Francesco Ria

Awareness of medical radiation exposure among patients: A patient survey as a first step for effective communication of ionizing radiation risks

INTRODUCTIONnThe European Directive 2013/59/EURATOM requires patient radiation dose information to be included in the medical report of radiological procedures. To provide effective communication to the patient, it is necessary to first assess the patients level of knowledge regarding medical exposure. The goal of this work is to survey patients current knowledge level of both medical exposure to ionizing radiation and professional disciplines and communication means used by patients to garner information.nnnMATERIAL AND METHODSnA questionnaire was designed comprised of thirteen questions: 737 patients participated in the survey. The data were analysed based on population age, education, and number of radiological procedures received in the three years prior to survey.nnnRESULTSnA majority of respondents (56.4%) did not know which modality uses ionizing radiation. 74.7% had never discussed with healthcare professionals the risk concerning their medical radiological procedures. 70.1% were not aware of the professionals that have expertise to discuss the use of ionizing radiation for medical purposes, and 84.7% believe it is important to have the radiation dose information stated in the medical report.nnnCONCLUSIONnPatients agree with new regulations that it is important to know the radiation level related to the medical exposure, but there is little awareness in terms of which modalities use X-Rays and the professionals and channels that can help them to better understand the exposure information. To plan effective communication, it is essential to devise methods and adequate resources for key professionals (medical physicists, radiologists, referring physicians) to convey correct and effective information.

Image noise and dose performance across a clinical population: patient size adaptation as a metric of CT performance.

Purpose Modern CT systems adjust X‐ray flux accommodating for patient size to achieve certain image noise values. The effectiveness of this adaptation is an important aspect of CT performance and should ideally be characterized in the context of real patient cases. The objective of this study was to characterize CT performance with a new metric that includes image noise and radiation dose across a clinical patient population. Materials and methods The study included 1526 examinations performed by three CT scanners (one GE Healthcare Discovery CT750HD, one GE Healthcare Lightspeed VCT, and one Siemens SOMATOM definition Flash) used for two routine clinical protocols (abdominopelvic with contrast and chest without contrast). An institutional monitoring system recorded all the data involved in the study. The dose–patient size and noise–patient size dependencies were linearized by considering a first‐order approximation of analytical models that describe the relationship between ionization dose and patient size, as well as image noise and patient size. A 3D‐fit was performed for each protocol and each scanner with a planar function, and the root mean square error (RMSE) values were estimated as a metric of CT adaptability across the patient population. Results The data show different scanner dependencies in terms of adaptability: the RMSE values for the three scanners are between 0.0385 HU1/2 and 0.0215 HU1/2. Conclusion A theoretical relationship between image noise, CTDIvol, and patient size was determined based on real patient data. This relationship may be interpreted as a new metric related to the scanners’ adaptability concerning image quality and radiation dose across a patient population. This method could be implemented to investigate the adaptability related to other image quality indexes and radiation dose in a clinical population.

Adaptability index: quantifying CT tube current modulation performance from dose and quality informatics

The balance between risk and benefit in modern CT scanners is governed by the automatic adaptation mechanisms that adjust x-ray flux for accommodating patient size to achieve certain image noise values. The effectiveness of this adaptation is an important aspect of CT performance and should ideally be characterized in the context of real patient cases. Objective of this study was to characterize CT performance with an index that includes image-noise and radiation dose across a clinical patient population. The study included 1526 examinations performed by three scanners, from two vendors, used for two clinical protocols (abdominopelvic and chest). The dose-patient size and noise-patient size dependencies were linearized, and a 3D-fit was performed for each protocol and each scanner with a planar function. In the fit residual plots the Root Mean Square Error (RMSE) values were estimated as a metric of CT adaptability across the patient population. The RMSE values were between 0.0344 HU1/2 and 0.0215 HU1/2: different scanners offer varying degrees of reproducibility of noise and dose across the population. This analysis could be performed with phantoms, but phantom data would only provide information concerning specific exposure parameters for a scan: instead, a general population comparison is a way to obtain new information related to the relevant clinical adaptability of scanner models. A theoretical relationship between image noise, CTDIvol and patient size was determined based on real patient data. This relationship may provide a new index related to the scanners adaptability concerning image quality and radiation dose across a patient population.

SU-F-I-48: Variability in CT Scanning Over-Range Across Clinical Operation

PURPOSEnInconsistency in the scan range for a given protocol can be a source of variability in patient dose. The purpose of this study was to determine the variability in the over-scan length in clinical CT operation for chest and abdominopelvic (A&P) protocols.nnnMETHODSnA total of 51 abdomen-pelvis and 121 chest CT exams were randomly selected from our clinical database. A commercial dose monitoring solution was used to extract and database the total exposure area and the geometrical information related to automatically-segmented anatomical landmarks for each target region. The data were exported off-line for the statistical analysis. The over-scan length (delta) was calculated as the difference between the real scanned length and ideal scanning length based on the anatomical landmarks for each target region.nnnRESULTSnThe mean delta for abdomen-pelvis exams was 12 mm (median 8 mm; min -191 mm; max 158 mm; standard deviation 71 mm). The average delta values at the interfaces with the chest and lower extremity regions were 69 mm and -57 mm, respectively. For chest exams, the average delta was 91 mm (median 93 mm; min 36 mm; max 190 mm; standard deviation 29 mm), and the average delta values at interfaces with the neck and abdomen regions were 26 mm and 65 mm, respectively. The percentage delta mean related to the abdomen-pelvis and chest lengths were 3% and 45%, respectively.nnnCONCLUSIONnAlthough there is greater over-scan in the chest region, there is considerably more variability in the over-scan area for abdomen-pelvis exams. Estimation of the over-scan length must be included in the effective dose estimates, which uses different coefficients for different target region (ICRP 102). Furthermore, knowledge of over-scan lengths and variability can guide steps to improve clinical consistency and operation.

102P: Ablative robotic radiosurgery for inoperable patients with stage IA–IB non small cell lung cancer

Background: The gold standard treatment for early stage non small-cell lung cancer (NSCLC) is surgical resection. For patients (pts) considered medically or functionally not amenable with surgery, radiotherapy is the alternative treatment. In the last years impressive local control (LC) rates have been reported using stereotactic radiotherapy treatment (SBRT) that provides an attractive option to deliver high dose per fraction and a high biological equivalent dose (BED). The purpose of our study is to evaluate outcome and follow-up data on our pts who underwent Cyberknife (CK) Radiosurgery for early NSCLC. Methods: Since February 2005 to October 2013, a total of 90 pts, median age of 76 years (range 42–90) with pathologically proven NSCLC, diagnosed as 41 stage IA and 56 stage IB were referred to our Radiotherapy Department for CK-SBRT. Selected tracking modalities depended on tumor size, location and extent of respiratory movement were performed. 27 pts with lower lobe lesions were treated with fiducial markers (1–3), in the others 70 fiducialless X sight option was used. The median tumor volume was 30 cc (range, 4–143). Depending on tumor size and location different curative dose regimens were used, but in all pts a high BED (>100Gy) was delivered to the tumor. The SBRT treatment dose of 25–60Gy was prescribed to the 75–85% isodose lines in 1–5 fractions. Median follow-up was 30 months (range, 2–102). Results: The Kaplan–Meier LC rate at 1, 3 and 5 years was respectively 98%, 88.5% and 81%. Reported acute side effects have generally been mild including esophagitis, fatigue, chest wall tenderness and cough. For the evaluation of toxicity we used the RTOG/EORTC scale. We detected a late radiation-induced local fibrosis using CT imaging in most pts, in 3 we observed grade 3 pneumonitis, in 1 patient chest wall pain and rib fracture and in another one G3 radiation induced mielopathy at an interval of 30 months following CK/SRS treatment. Conclusions: CK/SBRT for limited-stage primary lung cancer has been shown to be a promising treatment with high LC rates and very low toxicity. Prospective studies should be performed to determine whether this therapy may be an alternative option for surgery. Legal entity responsible for the study: Centro Diagnostico Italiano Funding: Centro Diagnostico Italiano Disclosure: All authors have declared no conflicts of interest. 103P Lobectomy for non-small cell lung cancer in octogenarians: A 7-year single center experience