pr pemeriksaan aliran darah otak
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Pemeriksaan Aliran Darah Otak
DSA (Digital Subtraction Angiography)
Pemeriksaan baku dan standar dari pembuluh darah otak untuk melihat aliran darah di pembuluh darah arteri sampai ke jaringan lalu ke pembuluh vena secara langsung dan terus menerus menggunakan alat angiografi atau keterisasi
DSA (Digital Subtraction Angiography) Angiografi yang dilakukan pada pembuluh
darah otak Memasukkan kateter ke dalam arteri pada
lengan maupun tungkai. Injeksikan kontras ke dalam pembuluh darah
menuju otak Cerebral angiogram lebih akurat dibanding
karotid Doppler
Menolong deteksi dan diagnosa stroke akut
Mendeteksi kelainan pembuluh darah yang menuju otak (misalnya, aneurisma, malformasi pembuluh darah, trombosis, penyempitan atau penyumbatan)
Pelajari PD otak yang letaknya abnormal (tumor, gumpalan darah, spasme, tekanan otak meningkat, atau hidrosefalus)
Bantu pembedahan
Angiografi tidak boleh dilakukan pada penderita penyakit hati, ginjal, atau tiroid, atau alergi kontras
Hasil abnormal
Spasme, plak, fistula, malformasi arteriovenosus, atau arteriosclerosis. Penurunan suplai aliran darah ke otak.
Pembuluh darah otak yang letaknya tidak lazim menunjukkan adanya tumor, daerah pembengkakan, atau penyumbatan aliran cairan spinal.
Transcranial Doppler
Teknik ultrasonografi non invasif yang mempunyai kemampuan untuk mengukur kecepatan dan arah aliran pembuluh darah di otak.
Kelebihan Transcranial Doppler (TCD) :
1. Menggunakan teknik sonografi yang non invasif sehingga menghindarkan pasien dari rasa tidak nyaman selama pemeriksaan2. Aman, karena teknik ini bebas dari bahaya radiasi3. Tidak memerlukan ruangan khusus dalam pelaksanaan 4. Dapat dilakukan berulang kali untuk monitoring tanpa adanya efek samping
5. Tidak memerlukan penggunaan zat kontras yang mempunyai resiko terjadinya efek samping seperti alergi6. Biaya yang lebih murah dibandingkan dengan teknik lain seperti arteriografi.
Peran TCD di bidang medis:
- Mendeteksi adanya gangguan aliran pembuluh darah otak- Menilai faktor resiko terjadinya stroke pada pasien beresiko - Mendeteksi adanya emboli- Menilai respon hasil terapi post stroke- Mendeteksi adanya vasospasme (spasme pembuluh darah) misalnya setelah terjadinya perdarahan sub arrachnoid
- Sebagai penunjang diagnosis bersama dengan pemeriksaan lain seperti CT scan, MRI, MRA.- Sebagai penunjang terapi (Sonotrombolisis)- Untuk mendeteksi kematian otak (Brain Death)
TCD dapat diaplikasikan pada kasus-kasus seperti :
• Resiko terjadinya stroke pada anak-anak penderita sickle cell anemia• TIA (Transient Ischemic Attack) dan Stroke untuk menilai stenosis pembuluh darah dan aliran kolateral.• Menilai adanya trombosis atau emboli pada TIA atau Stroke• Post Trauma kepala atau perdarahan dari aneurysma sub arachnoid yang beresiko terjadi vasospasme pembuluh darah
• Mengkonfirmasi diagnosis klinik dari kematian otak (Brain Death)• Vascular Headache ( seperti pada kasus migrain) dan beberapa kasus lain yang masih dalam tahap pengembangan dan penelitian
Cath Lab
Mendeteksi penyakit artherosclerosis pada arteri carotis di leher, yang menggangu aliran darah ke otak dan bahkan dapat menyebabkan stroke.
Kateter angiography dapat menampilkan gambar pembuluh darah secara detil, jelas dan akurat. Sangat membantu dalam tindakan prosedur operasi atau Percutaneous Transluminal Coronary Angioplasty (PTCA).
Computed Tomography Angiography (CTA) and Magnetic Resonance Angiography (MRA)
What Are They? Computed Tomography Angiography
(CTA) Imaging of the vasculature using CT techniques Can be 3-D Requires contrast
Magnetic Resonance Angiography (MRA) Imaging of the vasculature system using MRI
techniques Can be 3-D No contrast required
How Does CTA Work?
Uses X-rays Tube rotates around patient at high speed Detector picks up attenuated beam Computer generates the image Collects image in axial plane but can be
converted into sagittal, or coronal views Computer can generate 3-d images
How Does MRA work? Uses a large magnet align hydrogen atom in the
body Pulsed radio-waves cause hydrogen atoms to flip
out of alignment When the radio-waves are turned off the hydrogen
atom flip back and give off their own signal Signal is detected by the computer and used to
generate an image Different body tissues have different amounts of Hydrogen
What is CTA used for?
Imaging of calcified atherosclerotic plaqueAreas that are scan for plaque include:
Carotid Bulb Iliac arteries Coronary arteries
Used to detect legs clots before they break and cause pulmonary emboli
Calcified plaque seen on CTA Angiogram of the same vessel
What is MRA used for? MRA is used to image many peripheral vessels
Areas that are imaged include: Circle of Willis Cerebral Arteries Renal Arteries
If there is a contrast allergy then MRA is used
Benefits of CTA Detecting narrowing vessels in time for
intervention Better anatomical detail than with MRA or
ultrasound Can be used for screening for arterial disease Less costly and safer than conventional angiography Contrast reactions are less severe
Risks of CTA
Allergic reactions to contrast media Avoided in patients with kidney disease
due to contrast Ionizing radiation is used Pregnant women should not have a CT
due to radiation
Benefits of MRA Detailed images without damaging the artery with a
catheter Shorter procedure and recovery times than with
conventional angiography Less costly than catheter angiography No exposure to ionizing radiation Use of contrast is
not necessary to obtain good images
Risks of MRA
Metal implants may be affected by the magnetic field
Claustrophobic patients may need ot be sedated
It is unknown how the magnetic field affects the fetus so first trimester patients should not have an MRI
Limitations of CTA
Fuzzy images if there is patient movement Heart beat can blur images Blocked vessels are harder to interpret Not reliable for imaging small twisted
vessels in rapidly moving organsFaster gantry times will solve this problem
Limitations of MRA
Any metal object in the patient is contraindicative
Image clarity is not as good as conventional angiography
Cannot image calcified plaque Hard to image very small vessels
Accuracy of CTA
16-slice multidetector machineSensitive and specific for 2mm diameter or
greater 92-93% Ultra fast 16-slice multidetector machine
Sensitive and specific for 2mm diameter or greater 95-98%
64-slice multidetector machineSensitive and specific for 2mm diameter or greater
92-93%
Accuracy of MRA Detecting Cerebral aneurysms with an average
accuracy of about 70% without contrast False positives averaged approx. 27 With contrast 100% sensitive for aneurysmal
and stenotic lesions Specificity of completely occluded lesions also
100% Drops to 83.3% when only partially occluded
What’s to come? Improved spatial resolution
Resolutions due to software advancements are improving
Decreasing costs Screening
CTA screening for CAD Joint Modalities
Combining of the two for better images Better accuracy
New contrast medias for MR and faster CT machines
Bibliography Dargan, R., Volkin, L., New Application Enhances Capabilities of
Angiographic CT, retrieved February 5, from: www.asrt.org/content/News/IndustryNews Briefs/CT/NewApplica050318.aspx
Sheth, T. et. al., (2005), Coronary Computed Tomography Angiography: Emerging Technique for Coronary Artery Imaging, JACR 2005:56(1):15-24
Tripathi, RP, et. al., (2002), Three-Dimensional Contrast-Enhanced Magnetic Resonance Angiography- Our Preliminary Experience, Ind. J. Raiol. Imag. 2002, 12:2:179-188
www.cir.uc.edu/ research.html www.medscape.com/viewarticle/521872?rss
www.radiologyinfo.org/content/ct-angiography.htm
www.radiologyinfo.org/content/mr-angiography.htm