Functional aspects of anatomical imaging techniques 02/IT15 Nilendu Purandare - Functional... ·...
Transcript of Functional aspects of anatomical imaging techniques 02/IT15 Nilendu Purandare - Functional... ·...
Functional aspects of anatomical imaging techniques
Nilendu Purandare Associate Professor & Consultant Radiologist Tata Memorial Centre
Anatomical imaging techniques
•Ultrasonography •CT scan •MRI
Functional/metabolic/molecular imaging (radioisotope scanning)
•PET •SPECT
Location Size/dimensions Density Morphology Spatial relations
Perfusion,flow Metabolsim (glucose, AA) Receptor expression Hypoxia,Apoptosis
Oncology / tumor imaging
Functional imaging Tumors •Metabolism (glucose, amino acid) •Proliferation •Hypoxia •Angiogenesis •Apoptosis •Image receptors
PET
Functional imaging Tumors •Metabolism (glucose, amino acid) •Proliferation •Hypoxia •Angiogenesis •Apoptosis •Image receptors
•Angiogenesis •Perfusion •Diffusion characteristics •Metabolite quantification •Hypoxia
CT/MR
Tumor imaging
•Angiogenesis •Perfusion •Diffusion characteristics •Metabolite quantification •Hypoxia
CT/MR
Angiogenesis (DCE MRI and CT Perfusion)
Physiological imaging (ultrafast imaging) Follows the early enhancement kinetics of contrast within first few minutes of IV bolus injection (TIC). Depicts tissue vascularisation, capillary permeability, perfusion, volume of interstitial space, thus indirectly tissue cellularity.
Angiogenesis (CT Perfusion) Assesses physiological parameters •Blood flow (BF) •Blood volume (BV) •Mean transit time (MTT) •Capillary permeability (CP/PS) In vivo markers of micro vessel density and angiogenesis
Angiogenesis (CT Perfusion)
•De-convolution based analysis technique •Operative derived ROI are placed on artery and representative portion of the tumor for input functions •Functional maps of perfusion parameters obtained
Angiogenesis (CT Perfusion)
Angiogenesis (CT Perfusion)
Rectal Cancer : response to neo-adjuvant therapy
MR Perfusion / DSC MRI (Brain tumors)
SI
Time
• Cerebral blood volume
• Cerebral blood flow
• Mean Transit Time
• Time to Peak
MR Perfusion / DSC MRI (Brain tumors)
• Establish the diagnosis of tumor
• Pre- operative assessment of tumor histology
• Guide tumor biopsy
• Assessment of true lesion extent
• Monitoring response to therapy (surrogate marker)
MR Perfusion / DSC MRI (Brain tumors)
Hyperperfusion
Possible glioma
Delineation of true tumor extent
Radiation Necrosis Vs tumor recurrence
Dynamic contrast enhanced (DCE) MRI • Tissue characterization (vascularity & perfusion) • Identifying viable areas to biopsy • Staging of local extent •Monitoring response to therapy (surrogate marker)
Angiogenesis (bone & soft tissue tumors)
(K-trans, tissue permeability)
Advanced techniques : DCE MR- Curve types
Advanced techniques : MRI •Dynamic contrast enhanced (DCE) MRI Tissue characterization
Highly perfused and vascularised tumor with small volume interstitial space Type IV curve-malignant
Advanced techniques : MRI •DCE MRI : Ideal site for biopsy
Highly vascularised , highly perfused viable portion of tumor (Synovial Sarc) Avoid edema, necrosis, normal tissue
Advanced techniques : MRI • DCE MRI : Surrogate marker of response to chemo Rx
MFH
Advanced techniques : MRI • DCE MRI : Residual/recurrent tumor from post Rx change
Gradual slope – pseudonodule Bx- negative for malignancy
Tumor imaging
•Angiogenesis •Perfusion •Diffusion characteristics •Metabolite quantification •Hypoxia
Diffusion weighted imaging (DWI)
•Measures the motion of water molecules in the intra & extravascular spaces •Motion of water molecules is more restricted in tissues with high cellularity, intact cell membranes and reduced intracellular space •Malignant tumors in general have high cellularity and thus more restricted diffusion. •Quantitatively ADC values are used to study diffusion restriction
A B C
D E F
Diffusion weighted imaging (DWI)
Diffusion weighted imaging (DWI)
Diffusion weighted imaging (DWI)
Diffusion weighted imaging (DWI)
Synovial sarcoma –post surgery Enhancing nodule at surgery site ADC map- restricted diffusion Local recurrence
Tumor imaging
•Angiogenesis •Perfusion •Diffusion characteristics •Metabolite quantification •Hypoxia
Metabolite quantification MR spectroscopy • Maps metabolite signal intensity from tissues (choline, creatinine, lipids, NAA, lactate, citrate) • Detects increased levels of choline • Marker of cell membrane turnover- feature of malignancy • Proton (H1) MR spectroscopy is used.
Normal Brain spectrum
Glioma spectrum
Radiation Necrosis Vs tumor recurrence
Metabolite quantification-MR spectroscopy
MR spectroscopy : Response evaluation Metabolite quantification
Tumor imaging
•Angiogenesis •Perfusion •Diffusion characteristics •Metabolite quantification •Hypoxia
BOLD (Blood oxygen level dependant imaging)
•BOLD MR detects hypoxic subfraction and patients suitable for hypoxia modifying agents. •Provide a means of evaluating changes in tumor oxygenation in response to chemotherapy •Used for Brain, breast, pancreatic and prostate cancers
BOLD-MRI images are more likely to reflect on acute (perfusion-related) tissue hypoxia.
BOLD
Functional techniques Tumor imaging •Metabolism (glucose, amino acid) •Proliferation •Hypoxia •Angiogenesis •Apoptosis •Image receptors
•Size & Volume •Angiogenesis •Perfusion •Diffusion characteristics •Metabolite quantification •Hypoxia
PET
CT MRI
Neurology
Diffusion weighted imaging (DWI)
•Measures the motion of water molecules in the intra & extravascular spaces •Motion of water molecules is more restricted in tissues with high cellularity, intact cell membranes and reduced intracellular space • Infarcts show restricted diffusion in a few hours •Quantitatively ADC values are used to study diffusion restriction
Significance of penumbra
• Central irreversible infarcted tissue core
• Peripheral region of ischaemic but salvagable tissue called penumbra
Neurology
State of the art imaging of acute stroke
Mismatch
Comparison of Diffusion &
Perfusion Abnormalities
State of the art imaging
of acute stroke
Comparison of Diffusion &
Perfusion Abnormalities
Match
2 hours after deficit
7 days later
CBF MTT
3 hours
3 hours after deficit
7 days later
Penumbra is reversed after
endovascular clot retrieval &
revascularisation
Functional MRI ( F MRI)
BOLD
Functional MRI ( F MRI)
Defined cognitive task
Increased neuronal activity
Localized vasodilatation and
increase in blood flow
Signal response Increase in dimagnetic
oxyhemoglobin
Epilepsy: cortical dysplasia
Epilepsy: cortical dysplasia, fMRI
Cardiology
Cardiology MRI (Myocardial perfusion) use the “first pass” of an intravenously injected Gd contrast agent at rest and during administration of a vasodilator (i.e. adenosine ) to depict hemodynamically significant coronary artery stenosis
MRI (Cardiac Viability) Contrast enhanced CMR is a newly established technique for infarct assessment. Regions of myocardial infarction exhibit high signal intensity (contrast enhancement) on T1‐weighted images after administration of contrast such as gadolinium based agents.
Top panel:
Subendocardial infarct, prominent perfusion defects larger than infarct on stress MR
Bottom panel:
Matched stress and rest defects, no infarction, CA is normal- artifactual
MR Perfusion
MRI: Viability
58 yrs old man (EF-20%) Dilated cardiomyopathy Thinning of inferior wall on still images Late ce- MRI shows transmural enhancement suggesting old MI
In chronic CAD patients, myocardial enhancement in areas of dysfunctional myocardium corresponds closely to fixed defects on thallium SPECT, and areas of flow-metabolism matched defects on FDG-PET scans, histologically representing scarred or fibrotic tissue
Color Doppler Ultrasound
Estimates blood flow and velocity Locate and grade vascular stenosis
2D echo Pumping function (ejection fraction)
Summary
CT/MRI (DCE MRI, DWI, spectroscopy, BOLD)
•Oncology Angiogenesis (perfusion), diffusion, metabolites, hypoxia
•Neurology Functional maps, CBF,CBV, MTT (epilepsy, stroke)
•Cardiology Myocardial perfusion, viability