Imaging tests are useful tools to qualitatively and quantitatively assess the progression of Gaucher disease. Results of imaging tests can compliment routine diagnosis and help evaluate the extent of damage in the organs and systems, including the liver, spleen, and skeletal system, that are usually affected in people with Gaucher disease.
Common imaging tests for Gaucher disease include magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry (DXA). Other imaging techniques such as plain radiography (X-rays), computed tomography (CT), and radionuclide imaging also can be used.
Plain radiography (X-rays)
An X-ray is the most common and cheapest imaging tool for studying bone structure. However, the sensitivity of X-rays is not very high, and the technique cannot be used alone to diagnose Gaucher or to study improvements in skeletal structures following treatment. However, X-rays are still useful in detecting fractures or Erlenmeyer flask deformity (a deformity of the thigh bone that resembles a laboratory flask), or for monitoring the effectiveness of joint replacement therapy (arthroplasty) in Gaucher patients.
Magnetic resonance imaging (MRI)
MRIs use large magnets and radio waves to image different organs and tissues. An MRI scan can reveal a lot of information that cannot be seen using conventional X-rays.
Volumetric MRI is the preferred imaging technique for visualizing the extent of liver and spleen enlargement (hepatosplenomegaly). It also helps to understand how much the bone marrow has been infiltrated by Gaucher cells (cells with glycolipid accumulation).
While MRI is an effective tool to study the bone marrow in Gaucher disease, the clinician or radiologist should account for bone marrow color change from red to yellow that naturally occurs as a person ages. This color change can sometimes be mistaken for Gaucher cells, especially in children, leading to an incorrect diagnosis.
Dual-energy X-ray absorptiometry (DXA)
Dual-energy X-ray absorptiometry (DXA) is a quantitative imaging test that can help evaluate bone mineral density in patients with Gaucher disease. Bone densities are usually compared with that of healthy people of the same age, sex, and ethnicity to derive a T-score. A T-score between -1.0 and -2.5 indicates moderate loss of bone density (osteopenia) that also correlates with other Gaucher symptoms such as hepatosplenomegaly.
DXA can also be used to monitor improvements in bone mineral density as a result of enzyme replacement therapy or substrate reduction therapy, which are standard treatments for Gaucher disease. However, the effects of these therapies on bone density can take years to be perceivable by DXA.
Recent studies have shown that combining DXA techniques with the trabecular bone score (TBS) can help in better identifying the risk of bone fractures in Gaucher disease patients. Like MRI, DXA also is prone to false results depending on the condition of the bone being examined.
Computed tomography (CT)
Computed tomography (CT) provides both quantitative and qualitative measurement of bone structures. CT can measure bone density along the entire volume of the bone, which can provide a much better idea of bone density loss compared to DXA. CT can also help in improved assessment of the bone marrow to investigate for the presence of Gaucher cells.
A CT is only prescribed when X-ray and MRI results are inconclusive or if the patient cannot have an MRI. However, it is still valuable in measuring spleen and liver volume changes.
Radionuclides are unstable elements that emit radiation. These radionuclides can be incorporated into substances to form radiotracers that can accumulate in specific organs. The emitted radiation can then be recorded on film. For imaging bones in Gaucher disease patients, the radiotracer consists of diphosphonate, a substance that is useful in bone repair. Radionuclide imaging can help in assessing the amount of bone that is removed and formed every year (bone turnover) in Gaucher disease patients. This imaging test is very sensitive but is of a lower resolution compared with MRI.
Scintigraphy is a form of radionuclide imaging that uses a stationary camera, unlike a moving detector in the case of a radionuclide scan. In Gaucher patients, scintigraphy can help in the assessment of liver and spleen enlargement as well as bone defects. Sestamibi is a scintigraphy tracer that accumulates in the fatty bone marrow and is useful to study the infiltration of Gaucher cells.
A clinical trial (NCT00302146) evaluated the efficacy of positron emission tomography (PET) imaging in studying the association of Gaucher disease-causing mutations and Parkinson’s disease. The study has been completed, but no results have been published yet.
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