Performance of direct thrombus imaging by MRI in the diagnosis of acute recurrent deep-vein thrombosis

The clinical diagnosis of recurrent deep vein thrombosis (DVT) alone is
inaccurate. Although several diagnostic algorithms for suspected first DVT
have been validated, the diagnosis of recurrent DVT poses a significant
clinical dilemma. Venous compression echography( CUS) is the most widely used
non-invasive test for the investigation of a suspected first DVT. However, the
diagnosis of recurrent DVT by means of CUS is problematic because persistent
abnormalities are present in approximately 80% of patients 3 months and 50% of
patients 1 year after proximal DVT. Therefore, when a patient with suspected
recurrence has a non-compressible venous segment, it can be difficult to
determine wether this represents new disease or a residual abnormality from a
previous DVT. Measurement of thrombus diameter by CUS has been shown to
diagnose recurrent DVT, however inter-observer agreement is poor. CUS is
therefore only accurate when recurrent DVT occurs in another venous segment
than at the time of the first DVT.
Direct thrombus imaging by magnetic resonance technique (MRDTI) has been shown
a highly accurate diagnostic method for first DVT. The method is based on
measurement of the T1 signal which shortens as a result of the formation of
methemoglobin in a fresh thrombus. It does not require the injection of
gadolinium.
In a proof of principle study, we have shown that over six months the high
signal is extinguishing completely in all 35 patients with CUS prove first
episode DVT. This signal could thus potentially be used as a conclusive sign of
a new DVT when a patient presents with clinically suspected acute recurrent
DVT. As a consequence, this test should be negative in the presence of
residual abnormalities caused by old, inactive thrombi and positive with new,
actively forming thrombi. Therefore, the test has the potentiall to
differentiate old from new thrombosis in patients with suspected acute
recurrence.

The study has the objective to estimate the sensitivity and specificity of
DT-MRI in diagnosing acute recurrent deep venous thrombosis.

The study design is a prospective multicenter study. Two Dutch hospitals
participate in this research project, Leiden University Medical Centre and Haga
Leyenburg. For this study we'll need two groups of patients, group 1 has to
consist of 40 patients with clinically suspected acute recurrent DVT in the
ipsilateral leg and group 2 of 40 patients with a history of DVT. The patients
are included in a period of 1 year.
Group 1 will receive between 24-48 hours after the CUS a MRI examination and
will return after 6 weeks at the outpatient department for a physical
examination and a CUS.
The MRIs of group 2 will be scheduled. The MR images are interpreted in a
blinded fashion (i.e.without knowledge of group 1 or 2 status) by two
experienced readers who are not involved with the patients.

The patients of group 1 get as extra examination the MRI. In group 2 patients
get a D-dimer test (blood test), compression ultrasonography and MRI. Neither
the blood test, the compression ultrasonography and MRI have risks for the
patients. Before the patients undergo a MRI, all the contra-indications will be
evaluated. There are no known side-effects of a MRI examination.