Peter Hogg

Practitioner compression force variability in mammography: a preliminary study

OBJECTIVE This preliminary study determines whether the absolute amount of breast compression in mammography varies between and within practitioners. METHODS Ethics approval was granted. 488 clients met the inclusion criteria. Clients were imaged by 14 practitioners. Collated data included Breast Imaging Reporting and Data System (BI-RADS) density, breast volume, compression and practitioner code. RESULTS A highly significant difference in mean compression used by different practitioners (p<0.0001 for each BI-RADS density) was demonstrated. Practitioners applied compression in one of three ways using either low, intermediate or high compression force, with no significant difference in mean compression within each group (p=0.99, p=0.70, p=0.54, respectively). Six practitioners showed a significant correlation (p<0.05) between compression and BI-RADS grade, with a tendency to apply less compression with increasing BI-RADS density. When compression was analysed by breast volume there was a wide variation in compression for a given volume. The general trend was the application of higher compression to larger breast volumes by all three practitioner groups. CONCLUSION This study presents an insight into practitioner variation of compression application in mammography. Three groups of practitioners were identified: those who used low, intermediate and high compression across the BI-RADS density grades. There was wide variation in compression for any given breast volume, with trends of higher compression demonstrated for increasing breast volumes. Collation of further studies will facilitate a new perspective on the analysis of practitioner, client and equipment variables in mammography imaging. ADVANCES IN KNOWLEDGE For the first time, it has been practically demonstrated that practitioners vary in the amount of compression applied to breast tissue during routine mammography.

The readout thickness versus the measured thickness for a range of screen film mammography and full-field digital mammography units.

PURPOSE To establish a simple method to determine breast readout accuracy on mammography units. METHODS A thickness measuring device (TMD) was used in conjunction with a breast phantom. This phantom had compression characteristics similar to human female breast tissue. The phantom was compressed, and the thickness was measured using TMD and mammography unit readout. Measurements were performed on a range of screen film mammography (SFM) and full-field digital mammography (FFDM) units (8 units in total; 6 different models/manufacturers) for two different sized paddles and two different compression forces (60 and 100 N). RESULTS The difference between machine readout and TMD for the breast area, when applying 100 N compression force, for nonflexible paddles was largest for GE Senographe DMR+ (24 cm × 30 cm paddle: +14.3%). For flexible paddles the largest difference occurred for Hologic Lorad Selenia (18 cm × 24 cm paddle: +26.0%). CONCLUSIONS None of the units assessed were found to have perfect correlation between measured and readout thickness. TMD measures and thickness readouts were different for the duplicate units from two different models/manufacturers.

Clinical practice at an advanced level: an introduction

The way that healthcare is developing in Great Britain is unique because of the way the advanced clinical practice of the so-called ‘non-medical’ professions (e.g. nursing, radiography, physiotherapy etc.) has advanced at a phenomenal rate. At a local (hospital) level, radiographers are being encouraged to take on new roles; although in some sub-specialties of radiography, the rate of change has been more sedate. For example Holmes and Hogg [1] and also Huggett and McClellan [2] nicely illustrate this on the subject of image interpretation by non-medical staff or personnel in nuclear medicine. Nonetheless, it is well recognised that local variations exist, but the overall ambition (both politically and professionally) is for a greater engagement in advanced practice to improve patient care and management. One must accept that, for a variety of reasons, there will always be resistance to change; and perhaps in a future article, this topic could be the subject of a debate. On examination of the literature, onewill findmany articles and comments in journals, professional magazines and conference abstracts books on the various aspects of advanced practice. However, there is a lack of systematic documentary evidence that takes into account the current and future states of practice. Many of the publications and presentations on the advanced practice are often specific in nature—addressing a focused aspect, and often such valuable work adds to the general body of knowledge. In this series of articles, an attempt will be made to summarise and document generic (e.g. legal issues) and specific (e.g. the role of the gastro-intestinal (GI) specialist) themes on the advanced clinical practice. There is a dual purpose to this exercise: to formally record summary information for historical record; and to address more contemporary issues—such as the sharing of experience and knowledge in a bid to help meet common educational needs. Although most articles on the advanced practice are specific in nature, it is important to note that some review and debate articles do exist. In particular, we draw the attention to Hay’s [3] article. This article gives an excellent overview of skill mix and advanced practice in 1998. Then there is the more specific work of Price [4], a seminal piece, documenting how reporting for radiographers evolved throughout the ages. The work of Paterson [5] helps us to understand the need for publications addressing not only the current situation, but also the future development of the profession. This article commences with a review of the current position of advanced radiographic practice, which is followed by an examination of some catalysts that (Received 6 January 2003; accepted 17 January 2003)

The gastrointestinal advanced practitioner: an emerging role for the modern radiology service

Radiographer role development in the field of gastrointestinal (GI) imaging is a flourishing sub-speciality, with radiographers in many National Health Service (NHS) Trust hospitals performing a range of examinations that were formerly in the province of the radiologist. The emergence of this advanced role has been rapid and sustained, with practitioners continually pushing the traditional practice boundaries within this speciality. The purpose of this article is threefold. Firstly, it is important to document the historical context and justification for this change in practice; secondly, to provide an overview of the scope of practice currently seen across the UK; and finally, to consider the potential opportunities afforded to GI practitioners and their patients in the future.

A free-response evaluation determining value in the computed tomography attenuation correction image for revealing pulmonary incidental findings: a phantom study.

RATIONALE AND OBJECTIVES The purpose of this study was to compare lesion-detection performance when interpreting computed tomography (CT) images that are acquired for attenuation correction when performing single photon emission computed tomography/computed tomography (SPECT/CT) myocardial perfusion studies. In the United Kingdom, there is a requirement that these images be interpreted; thus, it is necessary to understand observer performance on these images. MATERIALS AND METHODS An anthropomorphic chest phantom with inserted spherical lesions of different sizes and contrasts was scanned on five different SPECT/CT systems using site-specific CT protocols for SPECT/CT myocardial perfusion imaging. Twenty-one observers (0-4 years of CT experience) searched 26 image slices (17 abnormal, containing 1-3 lesions, and 9 normal, containing no lesions) for each CT acquisition. The observers marked and rated perceived lesions under the free-response paradigm. Four analyses were conducted using jackknife alternative free-response receiver operating characteristic (JAFROC) analysis: (1) 20-pixel acceptance radius (AR) with all 21 readers, abbreviated to 20/ALL analysis, (2) 40-pixel AR with 21 readers (40/ALL), (3) 20-pixel AR with 14 readers experienced in CT (20/EXP), and (4) 20-pixel AR with 7 readers with no CT experience (20/NOT). The significance level of the test was set so as to conservatively control the overall probability of a type I error to <0.05. RESULTS The mean JAFROC figure of merit (FOM) for the five CT acquisitions for the 20/ALL study were 0.602, 0.639, 0.372, 0.475, and 0.719 with a significant difference in lesion-detection performance evident between all individual treatment pairs (P < .0001) with the exception of the 1-2 pairing, which was not significant (these differed only in milliamp seconds). System 5, which had the highest performance, had the smallest slice thickness and the largest matrix size. For the other analyses, the system orderings remained unchanged, and the significance of FOM difference findings remained identical to those for 20/ALL, with one exception: for 20/EXP analysis the 1-2 difference became significant with the higher milliamp seconds superior. Improved detection performance was associated with a smaller slice thickness, increased matrix size, and, to a lesser extent, increased tube charge. CONCLUSIONS Protocol variations for CT-based attenuation correction (AC) in SPECT/CT imaging have a measurable impact on lesion-detection performance. The results imply that z-axis resolution and matrix size had the greatest impact on lesion detection, with a weaker but detectable dependence on the product of milliamp and seconds.

Multi-centre analysis of incidental findings on low-resolution CT attenuation correction images

OBJECTIVE To review new incidental findings detected on low-resolution CT attenuation correction (CTAC) images acquired during single-photon emission CT (SPECT-CT) myocardial perfusion imaging (MPI) and to determine whether the CTAC images had diagnostic value and warrant reporting. METHODS A multicentre study was performed in four UK nuclear medicine departments. CTAC images acquired as part of MPI performed using SPECT were evaluated to identify incidental findings. New findings considered to be clinically significant were evaluated further. Positive predictive value (PPV) was determined at the time of definitive diagnosis. RESULTS Of 1819 patients studied, 497 (27.3%) had a positive CTAC finding. 51 (2.8%) patients had findings that were clinically significant at the time of the CTAC report and had not been previously diagnosed. Only four (0.2%) of these were potentially detrimental to patient outcome. CONCLUSION One centre had a PPV of 0%, and the study suggests that these CTAC images should not be reported. Two centres with more modern equipment had low PPVs of 0% and 6%, respectively, and further research is suggested prior to drawing a conclusion. The centre with best quality CT had a PPV of 67%, and the study suggests that CTAC images from this equipment should be reported. ADVANCES IN KNOWLEDGE This study is unique compared with previous studies that have reported only the potential to identify incidental findings on low-resolution CT images. This study both identifies and evaluates new clinically significant incidental findings, and it demonstrates that the benefit of reporting the CTAC images depends on the type of equipment used.

Accurate localization of incidental findings on the computed tomography attenuation correction image: the influence of tube current variation.

This observer performance study assessed lesion detection in the computed tomography attenuation correction image, as would be produced for myocardial perfusion imaging over a tube current (mA) range. A static anthropomorphic chest phantom containing simulated pulmonary lesions was scanned using the four available mA values (1, 1.5, 2 and 2.5) on a GE Infinia Hawkeye 4. All other computed tomography acquisition parameters remained constant throughout. Twenty-seven cases showing zero to four lesions were produced for a free-response receiver-operating characteristic method. Image observations were completed using our novel web-based ROCView software under controlled conditions. The Jackknife alternative free-response receiver-operating characteristic (JAFROC) figure of merit was used for significance testing, wherein a difference in lesion detection performance was considered significant at P values less than 0.05. Twenty readers with varying computed tomography experience (0–24 years) evaluated 108 images using an ordinal scale to score confidence. The JAFROC analysis showed that there was no statistically significant difference in performance between mA values (P=0.439) for this sample of observers. In conclusion, no significant difference in lesion detection performance was seen between the mA values. This suggests that there is no value in using anything other than the lowest mA value for the investigation of incidental extracardiac findings.

Clinical evaluation of the computed tomography attenuation correction map for myocardial perfusion imaging: the potential for incidental pathology detection.

The benefits of hybrid imaging in nuclear medicine have been proven to increase the diagnostic accuracy and sensitivity of many procedures by localizing or characterizing lesions or by correcting emission data to more accurately represent radiopharmaceutical distribution. Single-photon emission computed tomography/computed tomography (SPECT/CT) has a significant role in the diagnosis and follow-up of ischaemic heart disease with attenuation correction data being obtained on an integrated CT scanner. Initially, the CT component of hybrid SPECT/CT systems was what could be described as low specification utilizing fixed output parameters. As technology has progressed, the CT component of newer systems has specifications that are identical to that of stand-alone diagnostic systems. Irrespective of the type of scanner used, the computed tomography attenuation correction (CTAC) for myocardial perfusion imaging produces low-quality, limited-range CT images of the chest that include the mediastinum, lung fields and surrounding soft tissues. The diagnostic potential of this data set is unclear; yet, examples exist whereby significant pathology can be identified and investigated further. Despite guidance from a number of professional bodies suggesting that evaluation of the resulting images for every medical exposure be carried out, there is no indication as to whether this should include the evaluation of CTAC images. This review aims to initiate discussion by examining the ethical, legal, financial and practical issues (e.g. CT specification and image quality) surrounding the clinical evaluation of the CTAC for myocardial perfusion imaging images. Reference to discussions that have taken place, and continue to take place, in other modalities, current European and UK legislations, and guidelines and research in the field will be made.

Compression forces used in the Norwegian Breast Cancer Screening Program

OBJECTIVE Compression is used in mammography to reduce breast thickness, which is claimed to improve image quality and reduce radiation dose. In the Norwegian Breast Cancer Screening Program (NBCSP), the recommended range of compression force for full-field digital mammography (FFDM) is 11-18 kg (108-177 N). This is the first study to investigate the compression force used in the programme. METHODS The study included information from 17,951 randomly selected females screened with FFDM at 14 breast centres in the NBCSP, during January-March 2014. We investigated the applied compression force on the left breast in craniocaudal and mediolateral oblique views for breast centres, mammography machines within the breast centres and for the radiographers. RESULTS The mean compression force for all mammograms in the study was 116 N and ranged from 91 N to 147 N between the breast centres. The variation in compression force was wider between the breast centres than that between mammography machines (range 137-155 N) and radiographers (95-143 N) within one breast centre. Approximately 59% of the mammograms in the study complied with the recommended range of compression force. CONCLUSION A wide variation in applied compression force was observed between the breast centres in the NBCSP. This variation indicates a need for evidence-based recommendations for compression force aimed at optimizing the image quality and individualizing breast compression. Advances in knowledge: There was a wide variation in applied compression force between the breast centres in the NBCSP. The variation was wider between the breast centres than that between mammography machines and radiographers within one breast centre.

Breast image pre-processing for mammographic tissue segmentation

During mammographic image acquisition, a compression paddle is used to even the breast thickness in order to obtain optimal image quality. Clinical observation has indicated that some mammograms may exhibit abrupt intensity change and low visibility of tissue structures in the breast peripheral areas. Such appearance discrepancies can affect image interpretation and may not be desirable for computer aided mammography, leading to incorrect diagnosis and/or detection which can have a negative impact on sensitivity and specificity of screening mammography. This paper describes a novel mammographic image pre-processing method to improve image quality for analysis. An image selection process is incorporated to better target problematic images. The processed images show improved mammographic appearances not only in the breast periphery but also across the mammograms. Mammographic segmentation and risk/density classification were performed to facilitate a quantitative and qualitative evaluation. When using the processed images, the results indicated more anatomically correct segmentation in tissue specific areas, and subsequently better classification accuracies were achieved. Visual assessments were conducted in a clinical environment to determine the quality of the processed images and the resultant segmentation. The developed method has shown promising results. It is expected to be useful in early breast cancer detection, risk-stratified screening, and aiding radiologists in the process of decision making prior to surgery and/or treatment.