Soft tissue windows

Chondrosarcomas can be difficult to distinguish from benign cartilage lesions on conventional imaging modalities such as radiographs, CT, MRI and skeletal scintigraphy, as well as on histopathologic analysis. Chondrosarcomas particularly low grade lesions have been reported as having a predilection for low FDG uptake in comparison with other primary bone malignancies [ 17 - 20 ] which could also be confounding.

Factors that may contribute to the lower avidity include a high proportion of acellular gelatinous matrix with respect to cellular density and lower mitotic rates than higher grade tumors. Dedicated analysis of cartilage lesions as a whole has previously demonstrated the FDG avidity of malignancies to be significantly higher than benign lesions [ 18 , 21 ].

Our study showed that the average FDG uptake of chondrosarcomas was as high as Ewing sarcoma though lower than osteosarcoma. Excluding the mesenchymal chondrosarcoma, the mean SUVmax of the chondrosarcomas decreased from 8.

The adjusted value remains higher than the mean SUVmax of the benign cartilage lesions 2. While the SUVmax of the most avid benign cartilage lesion 3. Unlike other reported data [ 14 - 15 , 17 , 22 ] the mean FDG uptake of the benign fibrous lesions in our study did not approach the mean avidity of the malignancies. This may have been due to our small sample size. Chordoma, a relatively indolent malignancy with a strong tendency for local recurrence, demonstrated FDG uptake between the mean of the least avid malignancy Ewing sarcoma and the most avid benign lesion fibrous dysplasia.

Our results suggest that the FDG uptake across all of the tumors in our sample corresponds better with the locally destructive than the metastatic potential of the lesions Fig. Our mean sensitivity corresponds to the published number and our specificity is higher. This may have been due to our study design that mandated an in-depth review of the CT prior to evaluating the PET dataset. This suggests that the fine bony detail that is visible with CT-BW is useful for distinguishing benign from malignant lesions, and that this bony detail may be obscured by FDG uptake.

The margins of primary bone tumors are an important indicator of their biological potential [ 24 - 25 ]. Malignancies are more likely to produce a greater degree of osteolysis than benign lesions [ 24 - 25 ]. Soft tissue windows may over-emphasize tumor margins and spuriously make cortical or trabecular bone appear intact. Bone windows can reveal the osteolysis that is obscured by the soft tissue window setting Fig.

The emphasis that our study placed on CT was considered justified given the inability of priorPET-only investigations to reliably distinguish between malignant and benign bone lesions [ 14 - 15 ]. Radiographs were not evaluated by this study. Radiographs are recommended as the first step in the imaging diagnosis of bone lesions [ 24 , 26 ]. CT with bone windowing is immediately available and can be used as an adjunct to radiography.

It is of concern in this patient with osteosarcoma of the sacrum resected. Note is made of urinary incontinence accounting for the FDG accumulation in the perineal region. B CT-BW shows a cortically based lesion with a complete sclerotic rim and internal mineralization that is compatible with fibrous matrix.

The anatomic appearance of the lesion is indicative of nonossifying fibroma fibroxanthoma. Tumor of the anterior and medial walls of the right maxilla in an year-old woman.

Ill-defined margins are also now identified arrowheads , further supporting the diagnosis of malignancy. Biopsy indicated osteosarcoma. Tumor of the right tibial diaphysis in a year-old girl. Biopsy indicated Ewing sarcoma. Computed tomography in detecting calvarial metastases: a comparison with skull radiography and radionuclide scanning. Digital Imaging.

University of South Carolina. Spiral CT with multiplanar reconstruction in the diagnosis of sternoclavicular osteomyelitis. Skeletal Radiol. MRI and CT findings of the giant cell tumors of the skull; five cases and a review of the literature. Eur J Radiol. Observer variation in bone lesion detection in thoraco-abdominal visceral CT images. Liver and bone window settings for soft-copy interpretation of chest and abdominal CT. Computed tomography in suspected osteoid osteomas of tubular bones.

Bone metastases from breast cancer: value of CT bone windows. Mosby, St. Louis, pp. Euclid Seeram. Computed Tomography. ISBN: 3. Turner PJ, Holdsworth G. CT stroke window settings: an unfortunate misleading misnomer?.

The British journal of radiology. CT mucosal window settings: a novel approach to evaluating early T-stage head and neck carcinoma. American journal of roentgenology. Related articles: Imaging technology. Promoted articles advertising. Loading more images Close Please Note: You can also scroll through stacks with your mouse wheel or the keyboard arrow keys.

Loading Stack - 0 images remaining. By System:. Patient Cases. Contact Us. Here is a a key summary of how changing each setting will alter the image:.

Increasing the window width will DECREASE the contrast of the image: as the width of the window increases a larger change in density will be required to change the shade of grey that represents a a certain HU unit.

This results in a loss of contrast as more structures will appear similar despite having different densities. Decreasing the window width will INCREASE the contrast of the image: as the width of the window decreases, a smaller change in density will result in a change in color on the study images. This is because as the level is increased, higher HU values will be required to in order for a density to be represented as white. This is because as the level is decreased, lower HU values will be required to in order for a density to be represented as white.

Advantages: as the name suggests, this window is used to evaluate soft tissues. The window level is set at the density of soft tissues 50 HU and a moderate sized window is used to give a balance between contrast and resolution. Advantages: as the name suggests, this window is useful for viewing the bones. A high window level near the density of bone given its density the level is HIGH is used with a wide window to give good resolution.

Advantages: as the name suggests this window is used to evaluate the lungs. A high window level near the density of lung tissue given its low density the level is LOW and is used with a wide window to give good resolution and to visualzie a wide variety of densities in the chest such as the lung parenchyma as well as adjacent blood vessels.