field relative outputs,% Radiotherapy and Oncology 109, 350%355 (2013)] was found. For nominal side lengths of 10 cm, Sse was between 0.34 % 0.04% and 0.10 % 0.01% smaller than Sclin, while for 0.5 cm nominal side length Sse was between 9.5 % 0.6% and 7.4 % 0.7% smaller than Sclin. There was no significant difference in the goodness of the regression between using Sse or Sclin to fit field output factors with the function proposed by Sauer and Wilbert. Small fields were found to be more accurately characterized with superellipses. The advantages and disadvantages of describing field sizes with superellipses were examined. Field output factors can be derived with equivalent square small-field sizes based on the superellipse approach.
Ključne besede: superellipsa, small fields, dosimetry, radiotherapy
Objavljeno v DiRROS: 07.09.2022; Ogledov: 304; Prenosov: 183
.pdf Celotno besedilo (2,84 MB)
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Idiopathic pulmonary fibrosis in patients with early-stage non-small-cell lung cancer after surgical resection
Nežka Hribernik, Igor Požek, Izidor Kern, 2019, izvirni znanstveni članek

Povzetek: Background. The outcomes of patients with both lung cancer and idiopathic pulmonary fibrosis (IPF) are unfavorable. Therapeutic interventions for lung cancer such as surgery can cause acute exacerbation of IPF (aeIPF). This study aimed to assess the frequency of IPF in a group of patients with early-stage non-small-cell lung cancer (NSCLC) and to report clinical characteristics and outcomes of this cohort of patients. Patients and methods. This observational cohort retrospective study analyzed 641 pathological records of patients after surgical resection of early-stage non-small-cell lung cancer (NSCLC) at University Clinic Golnik from May 2010 to April 2017. Pathological records of NSCLC with coexisting IPF were reviewed. CT scans and biopsy specimens for this group of patients were analyzed by a thoracic radiologist and pathologist, independently. We searched radiological and pathological features of usual interstitial pneumonia (UIP) pattern in this group of patients. We report the clinical characteristics and outcome of this cohort of patients. Results. Out of 641 patients with early-stage NSCLC, only 13 (2.0%) had histologically and radiologically proven coexisting UIP/IPF. Squamous cell carcinoma was the most common type of lung cancer (7/13 patients). The majority of tumors were small size (all being pT1 or pT2), stage I–II (11/13 patients), located in the lower lung lobes (11/13 patients). Almost all patients were current or ex-smokers (11/13 patients). There were two pathologically confirmed fatal cases (15.4%) due to aeIPF in the first two months after radical treatment, one after adjuvant radiotherapy and the other after surgery. Out of 13 patients, one patient had a lung cancer relapse. Conclusions. Frequency of UIP/IPF in surgically treated early stage NSCLC is rather low. Our observational study shows that radical treatment of lung cancer can cause aeIPF with dismal outcome in this group of patients. The standard of care in these mostly elderly patients still remains unresolved.
Ključne besede: non-small-cell lung cancer, early-stage cancer, idiopathic pulmonary fibrosis, surgery, radiotherapy
Objavljeno v DiRROS: 07.10.2020; Ogledov: 1708; Prenosov: 815
.pdf Celotno besedilo (969,72 KB)

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