Qct Bone Density Measurement

What Is QCT (Quantitative Computed Tomography) Bone Density Measurement? In What Cases Is It Used?

Advancing age can negatively affect bone health. Osteoporosis, especially, increases the risk of fractures. For people with severe low back and joint pain or fractures even after minor trauma, obtaining detailed information about bone structure is important for treatment.

QCT (Quantitative Computed Tomography) bone density measurement makes it possible to analyze the internal structure of bone in three dimensions (3D). These detailed bone findings help determine the treatment plan.

Questions such as what QCT is, what the difference between QCT and DEXA is, and whether I will be exposed to radiation during a QCT scan are among the most common concerns. In this article, you can find answers to all your questions about QCT.

At Daviva Health Group’s Radiology Department, we aim to help safeguard your bone health through QCT measurements performed under the supervision of expert radiologists.

What Is QCT Bone Density Measurement?

QCT (Quantitative Computed Tomography) is an imaging method used to measure bone mineral density. QCT performed using Computed Tomography (CT) can provide 3D results, clearly distinguishing the trabecular bone structure from the dense bone structure. It is usually performed on the hip and lumbar spine.

In What Conditions and Diseases Is QCT Used?

• Osteoporosis Management

In the diagnosis of osteoporosis, commonly known as bone loss, QCT is one of the most sensitive methods for measuring the bone's true strength thanks to its 3D imaging capability. By showing the internal structure of the bone, it enables diagnosis at a much earlier stage.

• Steroid-Induced Bone Loss

Steroid use is among the most important causes that trigger bone loss. Steroids cause loss not in the bone's dense outer cortex, but in the spongy structure inside. For this reason, QCT's 3D approach provides an advantage for early diagnosis and monitoring.

• Hyperparathyroidism

This is a condition in which excessive secretion of parathyroid hormone by the parathyroid glands causes calcium levels in the blood to rise above normal. In hyperparathyroidism, bone breakdown accelerates. The spongy structure of the bones is especially affected by this breakdown.

QCT provides much more detailed information than DEXA in evaluating the soft tissue of bones. Thanks to its 3D measurement capability, it allows early detection of occult fracture risks.

• Spinal Abnormalities

QCT (Quantitative Computed Tomography) provides volumetric measurements. It can separately analyze the inner and outer parts of the bone.

It accurately measures bone strength to predict spinal fractures.

It evaluates degenerative spinal diseases such as disc space narrowing and bone spurs.

QCT can also be used to evaluate bone mineral density before spinal surgery.

How Is QCT Measurement Performed?

• If you are using calcium supplements, stop taking them one day before the QCT measurement. Calcium supplements may cause QCT values to be inaccurate.
• When coming for the examination, choose comfortable clothing. If possible, do not wear clothes with zippers or metal accessories.
• You do not need to come fasting for a QCT measurement. You can continue your daily activities as usual before the scan.
• QCT evaluation is performed on a Computed Tomography (CT) device. During the scan, you will lie on the CT table.
• Since measurements are usually taken from the spine and hip, the CT device will focus on these areas.
• You will be asked to remain still during the scan. In some cases, you may be asked to hold your breath so the measurements can be taken more clearly.
• You will not feel any pain or discomfort during QCT scans.
• The obtained three-dimensional images are analyzed using special software, and the volumetric density of the bone is calculated.

What Are the Differences Between QCT and DEXA? In Which Situation Is Which Test More Appropriate?

• DEXA evaluates by taking two-dimensional images. QCT, on the other hand, provides 3D analysis.
• DEXA gives an average of both the outer cortex and the spongy structure of the bone without separating them from each other. QCT can separately analyze the inner and outer parts of the bone.
• Obesity can be a misleading factor in DEXA measurements. QCT can also successfully measure in overweight patients.
• Both methods involve radiation exposure in practice. DEXA examinations are performed at much lower radiation doses than QCT measurements.

Both methods are used to evaluate bone health. The choice of method should be determined according to the person's needs and the condition they are experiencing.

DEXA is more commonly preferred in the following situations.

• DEXA, or Bone Densitometry, is the gold standard in general screening.
• Because radiation exposure is lower, DEXA is preferred for routine follow-up examinations.

QCT is more commonly preferred in the following situations.

• Since long-term steroid use can cause damage to the inner structure of bones, QCT provides more reliable results.
• QCT is preferred in such situations, especially because it can distinguish spinal degenerative changes.
• QCT comes to the forefront because it can detect the destructive effects of hyperparathyroidism on the bones at an early stage.

QCT Advantages

• By measuring true density, QCT allows a sensitive assessment of bone quality independent of bone size.
• It can especially isolate and measure the inner part of the bone. This enables earlier detection of bone loss.
• QCT can provide accurate results without being affected by degenerative conditions in the bones.
• It provides a detailed 3D anatomical image of the spine and hip, offering fracture risk assessment.

Frequently Asked Questions About QCT (Quantitative Computed Tomography)

What Do T-Score, Z-Score, and vBMD in the QCT Report Mean?

T-score; compares your bone mineral density with that of a healthy young adult of the same sex.

• A T-score of -1 indicates normal bone density
• A T-score between -1 and -2.5 indicates the beginning of bone loss, i.e. osteopenia
• A T-score of -2.5 and below means a diagnosis of osteoporosis.

Z-score; compares your bone mineral density with the average of people of the same age and sex.

• If the Z-score is below -2.0, it means bone density is low for your age.
• If the Z-score is above -2.0, it means your bone density is normal for your age.

vBMD: the value that reveals bone strength by measuring the actual mineral content in the bone.

• If the vBMD value is above 120, it indicates normality.
• A vBMD value between 80 and 120 means that bone density is reduced.
• If the vBMD value is below 80, it means bone density is low.

It should also be remembered that these values must be evaluated together.

How Long Does a QCT (Quantitative Computed Tomography) Scan Take?

A QCT (Quantitative Computed Tomography) scan for bone density is a quick and noninvasive procedure. The QCT scan usually takes 10–15 minutes.

Is a QCT Measurement a Painful Procedure?

During the QCT scan, the patient does not feel any pain or discomfort. The only thing that may inconvenience the patient is the need to remain still throughout the scan.

Can Pregnant Women or Those Suspecting Pregnancy Undergo QCT?

QCT measurement is performed using X-rays. This causes some radiation exposure, even if only a small amount. For this reason, QCT is not recommended for pregnant women or women who may be pregnant unless it is absolutely necessary.