Quantitative assessment of computed radiography quality control parameters

MAMMO_QC: Free software for quality control (QC) analysis in digital mammography and digital breast tomosynthesis compliant with the European guidelines and EUREF/EFOMP protocols

Quality Control (QC) tests in mammography are very important, since mammograms have been used as a population-based screening test for more than 30 years and QCs lead to better image quality and radiation safety for patients. European guidelines, EUREF and EFOMP protocols provide comprehensive QC guidelines for digital mammography (DM) and digital breast tomosynthesis (DBT) units, respectively. We developed a novel, fast, free and platform independent software (named MAMMO_QC) for QC performance tests in DM and tomosynthesis, based on the aforementioned guidelines. MAMMO_QC consists of a series of ImageJ plugins for DM and DBT. It does not require any programming knowledge and can be used to evaluate several performance parameters, such as pre-sampled modulation transfer function (pMTF), normalised noise power spectrum (NNPS), detective quantum efficiency (DQE), contrast-detail analysis based on the CDMAM 3.4 and 4.0 test tools, homogeneity and artefacts, automatic exposure control (AEC) performance. The user can use MAMMO_QC for acceptance, commissioning and routine QC performance analysis based on the European guidelines. We validated our results against well-established software products used in mammography and DBT (i.e., COQ, OBJ_IQ_reduced and Artinis CDMAM Analyzer). All the average relative differences were within 5.5%, and several years of usage and testing allows us to consider MAMMO_QC as an accurate and reliable tool for QC on DM and DBT systems. Our developed software for DM and DBT computes almost all the parameters stated in the European, EUREF and EFOMP guidelines. To the best of our knowledge, no such software has been developed so far.

Evaluation of US and MRI techniques for carotid stenosis: a novel phantom approach

Carotid atherosclerosis is very important in the pathogenesis of cerebral ischemia. Ultrasonography (US) and magnetic resonance imaging (MRI) are the predominant noninvasive techniques capable to identify the presence and stage of intra-plaque hemorrage. In this work, we propose a novel dedicated phantom that can be used for both US and MRI scanners to evaluate carotid atherosclerotic lesions. The phantom consists of a polymethyl metacrylate (PMMA) diagonally crossed by a PMMA hollow cylinder simulating a blood vessel. To simulate a stenosis, we inserted a plastic hollow tube inside the cylinder. Quantitative image analysis, based on accuracy measurements, was performed on two US and two MRI scanners. The accuracy measurements have highlighted the use of the 3.0 T MRI scanner to characterize the vessel stenosis. However, no significant difference between US and MRI techniques was found in Fisher exact test and inter-rater agreement. The concordance correlation coefficient showed a moderate agreement between some methods. Agreement between 3.0 T and other methods results poor, and this could be due to the fact that the 3.0 T has a better resolution compared to a US and MR 1.5 T. These methods seem to have similar efficacies for the evaluation of vessel stenosis, legitimizing the use of the developed phantom as a versatile and reproducible instrument that could be used during quality controls programs.

Method for automatic detection of defective ultrasound linear array transducers based on uniformity assessment of clinical images - A case study

The purpose of the present study was to test an idea of and describe a concept of a novel method of detecting defects related to horizontal nonuniformities in ultrasound equipment. The method is based on the analysis of ultrasound images collected directly from the clinical workflow. In total over 31000 images from three ultrasound scanners from two vendors were collected retrospectively from a database. An algorithm was developed and applied to the images, 150 at a time, for detection of systematic dark regions in the superficial part of the images. The result was compared with electrical measurements (FirstCall) of the transducers, performed at times when the transducers were known to be defective. The algorithm made similar detection of horizontal nonuniformities for images acquired at different time points over long periods of time. The results showed good subjective visual agreement with the available electrical measurements of the defective transducers, indicating a potential use of clinical images for early and automatic detection of defective transducers, as a complement to quality control.

CT and MRI slice separation evaluation by LabView developed software

The efficient use of Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) equipment necessitates establishing adequate quality-control (QC) procedures. In particular, the accuracy of slice separation, during multislices acquisition, requires scan exploration of phantoms containing test objects. To simplify such procedures, a novel phantom and a computerised LabView-based procedure have been devised, enabling determination the midpoint of full width at half maximum (FWHM) in real time while the distance from the profile midpoint of two progressive images is evaluated and measured. The results were compared with those obtained by processing the same phantom images with commercial software. To validate the proposed methodology the Fisher test was conducted on the resulting data sets. In all cases, there was no statistically significant variation between the commercial procedure and the LabView one, which can be used on any CT and MRI diagnostic devices.

Slice-thickness evaluation in CT and MRI: an alternative computerised procedure

PURPOSE

The efficient use of computed tomography (CT) and magnetic resonance imaging (MRI) equipment necessitates establishing adequate quality-control (QC) procedures. In particular, the accuracy of slice thickness (ST) requires scan exploration of phantoms containing test objects (plane, cone or spiral). To simplify such procedures, a novel phantom and a computerised LabView-based procedure have been devised, enabling determination of full width at half maximum (FWHM) in real time.

MATERIALS AND METHODS

The phantom consists of a polymethyl methacrylate (PMMA) box, diagonally crossed by a PMMA septum dividing the box into two sections. The phantom images were acquired and processed using the LabView-based procedure.

RESULTS

The LabView (LV) results were compared with those obtained by processing the same phantom images with commercial software, and the Fisher exact test (F test) was conducted on the resulting data sets to validate the proposed methodology.

CONCLUSIONS

In all cases, there was no statistically significant variation between the two different procedures and the LV procedure, which can therefore be proposed as a valuable alternative to other commonly used procedures and be reliably used on any CT and MRI scanner.