Part 1 Ventilation-Perfusion Lung Scan


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Part 1 Ventilation-Perfusion Lung Scan

  1. 1. Lung Scan & Rdn. VenographyJiraporn Sriprapaporn, M.D.Nuclear MedicineSiriraj HospitalMahidol UniversityThailandCopy Right By J Sriprapaporn
  2. 2. Contents-2 parts Part 1. V/Q Lung scansPart 2. Radionuclide venography Anatomy Technique Physiology Indications Mechanism Interpretation Part 1-Lung Scan_J SRIPRAPAPORN
  3. 3. PART 1
  4. 4. Respiratory SystemPerfusion lung scan: Tc-99m MAAVentilation lung scan: Xe-133, Tc-99maerosol, TechnegasMucociliary clearance: Tc-99m HSALung epithelial permeability: Tc-99mDTPA Part 1-Lung Scan_J SRIPRAPAPORN
  5. 5. AnatomyRight lung & left lungBronchopulmonarysegments(artery, vein, & bronchus)Right Lung: 3 lobes;RUL,RML, & RLLLeft Lung: 2 lobes; LUL(Lingular segments) & LLL Part 1-Lung Scan_J SRIPRAPAPORN
  6. 6. Bronchopulmonary Segments1. RUL 1. LUL Anterior Anterior Apical Apico-posterior Posterior Lingular : Superior2. RML : Inferior Medial Lateral 2. LLL3. RLL Superior Superior Anterior basal Anterior basal Lateral basal Lateral basal Posterior basal Posterio basal Part 1-Lung Scan_J SRIPRAPAPORN
  7. 7. Blood Supply2 Systems: Pulmonary arteries: 95% Bronchial arteries: 5% Part 1-Lung Scan_J SRIPRAPAPORN
  8. 8. PhysiologyAIR Respiratory tract: trachea--bronchi-bronchioles alveoliFunction: Gas exchangeDistribution of Q & V from apex to base is uneven inthe upright position (gravity effect)Gravity effects the distribution of both Q & V (affectsperfusion > ventilation) BOTTOM TOP Part 1-Lung Scan_J SRIPRAPAPORN
  9. 9. Ventilation & Perfusion Distribution Modified from West, J.B., Ventilation/Blood Flow and Gas Exchange, Oxford, 1977. Part 1-Lung Scan_J SRIPRAPAPORN
  10. 10. Effects of Gravity (Upright Position)APEX VENTILATION PERFUSION V/Q RATIOBASE 1.5-2 folds 3-5 folds Part 1-Lung Scan_J SRIPRAPAPORN
  11. 11. PathophysiologyVentilation abnormality redistribution ofpulmonary perfusionHypoventilation reflex vasoconstrictionhypoperfusionAcute hypoperfusion rarely produceshypoventilation or minimal; not clinicallysignificant Part 1-Lung Scan_J SRIPRAPAPORN
  12. 12. Lung ScanPERFUSION LUNG SCAN (Q) Tc-99m MAAVENTILATION LUNG SCAN (V) Xe-133, Xe-127, Kr- 81m Tc-99m DTPA/ phytate aerosol Technegas Part 1-Lung Scan_J SRIPRAPAPORN
  13. 13. Indications of V/Q Lung Scan Acute pulmonary embolism* Pulmonary hypertension Prior to thoracic surgery Right-to-left shunt Part 1-Lung Scan_J SRIPRAPAPORN
  14. 14. Pulmonary EmbolismMost important complication of DVT Symptomatic, fatal* Asymptomatic (silent)Origin: Leg DVT (70-80%) Part 1-Lung Scan_J SRIPRAPAPORN
  15. 15. DIAGNOSIS OF PULMONARY EMBOLISMClinicals : Inaccurate (dyspnea, chest pain,hemoptysis)Lab tests : D-dimerArterial Blood Gases: Hypoxemia, A-AgradientECG : Classic S1Q3T3 patternCXR : Normal or mild abn (*R/O otherdiseases)V/Q lung scan : V/Q mismatched defectsCTPA (CT Pulmonary Arteriography)Pulmonary Angiography*** Gold standardOthers: MRA Part 1-Lung Scan_J SRIPRAPAPORN
  16. 16. Clinical Diagnosis of PESymptoms: WELLS SCORE Pretest clinical probability assessment. [Wells PS, Clinical Triad: et al. Thromb Haemost. 2000 Mar;83(3): Dyspnea 416-20.] (shortness of breath), pleuritic chest pain, hemoptysis Dyspnea, tachypnea, cough, chest pain, cardiac arrythmia, syncopeSigns: Increased HR, AF, RR, hypotension, pleural rub, P2 Part 1-Lung Scan_J SRIPRAPAPORN
  17. 17. Part 1-Lung Scan_J SRIPRAPAPORN
  18. 18. Chest Radiograph (CXR)Atelectasis and/or parenchymal opacity(51%)Pleural effusion within the affectedhemithorax (35%)Fleischners sign (regional oligemia in thepresence of an ipsilateral enlarged PA)Westermarks sign (local pulmonary oligemia,11% of hemithoraces with PE)Hampton’s hump (a wedge-shaped pleuralbased density, 23% of hemithoraces with PE) Part 1-Lung Scan_J SRIPRAPAPORN
  19. 19. D-dimer Fibrin degradation product Sensitivity 90-95%, NOT Different techniques Different results ! specific ! High NPV; negative results with ELISA tests effectively rule out DVT or PE.•The diagnostic yield of D-dimer relies on its specificity, which variesaccording to patient characteristics.•The specificity of D-dimer in suspected PE decreases steadily withage and may reach 10% in patients above 80 years.81•D-dimer is also more frequently elevated in patients withcancer,82,83 in hospitalized patients84 and during pregnancy.85,86European Heart Journal 2008 29(18):2276-2315 Part 1-Lung Scan_J SRIPRAPAPORN
  20. 20. Multidetector Pulmonary CTA CTPA showing multiple filling defects of principal branches of the pulmonary arteries, due to acute and chronic PE. Rad. Exposure CTPA = 8-10 mSv V/Q = 2 mSv Sensitivity of CTA = 83 %, specificity = 96 % [Stein PD & PIOPED II_NEJM 2006] Part 1-Lung Scan_J SRIPRAPAPORN
  21. 21. Figure 1 A diagnostic algorithm for clinically suspected deep veinthrombosis or pulmonary embolism Use of CUS with suspected DVTand of MDCT angiography with PE. CUS=compression ultrasonography. Samuel Z Goldhaber , Henri Bounameaux Pulmonary embolism and deep vein thrombosis The Lancet Volume 379, Issue 9828 :2012;1835 - 1846 Part 1-Lung Scan_J SRIPRAPAPORN
  22. 22. Table 2. Performance of some tests or diagnostic algorithms to rule in or rule out PE Likelihood ratio (95% CI)To rule in PEHigh-probability V/Q lung scintigraphy 18·3 (10·3–32·5)Positive CTA 24·1 (12·4–46·7)Positive proximal vein CUS of the leg 16·2 (5·6–46·7)To rule out PENormal or near normal ventilation perfusion lung 0·05 (0·03–0·10) scintigraphyNegative CTA (mainly single detector) 0·11 (0·06–0·19)Negative CTA and proximal vein CUS of the leg 0·04 (0·03–0·06)Negative proximal vein CUS of the leg 0·67 (0·50–0·89)Quantitative ELISA D-dimer assay less than 500 μg/L 0·08 (0·04–0·18) Goldhaber SZ 2012 Part 1-Lung Scan_J SRIPRAPAPORN
  23. 23. Part 1-Lung Scan_J SRIPRAPAPORN
  24. 24. Perfusion Lung Scan: PrincipleTracer: Tc-99m MAA, particle size=10-30 uMechanism: Capillary blockade -lodged in precapillaryarterioles in proportion to regional blood flowNumber of particles: Minimum = 100,000 Optimum = 200,000-600,000About 1/1000 ( 0.1 %) capillaries are blockedBiological T 1/2 in the lungs = 2-4 hr RE system Defects from PE // bronchopulmonary segments Part 1-Lung Scan_J SRIPRAPAPORN
  25. 25. Reduced Number of Particles Injected Pediatric patients Suspected or known Rt-to-Lt shunt Severe pulmonary hypertension Prior pneumonectomy Single lung transplant 100,000 to 200,000 particles Part 1-Lung Scan_J SRIPRAPAPORN
  26. 26. Perfusion Lung Scan: Techniques Critical organ = lungsDose: Tc-99m MAA 3-5 mCiInjection: in supine positionม avoidinjecting via the indwelling catheter portcontaining a filterDo not draw blood into syringe; “hot spots” in Q lung scan***Static planar images 6-8 views, 500 kctsSPECT imaging Part 1-Lung Scan_J SRIPRAPAPORN
  27. 27. Multiple hot spots in Q lung scan Part 1-Lung Scan_J SRIPRAPAPORN
  28. 28. Ventilation Lung Scan: PrincipleGas: most physiologic !Particles: smaller size deeper!Tracers Inert gas: 133Xe, 127Xe, 81mKr Aerosol* (0.5 u): 99mTc-DTPA/ phytate Technegas: Tc-99m aerosol particle size: 0.02-0.2um Part 1-Lung Scan_J SRIPRAPAPORN
  29. 29. Ventilation Agents Xe-133 Xe-127 Kr-81m Tc-99m Technegas/ radioaerosol PertechnegasT1/2 5.3d 36.4d 13s 6h 6hγ energy 80 203 190 140 140Status Gas Gas Gas Aerosol Gas-like (0.5-3 um) (0.02-0.2 um)Cost Low High High Low HighBefore/After Q B A A B BscanMultiple V N N Y Y Y Part 1-Lung Scan_J SRIPRAPAPORN
  30. 30. TECHNEGAS vs PERTECHNEGASBurning 99mTcO4- in a Burning 99mTcO4- in a carboncarbon crucible at high crucible at high TempTemp Ultrafine radiolabeledUltrafine radiolabeled aerosol (0.02-0.2um)aerosol (0.02-0.2um) Is purged with 5%O2 + 95% argonIs purged with 100% More penetrate alv epithelialargon membraneLittle transalveolar or Shorter residence time inmucociliary Clearance the lungLonger residence time in Tbio = 6-10 minthe lungTbio = 6 hr. Part 1-Lung Scan_J SRIPRAPAPORN
  31. 31. Ventilation Lung Scan: TechniquesPatient preparation: NonePatient cooperation: YesTechniques: Inhalation, upright position is preferred. Part 1-Lung Scan_J SRIPRAPAPORN
  32. 32. Xe-133 Ventilation Lung Scan Single view-3 phases: Washin-Equilibrium-Washout Part 1-Lung Scan_J SRIPRAPAPORN
  33. 33. Xe-133 Ventilation Lung ScanSingle view, 3 phases: Washin Equilibrium Washout : most sensitive to diagnose obstructive airway diseaseXenon is fat soluble uptake in the liverrefers to fatty liver. Part 1-Lung Scan_J SRIPRAPAPORN
  34. 34. Radio-aerosol Ventilation Lung Scan O2• Imaging of multiple views• Relatively large particles centralairway deposition ! Part 1-Lung Scan_J SRIPRAPAPORN
  35. 35. Radio-aerosol Ventilation Lung ScanTc-99m DTPA aerosol can cross alveolar capillarymembrane shorter residence time ascompared to Tc-99m sulfur colloid aerosol. [halftime is about 1 hr.]Only 2-10% of administered radioactivity goes tothe lungs. [30 mCi 1-2 mCi]Central deposition of the radioactivity is commonin COPD. Part 1-Lung Scan_J SRIPRAPAPORN
  36. 36. TECHNEGASPart 1-Lung Scan_J SRIPRAPAPORN
  37. 37. Technegas Ventilation Scan• Ultrafine particles• Ideal for ventilation lung SPECT Part 1-Lung Scan_J SRIPRAPAPORN
  38. 38. Figure 1. Normal V/Q SPECT. using Technegas and 99mTc-MAA are aligned and displayed in transverse, coronal and sagittal planes Roach PJ, et al SNM08Part 1-Lung Scan_J SRIPRAPAPORN
  39. 39. Interpretation of Lung Scan1. Pretest clinical probability2. Perfusion Lung Scan (Q)3. Ventilation Lung Scan (V)4. CXR (within 12-24 hrs) Part 1-Lung Scan_J SRIPRAPAPORN
  40. 40. Normal Lung ScanUniform distributionof the radioactivityNo V/Q defect Part 1-Lung Scan_J SRIPRAPAPORN
  41. 41. Abnormal Lung Scan1. Nonuniform distribution2. Perfusion and/ or ventilation defect Nonsegmental defect Segmental defect: wedged- shaped & pleural-based defect Large defect: > 75% of segment Moderate defect: 25-75% of segment Small defect: < 25% of segment Part 1-Lung Scan_J SRIPRAPAPORN
  42. 42. V/Q Match vs MismatchV/Q matched defect: Abn both Q & VV/Q mismatch defect: Abn Q, Normal V Pulmonary Embolism Part 1-Lung Scan_J SRIPRAPAPORN
  43. 43. Segmental Non-segmentalPulmonary embolism TumorsPulmonary infarct Pleural effusion Cardiomegaly Mediastinal or hilar adenopathy Pneumonia Bullae Metal artifacts Part 1-Lung Scan_J SRIPRAPAPORN
  44. 44. Non-PE Diseases/ConditionsPatchy distributionNonsegmental defectMatched V/Q defect(s)Causes eg. metallic artifact, enlarged LN,tumor, heart, pneumonia, effusion Part 1-Lung Scan_J SRIPRAPAPORN
  45. 45. V/Q Matched AbnormalitiesCOPDBlebs, bullaePulmonary edema, CHFPleural effusionAsthmaPulmonary traumaMucous plugBronchogenic CA Part 1-Lung Scan_J SRIPRAPAPORN
  46. 46. V/Q Mismatches: Causes Acute PE Previous PE Bronchogenic carcinoma Vasculitis Previous radiation therapy Pulmonary vascular anormalies Part 1-Lung Scan_J SRIPRAPAPORN
  47. 47. Interpretation of Acute PE “PIOPED CRITERIA” Normal R/O significant PE !- likelihood of PE < 5% Very low probability: < 10% Low probability : < 20% Intermediate : 20-80% High probability: > 80%. At least 2 large segmental mismatched V/Q defects, negative CXRPIOPED " The Prospective Investigation of Pulmonary Embolism Diagnosis " Part 1-Lung Scan_J SRIPRAPAPORN
  48. 48. PIOPED PIOPED I V/Q Lung scan" The Prospective Investigation of Pulmonary Embolism Diagnosis “ Used pulmonary angiogram as a gold standard. The criteria were developed in late 1983 The largest study of accuracy of lung scan in the Dx of acute PE 6 medical centers in U.S.A. PIOPED II CTA PIOPED III MRA Part 1-Lung Scan_J SRIPRAPAPORN
  49. 49. Original PIOPED CriteriaHigh Probability: > 2 large segmental perfusion defects without corresponding ventilation or roentgenographic abnormalities or substantially larger than either matching ventilation or CXR abnormality. > 2 moderate segmental perfusion defects without corresponding ventilation or roentgenographic abnormalities and 1 large mismatched segmental defect. > 4 moderate segmental perfusion defects without ventilation or CXR abnormalities.Intermediate probability (indeterminate): Not falling into normal, very-low-, low-, or high-probability categories. Borderline high or borderline low. Difficult to categorize as low or high.Low probability: Nonsegmental perfusion defects Single moderate mismatched segmental perfusion defect with normal CXR Any perfusion defect with a substantially larger CXR abnormality. Large or moderate segmental perfusion defects involving no more than 4 segments in 1 lung and no more than 3 segments in 1 lung region with matching ventilation defects either equal to or larger in size and chest roentgenogram either normal or with abnormalities substantially smaller than perfusion defects. >3 small segmental perfusion defects with a normalVery low probability: <3 small segmental perfusion with a normal CXR.Normal: No perfusion defects NOTE:CXR=chest roentgenogram. JAMA 1990 Part 1-Lung Scan_J SRIPRAPAPORN
  50. 50. V/Q Lung Scan for Detection of PE on PAG Sensitivity SpecificityProbability Biello McNeil PIOPED Biello McNeil PIOPED PPVHigh 57 53 41 90 91 97 81%High/Interm. 69 61 82 75 79 52High/Interm. 97 98 98 51 51 10 /Low NB. High number of intermediate prob., 39% of the total population studied (364 of 931), while 68% of the subjects were inpatients. [Freeman LM SNM 2008] [Worsley DF et al. Radiologic Clinics of N America 1993] Part 1-Lung Scan_J SRIPRAPAPORN
  51. 51. V/Q Lung ScanHigh prob NPV = 91% PPV = 81% for all types of Pts PPV = 91% for Pts without prior PE PPV = 74% for Pts with prior PELow prob NPV = 84% Low prob VQ +ve PE in 15% of Pts. Thus, should not misinterprete low-prob lung scan as R/O PE Part 1-Lung Scan_J SRIPRAPAPORN
  52. 52. PPV of V/Q Lung Scan in Diagnosis of PE Clinical ProbabilityScan Category 80-100% 20-79% 0-19%High 95% 85% 83%Intermediate 71% 29% 14%Low 43% 16% 4%Normal/NN 0% 7% 2% [PIOPED JAMA 1990, Sostman HD Radiology 1994] Part 1-Lung Scan_J SRIPRAPAPORN
  53. 53. Ventilation-Perfusion Scintigraphy in the PIOPED Study. Part II. Evaluation of the Scintigraphic Criteria and Interpretations we recommend that 3 criteria should be reconsidered:1. A single moderate perfusion defect is appropriately categonzed as intermediate, rather than as low probability.2. Extensive matched V/Q abnormalitiesare appropriate for low probability, provided that the CXR is dear. Single-matched defect may be better categonzed as intermediate probability. [small number of cases].3. 2 segmental mismatches may not be the optimum threshdd for high probability, and in some cases should be considered for intermediate probability. [small number of cases] Gottschalk A, et al. J NucIMed1993;34:1119-1126 Revised PIOPED V/Q Scan Criteria Part 1-Lung Scan_J SRIPRAPAPORN
  54. 54. Ventilation-Perfusion Scintigraphy in thePIOPED Study. Part II. Evaluation of theScintigraphic Criteria and Interpretations Part 1-Lung Scan_J SRIPRAPAPORN Gottschalk A, et al. J Nucl Med 1993;34:1119-1126 PMID: 8315488
  55. 55. Revised paper_by Sostman Radiology 1994Part 1-Lung Scan_J SRIPRAPAPORN
  56. 56. AIM: To compare original, revised PIOPED & gestalt interpretation.RESULTS: The gestalt probability estimate was the most accurate for assessing the likelihood of PE. [area under the ROC curve 0.836] The revised PIOPED criteria (area under the ROC curve = 0.753) were more accurate than the original PIOPED criteria.CONCLUSION: The revised PIOPED criteria are more accurate than the original PIOPED criteria. Experienced readers of lung scans can achieve highest accuracy Sostman HD Radiology 1994; 193:103-107 Part 1-Lung Scan_J SRIPRAPAPORN
  57. 57. Lung Scan v4_SNM Guideline Mar 2012Part 1-Lung Scan_J SRIPRAPAPORN
  58. 58. TRIPLE MATCHDef: a matching perfusion, ventilation,and CXR abnormalityUpper & middle lung zones =Very low probof PE (4%) [Stein PD & Gottschalk A. RadioGraphicsJanuary 2000:20;99-105]Lower lung zone = Intermediate prob of PE(33%) [Worsley DF, Alavi A. J Nucl Med 1995; 36: 2380-2387 Worsley DF, et al. J Nucl Med 1993; 34: 1851-1853] Part 1-Lung Scan_J SRIPRAPAPORN
  59. 59. STRIPE SIGN"Stripe Sign" = A thin line (stripe) of activity (perfusion) at the pleural surface of a Q defect.The finding is associated is likely related tospared perfusion in the cortex of the lung[Sostman HD, Gottschalk A. Radiology 1992 ]"Stripe Sign" is suggested to indicate verylow probability = 7% of lung zones with thestripe sign had PE present on PAG in thePIOPED study [Gottschalk A, et al. J Nucl Med 1993] Part 1-Lung Scan_J SRIPRAPAPORN
  60. 60. Low prob misleading due to sig. PE prevV/Q Lung Scan Classification Stein PD & Gottschalk A. RadioGraphics January 2000:20;99-105 Part 1-Lung Scan_J SRIPRAPAPORN
  61. 61. Stein PD & Gottschalk A. RadioGraphics January 2000:20;99-105Criteria for Very-low Probability PPV < 10 %Interpretation of VQ Lung Scans No. of Patients, Criterion No. of Cases Lungs, or Lung PPV(%) of PE Zones or Regions Nonsegmental perfusion 8 103* 8 abnormality Q defect smaller than 3 40* 8 corresponding radiographic defect Matched V/Q defects in 2 or 3 1 30* 3 zones of a single lung (normal radiograph) 1-3 small segmental Q defects 1 68† 1 Triple matched defect in the 1 27‡ 4 upper or middle lung zone Stripe sign 6 85§ 7 *Individual lungs were evaluated. †Patients were evaluated. ‡Lung zones Part 1-Lung Scan_J SRIPRAPAPORN were evaluated §Lung regions were evaluated.
  62. 62. Causes of Decreased Perfusion to One LungPulmonary agenesis or stenosisSwyer-James syndromeEmbolusPneumothoraxMassive pleural effusionMediastinal fibrosisTumor Part 1-Lung Scan_J SRIPRAPAPORN
  63. 63. Typical Scintigraphic Findings For PEMultiple segmentalperfusion defectsNormal ventilationUsually normalCXR“Mismatched V/Qdefects” Part 1-Lung Scan_J SRIPRAPAPORN
  64. 64. Resolution of Q Defects in Acute PEFirst 2 weeks rapid resolution, then slowerover the next 3 Mo33% of Pts with major emboli have perfusiondefects beyond 12 MoThe resolution is slower with increasing age &in the presence of cardiovascular disease (Tom& Wagner 1967)15-35% of Pts have recurrent PE with in thefirst yr. Part 1-Lung Scan_J SRIPRAPAPORN
  65. 65. Resolution of Perfusion Defect Q Defect 2 Wk 3 Wk 4 Wk Recover Improve 4 Mo 4 MoSmall 40% 67% 75%Moderate 30% 38% 51%Severe 20% 20% 70%Note: Small: <15%, Moderate 15-30%, Severe >30% reduced pulmonary bloodflow (Tom & Wagner 1967) Part 1-Lung Scan_J SRIPRAPAPORN
  66. 66. Pulmonary Embolism:Before & After Anticoagulant Rx Part 1-Lung Scan_J SRIPRAPAPORN
  67. 67. Acute Pulmonary EmbolismPerfusion-Ventilation lung scan ***Multiple mismatched V/Q defects (segmental),No radiographic abnormalityIncreasing no. of defects increasingspecificityPulmonary angiography is the gold standard.V/Q scan cannot DDx acute from chronic PE, soF/U scan to evaluate the lung status post Rx*** (Baseline for the new episode, if any) Part 1-Lung Scan_J SRIPRAPAPORN
  68. 68. Pulmonary HypertensionDef: Mean pulm arterial P > 25 mmHgCauses of PHT: PPHT (idiopathic, chr thromboembolic, leftheart disease, pulm parenchymal disease)Primary PHT Idiopathic PHT, small vv., obliterative Dx by exclusion criteria Lung scan: Nonsegmental patchy Q defectThromboembolic PHT Large vv TreatableV/Q lung scan can help Dx thromboembolic PHT (found <5% of PHT cases) Sen > CTA; sen > 96%, spec 95%, accuracy 95% Part 1-Lung Scan_J SRIPRAPAPORN
  69. 69. PE in ThailandPalwatwichai A, et al. J Med Assoc Thai. 2000Retrospective review of 49 patients diagnosedas PE in Phramongkutklao Hosp. between1994 and 1998The mortality rate was 10%.Chronic thromboembolic pulmonary HT wasdiagnosed in 12% of the patientsHigh-probability VQ lung scan and DVT weredemonstrated in 93% and 55%, respectively. Part 1-Lung Scan_J SRIPRAPAPORN
  70. 70. PE in ThailandPrevalence of pulmonary embolism inpatients with deep venous thrombosis(Mangkharak et al.)Prospective study of 48 cases with provenleg DTV 12 cases (25%) had high-prob lung scan 7 cases (58%) - No resp symptom (asymptomatic PE) 5 cases (42%) - with resp symptom (symptomatic PE) Part 1-Lung Scan_J SRIPRAPAPORN
  71. 71. V/Q Lung Scan for Dx PE ADVANTAGES VS DISADVANTAGESSimple, noninvasive, Not widely availablesafe, and economical Minimal radiationHigh specificity (98%) Low sensitivity (41%)esp. increasing no. of Limitation in abn CXRdefects V/Q scan cannot DDxThe usefulness is well acute from chronic PEdocumented. need F/U scan Part 1-Lung Scan_J SRIPRAPAPORN
  72. 72. Is Follow-up Lung Scan Useful ?Because resolution of Q defect may not be complete,depending on defect size, duration, also Pt’s age &underlying cardiovascular diseases (Tom & Wagner1967) [33% of Pts with major emboli have perfusiondefects beyond 12 Mo]And 15-35% of Pts have recurrent PE with in the firstyr.Since VQ lung scan cannot DDx new or old emboliF/U V/Q scan at least at 3 Mo is useful as thebaseline for the next episode. (slower resolutionoccurs after 3 Mo) That’s why we need F/U lung scan ? Part 1-Lung Scan_J SRIPRAPAPORN
  73. 73. Part 1-Lung Scan_J SRIPRAPAPORN
  74. 74. Applications for Non-embolic Lung DisordersRight-to-left shunt ***Prior thoracic surgery: Lung cancer,Other lung diseasesLung transplantationInflammatory lung diseasesOthers Part 1-Lung Scan_J SRIPRAPAPORN
  75. 75. Right-to-Left ShuntIntracardiac shuntIntrapulmonary shunt Through pulm AV fistulas Tiny abn, difficult to demonstrate by angiography Produce hypoxemia, & asso with significant intraop. & PO. risk Relative C/I to liver transplant Part 1-Lung Scan_J SRIPRAPAPORN
  76. 76. Right-to-left Shunt Systemic Circulation Part 1-Lung Scan_J SRIPRAPAPORN
  77. 77. Lung Scan in Rt-to-Lt Shunt Presence of Tc-99m MAA in the systemic circulation; brain & kidneys Technique: Limited MAA particles. Part 1-Lung Scan_J SRIPRAPAPORN
  78. 78. Prior Thoracic SurgeryQuantitative lung function studyGeometric mean: √CANT . C POSTEquivocal lung function test (eg. FEV1, FVC)To evaluate regional lung function andpredict residual lung function post surgicalresection Lung cancer Other lung diseases Part 1-Lung Scan_J SRIPRAPAPORN
  79. 79. QuantitativeLung Function Study FIGURE 12. Quantitative perfusion scan Large perfusion defect from tumor on posterior image (arrow). Left lung contributes 30.6% and right lung 69.4% of total pulmonary function (arrowheads). Hence, it is anticipated that removal of left lung will result in decrease of approximately 30% of total pulmonary function. JNMT March 2009 vol. 37 no. 1 1-13 Part 1-Lung Scan_J SRIPRAPAPORN
  80. 80. Wells PS. Pulmonary embolism: a clinicians perspective. Semin Nucl Med. 2008 Nov;38(6):404-11........ Diagnostic strategies should include pretest clinicalprobability,D-dimer assays, and imaging tests.Approaches that use CTPA or V/Q scanning appear equally safe, buteach approach hasadvantages and disadvantages that should beappreciated to provide the best care.Importantly, patients at low risk with a negative D-dimer can avoidimaging testsV/Q scanningmay be more appropriate in premenopausal women,in those with renal dysfunctionor diabetes, in those with knowncontrast allergies, and perhaps in patients withknown familyhistory of breast cancer. Part 1-Lung Scan_J SRIPRAPAPORN
  81. 81. Prof Leonard M. FreemanMontefiore Medical CenterAlbert Einstein College of MedicineBronx, New York •VQ Scan as a primary examination •VQ scan as a F/U study 1/4 Part 1-Lung Scan_J SRIPRAPAPORN
  82. 82. VQ Scan as a primary examinationDrawbacks with using MDCTA for Suspected1. Contrast-related Contrast Allergy Nephrotoxicity2. Instrument-related Claustrophobia Obesity3. Radiation exposure-related Children Pregnant women-fetus Young women-breast tissue 2/4 Part 1-Lung Scan_J SRIPRAPAPORN
  83. 83. VQ scan as a F/U studyIt is most beneficial to follow all positive CT studies with abaseline V/Q study for the purpose of long-term follow-up. DDx old vs new clot facilitate such importantdecisions.A baseline V/Q study should be routinely performed inpatients with DVT since the incidence of silent PE is about38% or greater.In a DVT patient who has been anticoagulated and,subsequently, presents with suspected PE judge whetherthe embolus has occurred before or after the start of theanticoagulation. If the PE was present at the time of DVT diagnosis, continuation of anticoagulant therapy will suffice. (be sufficient) If the latter IVC ‘‘umbrella’’ procedure may be warranted. 3/4 Part 1-Lung Scan_J SRIPRAPAPORN
  84. 84. Conclusion1. It is the responsibility of the imaging physician to be knowledgeable about the relative value and the benefit-to-risk ratio of each procedure to properly advise the referring physician.2. Most medical centers do not offer ‘‘after hours’’ nuclear medicine services on nights and weekends while there is 24-h ready availability of CT scanners prefer MDCT3. It is my belief that a plain CXR can be useful to determine which procedure should be performed * Normal or near-normal CXR V/Q scan * Abnormal CXR MDCTA.4. It also is the inherent responsibility of all radiologists and NM physicians to educate our referring clinicians about the excessive radiation exposure associated with MDCTA, particularly to the female breast. 4/4 Part 1-Lung Scan_J SRIPRAPAPORN
  85. 85. SummaryMultidetector CTA and V/Q lung scintigraphy are bothexcellent imaging examinations to evaluate patients withsuspected PE.Because of the much greater radiation exposure,particularly to the female breast, associated with CTA, itis desirable to use V/Q imaging when possible.The major problem causing difficulty in interpreting V/Qstudies is underlying pulmonary disease, such aspneumonia, significant atelectasis, pleural effusions, andchronic obstructive lung disease. If abnormal CXR,directing to a CTA.Most importantly, it is the responsibility of the imagingphysician to be knowledgeable about the relative valueand the benefit-to-risk ratio of each procedure toproperly advises the referring physician. Part 1-Lung Scan_J SRIPRAPAPORN
  86. 86. Well’s Criteria for PE: Program Calculation Part 1-Lung Scan_J SRIPRAPAPORN
  87. 87. Suggested ReadingEssentials of Nuclear Medicine ImagingThe Requisites: Nuclear Medicine Part 1-Lung Scan_J SRIPRAPAPORN
  88. 88. Continue for part 2. Radionuclide Venography