Magseed localisation of non-palpable breast lesions: experience from a single centre

AIM

To prospectively analyse patients undergoing magnetic seed (Magseed) localisation (MSL) to evaluate the outcome, and to retrospectively compare re-excision rates for MSL with previous wire-guided localisation (WGL) to assess the hypothesis that the introduction of MSL may lead to a lower re-excision rate.

MATERIALS AND METHODS

MSL commenced at University Hospital Crosshouse in December 2017. No other changes were made to radiological or surgical practice during this time. Data were collected prospectively on all patients undergoing MSL between December 2017 and December 2019, in a single breast unit. Data were gathered retrospectively on patients who had undergone localised breast procedures between January 2016 and December 2019 for comparison of re-excision rates.

RESULTS

Two hundred and fifty-five patients underwent MSL surgery between December 2017 and December 2019. Of those, 98% (n=250) patients underwent successful MSL at the first attempt. The Magseed was identified intraoperatively in 100% patients and surgical excision was performed. The re-excision rate reduced from 18.9% in 2016/2017, to 11.6% in 2018/2019 (p=0.098).

CONCLUSION

In conclusion, Magseed localisation has proved to be a safe and effective way of localising breast lesions, with the advantage of high accuracy. The reduction in re-excision rates at University Hospital Crosshouse with the introduction of Magseed® localisation is a potential benefit, which requires further study.

Medical Devices; Radiology Devices; Classification of the Rectal Balloon for Prostate Immobilization. Final order

The Food and Drug Administration (FDA or we) is classifying the rectal balloon for prostate immobilization into class II (special controls). The special controls that apply to the device type are identified in this order and will be part of the codified language for the rectal balloon for prostate immobilization's classification. We are taking this action because we have determined that classifying the device into class II (special controls) will provide a reasonable assurance of safety and effectiveness of the device. We believe this action will also enhance patients' access to beneficial innovative devices, in part by reducing regulatory burdens.

[Fundamental Study of Three-dimensional Fast Spin-echo Imaging with Spoiled Equilibrium Pulse]

Three-dimensional fast spin-echo (3D FSE) imaging with variable refocusing flip angle has been recently applied to pre- or post-enhanced T₁-weighted imaging. To reduce the acquisition time, this sequence requires higher echo train length (ETL), which potentially causes decreased T₁ contrast. Spoiled equilibrium (SpE) pulse consists of a resonant +90° radiofrequency (RF) pulse and is applied at the end of the echo train. This +90° RF pulse brings residual transverse magnetization to the negative longitudinal axis, which makes it possible to increase T₁ contrast. The purpose of our present study was to examine factors that influence the effect of spoiled equilibrium pulse and the relationship between T₁ contrast improvement and imaging parameters and to understand the characteristics of spoiled equilibrium pulse. Phantom studies were conducted using an magnetic resonance imaging (MRI) phantom made of polyvinyl alcohol gel. To evaluate the effect of spoiled equilibrium pulse with changes in repetition time (TR), ETL, and refocusing flip angle, we measured the signal-to-noise ratio and contrast-to-noise ratio (CNR). The effect of spoiled equilibrium pulse was evaluated by calculating the enhancement rate of CNR. The factors that influence the effect of spoiled equilibrium pulse are TR, ETL, and relaxation time of tissues. Spoiled equilibrium pulse is effective with increasing TR and decreasing ETL. The shorter the T₁ value, the better the spoiled equilibrium pulse functions. However, for tissues in which the T₁ value is long (>600 ms), at a TR of 600 ms, improvement in T₁ contrast by applying spoiled equilibrium pulse cannot be expected.

[Comparison of Analytical Values in Diffusion Kurtosis Imaging among Different MRI Units]

Diffusion kurtosis imaging (DKI) is a method of analyzing restricted diffusion. Mean kurtosis (MK) is obtained from DKI. It is not known how different MRI scanners and coil systems will change MK when the same imaging parameters are used. The purpose of this study is to identify tendencies in MK when using various MRI scanners and coil systems. A total of 27 healthy volunteers were enrolled in this study. DKI was performed on the brain for each volunteer on five MRI scanner/coil system combinations using the same scan parameters. MK of 10 anatomical areas of the brain were compared, and the signal-noise ratios (SNRs) of b-2000 s/mm² images were measured in identical areas. There were no significant differences among MKs from multi transmit (MT) MRI systems, but MK was significantly lower on the single transmit MRI system because of pepper artifact caused by low SNR. In conclusion, we found no significant differences in MK among MT systems, and MK was significantly lower without MT.

[Basic Study on Visibility and Water Equivalency of a New Colorless Transparent Bolus for Electron Radiotherapy]

Boluses used in electron radiotherapy need to have radiation field visibility and water equivalence. In this report, we have examined field visibility and water equivalence of a new colorless transparent bolus. We examined field visibility, water equivalence, and dose profile. Field visibility was evaluated by comparison to conventional bolus. Water equivalence was investigated by a measured fluence scaling factor. The dose profile was measured by using radiochromic film with the bolus and an ionization chamber in water. We confirmed that the irradiation field could clearly be seen through the transparent colorless bolus. The bolus did not cast a field edge as compared with the conventional bolus. The fluence scaling factor was less than 0.8% as compared to water. We confirmed that the colorless transparent bolus was treated as a water equivalent material. The percentage depth dose (PDD) measured by using radiochromic film with the bolus matched the PDD measured with an ionization chamber in water. R₅₀ was less than 1 mm as compared to PDD measured with an ionization chamber. It was confirmed that the colorless transparent bolus can use to set up patient without losing visibility on flat ground planes. The fluence scaling factor and dose profile measured by using the bolus matched the results measured in water. Therefore, the new colorless transparent bolus has feasibility to improve patient setup efficiency and can improve calculation accuracy by using the fluence scaling factor.

DOSE TO RADIOLOGICAL TECHNOLOGISTS FROM INDUCED RADIONUCLIDES IN CARBON ION RADIOTHERAPY

Radioactive nuclides are induced in irradiation devices and patients during high-energy photon and ion beam radiotherapies. These nuclides potentially become sources of exposure to radiation workers. Radiological technologists (RTs) are often required to enter an irradiation room and approach activated devices and patients. In this study, annual doses to RTs working in a carbon ion radiotherapy facility were estimated based on measurements with the Si-semiconductor personal dosemeter. In addition, the time decay of dose around a patient couch after irradiation was obtained by phantom experiments. The annual Hp(10) values for passive and scanned beams were estimated to be 61 and 2 μSv, respectively, when assuming the number of treatments in 2013. These are much lower than the ICRP recommended dose limit for radiation workers. The time-series data of dose to RTs during their work and the time decay of the dose should be helpful for reducing their dose further.

[A Novel Evaluation Method for Displacement between Carbon Beam Axis and Positioning X-ray Axis Using an Imaging Plate]

PURPOSE

We developed an evaluation method for easily calculating displacement directly between the carbon beam axis and positioning X-ray axis.

METHODS

A verification image was acquired by irradiating an imaging plate with a carbon beam and X-ray. The X-ray passed through a lead plate inserted in the range compensator holder. The displacement was calculated on the verification image from the center of a wire irradiated with carbon using a multi leaf collimator (MLC) and a wire irradiated with X-ray also using MLC. The accuracy of the method was evaluated by moving the carbon beam axis, the X-ray axis, and the setup angle. The weekly changes of vertical and lateral beams in all rooms were also evaluated.

RESULTS

The displacements of the carbon beam axis and the setup angle did not influence the calculation results, whereas the displacement of the X-ray axis did (R=0.999). The displacements including weekly changes were all less than 1.00 mm.

CONCLUSION

An evaluation method for calculating the displacement directly and simply between the carbon beam axis and positioning X-ray axis was developed and verified. The weekly changes of displacement between axes were evaluated to be acceptable at our facility.

Analysis of licensed South African diagnostic imaging equipment

INTRODUCTION OBJECTIVE

To conduct an analysis of all registered South Africa (SA) diagnostic radiology equipment, assess the number of equipment units per capita by imaging modality, and compare SA figures with published international data, in preparation for the introduction of national health insurance (NHI) in SA.

METHODS

The SA Radiation Control Board's database of registered diagnostic radiology equipment was analysed by modality, province and healthcare sector. Access to services was reflected as number of units/million population, and compared with published international data.

RESULTS

General X-ray units are the most equitably distributed and accessible resource (34.8/million). For fluoroscopy (6.6/million), mammography (4.96/million), computed tomography (5.0/million) and magnetic resonance imaging (2.9/million), there are at least 10-fold discrepancies between the least and best resourced provinces. Although SA's overall imaging capacity is well above that of other countries in sub-Saharan Africa, it is lower than that of all Organisation for Economic Co-operation and Development (OECD). While SA's radiological resources most closely approximate those of the United Kingdom, they are substantially lower than the UK.

CONCLUSION

SA access to radiological services is lower than that of any OECD country. For the NHI to achieve equitable access to diagnostic imaging for all citizens, SA will need a more homogeneous distribution of specialised radiological resources and customized imaging guidelines.

Technical Performance of Universal and Enhanced Intraoral Imaging Rectangular Collimators

PURPOSE

The purpose of this study was to compare the number and type of technical errors between 2 rectangular collimators, time/motion effort and radiographer preference.

METHODS

Subjects (n=17) were recruited to expose an 18 projection full mouth series (FMX) using Tru-Align™ (enhanced) and Rinn® (universal) collimator devices. Both FMXs were exposed using photostimulable phosphor (PSP) digital sensors on a DXTTR manikin with an intraoral x-ray unit. A 5-question survey evaluated ease of device use, time required and device preference. Data were analyzed using frequencies, paired t-test, ANOVA and least squares means using a general linear model.

RESULTS

A lower mean number of technique errors per FMX occurred with the enhanced device (9.7) compared to the universal device (12.1). Collimator centering errors occurred 3-times more often with the universal device. The mean numbers of diagnostically unacceptable errors per FMX were similar (Universal=3.2 vs Enhanced=2.9). The least squares means adjusted model showed a statistically significant difference of errors between the 2 devices (p=0.0478) and errors by location when comparing posterior to anterior and posterior to bitewing (p<0.0001). Subjects (94%) preferred the enhanced device and found it easier to use compared to the universal device. Significantly less time was needed to expose an FMX (4 min) when using the enhanced device (p=0.0001).

CONCLUSION

The enhanced device enabled subjects to expose diagnostically acceptable radiographs more efficiently with fewer collimator centering errors; however, it does so with a 35% greater exposure area and a concomitant increase in patient dose.

Review on the characteristics of radiation detectors for dosimetry and imaging

The enormous advances in the understanding of human anatomy, physiology and pathology in recent decades have led to ever-improving methods of disease prevention, diagnosis and treatment. Many of these achievements have been enabled, at least in part, by advances in ionizing radiation detectors. Radiology has been transformed by the implementation of multi-slice CT and digital x-ray imaging systems, with silver halide films now largely obsolete for many applications. Nuclear medicine has benefited from more sensitive, faster and higher-resolution detectors delivering ever-higher SPECT and PET image quality. PET/MR systems have been enabled by the development of gamma ray detectors that can operate in high magnetic fields. These huge advances in imaging have enabled equally impressive steps forward in radiotherapy delivery accuracy, with 4DCT, PET and MRI routinely used in treatment planning and online image guidance provided by cone-beam CT. The challenge of ensuring safe, accurate and precise delivery of highly complex radiation fields has also both driven and benefited from advances in radiation detectors. Detector systems have been developed for the measurement of electron, intensity-modulated and modulated arc x-ray, proton and ion beams, and around brachytherapy sources based on a very wide range of technologies. The types of measurement performed are equally wide, encompassing commissioning and quality assurance, reference dosimetry, in vivo dosimetry and personal and environmental monitoring. In this article, we briefly introduce the general physical characteristics and properties that are commonly used to describe the behaviour and performance of both discrete and imaging detectors. The physical principles of operation of calorimeters; ionization and charge detectors; semiconductor, luminescent, scintillating and chemical detectors; and radiochromic and radiographic films are then reviewed and their principle applications discussed. Finally, a general discussion of the application of detectors for x-ray nuclear medicine and ion beam imaging and dosimetry is presented.

Increasing mobile radiography productivity

Mobile radiography using computed radiography (CR) cassettes is a common equipment combination with a workflow bottleneck limited by location of CR readers. Advent of direct digital radiography (DDR) mobile x-ray machines removes this limitation by immediate image review and quality control. Through the use of key performance indicators (KPIs), the increase in efficiency can be quantified.

Online documentation of equipment maintenance and performance

A radiology department or imaging center relies on the proper operation of its equipment. This is accomplished through appropriate maintenance and independent medical physics monitoring. These activities represent an expensive but necessary effort to protect the original investment. Effective management requires accurate, timely, and useful documentation. The Georgia Regents Medical Center Department of Diagnostic, Therapeutic, and Interventional Radiology developed a comprehensive database encompassing both maintenance and monitoring activities associated with imaging equipment. This database is accessible throughout the facility via a website, providing a central hub for information distribution and access. The radiology engineering supervisor and quality control technologist make extensive use of this system and were key to its implementation and ongoing improvement.

A clinical approach to technology assessment: how do we and how should we choose the right treatment?

The evidence required to support the use of new technology in medicine differs from that required for new drugs. On one extreme, very little may be required for small devices, but on the other strong evidence is required to support the use of truly novel, potentially dangerous, and high-cost machines. The randomized controlled trial is built into the evaluation of drugs and suits them well. It is not so well suited to the evaluation of major devices in which installation costs and return on investment are important. We discuss where the randomized controlled trial may still play a role and what alternatives may exist when this is not possible. We also discuss the role that independent bodies may have in determining whether or not a new device is not only safe but also adds to the medical landscape in a way that justifies its cost.

[The material and technical base of fluorographic units of primary health care facilities and its development promises]

The goal of the study was to assess the status of equipment and the staff potential in the fluorography and X-ray units of primary health care facilities and to define priorities and the volume of investments for their modernization. Two hundred and seventy-two health care facilities were studied through the use of questionnaires. The data were processed using standard statistical methods, such as calculation of the mean, median, and 95% confidence intervals. Prognosis was made for the idling period of equipment during stagnation of measures to improve the material and technical base of fluorography units. Priorities for modernizing the material and technical base and the staff potential were defined for the fluorography units of primary health care facilities. The volume of investments required for the modernization was estimated.

[A novel voltage multiplier for X-ray power supply]

In this paper, a seriesly connected three phase bipolar symmetrical voltage multiplier (VM) is proposed, which is a novel VM for X-ray power supply. It consists of three single phase bipolar symmetrical VM, which are connected in series at their smoothing columns. The charging and discharging process occurs six times in a cycle and the frequency of the output voltage ripple is six times as large as the drive signal frequency. The proposed VM has three times larger output voltage and three times smaller ripple factor as compared to single phase bipolar symmetrical VM, and smaller voltage drop and faster dynamic response than those of the series connected three phase symmetrical VM. The simulation is provided to show the feasibility of proposed VM.

Study of the response of superoxide dismutase in mouse organs to radon using a new large-scale facility for exposing small animals to radon

We examined dose-dependent or dose rate-dependent changes of superoxide dismutase (SOD) activity using a new large-scale facility for exposing small animals to radon. Mice were exposed to radon at a concentration of 250, 500, 1000, 2000, or 4000 Bq/m(3) for 0.5, 1, 2, 4, or 8 days. When mice were exposed to radon at 2000 day•Bq/m(3), activation of SOD activities in plasma, liver, pancreas, heart, thymus, and kidney showed dose-rate effects. Our results also suggested that continuous exposure to radon increased SOD activity, but SOD activity transiently returned to normal levels at around 2 days. Moreover, we classified the organs into four groups (1. plasma, brain, lung; 2. heart, liver, pancreas, small intestine; 3. kidney, thymus; 4. stomach) based on changes in SOD activity. Thymus had the highest responsiveness and stomach had lowest. These data provide useful baseline measurements for future studies on radon effects.

Real-time target position estimation using stereoscopic kilovoltage/megavoltage imaging and external respiratory monitoring for dynamic multileaf collimator tracking

PURPOSE

To develop a real-time target position estimation method using stereoscopic kilovoltage (kV)/megavoltage (MV) imaging and external respiratory monitoring, and to investigate the performance of a dynamic multileaf collimator tracking system using this method.

METHODS AND MATERIALS

The real-time three-dimensional internal target position estimation was established by creating a time-varying correlation model that connected the external respiratory signals with the internal target motion measured intermittently using kV/MV imaging. The method was integrated into a dynamic multileaf collimator tracking system. Tracking experiments were performed for 10 thoracic/abdominal traces. A three-dimensional motion platform carrying a gold marker and a separate one-dimensional motion platform were used to reproduce the target and external respiratory motion, respectively. The target positions were detected by kV (1 Hz) and MV (5.2 Hz) imaging, and external respiratory motion was captured by an optical system (30 Hz). The beam-target alignment error was quantified as the positional difference between the target and circular beam center on the MV images acquired during tracking. The correlation model error was quantified by comparing a model estimate and measured target positions.

RESULTS

The root-mean-square errors in the beam-target alignment that had ranged from 3.1 to 7.6 mm without tracking were reduced to <1.5 mm with tracking, except during the model building period (6 s). The root-mean-square error in the correlation model was submillimeters in all directions.

CONCLUSION

A novel real-time target position estimation method was developed and integrated into a dynamic multileaf collimator tracking system and demonstrated an average submillimeter geometric accuracy after initializing the internal/external correlation model. The method used hardware tools available on linear accelerators and therefore shows promise for clinical implementation.

Radiation biology and protection

To protect themselves, their patients and their coworkers, radiologic technologists should regularly refresh and reinforce their understanding of key radiation biology and protection principles. This article reviews the concepts of radiation physics, human biology and radiation protection strategies, with emphasis on how historical events and developing research affect radiation protection understanding and practice.

Multileaf collimator characteristics and reliability requirements for IMRT Elekta system

Understanding the characteristics of a multileaf collimator (MLC) system, modeling MLC in a treatment planning system, and maintaining the mechanical accuracy of the linear accelerator gantry head system are important factors in the safe implementation of an intensity-modulated radiotherapy program. We review the characteristics of an Elekta MLC system, discuss the necessary MLC modeling parameters for a treatment planning system, and provide a novel method to establish an MLC leaf position quality assurance program. To perform quality assurance on 40 pairs of individual MLC leaves is a time-consuming and difficult task. In this report, an effective routine MLC quality assurance method based on the field edge of a backup jaw as referenced in conjunction with a diode array as a radiation detector system is discussed. The sensitivity of this test for determining the relative leaf positions was observed to be better than 0.1 mm. The Elekta MLC leaf position accuracy measured with this system has been better than 0.3 mm.

The impact of advanced technologies on treatment deviations in radiation treatment delivery

PURPOSE

To assess the impact of new technologies on deviation rates in radiation therapy (RT).

METHODS AND MATERIALS

Treatment delivery deviations in RT were prospectively monitored during a time of technology upgrade. In January 2003, our department had three accelerators, none with "modern" technologies (e.g., without multileaf collimators [MLC]). In 2003 to 2004, we upgraded to five new accelerators, four with MLC, and associated advanced capabilities. The deviation rates among patients treated on "high-technology" versus "low-technology" machines (defined as those with vs. without MLC) were compared over time using the two-tailed Fisher's exact test.

RESULTS

In 2003, there was no significant difference between the deviation rate in the "high-technology" versus "low-technology" groups (0.16% vs. 0.11%, p = 0.45). In 2005 to 2006, the deviation rate for the "high-technology" groups was lower than the "low-technology" (0.083% vs. 0.21%, p = 0.009). This difference was caused by a decline in deviations on the "high-technology" machines over time (p = 0.053), as well as an unexpected trend toward an increase in deviations over time on the "low-technology" machines (p = 0.15).

CONCLUSIONS

Advances in RT delivery systems appear to reduce the rate of treatment deviations. Deviation rates on "high-technology" machines with MLC decline over time, suggesting a learning curve after the introduction of new technologies. Associated with the adoption of "high-technology" was an unexpected increase in the deviation rate with "low-technology" approaches, which may reflect an over-reliance on tools inherent to "high-technology" machines. With the introduction of new technologies, continued diligence is needed to ensure that staff remain proficient with "low-technology" approaches.

[Use of radiography in outpatient care]

Various types of portable X-ray apparatuses are compared. These apparatuses can be used for roentgenography under nonstationary conditions, in particular, at home. Various configurations of equipment for mobile X-ray systems (including X-ray image detectors, processing machines, information read-out and processing devices, X-ray protection equipment) are considered.