Information Technology Reference
In-Depth Information
the occurrence is in the approximate range 15
30 % [
2
]. Morbidity associated with
solid tumor metastasis to the skeleton is frequent and often debilitating, with sec-
ondary skeletal complications (skeletal related events or SRE
-
s) occurring in
approximately 50 % of patients [
1
]. Overall, the spine is the most frequent location
for skeletal metastases [
3
]. Vertebral metastases may be associated with SREs
including pain, pathologic compression fractures, spinal cord compression, and
hematopoietic abnormalities [
2
'
5
]. Prior studies have demonstrated diminished
functional independence associated with SREs and reduced patient survival after
pathological fractures [
6
-
8
]. Patient outcomes are improved with early detection and
treatment of vertebral metastases before the onset of signi
-
11
].
Traditionally categorized as sclerotic or lytic, a metastatic bone lesion is now
thought to exist as a continuum, and may in fact interconvert as part of its natural
history [
12
,
13
]. Patients may have lytic, sclerotic or mixed density metastatic
lesions. The majority of patients with breast cancer have predominantly lytic
lesions, although a subset of breast cancer patients of at least 15
cant morbidities [
9
-
20 % have
predominantly sclerotic lesions. In contrast, the lesions in prostate cancer are pre-
dominantly sclerotic. Both lytic and sclerotic metastatic disease can act to biome-
chanically weaken bone and lead to pathologic fractures. Whereas lytic metastases
frankly destroy the osseous matrix to weaken bone, in the case of sclerotic
metastases, this weakening occurs via bone replacement with irregularly mineral-
ized and disorganized matrix produced as woven bone [
4
,
14
-
16
]. Fractures in
pathologically weakened bone occur most commonly in the spine in the proto-
typical example of sclerotic metastases due to prostate cancer [
4
].
Metastases to the spine can involve the bone, epidural space, leptomeninges, and
spinal cord. Various imaging modalities have been employed to diagnose different
aspects of bone metastases. Radiographs are a ubiquitous modality in most hos-
pitals and routinely used for screening in the evaluation of back or neck pain.
However, up to 40 % of bone lesions will not be identi
-
film X-ray
studies, thus presenting many false-negative results [
17
]. Bone scintigraphy, a
physiologic imaging method, has also found use as a screening modality for skeletal
metastases, but this technique suffers from obscuration of lesions by overprojecting
structures, and is sensitive to the level of vascularization, and also has known false
negative issues. Single-photon-emission computed tomography (SPECT), a cross-
sectional imaging method, improves on the sensitivity of bone scintigraphy, but
regions of radionuclide uptake are often nonspeci
ed by plain
c and result
in many false
positives. [
18
F]
fluoro-2-deoxy-d-glucose positron emission tomography (FDG-
PET) can detect increased glucose metabolism of neoplastic cells in the bone
marrow, making it a sensitive method for assessment of cortical and medullary
metastases, but it suffers from relative low spatial resolution. Computed tomogra-
phy (CT) scans typically have excellent spatial resolution with superb osseous
delineation, and enable the direct detection of cortical destruction [
17
]. PET/CT
hybrid scanners, where both PET and CT are acquired in the same session so that
the two modalities are inherently registered and multi-spectrum features can be
fl
