Biomedical Engineering Reference
In-Depth Information
have demonstrated a very high effi cacy of ferumoxtran-10-enhanced MRI in the
detection of lymph node metastases for a variety of tumors [202, 210]. For example,
Nishimura
et al.
reported an accurate detection of metastases to lymph nodes in
patients with esophageal cancer by using MRI with ferumoxtran-10. In this study,
the authors achieved an astonishing 100% sensitivity, 95.4% specifi city, and 96.2%
accuracy for lymph node metastases at 24 h after intravenous administration of the
agent [211]. The same USPIO contrast agent was also used to detect pelvic lymph
nodes in patients with primary urologic and pelvic cancers [212, 213], as well as in
nodal staging in patients with breast [214], urinary bladder [202], and rectal cancer
[215]. In addition, ferumoxtran-10 showed excellent sensitivity for measuring the
magnetic tissue parameters of cancer metastases and normal unmatched lymph
nodes in various types of cancer, using the LMRI technique. The use of ferumox-
tran-10 permitted metastatic nodes to be distinguished from normal nodes, with
an overall sensitivity of 98% and specifi city of 92%. Most importantly, these param-
eters could be applied to datasets in a semi-automated fashion, allowing a three-
dimensional reconstruction of complete nodal anatomy for different primary
cancers. An example of breast cancer mapping is shown in Figure 4.7 [216] .
4.5.1.4
Bone Marrow Imaging
The main role of the bone marrow is to provide erythrocytes, leukocytes and
platelets in order to maintain the oxygenation, immune function and auto-
restoration of the body. MRI is a very sensitive technique for the detection of
marrow lesions [8], especially when monitoring bone marrow pathologies in
patients following radiotherapy and chemotherapy [217].
The concept of bone marrow MRI using nanoparticle-based T
2
contrast agents
is similar to that used when imaging the liver. USPIO contrast agents are taken
up extensively by macrophages in normal bone marrow (via the process of phago-
cytosis), where they induce a T
2
-shortening effect, but not by neoplastic marrow
infi ltrates, which do not contain macrophages. This allows a distinction to be made
between hypercellular normal and neoplastic marrow [217 - 219] .
Ferumoxtran-10 (Sinerem/Combidex) is the main USPIO to be used for bone
morrow imaging [220-222]. The intravenous injection of this contrast agent in
patients with cancer of the hematopoietic system (non- Hodgkin lymphoma)
allowed an increase in the bone marrow-to-tumor contrast and the consequent
differentiation between normal, hypercellular, and neoplastic bone marrow from
T
1
- and T
2
-weighted MR images taken before and after ferumoxtran administration
[218, 220, 221]. In another study, Metz
et al.
used ferumoxtran-10 for bone marrow
imaging in patients with malignant non-Hodgkin lymphoma before and after
conditioning therapy to quantify permeability changes of the blood-bone marrow
barrier (BMB), and also to detect malignant bone marrow infi ltrations. The iden-
tifi cation of focal bone marrow lesions (
1 cm) in patients with lymphoproliferative
disorders after the administration of USPIOs was signifi cantly higher than in
non- enhanced scans [222] .
Other USPIO-based MRI contrast agents (Table 4.1) currently in different stages
of preclinical and clinical trials include ferumoxides (Endorem® ) [218] , SHU555C/
<
