Getting a mammogram can stir up a mix of feelings — and questions. It's completely normal to wonder, "Is this really necessary?" or "What if they find something?" Also natural: Practical questions such as "Do I need a screening or a diagnostic mammogram?" and "What's a 3D mammogram?"

"It's not unusual for women to have questions about mammograms, especially if it's their first one," says Dr. Luz Venta, a breast radiologist at Houston Methodist. "There is a lot of terminology and technology that women may want to familiarize themselves with after their doctor mentions they need a mammogram."

Dr. Venta explains what women need to know about the different types of mammograms, as well as another factor that's important to consider.

What is a mammogram?

A mammogram is a specialized X-ray used to help detect breast abnormalities. This type of imaging works by creating detailed images of breast tissue, allowing a radiologist to closely examine breast tissue and look for changes or problems. It's a quick and typically easy test that can play a big role in catching breast cancer early, when it is easiest to treat.

Your technologist will guide you through each step during a mammogram — from positioning to when you should expect to feel compression. Two or three images are taken of each breast, but additional images may be taken if a specific abnormality needs to be evaluated or to better include all the breast tissue. (Related: What to Expect During a Mammogram)

Screening vs. diagnostic mammograms

One of the most common questions about mammograms is the difference between screening and diagnostic types.

"A screening mammogram is a routine check-up, similar to an annual well-woman exam," says Dr. Venta. "It doesn't address a specific clinical question but instead serves as a preventive measure to help catch a breast abnormality early, before symptoms develop. It's performed when a woman is due for her annual imaging."

Screening mammograms are recommended annually starting at age 40 for women with average risk of breast cancer. Those who are at higher risk may need earlier screening and additional types of imaging. Dr. Venta describes screening mammograms as "a key tool in early detection, playing a crucial role in improving breast cancer outcomes and saving lives." (Related: Who Needs a Screening Mammogram Before Age 40?)

On the other hand, a diagnostic mammogram is used when there's a particular concern that needs closer examination. Your doctor will likely order one if you're experiencing noticeable symptoms, such as a breast lump and nipple discharge. A breast radiologist may recommend a diagnostic mammogram if something unusual or concerning is spotted on a screening mammogram. During a diagnostic mammogram, additional views of the breast are taken as the radiologist reads the mammogram in real-time.

"A diagnostic mammogram is targeted to a specific clinical question," says Dr. Venta. "It examines a specific area more closely, and may also be accompanied by a breast ultrasound to determine whether further steps, like a breast biopsy or a breast MRI, are necessary."

Dr. Venta highlights three potential outcomes of a diagnostic mammogram. "We may find something totally benign or normal; or we may see an irregularity that needs to be evaluated with a biopsy; or we may find something that's likely benign but should be re-evaluated after a few months."

The same machines are used for both screening and diagnostic mammograms. However, diagnostic mammography takes longer to perform than screening mammography and the total dose of radiation may be higher because more X-ray images are needed to obtain views of the breast from several angles.

3D vs. 2D mammograms

Another common question is whether it matters if you get a 3D or 2D mammogram. The answer is yes — you definitely want 3D.

A 3D mammogram — also known as digital breast imaging, digital mammography or breast tomosynthesis — differs from a traditional 2D mammogram by providing a more detailed view of breast tissue. During a 2D mammogram, the breast is imaged from two angles, which can sometimes result in overlapping tissue obscuring small lumps or abnormalities. A 3D mammogram, however, captures multiple digital images from various angles, creating a series of thin "slices" that allow radiologists to examine breast tissue layer by layer.

"3D mammography is a highly efficient and accurate digital technology that provides the clearest picture of your breasts and helps identify very small tumors," explains Dr. Venta. "This helps reduce the chance of being called back for follow-up imaging and improves the chance of catching breast cancer specially in women with dense breast tissue."

As you research your options, make sure you're looking at facilities that use 3D mammograms. Most do offer 3D mammograms these days, but it's important to do your homework and be sure.

It's not just type — where you get your mammogram also matters

The type of mammogram you need isn't the only thing to consider when scheduling your appointment. The facility you choose matters, too.

Questions to consider when choosing where to get a mammogram include:

• Does the facility specialize in breast imaging?
• Are the radiologists fellowship-trained in breast radiology?
• In addition to screening mammograms, are diagnostic mammograms, breast ultrasound and breast biopsy also offered?
• Does the facility use the latest, most up-to-date equipment?
• Is the facility part of a larger health care system that offers other women's health services, including breast cancer treatment?

(Related: 5 Things to Consider When Choosing Where to Get Your Annual Mammogram)

Once you find a breast imaging facility you like and trust, stick with it.

"One of the most important parts of mammography is going to the same place for all of your breast imaging, so your radiologist has the advantage of being able to view your prior images," says Dr. Venta. "Everyone's breast tissue is unique, and having prior images helps make even the slightest changes in breast tissue easier to notice."