Functional aspects of anatomical imaging techniques

Transcription

1 Functional aspects of anatomical imaging techniques Nilendu Purandare Associate Professor & Consultant Radiologist Tata Memorial Centre

2 Functional/metabolic/molecular imaging (radioisotope scanning) PET SPECT Perfusion,flow Metabolsim (glucose, AA) Receptor expression Hypoxia,Apoptosis Anatomical imaging techniques Ultrasonography CT scan MRI Location Size/dimensions Density Morphology Spatial relations

3 Oncology / tumor imaging

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5 Functional imaging Tumors Metabolism (glucose, amino acid) Proliferation Hypoxia PET Angiogenesis Apoptosis Image receptors

6 Functional imaging Tumors Metabolism (glucose, amino acid) Angiogenesis Proliferation Perfusion Hypoxia Diffusion characteristics Angiogenesis Metabolite quantification Apoptosis Hypoxia Image receptors CT/MR

7 Tumor imaging Angiogenesis Perfusion Diffusion characteristics CT/MR Metabolite quantification Hypoxia

8 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.

9 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

10 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

11 Angiogenesis (CT Perfusion)

12 Angiogenesis (CT Perfusion) Rectal Cancer : response to neo-adjuvant therapy

13 MR Perfusion / DSC MRI (Brain tumors) SI Time

14 MR Perfusion / DSC MRI (Brain tumors) Cerebral blood volume Cerebral blood flow Mean Transit Time Time to Peak

15 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)

16 Hyperperfusion Possible glioma

17 Delineation of true tumor extent

18 Radiation Necrosis Vs tumor recurrence

19 Angiogenesis (bone & soft tissue tumors) Dynamic contrast enhanced (DCE) MRI Tissue characterization (vascularity & perfusion) Identifying viable areas to biopsy Staging of local extent Monitoring response to therapy (surrogate marker) (K-trans, tissue permeability)

20 Advanced techniques : DCE MR- Curve types

21 Advanced techniques : MRI Dynamic contrast enhanced (DCE) MRI Tissue characterization Highly perfused and vascularised tumor with small volume interstitial space Type IV curve-malignant

22 Advanced techniques : MRI DCE MRI : Ideal site for biopsy Highly vascularised, highly perfused viable portion of tumor (Synovial Sarc) Avoid edema, necrosis, normal tissue

23 Advanced techniques : MRI DCE MRI : Surrogate marker of response to chemo Rx MFH

24 Advanced techniques : MRI DCE MRI : Residual/recurrent tumor from post Rx change Gradual slope pseudonodule Bx- negative for malignancy

25 Tumor imaging Angiogenesis Perfusion Diffusion characteristics Metabolite quantification Hypoxia

26 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

27 Diffusion weighted imaging (DWI) A B C D E F

28 Diffusion weighted imaging (DWI)

29 Diffusion weighted imaging (DWI)

30 Diffusion weighted imaging (DWI) Synovial sarcoma post surgery Enhancing nodule at surgery site ADC map- restricted diffusion Local recurrence

31 Tumor imaging Angiogenesis Perfusion Diffusion characteristics Metabolite quantification Hypoxia

32 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.

33 Normal Brain spectrum

34 Glioma spectrum

35 Metabolite quantification-mr spectroscopy Radiation Necrosis Vs tumor recurrence

36 Metabolite quantification MR spectroscopy : Response evaluation

37 Tumor imaging Angiogenesis Perfusion Diffusion characteristics Metabolite quantification Hypoxia

38 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.

39 BOLD

40 Functional techniques Tumor imaging Metabolism (glucose, amino acid) Proliferation Hypoxia Angiogenesis Apoptosis Image receptors PET CT MRI Size & Volume Angiogenesis Perfusion Diffusion characteristics Metabolite quantification Hypoxia

41 Neurology

42 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

43 Central irreversible infarcted tissue core Neurology Significance of penumbra Peripheral region of ischaemic but salvagable tissue called penumbra

44 Comparison of Diffusion & Perfusion Abnormalities Mismatch State of the art imaging of acute stroke

45 Comparison of Diffusion & Perfusion Abnormalities Match State of the art imaging of acute stroke

46 2 hours after deficit CBF MTT 7 days later

47 3 hours

48 3 hours after deficit 7 days later Penumbra is reversed after endovascular clot retrieval & revascularisation

49 Functional MRI ( F MRI) BOLD

50 Functional MRI ( F MRI) Defined cognitive task Increased neuronal activity Localized vasodilatation and increase in blood flow Increase in dimagnetic oxyhemoglobin Signal response

51 Epilepsy: cortical dysplasia

52 Epilepsy: cortical dysplasia, fmri

53 Cardiology

54 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.

55 MR Perfusion 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

56 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

57 Color Doppler Ultrasound Estimates blood flow and velocity Locate and grade vascular stenosis 2D echo Pumping function (ejection fraction)

58 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

59 Thank you