Role of Nuclear Medicine in Respiratory Diseases Dr Iman Al Shammeri

Role of Nuclear Medicine in Respiratory Diseases DR. IMAN M S AL-SHAMMERI Pulmonary nuclear medicine application = V/ Q scan Role of Nuclear Medicine  Suspected Pulmonary Embolism     Inflammatory diseases Obstructive airway disease Evaluation of permeability Preoperative quantitation PULMONARY EMBOLISM condition  10% of pt die w/n 1hr  Heparin rank 1st in drug related deaths  Fatal PULMONARY EMBOLISM    Mortality: Untreated : 30% - 38% Treated :2.5% - 8% Only 24% of fatal emboli were diagnosed premortemly PULMONARY EMBOLISM   Mostly thromboemboli Fat, air or tumor emboli are rare  90% of pulmonary thromboemboli originate from the lower extremities and pelvis. PULMONARY EMBOLISM  Accurate & prompt Dx is needed to mortality & morbidity due coagulation Rx. PE RISK FACTORS      Recent surgery immobilization Hip fractures thrombophlebitis Any condition inc thromboembolic state PE RISK FACTORS      Men higher mortality Increase with age Sedentary life style Prolonged recovery CHF     Pregnancy Estrogen intake Malignancy Hypercoagulative state PE symptoms- nonspecific Chest pain Pleuritic chest pain Dyspnea Cough Hemoptysis Palpitations Syncope Sweating SIGNS OF PE      Tachycardia Tachypnea Cyanosis Rales (crackles) Pleural rub Chest X-ray Findings in Patients With & Without Proven PE Finding PE present PE absent Atelectasis Pleural effusion Pleural-based opacity 91/128 (71%) 133/246 (54%) 41/117 (35%) 155/334 (46%) 176/481 (37%) 53/247 (21%) Elevated hemidiaphragm Oligemia Prominent pulmonary artery Cardiomegaly Pulmonary edema Westmark’s sign* * Prominent 74/246 (30%) 25/117 (21%) 61/235 (26%) 18/128 (14%) 5/117 (4%) 15/118 (13%) 109/481 (23%) 30/247 (12%) 90/394 (23%) 43/334 (13%) 31/247 (13%) 5/147 (3%) central pulmonary artery and decreased pulmonary vascularity. DIAGNOSIS     Clinical diagnosis: Difficult Angiography: the most accurate Imaging Advantages of Scintigraphy Provides information that is  Physiologic, Regional, Quantitative  Cost effective  noninvasive  Acceptable radiation dose  V/Q Perfusion  Patient preparation  Radiopharmaceuricals: Tc99m MAA Technique Pulm. Vessels Capillaries Precap. arterioles Terminal arterioles Approx. diameter Number in adults 7-10 microns 35 microns 100 microns Approx. 300 billion Approx. 300 million Thousands  Ventilation Patient preparation  Radiopharmaceuricals   Gases Xenon 133 Krypton 81 Xenon 127  Aerosols aerosol aerosol 99mTc-DTPA 99mTc-pyrophosphate Technegas PULMONARY EMBOLISM   Decrease of perfusion distal to the occluded vessel Transient decrease of ventilation to the effected segment Interpretation of V/Q studies   Concept (MISMATCH) Prospective studies Biello  McMaster   Prospective studies Streptokinase  PIOPED  Biello’s criteria for interpreting V/Q scans Category Pattern Approximate frequency of PE 0 10 Normal Low probability No perfusion defects Small V/Q mismatches, V/Q matches without corresponding x-ray changes, perfusion defects substantially smaller than x-ray density Severe obstructive pulmonary disease with perfusion defects, perfusion defects of the same size as x-ray changes, single moderate or large V/Q mismatches Intermediate probability 30 High probability Two or more medium or large V/Q mismatches, perfusion defects substantially larger than x-ray density 90 Modified.. Modified..Criteria Category Normal Pattern No perfusion defects with or without impressions explained by enlarged heart or other hilar structures as seen on chest x-ray Near normal Low Nonuniform uptake with no definite segmental or subsegmental perfusion defects Any number of small defects regardless of chest x-ray or ventilation findings, any number of ventilation and perfusion matches with no corresponding chest x-ray abnormalities, stripe sign, nonsegmental perfusion defects other than thoseexplained by cardiomegaly or other prominent hilar structures,moderate or large (nonsmall) perfusion defects with disproportionately larger chest x-ray densities High >_2 segmental perfusion defects or their equivalents of moderate and/or large (nonsmall) defects with no corresponding ventilation or chest x-ray abnormalities, perfusion defects with disproportionately smaller chest x-ray abnormalities. Intermediate Patterns that do not correspond to any of the above Elgazzar: N M Annual, 1997 Interpretation Normal perfusion • No evidence of clinically significant pulmonary emboli • Stop anticoagulants • Look for another explanation for S & S V P Interpretation High Probability Crypton-81 Tc99m MAA Posterior Posterior Posterior LPO LPO Low Probability Intermediate probability RESOLUTION     Occurs spontaneously or with treatment Dependant on: Patient’s age, Age of the thrombus, Duration between the formation of embolus and the institution of proper anticoagulation May start within hrs and seen on perfusion scans as early as 24 hrs. 120 100 Progressively noted up 80 to 3 mo with insignificant 60 40 change at 6 mo Resolution 20 0 ho ur s on th s m on th 12 s m on th s 6 da ys da ys da ys da ys da ys 3 24 14 m 2 3 5 7 (%) Time after event Recurrence     In up to 50% of patients PIOPED patients was only 8.3% The vast majority of patients who die of pulmonary emboli died of recurrent emboli May occur at the same site as the original throboembolus Utilization Normal and high probability studies  Others: Combine  Pre scan clinical probability Scan probability Patient or diagnostic probability  Decision making utilizing DVT studies & Spiral CT in non conclusive cases Sarcoidosis Ga-67 Inflammatory disease Diffuse Interstitial Fibrosis Mucus plug A Evaluation of Basement Membrane Permeability Tc99m DTPA aerosol Neoplastic disease F-18 FDG Left lower lobe lung tumor (NSCLC) Preoperative Quantitation Summary and conclusions     Nuclear medicine has a complementary role to other imaging modalities in the diagnosis and follow up of chest diseases. Pulmonary embolism continued to be underdiagnosed. Till further development, proper utilization of V/Q scans along with the DVT tests and Spiral CT solves most diagnostic problems and decreases the need for angiograms. It is particularly important in the screening and follow up of PE, certain inflammatory diseases, and diagnosis and follow up of lung cancer. Thank you