Low Dose MBI Technology

Collaborating with other thought leaders in the field of advanced imaging, Kromek is working towards the common goal of improving early breast cancer detection for women with dense breasts; developing technology with life-saving potential.

Summary

The Need

Mammography is a widely used breast cancer screening technology. However, it is challenging to detect tumours in breasts with radiographically dense tissue. Molecular Breast Imaging (MBI) is able to overcome this problem. When used alongside existing techniques, MBI significantly increases the breast cancer detection rate by a factor of 4. Smaller tumours in the early stages of breast cancer are less likely to be missed in dense breast tissue. However, MBI has not yet been widely adopted in Europe or the UK, due to its long scan times and its relatively high patient effective dose (radiation exposed to the patient during the procedure).

The Solution

In 2018, Kromek began developing a solution to overcome these two main limitations of MBI, working alongside UCL and the Newcastle Upon Tyne Hospitals NHS Foundation Trust. The goal of the Low Dose MBI project is to decrease the scan time and effective dose of MBI, so it becomes a more adoptable solution in breast cancer screening and diagnosis. So far, using results from simulations, we expect to achieve an overall reduction factor of 8 in dose, scan time, or, in a combination of both. This will bring the scan time and effective dose of Low Dose MBI down to a level more comparable to mammography and other alternative techniques.

The Next Step

The next phase of the project is to continue with experimental trials. The results so far indicate the potential of Low Dose MBI to increase the effectiveness of breast cancer detection in women with dense breasts, ultimately saving lives.

Keep scrolling for the full project story below!

Statistics graphic with key figures from a study with MBI in 2015. Text reads: If introduced alongside existing techniques, MBI has the potential to: increase cancer detection rate by factor 4 and to increase the sensitivity from 24% to 81%.

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Approaching breast cancer from a different angle

Kromek attended the 6th Workshop on Medical Applications of Spectroscopic X-ray Detectors (SpecXray), hosted by CERN. Here, our collaborator Dr. Thomas Zillhardt from the University of Manchester showcased our joint progress in our funded Quantum Digital Tomosynthesis (QDT) project.

 

CZT use in breast imaging

An eye-opening TED Talk

Dr. Deborah Rhodes of Mayo Clinic gives a fascinating talk on the limitations of breast cancer detection in dense breasts, and the potential of MBI and CZT to overcome this

The Full Story

Breast cancer affects everyone

Breast cancer is something everybody is familiar with. Around the world, as reported by the WHO, 2.3 million women were diagnosed with breast cancer in 2020. In the UK specifically, breast cancer comprises 15% of new cancer cases. Even with a universal impact, the current state of breast cancer detection technology isn’t universally effective.

Detection of breast cancer in dense breasts is challenging in Mammography

Depending on country, ethnic origin, age, or family history, between 25% to 50% of women have dense breast tissue, and this is especially common in women under 50 years old.

In a mammogram, a tumour would be clearly seen in a breast with fatty or scattered tissue. However, dense tissue appears as a white cloudy structure, which is likely to mask a tumour. This means that the sensitivity (true positives i.e. finding and correctly detecting cancerous tumours) of mammography is limited when trying to detect breast cancer in dense tissue. More tumours are likely to be missed, especially in the early stages when they can’t be felt through the breast tissue.

Therefore, there is an urgent need to broaden the capabilities of breast cancer detection, especially for women with denser breasts.

Alternative Solutions

There are several techniques which could improve the detection of breast cancer in dense breast tissue, such as MRI, US (Ultra-Sound), DBT (Digital Breast Tomography), and Breast CT. However, none of these alternatives are able to provide a solution combining a good sensitivity (high number of true positives), good specificity (low number of false positives i.e. non-cancerous tissue falsely detected as cancerous), a low cost to hospitals and shorter waiting times. The latter is especially important when carrying out large-scale breast screening programs. Contrast agents are also used to produce images of the breasts in MRI (gadolinium-based agent) DBT, and Breast CT (iodine dye), and they have a small chance of causing a significant allergic reaction. Therefore, although acceptable and fully-approved for diagnostic purposes, these techniques could pose several challenges if used in screening programs involving a large proportion of the general population.

The Benefits of MBI

The emerging technique which appears to combine the advantages of the existing, competitive techniques for breast screening with dense tissue is MBI, or Molecular Breast Imaging. MBI is a type of nuclear imaging where a patient is intravenously injected with a radioactive tracer, which then spreads through the body via the bloodstream. The breast image is taken with an MBI scanner which visually resembles a mammography machine, but operates based on different principles.

How does this work?

Cancerous cells take up much more of the radioactive tracer than normal cells. This is due to their higher activity e.g. increased metabolism and lots of new blood vessel growth around the tumour. Therefore, they appear as hotspots in the image taken by gamma cameras positioned at opposite sides of the breast. The photons emitted from the tracer are what forms these images. The breast is immobilised by a slight compression between the two gamma cameras when the image is being taken. The pressure experienced by the patient is considerably lower compared to mammography, increasing comfort. The radioactive tracer used in MBI (Tc-99m-sestamibi) emits photons which have a higher energy than the x-rays used in mammography. The higher energy of the photons make them much less sensitive to variations in breast tissue density, making it easier to detect tumours in dense breasts. Unlike DBT or Breast CT, no contrast agents are needed to highlight the presence of a tumour. Therefore, the risk of patients experiencing an allergic reaction is reduced.

The video below explains how an MBI would be carried out for a patient:

As reported in clinical studies conducted by Mayo Clinic (doi: 10.2214/AJR.14.13357), when mammography and MBI are combined, the cancer detection rate is increased by a factor of 4, compared to relying on mammography alone. The sensitivity rate also increases from 24% to 81% so there are more true positives i.e more tumours correctly detected.

Here in this short video, Dr. Deborah Rhodes from Mayo Clinic summarises the key roles of MBI in detecting breast cancer in women with dense breasts

So why isn’t MBI used worldwide?

Currently, MBI is an FDA approved technique in the USA. It has been adopted by a number of selected hospitals and practices mostly in the USA, but remains largely overlooked in Europe, the UK, and other countries.

This is due to two major limitations:

  1. The patient effective dose (amount of radiation exposed to the patient’s body) is higher in MBI than mammography by up to a factor of five. Although this dose is within the acceptable limits for screening purposes, there is still an understandable resilience to adopt a technology with significantly higher dose, due to the risks that come with radiation exposure
  2. The scan time is about four times longer in MBI than in mammography (40 minutes vs 7-10 minutes). This decreases patient throughput (fewer patients seen in a given time) and prolongs the discomfort experienced by the patient during the procedure

Low Dose MBI Technology

In 2018, Kromek received funding from Innovate UK to begin a 3 year programme to develop an innovative solution to decrease the scan time and effective dose of MBI. This could make it a more adoptable solution worldwide so the life-saving benefits of MBI are no longer waiting on the sidelines.

At Kromek, this project is led by Alexander Cherlin, our Principal Physicist. By working with other world-leaders in this field such as the world-renowned imaging construction group from UCL, and one of the UK’s ‘outstanding’ NHS trusts: the Newcastle Upon Tyne Hospitals NHS Foundation Trust, we have been able to develop a new, disruptive scanner design; the Low Dose MBI.

The results

The current results have been obtained from a series of simulations and starting experimental measurements. So far, the results suggest that we expect to achieve an overall reduction factor of 8 in dose, scan time, or, in a combination of both.

This would allow the patient dose to be reduced to twice the value of the mammography dose, equaling the dose used in DBT or Breast CT. Scan time could also be decreased to about 10 minutes, making the scan time comparable to mammography, DBT or Breast CT.

The Significance of CZT

As with Kromek’s other detectors used in medical applications, CZT (Cadmium Zinc Telluride) is also a key element of the Low Dose MBI technology. Compared to other semi-conductors, CZT is much more efficient at detecting the incoming flux of photons from the radiotracer, at room temperature. Lower doses of radiation are needed to produce the necessary images, therefore, less radiation is exposed to patients undergoing screening or diagnostic tests. This reduces the risks of radiation exposure, keeping patients as safe as possible.

Furthermore, CZT helps to produce more accurate results to increase confidence in any diagnoses made. This is beneficial not only in early breast cancer detection, but also in the diagnosis of osteoporosis and cardiac conditions.

large_CZT_detector

Looking to the future

Making progress like this in breast cancer diagnosis is vital. The two major obstacles have been overcome in the results so far, bringing the lifesaving capabilities of Low Dose MBI closer to reality. Higher-confidence tools like this could be more effective at identifying breast cancer in its earlier stages during screening. The accuracy of diagnosis amongst women and others with more dense breast tissue could also be significantly improved. More lives could be saved with earlier, more assured breast cancer detection in women with dense breasts.

The next steps forward are to replicate simulation results in further experiments.

The development of new medical imaging technology like Low Dose MBI is also beginning to reveal the full potential of CZT detectors. It highlights the possibility for their inclusion in other medical applications, widening the scope for improving the accuracy of diagnosis over a large range of conditions.

 

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