Variation in digital breast tomosynthesis image quality at differing heights above the detector

Introduction

The aim of this preliminary work was to determine if image quality in digital breast tomosynthesis (DBT) changes when tomosynthesis image slices were obtained at differing heights above the detector and in differing breast thicknesses.

Methods

A CIRS Model 020 BR3D breast imaging phantom was used to obtain the DBT images. The images were also acquired at different tube voltages, and each exposure was determined by the automatic exposure control system. Contrast‐to‐noise ratio (CNR) and figure‐of‐merit (FOM) values were obtained and compared.

Results

At a phantom thickness of 5 cm or greater, there was a significant reduction (P ≤ 0.05) of image CNR values obtained from the images near the top of the phantom to those obtained near the bottom of the phantom. When the phantom thickness was 4 cm, there was no significant difference in CNR values between DBT images acquired at any height in the phantom. FOM values generally showed no difference when images were obtained at differing heights above the detector.

Conclusion

Image quality, as measured by the CNR, was reduced when tomosynthesis slice image heights were at the top of the phantom and when the thickness of the phantom was more than 4 cm. From this preliminary work, clinicians need to be aware that DBT images obtained near the top of the breast, when breast thickness is greater than 4 cm, may have reduced image quality. Further work is needed to fully assess any DBT image quality changes when images are obtained near the top of the breast.

Can we rely on surgical clips placed during oncoplastic breast surgery to accurately delineate the tumor bed for targeted breast radiotherapy?

PURPOSE

Oncoplastic breast surgery (OBS) is gaining popularity among surgeons for breast-conserving surgery treatments. OBS relies on complex relocation and deformation of breast tissue involving the tumor bed (TB). In this study, we investigate the validity of using surgical clips with OBS for accurate TB delineation in adjuvant, targeted breast radiotherapy.

METHODS

Different OBS techniques were simulated on realistic breast phantoms. Surgical clips were used to demarcate the TB. Following tumor resection and closure, the true TB (TB_True) was extracted. Each phantom was CT imaged at several phases of surgery in order to record pre- and post-OBS closure surgical clip displacements. Two senior radiation oncologists (ROs) were asked to delineate TBs on CTs by relying on surgical clips placed as per standard protocol, and by referring to operative notes. Their original contours, as well as those expanded using 5-15 mm margins, were compared with the accurate TB_True using the dice similarity coefficient (DSC), Hausdorff Distance (HD), and over- and under-contoured volumes. Inter- and intra-RO contour agreements were also evaluated.

RESULTS

Post-OBS surgical clips were significantly displaced outside the original breast quadrant. Inter- and Intra-RO TB contours were consistent, yet systematically differed from TB_True (DSC values range = 0.38 to 0.69, and maximum HD range = 17.8 mm to 38.0 mm). Using expansion margins did not improve contour congruence and caused significant over-contoured volumes.

CONCLUSION

Following OBS, surgical clips alone are not reliable radiographic surrogates of TB locations and accurate TB delineation is challenging. For complex OBS cases, indication of any type of partial breast irradiation is very questionable.

Imaging properties of 3D printed breast phantoms for lesion localization and Core needle biopsy training

Background

Breast cancer is the most commonly diagnosed malignancy in females and frequently requires core needle biopsy (CNB) to guide management. Adequate training resources for CNB suffer tremendous limitations in reusability, accurate simulation of breast tissue, and cost. The relatively recent advent of 3D printing offers an alternative for the development of breast phantoms for training purposes. However, the feasibility of this technology for the purpose of ultrasound (US) guided breast intervention has not been thoroughly studied.

Methods

We designed three breast phantom models that were printed in multiple resins available through Stratasys, including VeroClear, TangoPlus and Tissue Matrix. We also constructed several traditional breast phantoms using chicken breast and Knox gelatin for comparison. These phantoms were compared side-by-side for ultrasound penetrance, simulation of breast tissue integrity, anatomic accuracy, reusability, and cost.

Results

3D printed breast phantoms were more anatomically accurate models than traditional breast phantoms. The chicken breast phantom provided acceptable US beam penetration and material hardness for simulation of human breast tissue integrity. Sonographic image quality of the chicken breast phantom was the most accurate overall. The gelatin-based phantom also had acceptable US beam penetration and image quality; however, this material was too soft and poorly simulated breast tissue integrity. 3D printed phantoms were not visible under US.

Conclusions

There is a large unmet need for a printable material that is truly compatible with multimodality imaging for breast and other soft tissue intervention. Further research is warranted to create a realistic, reusable and affordable material to 3D print phantoms for US-guided intervention training.

Comparison of dedicated breast positron emission tomography and whole-body positron emission tomography/computed tomography images: a common phantom study

OBJECTIVE

High-resolution dedicated breast positron emission tomography (dbPET) can visualize breast cancer more clearly than whole-body PET/computed tomography (CT). In Japan, the combined use of dbPET and whole-body PET/CT is necessary in indications for health insurance. Although several clinical studies have compared both devices, a physical evaluation by the phantom test has not been reported. The aim of this study was to compare the ability of ring-shaped dbPET and whole-body PET/CT using a common phantom with reference to the Japanese guideline for the oncology ¹⁸F-fluorodeoxyglucose (FDG)-PET/CT data acquisition protocol.

METHODS

A cylindrical breast phantom with four spheres of different diameters (16, 10, 7.5, and 5 mm) filled an FDG solution at sphere-to-background radioactivity ratios (SBRs) of 2:1, 4:1, and 8:1 was prepared. Images were then acquired by whole-body PET/CT and subsequently by dbPET. The reconstructed images were visually evaluated and the coefficient of variation and uniformity of the background (CV_background and SD_ΔSUVmean), percentages of contrast and background variability (%Q_H,5mm and %N_5mm), and their ratio (%Q_H,5mm/N_5mm), and relative recovery coefficient were compared with the standards defined in the protocol for whole-body PET/CT.

RESULTS

The parameters were calculated at an SBR of 8:1, which was the only SBR in which a 5-mm sphere was visible on both devices. The standards were defined as < 10% for CV_background, ≤ 0.025 for SD_ΔSUVmean, < 5.6% for %N_5mm, > 2.8 for %Q_H,5mm/N_5mm, and > 0.38 for the relative recovery coefficient of the smallest sphere (10 mm in diameter) in the protocol for whole-body PET/CT (the %Q_H,5mm was not determined for that protocol); the respective values were 6.14%, 0.024, 4.55%, 3.66, and 0.33 for dbPET and 2.21%, 0.021, 3.11%, 1.72, and 0.18 for PET/CT. The Q_H,5mm was 16.67% for dbPET and 5.34% for PET/CT. The human images also showed higher lesion-to-background contrast on dbPET than on PET/CT despite the noisier background observed with dbPET.

CONCLUSION

The common phantom study showed that the background was noisier and that the contrast was much higher in the dbPET image than in the PET/CT image. The acquisition protocol and standards for dbPET will need to be different from those used for whole-body PET/CT.

3D-printed breast phantom for multi-purpose and multi-modality imaging

Background

Breast imaging technology plays an important role in breast cancer planning and treatment. Recently, three-dimensional (3D) printing technology has become a trending issue in phantom constructions for medical applications, with its advantages of being customizable and cost-efficient. However, there is no current practice in the field of multi-purpose breast phantom for quality control (QC) in multi-modalities imaging. The purpose of this study was to fabricate a multi-purpose breast phantom with tissue-equivalent materials via a 3D printing technique for QC in multi-modalities imaging.

Methods

We used polyvinyl chloride (PVC) based materials and a 3D printing technique to construct a breast phantom. The phantom incorporates structures imaged in the female breast such as microcalcifications, fiber lesions, and tumors with different sizes. Moreover, the phantom was used to assess the sensitivity of lesion detection, depth resolution, and detectability thresholds with different imaging modalities. Phantom tissue equivalent properties were determined using computed tomography (CT) attenuation [Hounsfield unit (HU)] and magnetic resonance imaging (MRI) relaxation times.

Results

The 3D-printed breast phantom had an average background value of 36.2 HU, which is close to that of glandular breast tissue (40 HU). T1 and T2 relaxation times had an average relaxation time of 206.81±17.50 and 20.22±5.74 ms, respectively. Mammographic imaging had improved detection of microcalcification compared with ultrasound and MRI with multiple sequences [T1WI, T2WI and short inversion time inversion recovery (STIR)]. Soft-tissue lesion detection and cylindrical tumor contrast were superior with mammography and MRI compared to ultrasound. Hemispherical tumor detection was similar regardless of the imaging modality used.

Conclusions

We developed a multi-purpose breast phantom using a 3D printing technique and determined its value for multi-modal breast imaging studies.

Design of a slab phantom for breast dosimetry applications

Background

Design of phantoms for use in radiotherapy should consider the complex geometry of breast tissue and inhomogeneity. The aim of this study is design of a slab phantom for breast dosimetry applications.

Materials and Methods

In this study, an anatomical slab phantom was designed with cork lung inhomogeneity and plexi colored heart part, also describes the different size of breast and chest wall phantom that have been designed and constructed for dosimetry. Three size different phantoms have been manufactured that installed in one trunk, as "small," "medium," and "large," two breast size fixed and one size was movable on a chest wall phantom. Two different dosimeters selected to dosimetry in this phantom, film was chosen for this dosimetry since it provides good spatial resolution and suitable for two-dimensional dosimetry also measure dose distribution used a point dosimetry with thermoluminescent dosimeter (TLD).

Results

The results were shown near date due to either software or phantom calculation.

Conclusion

Application include assessment dose in the junction region between the tangential fields and the supraclavicular fossa field, as well as assess dose in inhomogeneities, the phantom were formed from a variety of tissue substitute materials.

Silicone-based composite materials simulate breast tissue to be used as ultrasonography training phantoms

A silicone-based composite breast phantom is fabricated to be used as an education model in ultrasonography training. A matrix of silicone formulations is tracked to mimic the ultrasonography and tactile response of human breast tissue. The performance of two different additives: (i) silicone oil and (ii) vinyl-terminated poly (dimethylsiloxane) (PDMS) are monitored by a home-made acoustic setup. Through the use of 75 wt% vinyl-terminated PDMS in two-component silicone elastomer mixture, a sound velocity of 1.29 ± 0.09 × 10³ m/s and an attenuation coefficient of 12.99 ± 0.08 dB/cm-values those match closely to the human breast tissue-are measured with 5 MHz probe. This model can also be used for needle biopsy as well as for self-exam trainings. Herein, we highlight the fabrication of a realistic, durable, accessible, and cost-effective training platform that contains skin layer, inner breast tissue, and tumor masses.

Assessment of Mean Glandular Dose in Mammography System with Different Anode-Filter Combinations Using MCNP Code

Background

X-ray mammography is one of the general methods for early detection of breast cancer. Since glandular tissue in the breast is sensitive to radiation and it increases the risk of cancer, the given dose to the patient is very important in mammography.

Objectives

The aim of this study was to determine the average absorbed dose of X-ray radiation in the glandular tissue of the breast during mammography examinations as well as investigating factors that influence the mean glandular dose (MGD). One of the precise methods for determination of MGD absorbed by the breast is Monte Carlo simulation method which is widely used to assess the dose.

Materials and Methods

We studied some different X-ray sources and exposure factors that affect the MGD. “Midi-future” digital mammography system with amorphous-selenium detector was simulated using the Monte Carlo N-particle extended (MCNPX) code. Different anode/filter combinations such as tungsten/silver (W/Ag), tungsten/rhodium (W/Rh), and rhodium/aluminium (Rh/Al) were simulated in this study. The voltage of X-ray tube ranged from 24 kV to 32 kV with 2 kV intervals and the breast phantom thickness ranged from 3 to 8 cm, and glandular fraction g varied from 10% to 100%.

Results

MGD was measured for different anode/filter combinations and the effects of changing tube voltage, phantom thickness, combination and glandular breast tissue on MGD were studied. As glandular g and X-ray tube voltage increased, the breast dose increased too, and the increase of breast phantom thickness led to the decrease of MGD. The obtained results for MGD were consistent with the result of Boone et al. that was previously reported.

Conclusion

By comparing the results, we saw that W/Rh anode/filter combination is the best choice in breast mammography imaging because of the lowest delivered dose in comparison with W/Ag and Rh/Al. Moreover, breast thickness and g value have significant effects on MGD.

Experimental dosimetry in conformal breast teletherapy compared with the planning system

The objective of this study was to compare and analyse the absorbed dose profiles from the conformal radiotherapy planning and experimental dosimetry taken in a breast anthropomorphic and anthropometric phantom. Conformal radiotherapy planning was elaborated in the Treatment Planning System (TPS). EBT2 Gafchromic radiochromic films were applied as dosimeters, positioned internally and superficially in the breast phantom. The standard radiation protocol was applied in the breast phantom. The films were digitalised, and their responses were analysed in RGB. The optical densities were processed, reproducing the spatial dose distribution.