Category: Molecular Imaging

30 Jun 2023
Diagnostic and Radiation Therapy Examples

Other Forms of Radiation Therapy and Diagnostic Machines

In our last blog post, we explored the timeline of diagnostic imaging and radiotherapy developed using x-rays. It was the original discovery of x-rays by Röntgen that led to the creation of these medical practices. However, other researchers of the 20th century also invented diagnostic tools and radiation therapy without x-ray involvement at all. We will explore a few of these imaging and radiotherapy machines or procedures in this blog.

Diagnostic Imaging

MRI

One of the most well-known imaging procedures is MRI, which stands for Magnetic Resonance Imaging. Research for MRI began early in the 1970s, but investigation of the magnetic resonance principles started as early as 1945. By happenstance, Felix Bloch, a Swiss physicist working at Stanford, and American physicist, Edward Mills Purcell at Harvard, conducted—nearly simultaneously—an experiment for a new mode of nuclear induction. This led to published papers from both physicists on nuclear magnetic resonance. After publication, both Purcell and Bloch won the 1952 Nobel Prize for this research.1

The process to produce 2D images in an MRI using nuclear magnetic resonance (NMR) was discovered by Paul Lauterbur and Peter Mansfield. Lauterbur published the first nuclear magnetic image in 1973, eventually producing 3D images as well. However, he still had long to go before these images would be practical for application with actual patients. Mansfield continued to expand on Lauterbur’s work, developing the echo-planar imaging technique to improve image quality and scan time in the late 1970s.  By 1977, physician Raymond Damadian created the first full body MRI machine. Through continuous improvements and further research, today’s MRI provides a safe, effective way of capturing images in the brain, portions of the body, the cardiovascular system, and central nervous system. MRIs provide information on size, location, classification, and grade of lesions so as to aid diagnosing stroke, MS, blood supply issues, and any brain damage.2

Ultrasound

Today, ultrasound is most widely known in the OB/GYN field of medicine. Through its invention, however, this diagnostic tool proved its range of utility before becoming a staple in wellness checks during pregnancies. The origin of ultrasonography is often credited to Lazzaro Spallananzi, a physiologist who discovered echolocation throughout 1794 from various experiments involving bats. The principles that serve as a basis for echolocation are also those functioning for medical ultrasound technology today. In 1942, neurologist Karl Dussik first used ultrasonic waves in a diagnostic procedure while attempting to find brain tumors. He later published a report of musculoskeletal ultrasonography in 1958, laying the groundwork for diagnostic musculoskeletal ultrasound.3

Professor Ian Donald from the University of Glasgow was responsible for the development of medical ultrasound in clinical practice. During his research from the late 1950s into the 1960s, there was clinical skepticism about the use of ultrasound. Many doctors felt that manual abdominal and pelvic examinations had proven adequate for medical diagnoses. With his co-workers, Donald performed several studies to show the likelihood of misdiagnoses of a cyst versus a malignant mass. By publishing the findings in 1958, this became a critical point in time for encouraging use of the medical ultrasound. Donald and his colleagues eventually developed an automatic scanner that utilized a full bladder for early pregnancy detection in 1963. This set the path to the now common practice of ultrasounds in the OB/GYN field today.4

PET Scans

Experimental physicist, C.D. Anderson, observed particles from cosmic rays in 1932 that were the same mass as an electron, but which moved in a strong magnetic field along a path opposite to that of an electron indicating a positive charge. He named these particles as “positrons” or positive electrons.

Emission of these positrons was the proof that Irène Joliot-Curie and Frédéric Joliot-Curie used to prove the artificial creation of radioactive elements to win the 1935 Nobel Prize in Chemistry. The creation of these artificial elements was the main focus over the following years due to their significance to military research from the late 1930s until the 1950s. Imaging studies began taking strides as a result of the desire by Louis Sokoloff, an American neuroscientist who hoped to relate mental function to brain function. This encouraged research through the 1950s until the first tomography unit attempt in 1968. This was the turning point in which PET scan development accelerated into the machines we are more familiar with today.5

PET scans can provide imaging through the detection of the gamma ray pairs that are created when a positron annihilates with an electron inside the tissue where the positron emitting isotope has collected. Whereas other diagnostic scans capture the form of an object, PET scans correlate with the metabolic functions of the tissues that uptake the radioactive compound. The compound with the radioactive tracer is typically a form of glucose called FDG (fluorodeoxyglucose), which is used as an energy source by cells and is given to the patient by means of an IV injection. The more rapid the metabolism of the cells in a tissue, as you have with cancer cells, the more uptake of the FDG. This differential uptake is then seen as an enhanced region on a PET scan. 5

Radiation Therapy

Gamma Rays – Gamma Knife (and Cobalt Therapy)

Gamma radiation from radioactive cobalt sources has been harnessed to create an alternative method for producing therapeutic radiation beams. Similar in design to the previously discussed LINAC machines, a Cobalt unit uses a single Co-60 source to produce the radiation beam for treatment. A machine of a fundamentally different design, the Gamma Knife was developed for the treatment of brain tumors. The Gamma Knife is a stereotactic radiosurgery technique that allows for functional neurological surgery. This machine uses anywhere from 192 to 201 C0-60 arrayed in a semi-spherical shield with each source collimated to point their radiation to the same point in space. This type of precision allows for the potential to treat brain tumors and, in turn, pain, movement disorders, and even some behavioral disorders for patients who had not been responsive to other treatment.6

The Gamma Knife was created through the inspirations of Swedish professors Borje Larsson and Larks Leksell in the 1950s. After an investigation using proton beams with stereotactic devices capable of pinpointing targets in the brain, the researchers eventually gave up on that approach due to cost and complexity. Motivated to find an alternative, Larsson and Leksell went on to create a prototype Gamma Knife system in 1967. The prototype unit was a success, used in Sweden for twelve years  and led to a second Gamma Knife in 1975, before other units began appearing globally in the 1980s.6

Proton Therapy

Protons were discovered in the early 1900s. New Zealand physicist Ernest Rutherford’s research during this time led to his discovery of a nuclear reaction that led to the “splitting” of an atom, where he found protons. As a charged particle, the protons have a finite range in matter. The proton’s interaction with matter produces ionization as the proton slows down along its path, losing energy. A peak of deposited dose then occurs at a depth that is proportional to the proton’s original energy.7

The cyclotron, invented by the American physicist Ernest O. Lawrence along with his associates in 1929, proved an efficient way to produce beams of protons. The cyclotron was capable of accelerating protons to high enough energy that, towards the middle of the 20th century, it was suitable for application in cancer treatments.

Dr. Robert Wilson, another American physicist, was the one to spark the idea of proton therapy for battling cancer. He wrote a seminal paper on the functionality of particle beams (comprised of either protons or other heavy-charged particles) and their ability to disperse their energy in the body—the initial release would be small, then exponentially grow when the beam reaches the end of its path for maximum effect against the tumor. Dr. Wilson published the paper in 1946 and received credit to being the inspiration of further research on proton therapy and the continued development of cyclotrons.7

Brachytherapy and Interstitial Therapy

Brachytherapy is an internal radiation therapy technique involving direct placement of radiation inside a patient’s body cavity. This procedure involves small, radioactive source implants that are generally positioned in a body cavity to be near a cancerous tumor. The radioactive material, typically encapsulated within suitable housing material such as titanium, constantly exposes the tumor to a stream of radiation until removal of the radioactivity. These implants will be temporary, and the patient is either hospitalized or kept in a special suite for the duration of the treatment.

Another form of therapy, interstitial therapy (or interstitial brachytherapy), uses sources that are placed directly into the tissue. These may either be temporary or permanent implants of small, encapsulated sources on the order of the size of a rice grain. For treatments with permanent implants, it is safe enough for the patient to go home with a few simple safety guidelines to follow.8

Brachytherapy was first used in 1901 during an attempt to treat lupus. Alexandre Danlos and Paul Bloch completed this treatment with a radioactive sample from Marie Curie. Shortly after, in 1903, Margareth Cleaves used brachytherapy to treat cervical cancer. It became a popular radiotherapy technique to treat breast, cervical, and prostate cancer. As technology advanced along with the use of brachytherapy through the 1900s, imaging-guidance became a valuable asset. More precise dosimetry became possible and allowed for better brachytherapy planning when doctors could use diagnostic modalities such as CTs, MRIs, or ultrasounds. Today, brachytherapy is a more popular treatment for conditions ranging through gynecological, genitourinary, ocular, and head & neck cancers.9

Summary and Conclusion

The 20th century saw tremendous growth and development in diagnostic machinery and radiotherapy. From soundwave technology that gave way to ultrasound, magnetic resonance inspiring MRIs, and the discovery of positrons, medical and non-medical fields can run diagnostic imaging that suits their needs exactly for the most effective information. Radiation therapy research continuously improves the technology and practices used for the wellbeing of patients. Precision instruments such as the Gamma Knife, Cyberknife, and modern LINACs permit for types of treatments that would otherwise be impossible whilst at the same time reducing the side effects associated with external beam therapy. Proton therapy calculations allow for precise travel through the body for maximum effect against cancerous tumors. Brachytherapy provides a treatment option that directly targets tumors without having radiation travel through the body to the target tissue. Modern image guidance ensures source placement exactly where treatment is necessary and that externally directed therapy beams hit their target. As these modalities evolve, we witness the growing reality of safer, more effective diagnoses and cancer treatments within our lifetimes.

The Versant Physics team has experience that covers a range of equipment. This includes dental units, mobile c-arms and Cone-beam CTs, as well as high energy LINACs and even Proton Therapy units and Cyclotrons. To learn more about how our services can help you, contact us to set up a meeting.

Sources

1. NMR Basics | Nuclear Magnetic Resonance Spectroscopy Facility | University of Colorado Boulder. www.colorado.edu. https://www.colorado.edu/lab/nmr/nmr-basics

2. The History of the MRI – DirectMed Parts & Service. https://directmedparts.com/history-of-the-mri/

3. D. Kane and others, A brief history of musculoskeletal ultrasound: ‘From bats and ships to babies and hips’, Rheumatology, Volume 43, Issue 7, July 2004, Pages 931–933, https://doi.org/10.1093/rheumatology/keh004

4. History of Ultrasound – Overview of Sonography History and Discovery. Ultrasoundschoolsinfo.com. Published December 27, 2021. https://www.ultrasoundschoolsinfo.com/history/

5. Henry N. Wagner, A brief history of positron emission tomography (PET), Seminars in Nuclear Medicine, Volume 28, Issue 3, 1998, Pages 213-220, ISSN 0001-2998, https://doi.org/10.1016/S0001-2998(98)80027-

6. History and Technical Overview | Neurosurgery. Neurosurgery. Published 2018. https://med.virginia.edu/neurosurgery/services/gamma-knife/for-physicians/history-and-technical-overview/

7. History of Proton Therapy – NAPT. NAPT. Published 2018. https://www.proton-therapy.org/about/history-of-proton-therapy/

8. Radiation Oncology. Radiation Answers. Accessed May 31, 2023. https://www.radiationanswers.org/radiation-sources-uses/medical-uses/radiation-oncology.html

9. Mayer C, Kumar A. Brachytherapy. PubMed. Published 2021. https://www.ncbi.nlm.nih.gov/books/NBK562190/

01 Oct 2021

How Molecular Imaging and Radiation Therapy Help Fight Breast Cancer

It is estimated that 1 in 8 women in the United States will develop invasive breast cancer within their lifetimes. It is an incredibly devastating disease that affects thousands of people a year. This year alone, 281,550 women in the United States will be diagnosed.

Screening efforts and treatment therapies involving molecular imaging and radiation therapy are key to helping detect and successfully treat breast cancer.

Breast Cancer Statistics

  • Breast cancer is the most diagnosed cancer in women.
  • Breast cancer in women has the highest rate of death compared with any other cancer, besides lung cancer.
  • It is more commonly diagnosed in black women under the age of 45 than white women.
  • Minority women are 72% more likely than white women to be diagnosed with breast cancer before age 50 and are 127% more likely to die of breast cancer before age 50.
  • Men have a 1 in 833 chance of getting breast cancer.
  • In 2021, the World Health Organization reported that breast cancer accounted for 12% of all new, worldwide cancer cases.

Breast Cancer Risk Factors

Age and being born female are the biggest risk factors for breast cancer. Women that have direct relatives with a history of breast or cervical cancers such as mothers, sisters, and grandmothers have a higher risk of developing breast cancer in their lifetimes.

There are several known gene mutations that can be inherited from either parent which grant a higher lifetime risk of developing breast cancer as well.

When functioning correctly, these genes, called Breast Cancer Gene 1 (BRCA1) and Breast Cancer Gene 2 (BRCA2), produce proteins that help repair DNA. These tumor suppressor proteins actually help protect from certain cancers by slowing abnormal cell growth and forcing certain damaged cells to stop working entirely.

However, when present, the BRCA gene mutation can prohibit these proteins from working and building correctly, resulting in cancerous tumors.

By age 80, 55%-72% of women with an inherited BRCA1 mutation and 45%-69% with an inherited BRCA2 mutation will develop breast cancer. People with a BRCA variant also tend to develop breast cancer at a much younger age than those without.

There are also higher instances of BRCA1 and BRCA2 gene mutations in certain racial and ethnic groups. For instance, 2% of Ashkenazi Jewish people carry one of the variants. A study in 2009 determined that black and Latin American women were more likely to have BRCA1 mutations.

Signs & Symptoms

The most common symptoms of breast cancer include a lump or mass in the breast, but physical changes in the appearance of the breast are also reported. This includes skin redness or swelling, bloody or abnormal discharge, thickening of the skin, or scaliness.

Breast cancer can develop without presenting any physical symptoms, however, which is why regular screening and breast exams are so important for prevention.

Screening Recommendations

Regular breast cancer screenings can help discover breast cancer in its early stages before it has spread to other parts of the body, therefore, limiting treatment options and increasing mortality rates. Mortality rates can be reduced by 40% with regular screenings.

Mammography

Mammography is a low-dose x-ray procedure used to detect breast cancer in its early stages, often before a patient has experienced any symptoms like lumps or skin alterations.

This type of x-ray exam exposes the patient to low doses of ionizing radiation to produce an image of breast tissue or the inside of the breast.  

During a mammography procedure, the breast is flattened between two plates on the x-ray unit for several seconds while an x-ray beam is carefully aimed at the area of concern by the radiologist or technologist performing the procedure. It is standard during a normal screening for two views of each breast to be taken. The mammograms are then reviewed by a radiologist, who looks for early signs of cancer or other abnormalities.

Mammograms can also be used if a patient has experienced symptoms of breast cancer and to screen patients who have been previously treated for breast cancer. This diagnostic mammogram includes additional views of the breast not normally taken during a screening.

Radiation received from regular mammograms is cumulative, however, it does not significantly increase breast cancer risk. In the case of screening for cancer, it is more beneficial in the long run to receive a low radiation dose. 

Screening Frequency

Various medical and cancer-related institutions have different guidelines on when it is appropriate or necessary to schedule a mammogram.

The American Cancer Society recommends patients with an average risk of breast cancer between the ages of 45-54 get annual mammograms. Patients aged 55 and older have the option to get a mammogram every other year.

The American College of Radiology (ACR) and the Society of Breast Imaging (SBI) recommend annual mammograms begin at age 40 and continue past age 74.

Molecular Imaging & Breast Cancer

Molecular Imaging is a medical imaging procedure used to help locate breast cancer tumors and determine if cancer has spread to other parts of the body. It is a vital part of the diagnosis and treatment process because it measures biological and chemical processes within the body, compared with regular x-rays which focus on static anatomical images.

Molecular imaging helps physicians determine the appropriate treatment therapies, study the patient’s response to drugs, and closely monitor changes in cellular activity. It is also useful for identifying whether the prescribed therapies are effective and monitoring for reoccurrences.

There are a variety of medical imaging procedures that help visualize chemical processes in the body such as blood flow, oxygen use, or metabolism. Many procedures require an imaging agent such as a radiotracer—a compound containing a small amount of radioactive material—being introduced into the body usually via injection into the bloodstream.

This radiotracer is designed to accumulate in the body in different organs which are then picked up by the imaging device.  It can also attach to different cells or groups of cells and paint a clear picture about precisely where abnormal amounts of metabolic activity are occurring.

PET/PET-CT

Positron Emission Tomography (PET) scans alongside Computer Tomography (CT) are one of the most common molecular imaging technologies used for breast cancer. The combination of these two imaging modalities helps physicians determine the exact location of the tumor, what stage the cancer is at, if it has spread, and what type of treatment will be best moving forward.

In this procedure, a radiotracer that naturally emits positrons as it decays is injected into the bloodstream. These positrons react with electrons in the body and produce energy in the form of photons. These photons are detected by the PET scanner, producing 3D images which show how the radiotracer is being distributed.

On a PET scan, the areas where the radiotracer has accumulated appear brighter and more intense than in the surrounding tissue. This is because cancer cells, when active, absorb more glucose. The higher instance of this metabolic activity is made clear thanks to these “hot spots” on the PET scan.

The PET scan is combined with the CT scan to produce a detailed image of both the patient’s anatomy and the metabolic activity present.

Surgical Treatment Options

In addition to chemotherapy, there are several other treatment options for breast cancer that typically precede radiation therapy.

Lumpectomy

A lumpectomy, also known as a partial mastectomy, re-excision, or biopsy, is a breast-conserving surgery that involves removing part of the breast tissue. The surgery removes the lump or tumor plus a small amount of the healthy tissue that surrounds it.

Mastectomy

A mastectomy is a surgical procedure that removes the entire breast. There are different kinds of mastectomies with varying degrees of severity. The type of mastectomy a patient receives will depend on the stage the cancer is at and if it has spread to the lymph nodes or other areas of the body. 

Radiation Therapy & Breast Cancer

Radiation therapy delivers ionizing radiation particles to specific areas of the body to destroy cancer cells, either as a standalone treatment or in conjunction with other treatment options like surgery. Brachytherapy and External Beam Radiation Therapy are the two most common treatment types.

Brachytherapy

Brachytherapy is a procedure that involves placing small, sealed radioactive material sources inside the body, either directly inside or next to a tumor. Also known as internal beam radiation, this procedure is used to treat cancer by allowing doctors to deliver higher doses of radiation via a needle or catheter to specific areas of the body.

Compared to other types of radiation treatments, brachytherapy is best for cancers that have not metastasized. It is considered as effective as—and sometimes used in conjunction with—external beam therapy. Due to the nature of brachytherapy procedures, there is a smaller chance of radiation exposure to surrounding healthy tissue and organs than with external radiation as it targets the tumor directly.

Because healthy tissue and organs surrounding the tumor are not as affected by the radiation treatment, most people experience few or less serious side effects than occur with external beam therapy. In addition to tenderness, bleeding, or swelling at the treatment area, the side effects a patient could experience depend largely on the type of cancer and therapy being performed. Fatigue is common.

External Beam Radiation

According to the American Cancer Society, external beam radiation is the most common type of radiation therapy used to treat breast cancer. It can be used in both early-stage breast cancer as well as for advanced stages that cannot be removed with surgery.

EBRT normally occurs 3 to 6 weeks after a patient has undergone surgery and/or completed chemotherapy. Small doses of ionizing radiation are delivered to cancer to destroy the cancerous cells. This process is normally a painless outpatient procedure that lasts up to 5 days a week for anywhere from 2 to 9 weeks.

During EBRT, the patient is usually positioned on their back with their ipsilateral arm placed above their head and their shoulder rotated outward. Then, radiation is precisely applied to the area according to the radiation treatment plan.

Throughout the process, a radiation oncologist monitors a patient’s response to the treatment and may alter the prescribed radiation dose or the number of treatments accordingly.

One 2021 study suggests that a lumpectomy plus radiation therapy offers better survival rates than a standalone mastectomy for early-stage breast cancer. Other studies have discovered that the risk of recurrence in a patient who undergoes radiation therapy is between 5% to 10%, while patients who do not receive radiation therapy have a 20% to 40% recurrence rate.

The Radiation Therapy Team

Each patient who undergoes radiation therapy has a dedicated team of radiation professionals on their side who determine exactly how they will be treated. Throughout the treatment process, they also determine if any changes to the radiation treatment plan need to be adjusted.

A radiation oncologist is a specialist in treating cancer with radiation. Their job is to determine which therapy is the best fit for the patient based on their medical history and physical health.

A medical physicist and dosimetrist will also be a part of this team. They work together with the physician to create the treatment plan.

Radiation therapists and technologists are the individuals who physically administer the radiation therapy treatments and operate the equipment. They are the people patients will interact with the most during their treatment.

The Takeaway

There are a variety of available breast cancer treatment therapies including radiation therapy and surgery. Radiation therapies administered in conjunction with chemotherapy and surgical treatment options have a much lower recurrence rate than standalone treatments.

Proper screening and regular exams are the best way to detect breast cancer when it is in its earliest and most treatable stages. If a patient is 40 or older, it is in their best interest to begin scheduling annual mammograms.

In honor of Breast Cancer Awareness month, check out the following organizations providing patient support services and making great strides in research and awareness: