Nuclear Medicine Relevant to General Practice

Transcription

1 Relevant to General Practice Dr Tony Hannah FRACP, FAANMS

2 A Few General and Imaging Principles

3 [Pb-212] Home Economics QC (1913): De Hevesy s Tracer Study

4 Mimicking Biological Molecules In (Molecular) Imaging biological molecules or analogues are trace labelled to map the function of selected tissues and organs. In disease these functions are frequently abnormal and physiological / functional changes can detect and give clues to the degree and extent of disease processes. A change in physiology frequently precedes any change in anatomy which may be detected by structural imaging (at times this can be a frustrating aspect of the specialty, high sensitivity and sometimes annoyingly nonspecific

5 Imaging Matrices & Greyscales Pixels with most counts Pixel count values assigned colour on graduated scale Counts assigned to each pixel Detector g rays *?: Biodistribution of tracer 2D Spatial Distribution of Activity Pixels with least counts

6 Plane x-ray : Planar Image Photons: Transmission Image

7 Computerised Tomographic Imaging (CT) Photons: Transmission Advantage of Tomography: Improved contrast Removal of overlap Image

8 Single Photon Emission Computerised Tomographic Imaging (SPECT) Advantage of Tomography: Improved contrast Removal of overlap Photons: Emission Image

9 SPECT/CT Conventional Gamma Camera with CT Scanner CT Gamma Camera Heads

10 Bone SPECT/CT Axial Slices Reporting Display

11 Fusion "Weighted" Images Coronal Slice Bone SPECT/CT For display the contribution of the functional image and anatomical image can be varied

12 Range of Topics Bone Scan Myocardial Perfusion Imaging Ventilation/Perfusion Lung Scanning Renal DTPA / MAG3 / DMSA Thyroid Scintigraphy Parathyroid Adenoma Detection Cerebral Perfusion Studies Infection imaging WBC / Gallium Focus on: Bone Scan inordinate time!! Myocardial Perfusion Imaging Ventilation/Perfusion Lung Scanning Thyroid Scintigraphy Parathyroid Adenoma Detection Quantitative Gastric Emptying Quantitative Hepatobiliary Scintigraphy Labelled Peptide Imaging 123 I MIBG / 111 In Octreotide Quantitative Gastric Emptying / Colonic Transit / Oesophageal Transit Scintigraphy Quantitative Hepatobiliary Scintigraphy Blood Pool Imaging Gated Cardiac, Haemangioma Diagnosis, Acute GI Blood Loss Quantitative Lymphoscintigraphy Sentinel Node Localisation Therapies: 131 I for thyrotoxicosis, 89 Sr / 153 Sm for bone metastases (prostate/breast) FDG- PET/CT

13 Bone Scan Indications - Community Undifferentiated bone pain localised/multifocal/diffuse Sub-radiographic fracture/s athlete or elderly (injury or insufficiency / stress) Poly-arthropathy / -arthritis Multifocal or diffuse malignant infiltration To Assess for: Prosthetic joint loosening Avascular necrosis Complex regional pain syndrome (RSD) Osteomyelitis associated with cellulitis or skin ulceration Explain abnormal biochemistry: ALP (?Paget s); (hypercalcaemia) Characterise bone lesions seen on structural imaging.

14 Radiopharmaceuticals and the Bone Remodelling Cycle Radiopharmaceuticals used for bone scans are derivatives of bisphosphonates. Their uptake in bone is an index of osteoblastic activity and blood flow (delivery) Bisphosphonate Chemisorption to Hydroxyapatite. (& F - )

15 Normal 3 Phase Bone Scan Adolescent 99m Tc HDP Inj. Blood flow Blood Pool Osteoblastic activity T=0 30sec. T = 5+minutes 3-4 Hours (limited to one field of view)

16 Normal 3 Phase Bone Scan - Adult 99m Tc HDP Anterior Posterior Anterior Posterior Inj. Blood flow Blood Pool Osteoblastic activity T=0 30sec. T = 5+minutes 3-6 Hours (limited to one field of view)

17 Sensitivity of Bone Scan - stress on normal bone - asymptomatic Exquisitely sensitive and frequently demonstrates subtle alterations in bone remodelling in response to various abnormal mechanical factors. Painful left knee arthropathy right hamstrings origin enthesopathy Drummer's Enthesopathy

18 Injury stress on normal bone Enthesopathy - symptomatic "Shin Splints periosteal reaction 99m Tc-HDP Bone Scan Blood Pool Phase Delayed Phase

19 Injury stress on normal bone Stress Fracture Tibia 99m Tc-HDP Bone Scan Blood Pool Phase Delayed Phase

20 Injury Stress Fracture 2 nd Metatarsal (2 Patients) 99m Tc-HDP Bone Scan Blood Pool Phase Delayed Phase

21 Subradiographic Fractures 99m Tc-HDP Bone Scan Various sub-radiographic fractures: 1. Compression-type left femoral neck stress fracture 2 2. Traction-type right femoral neck stress fracture (older age group insuffiency) 3. Right calcaneal stress fracture secondary to left hip arthritis

22 Subradiographic Fractures 99m Tc-HDP Bone Scan Acutely, bone scan is positive in 24-72hours for undisplaced fractures Various sub-radiographic fractures: 1. Undisplaced left femoral intertrochanteric fracture 2. Right scaphoid fracture 3. Bilateral femoral neck fractures and rib fractures in osteoporosis, with vertebral body compression fractures of various ages.

23 Undisplaced Left Intertrochanteric Femoral Fracture Plain x-ray (difficult) 99mTc HDP Bone Scan CT (resorption) CT Left Hip Coronal Slices 29/8/11 30/8/11 3/9/11

24 Localisation with SPECT/CT Hamate Fracture 99m Tc-HDP Bone Scan

25 Undifferentiated Bone/Joint Pain Pain Everywhere - Polyarthritis 99m Tc-HDP Bone Scan

26 Undifferentiated Bone/Joint Pain Pain Everywhere - Polyarthritis + Fracture 99m Tc-HDP Bone Scan

27 Talonavicular Arthropathy or Navicular Stress Fracture?? 99m Tc-HDP Bone Scan

28 Undifferentiated Pain THR (2months) : buttock pain facet joint arthritis 99m Tc-HDP Bone Scan SPECT/CT

29 Facet Joint Arthritis Which Facet Joint? 99m Tc-HDP Bone Scan SPECT/CT

30 Left lower back pain - Sacroiliitis 99m Tc-HDP Bone Scan

31 Undifferentiated Bone/Joint Pain Right Wrist pain Inflammatory Arthritis? de Quervain s Tenosynovitis 99m Tc-HDP Bone Scan

32 Bone Scan 99m Tc-MDP Complex Regional Pain Syndrome Injury / Surgery Rt Delayed Images Rt Delayed Images Rt Metastatic Malignancy Staging Cause of pain Paget s Disease Isolated ALP Activity in known disease Location of active disease Delayed Images Colle s #

33 Bone Scan and Metastatic Cancer Staging and restaging Detection of metastatic spread Directing treatment Detecting potential at risk sites (longbones, spine) Breast 70+% Prostate 70% Lung 30% Renal Cell 25% Multiple Myeloma - 80% 80% of all bone met s Usually carries an adverse prognosis

34 Bone Scan and Metastatic Cancer Spectrum: Osteolytic Osteoblastic Imbalance between formation and resorption of bone determined by the presence of malignant cells

35 Breast Cancer: 99m Tc-HDP Bone Scan

36 Breast Cancer: 99m Tc-HDP Bone Scan Bone SPECT/CT Degenerative (sagittal) Malignant Disease (axial)

37 Indications for Myocardial Perfusion Imaging (MPI) Coronary Artery Disease (CAD) BROADLY Diagnosis Presence, Location, Severity (volume of myocardium at risk) Assessment of known CAD On CT coronary or conventional angiography Symptomatic following revascularisation?asymptomatic following remote revascularisation Follow up of medical therapy Risk Assessment Pre-operative for major non-cardiac surgery (Following MI)

38 Not for MPI Acute ischaemic equivalent symptoms (Casualty) Ischaemic equivalent symptoms with low pre-test likelihood and interpretable ECG able to exercise (ExECG) Ischaemic Equivalent: Chest pain, tightness, burning, shoulder pain, palpitations, jaw pain, dyspnoea on exertion, worsening effort tolerance

39 Indications for Myocardial Perfusion Imaging (MPI) Symptomatic Ischaemic equivalent symptoms with uninterpretable ECG e.g. LBBB Ischaemic equivalent symptoms and unable to exercise (arthritis, back pain, etc.) Ischaemic equivalent symptoms with intermediate or high pre-test likelihood Ischaemic equivalent symptoms post-revasularisation Newly diagnosed heart failure Asymptomatic With intermediate or high pre-test likelihood Pre operative major surgery [>2yrs following PCI or >5yrs following CAGS] High coronary calcium score (>400) Coronary stenosis of uncertain significance Ischaemic Equivalent: Chest pain, tightness, burning, shoulder pain, palpitations, jaw pain, dyspnoea on exertion, worsening effort tolerance

40 Physiological Events Leading to Symptoms of Myocardial Ischaemia Coronary Flow : Metabolic Needs Supply : Demand Imbalance Abnormal Wall Motion LV Diastolic Dysfunction LV Systolic Dysfunction Ischaemia on ECG Angina Reduced Coronary Flow Reserve MYOCARDIAL PERFUSION IMAGING (MPI) ECHOCARDIOGRAM EXERCISE ECG CLINICAL Sensitivity 90% Specificity 80% Sensitivity 80% Specificity 90% Sensitivity 50% Specificity 90% The aim of any testing is to detect one or more of these factors by using stressors to increase coronary blood flow and create an imbalance between that flow and the metabolic needs of the myocardium, or simply to create a detectable reduced differential blood flow to myocardium supplied by stenotic vessels (i.e. demonstrate reduced relative coronary flow reserve).

41 Myocardial Perfusion Imaging Relative Coronary Flow Reserve 100% NORMAL ARTERY Myocardial Tracer Uptake Tracer uptake into myocardium is blood flow dependent within limits linear portion of sigmoid curve STENOTIC ARTERY FAILURE TO INCREASE FLOW (POOR rcbf Reserve) Coronary Flow increased by exercise or pharmacological means

42 Stress Myocardial Perfusion Imaging Prognosis DEFECT SIZE SMALL MEDIUM LARGE VESSEL TERRITORY < CIRCUMFERENTIAL <10% 10-20% >20% ANNUAL CARDIAC EVENT RATE 1% MORTALITY 5-10% 10-30% 3% MI rate Highe r w ith TID, Lung Up take CORONARY ANGIOGRAPHY No t Usually Pro bably Always

43 20 SEGMENT MODEL FOR SUMMED STRESS SCORE CALCULATION LAD RCA LCx apex mid Perfusion Defect Severity 0 = Normal 1 = Slight Reduction (equivocal) 2 = Moderate Reduction (significant) 3 = Severe Reduction (still greater than background) 4 = Absent Uptake SSS (Summed Stress Score) SRS (Summed Rest Score) SDS (Summed Difference Score) = Segments x Stress Perfusion Score = Segments x Rest Perfusion Score = SSS - SRS SSS Event Rate per Year (%) MI Cardiac Death < 4 (normal) (mild abn) (moderate abn) > 13 (severe abn) base SDS Category 0-1 Normal 2-4 Mild Ischaemia 5-7 Moderate Ischaemia 8 Severe Ischaemia

44 Imaging: Orthogonal Axes of the Heart Vertical Long Axis Short Axis Ant erior Sep tum Inf erior Lat eral Horizontal Long Axis

45 Normal Study 99m Tc SestaMIBI; Exercise Stress Stress Short Axis Vertical Long Axis Horizontal Long Axis Rest Stress Rest Stress Rest Stress Rest Polar map Constructed of successive short axis slices from apex(centre) to base

46 50 year old man with exertional interscapular, neck & upper chest pain. Exercise: 10METs, usual pain, 1mm ST dep. V5/V6 Anteroseptal & apical ischaemia (proximal LAD) + transient ishaemic dilatation.

47 75 year old man with previous circumflex angioplasty 5 months ago. Recurrent symptoms. Adenosine: No pain, No ECG changes Lateral wall reversible defect typical of circumflex territory

48 Adenosine + Exercise: 2METs Chest pain, No ECG changes 49 year old man with recent MI stented LAD and 60% mid-rca and severe distal RCA stenoses on angiography. Inferior and inferoseptal reversible defect.

49 74 year old man with history of MI many years ago and new exertional chest pain Exercise: 5 METs Limiting chest pain, 1.5mm ST depression I, II, avf, Post-stress LVEF(QG) = 43% Resting LVEF(QG) = 62% Severe widespread ischaemia, TID, Ischaemic stunning and lung uptake post stress,

50 Ventricular Function Gated Blood Pool Study (GBPS, RNVG) Left and Right Ventricular Ejection Fraction Trace Label: Blood Compartment - labelled RBC ( 99m Tc) Accurate and reproducible Count-based Gated Myocardial Perfusion Imaging Volume based in MPI

51 Ventilation Perfusion Lung Scan (V/Q scan) Indications for Lung Scans Acute Pulmonary Embolism diagnosis and monitoring Detection of chronic untreated pulmonary embolism (e.g. PHT) Regional ventilation and perfusion - reduction surgery Special Current Considerations: Renal Impairment - pre-lobectomy (Ca) Young women still an accurate simple low dose study in anyone with normal lungs otherwise!! Right to left shunt detection and quantitation Baseline for follow up after CTPA diagnosis Alveolar capillary permeability (pertechnegas) - ILD This still has a valuable place in the context of patients with otherwise normal lungs low radiation dose. Normal scan has excellent prognosis.

52 Thyroid Scintigraphy Aetiology of thyrotoxicosis Functional characterisation of thyroid nodules Guide to dosimetry of 131 I therapy

53 Thyroid Iodide Metabolism and the Sodium Iodide Symporter (NIS) TSH stimulates transcription of NIS and regulates NIS distribution between the plasma membrane where it is functional and the intracellular compartment, where it is not NIS couples inward Na + downhill (c/o Na + /K + ATPase) translocation to inward I - uphill translocation Establishes a fold [I - ] gradient

54 Thyroid Scintigraphy 99m Tc Pertechnetate I.V. Inj. Uptake Period T = 20 minutes

55 Thyroid Scintigraphy Aetiology of Hyperthyroidism Graves Disease Circulating thyroid stimulating Immunoglobulin Subacute Thyroiditis* Follicular distruction Hyperfunctioning Nodule Toxic MNG Nodular Hyperfunction Autonomous Nodule * Also iodide loading (saturation of trapping),

56 Guidelines

57

58 Scintigraphic Parathyroid Adenoma Localisation Tracer Characteristics (Ideally need a tracer specific for parathyroid tissue do not have this) Use tracers taken up by thyroid and parathyroid Dual tracer subtraction techniques Single tracer, dual phase techniques - SestaMIBI / Pertechnetate

59 Parathyroid Scintigraphy SestaMIBI Mechanisms? Taken up by thyroid and parathyroid Accumulation in PT adenoma is a function of : - mitochondrial / metabolic activity - blood flow - lesion size Differential washout of SestaMIBI - Washout from thyroid > Washout from adenoma -?downregulation of P-glycoprotein in PT (outflux carrier molecule for various substrates)

60 Parathyroid Adenoma Dual Tracer Single Phase 99m Tc Petechnetate/ 99m Tc SestaMIBI 1. 99m Tc Pertechnetate injection THYROID m Tc SestaMIBI THYROID + PARATHYROID ADENOMA 3. 99m Tc SestaMIBI - 99m Tc Pertechnetate (Normalised) = PARATHYROID ADENOMA 3 3 Key: Spatial or intensity discordance

61 Gastrointestinal Quantitative Studies

62 Gastric Emptying Studies Release Storage 99m Tc Labeled egg or porridge Analysis of clearance Mixing and Grinding Potential gastroparetic syndromes Unexplained nausea and vomiting Gastro-oesophageal reflux Persistent symptoms following UGI surgery Follow-up of patients after surgery / medical treatment

63 Gastroparesis: pre- and post-treatment (pharmacological) Pre- Teatment With Pro-kinetic Treatment

64 Hepatobiliary Scintigraphy Oral Cholecystogogue Unexplained right upper quadrant abdominal pain normal ultrasound Assessment for : Chronic (alcalculous) cholecystitis, Sphincter of Oddi syndrome Note: The examples on the following slides CCK infusion as a choloecystogogue this product is no longer manufactured and an oral cholecystogougue is now employed (known fat content) - validated with good results Krishnamurthy et al JNM 38(11) 1997

65 Normal Hepatobiliary Study with CCK 99m Tc IDA (iminodiacetic acid) Pre-CCK CCK Gallbladder Ejection Fractions Gallbladder ROI

66 Chronic Cholecystitis / Cystic Duct Syndrome Hepatobiliary Study with CCK 99m Tc IDA Pre-CCK CCK Gallbladder ROI

67 Presentations Bone Scan Localised or generalised undifferentiated bone pains Without evident clinical disease Arthritis, fractures, malignancy, To confirm / add weight to possible diagnosis Subradiographic fracture Arthropathy AVN Pagets disease Osteomyelitis associated with cellulitis Prosthetic joint complications (infection / loosening) Malignant aetiology or other disease Further characterise known bony pathology Sclerotic / lytic lesions on radiographs / CT (often incidental) Gastric Emptying Study Gastrointestinal syndromes gastroparesis, Thyroid Scan Thyrotoxicosis aetiology Thyroid nodule characterisation Myocardial Perfusion Scan Myocardial ischaemic equivalent New left heart failure High coronary calcium score Coronary stenosis on CTCA Risk stratification diabetes, pre-surgery. SestaMIBI Parathyroid scan Primary hyperparathyroidism Hepatobiliary Scintigraphy RUQ pain, Other possible biliary pain