Medical Imaging & Radiation Therapy Primer
Computed Tomography (CT)
Computed Tomography (CT), also commonly referred to as a CAT scan, is a medical imaging method that combines multiple X-ray projections taken from different angles to produce detailed cross-sectional images of areas inside the body. CT images allow doctors to get very precise, 3-D views of certain parts of the body, such as soft tissues, the pelvis, blood vessels, the lungs, the brain, the heart, abdomen and bones. CT is also often the preferred method of diagnosing many cancers, such as liver, lung and pancreatic cancers.
CT is often used to evaluate:
- Presence, size and location of tumors
- Organs in the pelvis, chest and abdomen
- Colon health (CT colongraphy)
- Vascular condition/blood flow
- Pulmonary embolism (CT angiography)
- Abdominal aortic aneurysms (CT angiography)
- Bone injuries
- Cardiac tissue
- Traumatic injuries
- Cardiovascular disease
- Lung Cancers Diagnosed at Annual CT Screening: Volume Doubling Times
Researchers observed that CT scans are more effective at identifying aggressive lung cancers in their most treatable stages than traditional detection methods.
- National Trends in Use of Computed Tomography in the Emergency Department
This retrospective study found that a recent increase in CT use in the emergency department has been associated with a decline in admissions or transfers.
- CT Screening Catches Small Cell Lung Cancers Earlier
Radiologists found that CT screening and treatment when indicated may spare the lives of patients with small cell lung cancer.
- Reduced Lung-Cancer Mortality with Low-Dose Computed Tomographic Screening
In this pivotal clinical trial, low-dose CT was significantly associated with a 20 percent reduction in lung cancer related mortality and 6.7 percent reduction in all-cause mortality compared to screening with radiography.
- An Actuarial Analysis Shows that Offering Lung Cancer Screening as an Insurance Benefit Would Save Lives at Relatively Low Cost
Model results projected that there would be approximately 130,000 additional lung cancer survivors in 2012 if smokers were screened with low-dose CT vs. a scenario of no screening.
- Accuracy of CT Colonography for Detection of Large Adenomas and Cancers
In more than 2,500 patients undergoing both a CT colonography and standard colonoscopy procedure, 90 percent of all large lesions (≥10 mm) were detected with CT colonography compared to standard colonoscopy.
- The CT-STAT (Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment) Trial
Researchers found that computed tomography (CT) angiography can save an estimated $1,455 per patient by reducing unnecessary cardiac catheterizations.
Magnetic Resonance Imaging (MRI)
Magnetic Resonance Imaging (MRI) is a medical imaging technology that uses radio waves and a magnetic field to create detailed images of organs and tissues. MRI has proven to be highly effective in diagnosing a number of conditions by showing the difference between normal and diseased soft tissues of the body.
MRI is often used to evaluate:
- Blood vessels
- Abnormal tissue
- Bones and joints
- Organs in the pelvis, chest and abdomen (heart, liver, kidney, spleen)
- Spinal injuries
- Tendon and ligament tears
- Can MRI Screen for CSF Biomarkers in Neurodegenerative Disease?
This study found that an MRI technique can help differentiate between Alzheimer’s disease and another type of dementia.
- Breast Cancer Risk Assessment and MRI
According to researchers, using radiation-free assessment techniques like MRI earlier in life may give a more accurate risk assessment of breast cancer with better chance of prevention.
- The Evolving Role of MRI in the Detection and Evaluation of Breast Cancer
This editorial demonstrated that a growing number of newly diagnosed breast cancer patients benefit from MRI evaluation to determine whether their cancer has spread throughout the breast tissue (multi-centric) or is localized in one particular area, allowing patients and physicians to make better therapy choices and reduce patients’ fear of recurrence from cancerous tissue missed in the initial diagnostic assessment.
- Magnetic Resonance Imaging Profiles Predict Clinical Response to Early Reperfusion: the Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution (DEFUSE) Study
This study found that MRI profiles could be used to select stroke patients who should undergo reperfusion within 3-6 hours of symptom onset and identify patients who would benefit from early reperfusion, those who would receive no benefit and those who could potentially be harmed.
- MRI Identifies Candidates for Prostate Cancer Surveillance
This retrospective study found that adding an MRI exam to the initial clinical evaluation of men thought to have low-risk prostate cancer can help identify the best candidate for active surveillance.
- The Value of MR Imaging When the Site of Uterine Cancer Origin Is Uncertain
Researchers found that MRI is useful in determining the anatomic origin of uterine cancer and also provides helpful information regarding invasion of adjacent structures.
- Magnetic Resonance Imaging Versus Arthroscopy in the Diagnosis of Knee Pathology, Concentrating on Meniscal Lesions and ACL Tears: A Systematic Review
This study found that MRI is highly accurate in diagnosing meniscal and anterior cruciate ligament (ACL) tears and is the most appropriate screening tool before therapeutic arthroscopy.
Positron Emission Tomography (PET)
Positron Emission Tomography (PET) is a nuclear imaging technique that provides physicians with information about how tissues and organs are functioning. PET, often used in combination with CT imaging, uses a scanner and a small amount of radiopharmaceuticals which is injected into a patient’s vein to assist in making detailed, computerized pictures of areas inside the body.
PET is often used to evaluate:
- Neurological diseases such as Alzheimer’s and Multiple Sclerosis
- Effectiveness of treatments
- Heart conditions
- The Beneficial Impact of PET Scanning on Cancer Management
Physicians reported that PET scanning allows them to avoid additional tests or procedures 77 percent of the time.
- PET Predicts Survival from Sarcomas
According to researchers, a PET scan after the first round of neoadjuvant chemotherapy can predict increased survival in patients with soft-tissue sarcomas.
- PET, MRI, Cerebrospinal Analysis Best for Alzheimer’s Test
Fluorodeoxyglucose-PET (FDG-PET), along with MRI and cerebrospinal analysis, was found to significantly increase the accuracy of predicting Alzheimer’s disease progression from mild cognitive impairment.
- Performance Characteristics of Amyloid PET with Florbetapir F 18 in Patients with Alzheimer’s Disease and Cognitively Normal Subjects
Researchers observed that florbetapir F 18 appears to have a wide effective dose range and high test-retest reliability for both quantitative (SUVr) values and visual assessment of the ligand.
For added precision, physicians use a medical imaging technique that combines PET and CT. This allows images acquired from both devices to be taken sequentially and combined into a single superposed image. PET-CT serves as a prime tool in the delineation of tumor volumes, staging and the preparation of patient treatment plans. The combination has been shown to improve oncologic care by positively impacting active treatment decisions, disease recurrence monitoring and patient outcomes, such as disease-free progression.
- The Clinical Impact of Integrated FDG PET-CT on Management
This study found that the addition of PET-CT to comprehensive evaluation of lung cancer can have significant clinical impact by improving the staging of disease, sparing patients unnecessary treatment and more appropriately targeting disease management.
- Significant Benefits of F-FDG PET in Evaluating Colorectal Liver Metastases
This study showed that F-FDG PET proved highly successful when combined with CT for staging and developing surgical recommendations.
- Technology Insight: Advances in Molecular Imaging and an Appraisal of PET-CT Scanning
Researchers have found that FDG-PET (a form of PET-CT) can detect a tumor’s response to radiation or chemotherapy within three to four weeks post-treatment, making it possible to modify therapy regimens more quickly and increase treatment effectiveness.
- Monitoring Cancer Treatment with PET-CT: Does it Make a Difference?
This review demonstrated that, given that chemotherapy prior to surgical tumor resection only improves survival for a small percentage of patients, PET-CT might help reduce costs and unnecessary exposure to toxic therapies by helping physicians to efficiently identify patients who will respond to initial therapy.
- Clinical Impact of Integrated PET-CT on the Management of Suspected Cervical Cancer Recurrence
This study found that, in patients with a suspected recurrence of cervical cancer, integrated PET-CT using (18)F-FDG provides good anatomic and functional localization of suspicious lesions, and the better diagnostic interpretation has an impact not only on clinical management and treatment planning of patients, but also on disease-free survival.
- The Clinical Impact of Integrated FDG PET-CT on Management
Radiation Therapy (RT)
Radiation therapy (RT) is used to treat a wide range of cancers by delivering highly targeted radiation to cancerous cells, destroying their ability to grow and divide while leaving healthy cells intact. Generally, RT is delivered through beams emitted from a machine outside the body or through brachytherapy, which involves placing the radiation source directly inside or near the site of the cancerous cells. Cancer patients may be treated with radiation therapy in combination with other methods such as chemotherapy, surgery, or hormone therapy, to maximize the benefit to the patient.
- Postop Radiation Slows PSA Rise in High-Risk Prostate Cancer
Researchers observed that men with high-risk prostate cancer had a significantly lower risk of biochemical relapse when treated with adjuvant radiation therapy after radical prostatectomy.
- Effectiveness of Radiation for Prevention of Mastectomy in Older Breast Cancer Patients Treated with Conservative Surgery
Researchers found that the receipt of RT after conservative surgery was associated with a greater likelihood of ultimate breast preservation for most older women with early breast cancer.
- Excellent Local Control with Stereotactic Radio Therapy Boost After External Beam Radio Therapy in Patients with Nasopharyngeal Carcinoma
According to researchers, stereotactic radiotherapy boost after external beam radiotherapy provides excellent local control for locally advanced nasopharyngeal carcinoma patients.
- Postop Radiation Slows PSA Rise in High-Risk Prostate Cancer
Diagnostic ultrasound, also known as medical sonography or ultrasonography, uses high frequency sound waves to create images of the inside of the body. The ultrasound machine sends sound waves into the body and is able to convert the returning sound echoes into a picture. Ultrasound technology can also produce audible sounds of blood flow, allowing medical professionals to use both sounds and visuals to assess a patient’s health.
Ultrasound is often used to evaluate:
- Abnormalities in the heart and blood vessels
- Organs in the pelvis and abdomen
- Symptoms of pain, swelling and infection
- The Role of Endoscopic Ultrasound in the Evaluation of Rectal Cancer
This study found that endoscopic ultrasonography is an important standard of care for identifying and guiding rectal cancer patients who are candidates for pre-operative neoadjuvant therapy.
- Consequences of Axillary Ultrasound in Patients with T2 or Greater Invasive Breast Cancers
Researchers found that ultrasonography has yielded savings of more than $4,000 per patient by reducing the occurrence of unnecessary, invasive breast cancer procedures.
- Opportunities to Improve Outcomes in Sickle Cell Disease
This article demonstrated that ultrasound screening can identify children who have abnormal transcranial blood flow velocity and who would benefit from transfusions to reduce the risk of stroke.
- Screening for Abdominal Aortic Aneurysm: A Best-Evidence Systematic Review for the U.S. Preventive Services Task Force
This analysis found that ultrasound screening can reduce mortality caused by a rupture of abdominal aortic aneurysms.
- Fine-Needle Aspiration Biopsy Versus Ultrasound-Guided Fine-Needle Aspiration Biopsy: Cost-Effectiveness as a Frontline Diagnostic Modality for Solitary Thyroid Nodules
This model estimated that ultrasound-guided fine-needle aspiration biopsy increased the correct classification of thyroid malignancies from 92 percent with conventional biopsy to 98 percent, and was a cost-effective strategy at $318 per additional cancer case that was correctly diagnosed.
- Detection of Breast Cancer with Addition of Annual Screening Ultrasound or a Single Screening MRI to Mammography in Women with Elevated Breast Cancer Risk
Researchers found that the addition of screening ultrasound to mammography in women at increased risk of breast cancer resulted in a higher cancer detection yield.
- Ultrasound Changes Care of Some Patients with Rheumatic Conditions
Ultrasound evaluations of 62 patients with rheumatic conditions resulted in a change of patient management for approximately half of them and researchers observed a significant decrease in the use of anti-rheumatic drugs (DMARDs).
X-ray technology is the oldest and most commonly used form of medical imaging. X-rays use ionizing radiation to produce images of a person’s internal structure by sending X-ray beams through the body, which are absorbed in different amounts depending on the density of the material. In addition, included as “x-ray type” devices are also mammography, interventional radiology, computed radiography, digital radiography and computed tomography (CT). Radiation Therapy is a type of device which also utilizes either x-rays, gamma rays, electron beams or protons to treat cancer.
X-ray images are typically used to evaluate:
- Broken bones
- Swallowed objects
- Blood vessels
- Breast (mammography)
- Impact of Mammography Detection on the Course of Breast Cancer in Women Aged 40–49 Years
This study found that mammography screening finds more breast cancers earlier and reduces mortality in women between the ages of 40 and 49.
- Mammography Screening and Risk of Breast Cancer Death: A Population-Based Case–Control Study
Researchers found that women who receive at least three screening mammograms have a 49 percent lower risk of dying from breast cancer.
- The Association of Breast Arterial Calcification and Coronary Heart Disease
This study found that a routine mammogram checking for breast cancer may also predict the future development of heart disease or stroke by determining the presence of breast arterial calcifications, which could allow for earlier detection and intervention.
A biomarker is a traceable substance in the body that indicates a particular disease state, organ function or other aspects of health. Physicians and researchers use biomarkers to help predict, diagnose and treat a variety of disease states and neuropsychiatric disorders.