Typical values of z-resolution for different Digital Breast Tomosynthesis systems evaluated in a multicenter study

PURPOSE

The aim of the present study, conducted by a working group of the Italian Association of Medical Physics (AIFM), was to define typical z-resolution values for different digital breast tomosynthesis (DBT) models to be used as a reference for quality control (QC). Currently, there are no typical values published in internationally agreed QC protocols.

METHODS

To characterize the z-resolution of the DBT models, the full width at half maximum (FWHM) of the artifact spread function (ASF), a technical parameter that quantifies the signal intensity of a detail along reconstructed planes, was analyzed. Five different commercial phantoms, CIRS Model 011, CIRS Model 015, Modular DBT phantom, Pixmam 3-D, and Tomophan, were evaluated on reconstructed DBT images and 82 DBT systems (6 vendors, 9 models) in use at 39 centers in Italy were involved.

RESULTS

The ASF was found to be dependent on the detail size, the DBT angular acquisition range, the reconstruction algorithm and applied image processing. In particular, a progressively greater signal spread was observed as the detail size increased and the acquisition angle decreased. However, a clear correlation between signal spread and angular range width was not observed due to the different signal reconstruction and image processing strategies implemented in the algorithms developed by the vendors studied.

CONCLUSIONS

The analysis led to the identification of typical z-resolution values for different DBT model-phantom configurations that could be used as a reference during a QC program.

National survey to update the diagnostic reference levels in interventional radiology procedures in Italy: working methodology

Interventional Radiology (IR) deals with the diagnosis and treatment of various diseases through medically guided imaging. It provides unquestionable benefits to patients, but requires, in many cases, the use of high doses of ionizing radiation with a high impact on radiation risks to patients and to overall dose to the population. The International Commission on Radiological Protection introduced Diagnostic reference levels (DRLs) as an effective tool to facilitate dose verification and optimize protection for patients undergoing radiological procedures. In addition, EURATOM Council Directive 2013/59 and its Italian transposition (Legislative Decree 101/2020) have reiterated that DRLs must be established for many common radiological diagnostic procedures to compare the radiation dose delivered for the same diagnostic examination. Within this framework, Istituto Superiore di Sanità-Italian National Institute of Health (ISS)-, in collaboration with relevant Italian Scientific Societies, has provided documents on DRLs in radiological practices such as diagnostic and IR and diagnostic nuclear medicine. These reference documents enable National Hospitals to comply national regulation. The implementation of DRLs in IR is a difficult task because of the wide distribution of doses to patients even within the same procedure. Some studies have revealed that the amount of radiation in IR procedures is influenced more by the complexity of the procedure than by the weight of the patient, so complexity should be included in the definition of DRLs. For this reason, ISS promoted a survey among a sample of Italian Centers update national DRL in IR procedures with related complexity factors than can be useful for other radiological centers and to standardize the DRLs values. In the present paper the procedural methodology developed by ISS and used for the survey will be illustrated.

EVALUATION OF AN ACTIVE PERSONAL DOSIMETRY SYSTEM IN INTERVENTIONAL RADIOLOGY AND NEURORADIOLOGY: PRELIMINARY RESULTS

Active personal dosimeters (APD) supply real-time data on radiation dose rates and equivalent doses, enabling reduction of operator exposure to radiation in diagnostic and surgical procedures. Data from the use of the Raysafe i2 APD system in an angiography room are reported. Preliminary characterisation of the APD system was first carried out in terms of angular dependence and of H_p(10) response during the simulation of five typical surgical protocols. Reference measurements, simultaneously obtained from TLDs, were used to obtain a correction factor. APD data for patients and for primary and secondary operators were then recorded over 52 surgical procedures. The correlation between kerma air product (KAP) and reference point air kerma (K_ar) and operator dose as a function of position with respect to the source of radiation is reported. The data indicate that the APD system could help operators to optimise behaviours and use of room protection to effectively minimise radiation dose.

Double stenting procedure and coil embolization in a patient with carotid stenosis and incidental ipsilateral intracranial aneurysm. A case report and dosimetric evaluation

We describe a case of incidental detection of an intracranial left ICA wide-necked aneurysm during digital subtraction angiography performed to assess a sub-occlusive and calcified stenosis in the extracranial portion of the same artery. Angioplasty and stenting of ICA stenosis, plus intracranial stent deployment across the aneurysm neck was performed during the same procedure. Aneurysm coil embolization was postponed to a further session one month later. The radiation dose and irradiated areas were also evaluated during endovascular procedures.

A study on maximum skin dose in cerebral embolization procedures

BACKGROUND AND PURPOSE

It is essential to measure the skin dose of radiation received by patients during interventional neuroradiologic procedures performed under fluoroscopic guidance, such as embolization of cerebral aneurysms, which is regarded as a high-dose interventional radiology procedure. In this study, we report a method for evaluating maximum skin dose (MSD), an ideal marker of radiation-induced effects, based on an innovative use of radiochromic films.

MATERIALS AND METHODS

Forty-eight procedures were studied in 42 patients undergoing embolization of cerebral aneurysms. Fluoroscopic and digital dose-area product (DAP), fluoroscopy time, and total number of acquired images were recorded for all procedures. The MSD was measured using Gafchromic XR type R films.

RESULTS

The MSD was measured in one group of 21 procedures. The coefficient (kappa) of the interpolation line between the skin dose and the DAP (kappa = 0.0029 cm(-2)) was determined. An approximate value of MSD from the DAP for the remaining 27 procedures was estimated by means of an interpolation line. The mean MSD was found to be 1.16 Gy (range, 0.23-3.20 Gy).

CONCLUSION

The use of radiochromic XR type R films was shown to be an effective method for measuring MSD. These films have the advantage of supplying information on both the maximum dose and the distribution of the dose: this satisfies the most stringent interpretation of Food and Drug Administration, American College of Radiology, and international recommendations for recording skin dose.

[Analysis and comparison of various quality protocols for radiotherapy linear accelerators]

The main parameters determining the quality of an electron beam produced by a linear accelerator for medical use were considered in this study, particularly: flatness, symmetry and uniformity. We analyzed and compared several protocols issued by national and international associations (such as the AAPM, IPSM, ICRU, NACP), the software protocol developed for the measurement system we used (Multidata) and the measurement instructions recommended by the accelerator manufacturer (Siemens). The above associations issue quality protocols to ensure system performances suitable for medical use, to increase patient safety and to improve the treatment outcome. Radiation therapy safety and improvement depend on correct dose measurements and dose distribution in the treated volume. Once the dose value per monitor unit ratio (Gy/M.U.) is determined, controls are necessary to be sure that the value does not change in time and that the dose distribution has the same effect in the whole treated volume. Our goal is to point out the differences and the affinities in the definition of the parameters, which change slightly in the different protocols, and to study the origin of the differences found when the experimental results were compared. Another important issue is represented by the frequency of quality controls, which are definitely different from the fast checks which are often performed. In conclusion, some suggestions are provided for the choice of the quality protocol to follow.