Dual Energy CT

Since November 2014, our Radiologie München practice at the Rotkreuzklinikum (hospital) has a dual energy CT scanner which will be updated with the newest technology and imaging capacity of two simultaneous CT data sets in 2017. The examination with different x-ray energies allows for a much more precise tissue differentiation than before, while the dose does not exceed that of a conventional CT exam. This imaging procedure only takes a few seconds.

Two colleagues of our Radiologie München team, Prof. Johnson and PD Dr. Graser, contributed substantially to the development of this technology, are internationally known specialists in this area, and have published a number of scientific papers and several textbooks on the subject.

This technology is of interest for:


detection and differentiation of kidney stones

The dual energy CT facilitates a non-invasive and reliable detection and typing of kidney stones in mere seconds, even in blocked efferent urinary tracts. In case of uric acid stones, a drug treatment, and, for other types of stones mechanical removal may be indicated. Besides calcium and uric acid, cystine and struvite stones can generally be differentiated so that corresponding medication, diet or antibiotic treatment can be indicated. The images show a calcium oxalate stone (blue) in the left ureter and an uric acid stone (red) in the right ureter.

Nachweis und Differenzierung von Nierensteinen (Bild 1)

Nachweis und Differenzierung von Nierensteinen (Bild 2)

Detection of Gout tophi

A dual energy CT can specifically detect gout tophi even in atypical locations and distinguish them from other erosions or osteolyses. It also provides an exact quantification and progress controls of the uric acid depot, which, compared to the serum level exam, allows for a much more targeted therapy management, e. g., with uricase. The image shows expansive gout tophi on the right knee.

Nachweis von Gicht-Tophi

Detection of silicone

This technology facilitates a specific detection of silicone in the tissue and lymph nodes. Thus, even for non MRI capable patients (e. g., with cochlea implant or pace maker), a comprehensive assessment of breast implants and, in case of ruptures, imaging of the draining lymph nodes is possible. The image shows a ruptured implant whose silicone is evacuated by the lymph nodes.

Nachweis von Silikon

Metal artifact reduction

In a dual energy CT scan metal artifacts can be significantly reduced; titanium can generally be fully removed as well as steel, depending on the alloy, up to a thickness of 1 cm, which allows for a much better assessment of osteosyntheses and the spinal canal. Even a loosening of pedicle screws or prosthetic sockets or cups can be much more accurately assessed with the artifact-free imaging of the metal-bone interface. The upper image shows the standard reconstruction and the lower image the result of the metal artifact reduction. The spinal canal becomes assessable and the loosening fringes of the pedicle screws are visible.

Metallartefakt-Reduktion (Bild 1)

Metallartefakt-Reduktion (Bild 2)

bone marrow edema

For a trauma diagnosis, only a CT scan can provide a precise and specific detection of the fracture line, while an MRI with its detection facility of a bone marrow edema is very sensitive, e. g., for osteoporodic vertebral fractures or fissures and fatigue fractures in extremities. The dual energy technology even provides a bone marrow edema detection in a CT scan, and thus combines high specificity with increased sensitivity. The image shows a bone marrow edema in the lateral femoral condyle.


pulmonary cirCulation Imaging

Besides the ventilation, the blood supply of the lungs is one of the most important function parameters. With the spectral information provided by the dual energy CT it is possible to visualize the contrast medium in the lung tissue and thus obtain circulatory information. Especially for smaller pulmonary embolisms (see image), repeated embolisms, unclear pulmonary hypertension, and lung tissue diseases this information is of great diagnostic significance as well as for treatment planning.

Even the pulmonary ventilation can be depicted in a dual energy CT scan (see image). For this purpose, however, xenon gas must be used as contrast medium, which is complex and expensive and the reason why this application is limited to very few cases, primarily in scientific studies.

The imaging of the pulmonary circulation on the other hand is provided in routine scans as additional information without any added strain on the patient.

Darstellung der Lungendurchblutung (Bild 1)

Darstellung der Lungendurchblutung (Bild 2)

CT angiography without bone overlap

Computer tomography can capture arteries both in the head and neck area as well as in the trunk and legs with high spatial resolution. Until recently, there has been a problem of calcifications and bones overlapping the depiction of the blood vessels and at times obstructing the measurement of constrictions. With the dual energy technology, calcifications and bones can be removed from the image data, thus facilitating an overlap-free depiction of the blood vessels as well as an exact graduation of constrictions. The images show cerebral arteries in white, cerebral veins in blue and the pelvic and leg arteries with atherosclerosis and multiple occlusions, but without bone overlap.

CT-Angiographie ohne Knochen-Überlagerung (Bild 1)

CT-Angiographie ohne Knochen-Überlagerung (Bild 2)

Differentiation of liver and kidney lesions

For liver and kidney lesions, contrast medium imaging often plays an important role to determine benign or malignant findings. In computer tomography, however, only one contrast phase is generally taken in order to minimize the x-ray dose. It is sometimes difficult to identify if a lesion contains contrast medium, which, for example, in the kidneys makes a distinction between bleeding cysts and kidney cell carcinomas impossible. A dual energy CT can detect the contrast medium and depict in color so that a distinct diagnosis can generally be established for the above case, and that without additional contrast medium or radiation dose. The image shows only bleeding cysts.

Differenzierung von Leber- und Nierenläsionen