Health Information Disclaimer: The information on this page is intended for educational purposes. It is not a substitute for medical advice. This information should be used to educate patients on the basic knowledge of radiation in diagnostic testing. If you have concerns about radiological testing you should always ask questions.

The radiation figures below are based on average doses. A patient's height, weight, age and other factors affect the necessary dose needed to aquire the images to make a confident diagnosis.

What is radiation?

Radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes electro-magnetic radiation such as radio waves, visible light and x-rays. Radiation may also refer to the energy, waves, or particles. Radiation is often categorized as either ionizing radiation or non-ionizing radiation depending on the energy of the radiated particles. In ionizing radiation this energy is more than 10 eV, enough to ionize atoms and molecules, and break chemical bonds. This is an important distinction due to the large difference in harmfulness to living organisms. Ionizing radiation can break important biomolecules such as DNA, damaging or killing the affected cell.

If you live in the US, you receive about 3.6 milliSieverts (360 millirem) of radiation each year. This is called “background radiation." MilliSievert (mSv) and millirem (mrem) are both units used to measure the effect of radiation on the body. 1 millirem = .01 milliSieverts.

Risk vs Benefit

Though there are some known risks from radiation exposure, statistically the benefits of early diagnosis using these tools can far outweigh the risks involved.

Early diagnosis = Early Treatment = Better Outcomes

The most important part is education. Educate yourself, read, ask questions, and speak to your physician or healthcare professional. We at Zwanger-Pesiri are always available to help.


You have many options for medical imaging. Learn more about our services below, and find out how much radiation, if any, they expose patients to.

The radiation figures below are based on average doses. A patient's height, weight, age and other factors affect the necessary dose needed to aquire the images to make a confident diagnosis.


MRI stands for Magnetic Resonance Imaging, a scan that uses magnetic and radio waves to produce detailed morphologic information of the organs, tissues and structures within the body. PET stands for Positron Emission Tomography an imaging test that helps to measure the functionality of tissues and organs within the body.

MRI/PET is a hybrid scanner that combines the two modalities into a single scan. Capturing metabolic activity and anatomy together offers doctors a more precise and accurate assessment of disease, as well as an improved understanding of the physiologic process. This allows for easier and faster detection, characterization, staging and treatment of oncologic, neurologic and cardiovascular diseases that expose patients to lower levels of radiation.

Modality Type Effective Radiation Dose Absorption Equivalent to: (chest X-ray)
1 chest X-ray=.1mSv
MRI 0 mSv 0 chest X-rays
MRI/PET 5 mSv 50 chest X-rays


Additional information & links:

MRI/PET is indicated for:
  • Oncology to improve the detection of primary cancers and metastases.
  • Neurology to improve the detection of brain tumors that can be underestimated on PET/CT. It can also be utilized to detect and monitor neurodegenerative diseases such as Alzheimer’s.
  • Pediatrics to minimize radiation dose exposure when indicated.

Read more about MRI/PET.

CT (Computed Tomography)

Computed Tomography (CT) is a technology that uses computer-processed X-rays to produce tomographic images (virtual 'slices') of specific areas of a scanned object, allowing the user to see inside the object without cutting. Digital geometry processing is used to generate a three-dimensional image of the inside of the object from a large series of two-dimensional radiographic images taken around a single axis of rotation.[1] Medical imaging is the most common application of CT. Its cross-sectional images are used for diagnostic and therapeutic purposes in various medical disciplines. CT scans use x-rays to create images.

Modality Type Effective Radiation Dose Absorption Equivalent to: (chest X-ray)
1 chest X-ray=.1mSv
Chest CT 7 mSv 70 chest X-rays
Abdomen & pelvic CT 10 mSv 100 chest X-rays
Coronary CT angiography (CCTA) 12 mSv 120 chest X-rays
Cardiac CT 3 mSv 30 chest X-rays


Additional information & links:

More than 8 CT scans can increase risk of developing second cancer.

  • Considering the high survival rates of patients treated for Hodgkin’s Lymphoma and Non-Hodgkin’s Lymphoma and the toxicity of radiation CT utilization needs to be evaluated.
  • Studies have shown that patients receiving 8 or more CTs have a 2-fold increase in secondary malignancies.
  • Surveillance imaging in early stage lymphomas should balance early detection of progression and relapse versus the risk of secondary malignancies, especially in young and curable patients.

At Zwanger Pesiri we are dedicated to providing Long Island with the latest CT technology for the most reliable diagnosis and the least amount of radiation. Our CT scanners have:

  • Unprecidented resolution and speed.
  • All CT exams are tailored to minimize any radiation to the patient. We follow the ALARA princinple (As Low as Reasonably Achievable).
  • Radiation Dose information is included in all radiology reports.



Read more about CT.

DXA Bone Densitometry

Dual-energy X-ray absorptiometry (DXA, previously DEXA) is a means of measuring bone mineral density (BMD). Two X-ray beams with different energy levels are aimed at the patient's bones. When soft tissue absorption is subtracted out, the BMD can be determined from the absorption of each beam by bone. Dual-energy X-ray absorptiometry is the most widely used and most thoroughly studied bone density measurement technology.

Modality Type Effective Radiation Dose Absorption Equivalent to: (chest X-ray)
1 chest X-ray=.1mSv
DXA .001 mSv Less than 1 chest X-ray


DXA Bone Densitometry is utilized to measure the density of the bones and assists in diagnosing osteoporosis.

Additional information & links:


  • Pencil Beam Technology (Provided at Zwanger-Pesiri) provides a lower dose of radiation.
  • The effective dose we receive from natural background radiation during one day is about 10 μSv. For a typical DXA examination, using technology that has become available over the last decade, the patient dose will be comparable to or (especially in the case of pencil beam scanners) less than this daily background dose.

Read more about DXA bone density.


Fluoroscopy is a type of medical imaging that shows a continuous X-ray image on a monitor, much like an X-ray movie. During a fluoroscopy procedure, an X-ray beam is passed through the body. The image is transmitted to a monitor so the movement of a body part or of an instrument or contrast agent (“X-ray dye”) through the body can be seen in detail. Fluoroscopy is especially useful for guiding a variety of diagnostic and interventional procedures.

Modality Type Effective Radiation Dose Absorption Equivalent to: (chest X-ray)
1 chest X-ray=.1mSv
Upper GI series 6 mSv 60 chest X-rays
Hysterosalpingogram 2 mSv 20 chest X-rays


Additional information & links:


  • By understanding the factors that affect patient doses, clinicians can help keep doses as low as possible without compromising image quality or the efficacy of interventional procedures. Direct monitoring of patient skin doses during procedures is highly desirable, but current methods still have serious limitations. Effective management of radiation exposures by proper use of equipment, adequate training of fluoroscopic operators, and frequent quality control can contribute to an overall reduction in patient and personnel exposures.

Read more about fluoroscopy.

Digital Mammography (2D & 3D)

Zwanger Pesiri has state-of-the-art 3D mammography, or breast tomosynthesis, is provided at 15 locations. 3D mammography has additional radiation but has proven to be superior to mammography alone with a higher cancer detection rate.

Digital mammography can detect breast cancer up to two years before an abnormality can be felt.

Modality Type Effective Radiation Dose Absorption Equivalent to: (chest X-ray)
1 chest X-ray=.1mSv
2D conventional mammogram 0.4 mSv 4 chest X-rays
3D mammogram 1 mSv 10 chest X-rays


Additional information & links:


  • Benefit outweighs the risk

Read more about mammography.


MRI (magnetic resonance imaging) is a medical imaging technique used in radiology to investigate the anatomy and physiology of the body in both health and disease. MRI scanners use strong magnetic fields and radio waves to form images of the body. The technique is widely used in hospitals for medical diagnosis, staging of disease and for follow-up without exposure to ionizing radiation.

For some types of exams MRI can replace CT.

Zwanger Pesiri Radiology is the leader in MRI on Long Island with 26 units. Our 3.0 and 1.5 Tesla MRI systems provide a level of detail and clarity never before possible. All of our MRI systems are designed to maximize patient comfort and claustrophobia.

MRI allows us to detect and diagnostic ailments in the body without the use of radiation. Instead, MRI uses magnetism and radio waves to produce remarkably clear images of tissues through the body. MRI is particularly useful for study the brain and spine, as well as muscles, ligaments, joints and tendons. MRI may also be performed to evaluate internal organs such as the heart, liver, kidneys, prostate and breasts.

Modality Type Effective Radiation Dose Absorption Equivalent to: (chest X-ray)
1 chest X-ray=.1mSv
MRI 0 mSv 0
Additional information & links:


Read more about MRI.

Nuclear Medicine

Nuclear medicine is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear medicine scans are usually conducted by Radiographers. Nuclear medicine, in a sense, is "radiology done inside out" or "endoradiology" because it records radiation emitting from within the body rather than radiation that is generated by external sources like X-rays. In nuclear medicine imaging, radiopharmaceuticals are taken internally, for example, intravenously or orally. Then, external detectors (gamma cameras) capture and form images from the radiation emitted by the radiopharmaceuticals. This process is unlike a diagnostic X-ray, where external radiation is passed through the body to form an image.

Nuclear Medicine imaging is unique because it provides doctors with information about the structure and function of virtually every major organ. Very small amount of radioactive materials (radiopharmaceuticals) are used to diagnose and treat disease. Nuclear Medicine is commonly used to evaluate the thyroid, brain, bones, lungs, heart, liver, and gallbladder.

Modality Type Effective Radiation Dose Absorption Equivalent to: (chest X-ray)
1 chest X-ray=.1mSv
Nuclear bone scan 6.3 mSv 63 chest X-rays
Gastric emptying 0.4 mSv 4 chest X-rays
Nuclear renal scan 2.6 mSv 26 chest X-rays


Additional information & links:

The benefits of nuclear medicine include:
  • Determines the presence of spread of cancer
  • Evaluates bones for fracture, infection, arthritis and tumors
  • Analyzes kidney function
  • Measures thyroid function
  • Visualizes blood flow and heart function
  • Identifies blockages in the gallbladder
  • Locates the presence of infection


Read more about Nuclear Medicine.


Positron emission tomography/computed tomography (better known as PET-CT or PET/CT) is a medical imaging technique using a device which combines in a single gantry system both a positron emission tomography (PET) scanner and an x-ray computed tomography (CT) scanner, so that images acquired from both devices can be taken sequentially, in the same session, and combined into a single superposed (co-registered) image. Thus, functional imaging obtained by PET, which depicts the spatial distribution of metabolic or biochemical activity in the body can be more precisely aligned or correlated with anatomic imaging obtained by CT scanning. Two- and three-dimensional image reconstruction may be rendered as a function of a common software and control system.

PET/CT has revolutionized medical diagnosis in many fields, by adding precision of anatomic localization to functional imaging, which was previously lacking from pure PET imaging. For example, many diagnostic imaging procedures in oncology, surgical planning, radiation therapy and cancer staging have been changing rapidly under the influence of PET/CT availability, and centers have been gradually abandoning conventional PET devices and substituting them by PET/CTs. Although the combined/hybrid device is considerably more expensive, it has the advantage of providing both functions as stand-alone examinations, being, in fact, two devices in one.

Modality Type Effective Radiation Dose Absorption Equivalent to: (chest X-ray)
1 chest X-ray=.1mSv
PET/CT 25 mSv 250 chest X-rays


Additional information & links:

The benefits of PET/CT include:
  • Early diagnosis of disease with accurate staging and restaging
  • Determines the location of disease for treatment planning, a biopsy procedure or surgery
  • Assesses effectiveness of treatments
  • Differentiates between malignant and benign tumors
  • Detects residual of recurrent disease


Read more about PET/CT.


Medical sonography (ultrasonography) is an ultrasound-based diagnostic medical imaging technique used to visualize muscles, tendons, and many internal organs, to capture their size, structure and any pathological lesions with real time tomographic images. Ultrasound has been used by radiologists and sonographers to image the human body for at least 50 years and has become a widely used diagnostic tool. The technology is relatively inexpensive and portable, especially when compared with other techniques, such as magnetic resonance imaging (MRI) and computed tomography (CT). As currently applied in the medical field, properly performed ultrasound poses no known risks to the patient. Sonography does not use ionizing radiation, and the power levels used for imaging are too low to cause adverse heating or pressure effects in tissue. Although the long-term effects due to ultrasound exposure at diagnostic intensity are still unknown, currently most doctors feel that the benefits to patients outweigh the risks. The ALARA (As Low As Reasonably Achievable) principle has been advocated for an ultrasound examination – that is, keeping the scanning time and power settings as low as possible but consistent with diagnostic imaging – and that by that principle non-medical uses, which by definition are not necessary, are actively discouraged.

Ultrasound is safe and painless, and high-frequency sound waves to produce pictures of inside the body. Because ultrasound images are captured in real-time, they show the structure and movement of the body’s internal organs, as well as blood flowing through the blood vessels.

Modality Type Effective Radiation Dose Absorption Equivalent to: (chest X-ray)
1 chest X-ray=.1mSv
MRI 0 mSv 0
Additional information & links:


Read more about ultrasound.