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Diagnostic Services - Magnetic Resonance Imaging
- The new MR machine available in Cairo Scan is considered unique advanced equipment in the field of radiology
- It is the latest product of Siemens 1.5Tesla symphony.
Symphony is anew technology in MR as regards its soft ware, examinations it can perform and its shape.
- Its small size and nice shape as well as short examination time allows the patient to be more comfortable during the examination even in claustrophobic patients.
- Symphony provides ultra fast examination with the highest signal to noise ratio and spatial resolution for all examinations.
The thinnest slice thickness and interspace allowing accurate and specific diagnosis for minute lesions as those of the inner ear.
In addition to all the standard techniques that can performed by the other two MR machines we have, such as the brain, spine, joints, abdomen and chest.
Symphony provides the most up to date examinations that proved out to be not only useful yet mandatory for sound proof diagnosis.
Symphony 1.5 tesla MR offers the capability of performing;
- MR diffusion and perfusion for the brain
- MR spectroscopy
- MR CSF flow metery
- MR cholangiopancreatography
- MR urography
- MRA for the thoracic abdominal aorta and distal limb vessels.
- MRI of the heart
- MRA of the coronary arteries.
MAGNETOM Symphony from 'SIEMENS medical' provides:
- A more open MRI
- High-resolution imaging of thorax (including heart) and abdomen.
- High resolution angiography of both legs including pelvis with best signal-to-noise ration.
- Visualization of the iliac arteries and aorta
- Peripheral MR Angiography run-off studies with CP Array coils
- Enables the visualization of vessels from the level of the diaphragm to the foot vessels
- Best visualization of small anatomical structures (e.g. Labrum)
- Reduced slice thickness or measurement times.
- Higher SNR and better field homogeneity either for the left or for the right shoulder
- Simultaneous visualization of the left and right TMJs (Temporo-Mandibular Joints) with high resolution
- Separate visualization of the left or right eye with excellent signal-to-noise ratio
- Separate visualization of the left or right wrist
- Imaging of large regions such as medium to larger shoulders, hip and knee
- Examination of upper or lower extremities (e.g. shoulder, axilla)
- Examination of small structures near the surface (e.g. joints of fingers and toes, wrist, skin, Temporo-mandibular Joints TMJ)
- Excellent visualization of the prostate, colon, rectum and cervix without the risk of invasive procedure
- Non-invasive preoperative diagnostic evaluation and treatment planning
- High resolution, high speed head or trunk imaging in combination with the "Integrated Parallel Acquisition Technique" (iPATplus) for highest PAT factors
- Cardiac, hepatic and muscular spectroscopy in combination with decoupling measurements using the Nuclear Overhauser Effect (NOE)
- Combined Head/neck examination
- High resolution imaging of the whole spine
Coronary MRI Angiography
Cardiovascular disease remains the leading cause of morbidity.
In patients with established CAD the clinician decisions regarding the selection of medical versus interventional / surgical therapies are usually done by conventional selective coronary catheterization.
Coronary MR Angiography has emerged a unique non invasive diagnostic imaging tool to visualize the coronary arteries and evaluate their integrity.
Coronary MR angiograraphy offers a rapid non invasive imaging with exquisitely high spatial resolution and unrestricted multiplanar 3 D images
This technique doesn’t involve the exposure for ionizing radiation and eliminates the need for iodinated contrast media with elimination of the risk of the conventional coronary angiography complications.
Clinical application
Evaluation of the coronary anomalies
Comparative studies with conventional x-ray angiography show coronary MRA to be eqiuvlant if not superior to conventional angiography and thus have become the gold standard for their evaluation.
Assessment of coronary artery aneurysm
Adequately visualize the aneurysm, size, location and extent. It is becoming the preferred modality for serial non invasive follow up.
Assessment of native coronary artery stenosis and CABG patients
Offers a very high sensitivity with nearly same specificity as x-ray angiography. Non invasive follow up for patients
Cost and time saving
MR Imaging of Myocardial
Perfusion and Viability
Myocardial ischemia and infarction caused by coronary artery disease are the leading causes of death and medical care expenses. Myocardial perfusion imaging is currently dominated by SPECT using thalium or technetium.
Recent improvements in cardio-vascular MR imaging techniques have made myocardial perfusion imaging with high resolution and wide cardiac coverage possible. These imaging techniques are now offered at Cairo Scan.
Myocardial perfusion (CMR) imaging requires a fast gradient echo technique, or, echo planner imaging. Both of these are available in our new MRI machine (Symphony 1.5 T - Siemens Medical Systems).
The high spatial resolution of contrast-enhanced MR imaging allows:
- Visualization of subendocardial infarcts and microinfarcts associated with successful PTCA.
- Detection of subendocardial infarction which may be missed by other techniques.
- Assessment of motion abnormalities.
- Detection of viable myocardium in patients with known coronary artery disease.
Signs of myocardial viability are absence of late gadolinium based contrast enhancement in region involved in recent infarct, any signs of wall thickening at rest, wall thickening after stimulation by low dose of dobutamine and preserved wall thickening
MR Spectroscopy
Magnetic Resonance Spectroscopy (MRS) is an important supplement to Magnetic Resonance Imaging (MRI) for the differential diagnosis of many diseases. MRS is based on the same physical principles as MRI but offers unique biochemical information that can improve tissue characterization in normal and pathological states. MRS is now readily available at Cairo Scan.
Clinical Applications:
MRS studies have been shown to be of significant diagnostic value, particularly for the evaluation of diseases that affect the brain and other organs:
Brain tumors: MRS has shown special diagnostic advantages when added to MRI in the evaluation of brain tumors. Its clinical applications include:
- The differentiation between benign and malignant lesions
- The assessment of tumor grade and relevant biochemistry of the lesion
- Monitoring tumor response to therapy
- Differentiation of post therapeutic changes from local tumor recurrence
Dementia: MRS helps to differentiate Alzheimer's disease (AD) from other forms of dementia with a negative predictive value of approximately 80% and a positive predictive value of 95% for patients with AD.
Focal disease: Many forms of focal disease of the brain, including white matter lesions, multiple sclerosis, and epileptogenic foci show certain patterns of spectra that can help to make an early diagnosis.
Head trauma without hemorrhage: MRS can identify subtle biochemical changes associated with diffuse axonal injury, hyperosmolar state, and hypoxic injuries when conventional MR images are negative for lesions.
Hepatic encephalopathy: MRS can be used to characterize patients with hepatic encephalopathy and to determine sub clinical conditions.
Inborn errors of metabolism: are identified with great specificity by MRS, making it the diagnostic test of choice for the work-up of difficult cases.
Infections: Abnormal MRS features are seen in association with, or possibly earlier than, MRI in cases with encephalitis, HIV and AIDS-related masses.
Pediatric hypoxia: MRS is the most sensitive and predictive test for perinatal hypoxic encephalopathy.
Stroke and cerebral ischemia: In general, MRS is more sensitive than MRI in detecting hypoxic damage related to vascular or other types of abnormality. The earlier MRS is performed, the more likely potentially salvageable tissues will be identified that can be conserved by therapy.
BENEFITS OF MRS
MRS can enhance the diagnostic capabilities and thereby improve the patient’s management and outcome. In many instances, MRS can replace some of the costly and invasive diagnostic procedures conventionally adopted. MRS is therefore widely considered a cost-effective and valuable diagnostic tool for the assessment of disease severity, the planning of treatment, and the monitoring of therapy.
MRS is also valuable when CMRI shows equivocal or even abnormal findings.
- MR diffusion imaging allows detection of cerebral ischemia within minutes of onset before T2 WI images demonstrates signal abnormalities.
- Diffusion WI images can differentiate acute from chronic stroke.
- T2 Wt MR imaging demonstrates infracted tissue.
- The ability of diffusion imaging to demonstrate infarction is not a point of debate.
- Before the ability of an efficacious treatment for acute cerebral ischemia, the emphasis of neuro-imaging was to exclude the presence of hemorrhagic and non-ischemia causes of an acute neurological deficit.
- However the purpose of neuro-imaging has changed after the recent demonstration of the efficacy of recombinant tissue plasminogen activator.
- Although CT has been used to detect infarction, this modality is relatively insensitive in the acute phase. Conversely, diffusion WI imaging is optimally suited to this test.
- As the diffusion changes indicate only the area of non-salvageable tissue, means of determining the extent of at-risk but salvageable tissue have also been investigated.
- One approach is concomitant MR perfusion imaging with diffusion WI images.
- MR perfusion imaging is taken after injection of a bolus of Gd-DTPA. Images acquired during the first path of the contrast agent through the brain can be analyzed to produce images of relative regional blood volume, mean transit time, regional cerebral blood flow and arrival time.
- In the management of stroke, it’s clear that early identification of the ischemic penumbra is the key to early therapy.
- The ischemic penumbra represents the undamaged and salvageable tissue in the ischemic zone.
- Diffusion imaging therefore allows detection of cellular dysfunction and potential cell damage.
- Perfusion reflects cerebral blood flow at the capillary level including collateral channels.
- Identification of the ischemic penumbra is the critical issue in improving therapeutic thresholds.
- Concomitant diffusion WI images and perfusion WI images or MR spectroscopy are thus useful tools in the detection of the ischemic penumbra.
- N-acetyl aspartate (NAA) level correlates with neuronal viability and the lactate level correlates with anaerobic glycolysis.
- A drop in the N-acetyl aspartate level and a rise in the lactate level indicates a loss of cell viability, whereas a slightly depressed N-acetyl level with an elevated lactate level suggest that therapeutic intervention may be helpful as the tissue is potentially salvageable.
- It has been reported that the area of diffusion abnormality and that follow up imaging usually shows a region of infarction larger than that seen on acute phase diffusion WI images although not as large as the initial perfusion deficit. Thus the area of mismatch may represent the ischemic penumbra.
- Combined diffusion and perfusion WI MR imaging has shown great promise in the diagnosis of acute stroke.
- Phase contrast MR angiography can provide complementary information along with diffusion and perfusion WI imaging in predicting the outcome of patients in acute stroke.
- MRS is a technique that allows the doctor to study a few metabolites in the brain or neoplasms without removing them from the patient.
- MRS can differentiate abscesses from ring enhancing neoplastic lesions.
- MRS is valuable in grading gliomas and in diagnosis of brain stem lesions.
- MRS can differentiate lymphoma and metastases from primary brain tumors.
- MRS has been successfully used to guide stereotactic biopsies, with sampling of higher choline areas yielding a high success rate and increased diagnostic confidence.
- MRS is helpful in treatment and in monitoring both pre and post treatment by recognizing reduction of the choline level and higher relative NAA with inverted doublet peak of lactate in the post treatment spectrum denoting good response.
Magnetic Resonance Angiography
Magnetic resonance angiography, now readily available at
Cairo Scan, is highly accurate for assessment of the entire lower extremity for
arterial disease. Three-dimensional Gd-enhanced MRA improves diagnostic
performance compared with 2-D MRA.
Contrast-enhanced moving-table MR angiography is a new
technique that may be an effective alternative to catheter arteriography in
endovascular and surgical treatment planning in selected patients with
peripheral arterial occlusive disease. |
