Nuc Med - Nuclear Medicine Nuclear Techniques in...

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Unformatted text preview: Nuclear Medicine Nuclear Techniques in Pulmonology Single most important application of Single pulmonary scintigraphy: Evaluation of suspected PE Other indications – Quantitative analysis of relative lung perfusion before lobectomy/pneumonectomy – ARDS VENTILATION SCINTIGRAPHY VENTILATION Radiopharmaceuticals Radioactive gases Radioactive Xe133 (most common) Xe127 Kr81m Xe133: t1/2 – 5.27 days Relative low energy (81-Kev)of its photon Difficult to perform V scan after using Tc99m for Q scan ∴ V scan performed first in combined V/Q scan Radioaerosols DTPA (Tc99m Pentetate) Ideal aerosol size: 0.1-0.5μ Localize in alveoli without significant large airway deposition Protocol for xenon-133 ventilation scintigraphy Protocol Technique: Radioactive gas Technique: Patient preparation: None Dosage and route of admission – Xenon133:10 to 20mCi dosage by inhalation Procedure Procedure – Use a wide-field-of-view camera with a parallel hole, all purpose collimator and a 20% window centered at 81 keV – The patient is seated with the camera positioned in the posterior view – First breath: patient exhales fully and is asked to take a maximal inspiration and hold it long enough, if possible, to obtain 100k counts – Equilibrium: Obtain two sequential 90 sec images while the patient breathes normally – Washout: Obtain sequential 45 sec posterior image then left and right posterior oblique images and a final posterior image Sitting position better: full Dm excursion, easier to obtain oblique views Radio aerosols: Radio – DTPA Nebulized over several min.[25-75mCi] – Views obtained [similar to gas studies] PERFUSION SCINTIGRAPHY PERFUSION Tc99m labelled Human Albumin Microspheres (Tc99m HAM) Tc99m labelled macroaggregated albumin (Tc99m MAA) ↓ (Commonly used) Tc99m MAA: 10-30μ Clearance from lungs – Mech. degradation of particles to smaller size → Phagocytosed by RES after passing into systemic circulation T1/2 : 2-3 hrs Dose: 60,000-400,000 particles/dose Dose: PROTOCOL FOR TECHNETIUM-99M MACROAGGREGATED PROTOCOL ALBUMIN PERFUSION SCINTIGRAPHY Patient preparation and precaution Right-to-left shunts are a relative Right contraindication Pregnant women: Adjust dosage and observe Pregnant requirement for a minimum of 60,000 particles Pulmonary hypertension or pneumonectomy: Pulmonary Reduce number of particles to 60, 000 Dosage and Route of Administration Tc-99 MAA: 4 mCi (148 MBq) adult dosage Tc Intravenous administration over several Intravenous respiratory cycles with the patient supine Procedure Procedure Use a wide-field of-view gamma camera with a Use low energy high-resolution or all-purpose collimator and a 20% window centered at 140keV Obtain anterior, posterior, right lateral, left lateral and right and left lateral posterior oblique images (anterior oblique images optimal) Obtain 500K to 750K counts/image Obtain Precaution Precaution – Avoid drawing blood into syringe ↓ Avoid spurious “Hot Spots” – Agitate syringe before inj. ↓ Avoids setting out and aggregation of particles APPEARANCE OF NORMAL APPEARANCE SCINTIGRAMS Ventilation Scan Wash in image equilibrium phase washout phase : Homogenous distr. of Xe133 : Homogenous : Progressive/uniform ↓ in activity from lung Aerosol Study Aerosol Distr. Similar to gas study Perfusion Scan Perfusion Normal/healthy individual Normal/healthy – Homogenous uniform distr. Extra pul. Activity: Extra – Positive– Rt. – Lt. shunt – Radiopharmaceutical contaminant in preparation PULMONARY EMBOLISM PULMONARY V/Q Mismatch Concept V/Q match - both scintigrams abnormal - defect of equal size V/Q mismatch - Abnormal perfusion in an area V/Q of normal ventilation or much larger perfusion abnormality then ventilation defect Terminology for V/Q scan Terminology Segmental defect Segmental – Characteristically wedge shaped and pleural based, segmental anatomy of the lung Large segmental defect Large >75% of a lung segment Moderate segmental defect Moderate – 25%-75% of a lung segment Small segment defect Small – <25% of a lung segment Non-segmental defect Non – Not conform to segmental anatomy, not appear wedge shaped or neither conforms to segmental anatomy nor appears wedge shaped Causes of Non-segmental Defects Causes Tumors Pleural effusion Pleural Trauma Trauma Hemorrhage Bullae Bullae Cardiomegaly Mediastinal and hilar adenopathy Atelectasis Pneumonia Aortic ectasia or aneurysm Aortic Revised PIOPED Criteria High probability (>80%) Two or more large mismatched segmental perfusion defects or the equivalent in moderate or large and moderate mismatched defects PIOPED II V/Q Scan Criteria High Scan probability Two or more large mismatched segmental defects or the equivalent in moderate or large and moderate defect Intermediate Probability (20%-79%) One moderate to one half large mismatched segmental perfusion defects or the equivalent in moderate segmental perfusion defects Single matched V/Q defect with clear chest radiograph radiograph Difficult to categorize as low or high, or not described as low or high Intermediate-indeterminate scan probability One half to one and one half segmental equivalents, difficult to categorize as high, Multiple opacities with associated perfusion defects Low probability (<19%) Non-segmental perfusion defects Any perfusion defect with a substantially larger chest radiographic abnormality Perfusion defects matched by ventilation abnormality provided that there are a clear chest radiography and some areas of normal perfusion in the lungs Any number of small perfusion with a normal chest radiograph Low Scan Probability Low A single matched V/Q defect More than three small segment lesions Probable pulmonary embolism mimic: one lung mismatched (without) with absent perfusion, solitary lobar mismatch Mass or other radiographic lesion causing all mismatch, moderate-sized pleural effusion Marked heterogeneous perfusion Very low Scan probability Non-segmental lesion Perfusion defect smaller than radiographic lesion Two or more V/Q matched defects with regionally normal chest radiograph One to three small segmental perfusion defect Stripe sign present around the perfusion defect Pleural effusion of one third with no perfusion defect Normal No perfusion defect Normal perfusion Scan Normal No perfusion defect High probability scan : Likelihood of PE: High 80% (N) perfusion scan : Likelihood < 5% Accuracy – PIOPED trial : Specificity - 97% Sensitivity - 41% – Occurrence of PE in: Low probability – 12% : Normal study – 4% D/D of V/Q mismatch D/D Acute pulmonary embolism Acute Chronic pulmonary embolism Chronic Other causes of embolism (drug abuse, Other iatrogenic) Bronchogenic carcinoma (other tumors) Bronchogenic Mediastinal or hilar adenopathy with obstruction Mediastinal of pulmonary artery or veins Hypoplasia or aplasia of pulmonary artery Swyer-James syndrome Swyer Post radiation therapy Post Vaculities Vaculities – Chr PE: Most common cause of false +ve interpretation – Hilar mass compressing pul artery → mimics PE V/Q Match Abnormalities V/Q Chronic obstructive pulmonary disease Chronic Bronchitis and bronchiectasis Bronchitis Blebs and bullae Congestive heart failure Pulmonary edema Pulmonary Pleural effusion Pleural Asthma Asthma Pulmonary trauma, hematoma Pulmonary Inhalation injury Mucus plugs Mucus Bronchogenic carcinoma (other tumors) Bronchogenic PIOPED STUDY PIOPED 933 recruited 933 931 → V/Q scan 755 → Pul. Angio. 931 PE → 251 (33%) PE High probability 88% had PTE High Intermediate probability 33% had PTE Intermediate Low probability 12% had PTE Low Normal Scan excluded PE Normal [JAMA 1990; 263: 2753-59] [JAMA Systematic review and meta analysis of Systematic strategies for Dx of suspected PTE Roy PM et al Roy – 48 articles analyzed – 11004 pts with suspected PTE – 3329 pts had PTE (30% prevalence) – Mod. – High pre-test probability High Probability V/Q > 85% post test Spiral CT +ve probability CSG +ve – Low clinical probability – above results req. confirmation by Pul. Angio. Low – Mod clinical Probability Low – Negative quantitative D-Dimer test (<500μg/L) – Spiral CT –ve – CSG –ve – Normal/near normal lung scan <5% post test probability High clinical probability → above results req. High confirmation by Pul. Angio. BMJ 2005; 331: 259-63 BMJ V/Q scan & Helical CT in Suspected PTE V/Q Hayashino et al Meta analysis of Dx performance 12 article included 12 Pooled sensitivity for Helical CTPA – 86% Pooled Specificity – 94% Specificity V/Q scan – High probability V/Q Sensitivity 39% Specificity 97% Conclusion: Conclusion: Normal 98.3% 4.8% – Helical CT has greater discriminatory power than V/Q scan with (N) threshold to exclude PTE – Helical CT & V/Q scan with high probability – Similar discriminatory power in Dx. of PTE GALLIUM & OTHER AGENTS GALLIUM Use of Ga67 declined over last decade Use Reasons : Lack of specificity : Delay between injection and imaging time : Relatively poor imaging characteristics PET/SPECT has replaced Ga scans as tumor imaging agent of choice MECHANISM OF UPTAKE: MECHANISM TUMOR & INF./INFL. Gallium – 67 Citrate Gallium Used since 1869 Used Acts as Iron analogue Acts Transported in blood bound to transferrin Tumors: – ↑ transferrin receptors in malignant cells, ↑ Ga – transferrin binds to these receptors – Ga incorporated in intracellular lysosomes – ↑ Lactoferrin levels in lymphoma (Lactoferrin binds to Ga) Inflammation Inflammation – ↑ lactoferrin levels in leucocytes & abscess fluids ∴ ↑ Ga uptake in infl. conditions [Lactoferrin released by leucocytes & Bacteria] – Highly conc. in sub-acute/chr. inf./infl. than acute processes Normal Distr. – Liver/spleen/skeletal system/colon varying degrees: salivary / laccrimal glands, nasal region, genitalia – Excreted: bowels – 80% kidneys – 20% Study Performed Study – Ga67 IV 8-10mCi – Whole body/localized imaging after 24-48hrs – Imaging can be repeated upto 96-120hrs. Pt. Preparation Pt. – No dietary restr. – No BT/Gad MRI in previous 24hrs. : interfere with normal Ga67 distr. Thalium-201 Chloride Thalium Mech. Of uptake – – – Analogue of K+ uses ATP pump Co-transport mech. in tumor cells inv. K+, Na+, ClLeaky capillaries Mainly accumulates at sites of tumor Min. uptake in infl. focus Study performed – Tl201 IV 3-5mci – Imaging started at 20min. and continued to 60min. – Lymphoma, kaposi’s sarcoma ↓ – Delayed images Pt. Preparation Pt. – 4 hrs. fasting (to min. salivary and splanchinic uptake) – Avoid physical exertion for at least 4 hrs. (to min. skeletal muscle and cardiac uptake) – (N) uptake – liver/heart Clinical Application Clinical – Diff. between benign/malignant disease – Grade of malignancy – Response to therapy/Recurrence Technetium 99m Sestamibi Technetium – Useful identifying primary tumor: Parathyroid adenoma, Breast, lung, bone, brain – Uptake depends on blood flow/leaky capillaries/ ↑Permeability Neuroendocrine Imaging Radiotracers Neuroendocrine – Used for imaging Pheochromocytomas, carcinoid tumors, neuroblastoma and other neuroendocrine tumors – Carcinoid tumors: I123 MIBG – 80% sensitive – I123-MIBG :10mCi IV followed by whole body imaging at 24 hrs. Pt. Preparation Pt. – KI (2dr. BD) x 1-3 days – No dietary restr. Octreoscan Octreoscan – Tumors esp. endocrine – high density of somatostatin receptors – In111 labelled somatostatin analogue effectively localizes tumor – Tc99m depreotide (Neotect), somatostatin receptor binding agent helpful in evaluation of Pul. Nodules – 6mCi IV – Whole body imaging – 6hrs. & 24hrs. – Well hydrated Gallium in Cancer Gallium – Most avid uptake in lymphoma/Lung cancer/ sarcoma/melanoma Lymphoma – Staging Sensitivity Specificity HD 86-97% 100% NHL 86-92% 100% – Residual disease Ga Scan Vs Sensitivity 96% Specificity 80% CT thorax 68% 60% – Specificity reduced by inflammatory changes (benign activity lower than malignant activity more often B/L and symmetric) Tl201 Vs Ga67 Tl – Good tool to evaluate malignant bone lesions Sensitivity – 88% Specificity – 94% – Inferior to Ga in staging lymphoma Lung Cancer Lung – Ga has high affinity for lung cancer Sensitivity : 85 – 97% – Superseeded by FDG for tumor identification staging – Absence of FDG availability: Response to therapy – Neotect useful in SPN evaluation Sensitivity – 97% Specificity – 73% Mesothelioma Mesothelioma – Ga reliable for assessing extent of Pl. inv. Only when Pl thickening > 6mm Carcinoids Carcinoids – Don’t take up Ga, FDG – Octreoscan and I123 MIBG used – Useful for staging In summary In – With advent of PET ↓ – Role of Ga in staging response to therapy – Has reduced – Useful when there is no access to PET Inflammation/Infection Inflammation/Infection Ga uptake generally associated with cellular Ga infiltration rather then fibrosis Sarcoidosis: signs on Ga scan that suggest Dx – Lambda Sign: Rt. Paratracheal, B/L Hilar adenopathy resembles letter lambda – Panda Sign: Uptake in B/L lacrimal & parotid glands resembles panda bear Either or both of these patterns on Ga scan with Either symmetric B/L Hilar LNE or B/L interstitial opacities are highly sensitive & specific for sarcoidosis however, Ga scan in isolation 48% overall diagnostic Ga sensitivity Panda Pattern may be seen Panda – – – – – HIV Sjogren’s syndr. RA SLE Head & neck RT for lymphoma Uptake due to Uptake – ↑ Capillary permeability – In corporation by activated infl. cell Various studies: Sensitivity of Ga scan for Dx Various 60-90% with poor specificity Ga scan helpful in cases when Bx is necessary Ga for Dx but Pt. is a poor candidate for FOB→ extra thoracic site identification for safer Dx Bx Combination of negative Ga scan & Combination SACE levels virtually excludes the Dx of sarcoidosis Ga scan more sensitive than SACE in identifying pts. with active sarcoidosis Clinical scenarios in which Ga scan is useful: – Assisting in Dx of difficult cases esp. those with isolated extra-thoracic disease – Identify active sites for Bx – Differentiating active disease from fibrosis in a lung transplant candidate Drug toxicity & Radiation pneumonitis Drug Routine use not recommended May precede CXR changes May Useful in establishing Dx in difficult cases Useful Not very sensitive in Ac. Radiation Pneumonitis Not Infl./Occupational/Chr. Lung disease Ga uptake sec. to - Ac. Infl. Component - ↑Alveolar capillary permeability Asbestosis : Ga uptake +ve in pts. With (N) CXR Asbestosis HRCT +GA scan:Helpful when clinical exam, CXR, PFT equivocal CVD: Ga scan may provide estimation of location CVD: Ga of inflammation & help guide BAL/Bx ↓ Not routinely used Summary Summary – Ga scan sensitive indicator of non-infectious, infl. lung disease – However, not specific, inconvenient imaging necessitating multiple visits to Nuclear Med. Dept. Relegated to problem solving role rather than Relegated routine practice Infectious Disease Infectious TB TB – – High sensitivity for detection of active disease Helpful in diff. active disease from fibrosis Other pul. inf: Difficult situations where inf. not readily appearent (PUO) Ga scan preferred over WBC scan in leucopenic Ga pts., pediatric population AIDS Diffuse Ga uptake in PCP has high sensitivity (80Diffuse 96%) but poor specificity Negative Ga scan in pts. with (N) CXR has high Negative negative pred. value in excluding Pul. disease Not routinely in PCP w/u Not Reasons: Reasons: Poor specificity Poor Delayed imaging (24-48hrs) HRCT favoured (sensitivity-100% specificity-89%, accuracy-90%) Ga scan reserved for situations where sputum analysis/BAL/HRCT – Non-diagnostic, empiric therapy not preferred A negative Ga scan with abnormal CXR highly negative suggestive of Kaposi sarcoma as KS is not Ga avid CMV mimics PCP but may have accompanying CMV adrenal, lacrimal, colonic inv. Pul. & Parotid uptake (+) LIP Pul Pul. & skeletal uptake (+) actinomycosis/nocardia Summary Summary – Not used routinely – Used occ. in distinguishing active diseases from scarring or when there is no other source of infection apparent LUNG CANCER LUNG Single Photon Radionuclide Imaging in Lung Single Cancer Despite the emergence of PET – widely accepted Despite Interest remains in single photon techniques Interest ↓Because COZ Wide availability of single photon equipment Ga67 – Not useful in detecting lesions < 1.5cm Ga – False negative scan in upto 22% pts. of lung ca. High PPV, low NPV Specificity for med. staging – 38-100% ∴ No current role for characterization of SPN & staging of lung ca Tll201 T – – – Like Ga cannot detect lesions <2cm Poor imaging characteristics Not widely accepted in assessment of SPN Tc99m tetro fosmin, Tc99m – MIBI scan Tc – < 1cm lesions – Poor sensitivity – Poor to FDG-PET in primary tumor visualization & detecting med. lymph mode metastasis Somatostatin receptor imaging Somatostatin – High affinity somatostatin receptors (+) variety of malignancies including SCLC – Lower frequency of expression in NSCLC – NSCLC constitutes majority of lung cancer ∴ This may hamper detection of malignancy within SPN – However studies showed sensitivity of upto 96% in lung cancer detection PET in NSCLC PET Basics Basics – FDG is a glucose analogue – Facilitated transport into cells via glucose memb. transporter [GLUT-1 to GLUT-7] – Within the cells FDG ↓ Phosphorylation by hexokinase 2 deoxy-glucose-6- Phosphate (Accumulates as no further metabolism takes place) NSCLC NSCLC – Increase in GLUT-1, and GLUT-3 expression – ↑ glucose use by tumor cells – Upregulation of hexokinase levels, down regulation of glu-6 phosphatase ↓ – Deoxyglucose retention with in cells SPN SPN 20-50% malignant Existing diagnostic modalities Existing – Radiology : Benign etiology suggested by Prolonged stability smooth control Calcification: Central/diffuse/Laminated/ Popcorn – However, majority of SPN after CT, remain indeterminate – Dual energy CT/contrast enhanced dynamic CT Sensitivity : 98% Specificity : 58% Histologic sampling Histologic – Indeterminate lesions ↓ – Obtain tissue Bx FOB: cytology & Bx – ↑ yield for TTNB: TTNB: - central lesions - endobronchial component - Bronchus entering prox. part of lesion Better for – Peripheral lesion, Better – FOB not available Sensitivity – 71-100% complications – Pneumothorax (61%) 5-27% req. ICT – Haemorrhage Thoracoscopy Thoracoscopy – Peripheral lung lesions – Complications : Mean hospital stay 2.4-5.7 days : Duration of ICT: 1.8-3.3 days Open thoracotomy – No definitive Dx. inspite of all less invasive diagnostic procedures FDG PET FDG – Sensitivity – PPV – Accuracy : 83-100%, : 92.6%, : 91.3% Specificity NPV : 52-100% : 87% FDG-PET is more sensitive & Specific in FDG characterization of SPN than any other currently available non-invasive method Either semi-quantitative/visual methods used for Either diff. bet benign & malignant SPN Most common semi-quantitative measurement is standard uptake value [suv] SUV of 2.5 at 1hr used to diff. bet benign and SUV malignant SPN False positive cause of FDG are pred. False inflammatory in origin Causes of False-Positive Findings with FDG-PET for characterization Granulomas Histoplasmosis Tuberculosis Schwannoma Chronic inflammation Chronic Aspergillus infection Abscess Acute blastomycosis Sarcoidosis Cryptococcus neoformans Wegener’s granulomatosis Aggressive neurofibroma Coccidiodomycosis False negative: small size (0.5cm) well diff. malignancies (carcinoids, well diff. adeno ca, BAC) Current clinical algorithm for the use of FDG-PET in characterization of SPNs Low probability of malignancy SPN confirmed on CT Watch and Benign Negative – Wait pathology Serial radiology Intermediate Probability of malignancy Attempt Indeterminate of non diagnostic biopsy FDG High probability of malignancy Investigate & treat as lung cancer biopsy PET Positive Malignant malignant Accuracy of PET for Dx of Pul Nodules/Mass Accuracy Gould MK et al Meta analysis Meta 40 studies 40 1474 focal pul. lesion 1474 Sensitivity/specificity – 91.2% In current practice: Sensitivity-96.8% Specificity-78% Sensitivity In No diff. in Dx. accuracy of Pul nodules C/w No lesion of any size Conclusion: – Accurate non-invasive imaging test for Dx of Pul. Nodules/Mass lesion JAMA 2001; 285: 914-924 Summary of Major Studies on FDG-PET in Summary Characterization of SPN Studies between 1990-2001 Studies 2079 pts 73.1% malignant lesions Sensitivity - 95.9% Sensitivity Specificity – 79% Specificity PPV – 92.6% NPV – 87% NPV Accuracy – 92% Accuracy Seminars in Nucl. Med. 2002; 240-271 STAGING OF NSCLC STAGING Existing Staging Procedures CT – – – – – – – – Useful in T staging N stage esp. mediastinum inv. Node >1cm in short axis By using above criteria CT has sensitivity – 78% Specificity – 79% for LN mets CT may over/under stage upto 40% pts. Useful in detection of distant mets Cerebral CT: if clinical exam reveals focal neurodeficit on finding of disseminated disease If solitary lesion identified – Bx preferred in v/o If false positive (11%) Bone Scan: Skelatal mets identification Mediastionoscopy Mediastionoscopy – Inoperable cases – Large Med. LNE Complications – 23% False Neg. – upto 10% – TBNA Sensitivity – 53% Specificity – 99% Complications – Haemorrhage – Pneumomediastinum Other Modalities Other – MRI useful for staging med LNE – Useful in assessment of indeterminate adrenal masses FDG-PET Staging the Primary FDG – Poorly suited to assess the stage of primary tumor (T). – CT better suited → Reason: Better resolution, provides more anatomatic detail Staging the mediastinum Staging – – – Sensitivity : 83.3% Specificity : 92.2% False positive usually d/t inflammatory pathology Causes of False-Positive findings in FDG-PET thoracic Lymph node staging – – – – – – – – – – – Bronchiectasis Upper respiratory tract infection/bronchitis Rheumatoid disease Proximity of tumor to mediastinum Pneumoconiosis Anthracosis/silicoanthracosis Hyperplastic lymph node/reactive hyperplasia/active Inflammation/Nonspecific inflammation Aspergilloma with reactive nodes Active granulomatous disease Active inflammation due to poststenotic pneumonia False Positive → False Relatively infrequent, may result in denying a pt. potentially curative Sx ↓ ∴ Recommended: Invasive Sx staging False Negative False – Nodes immediately adjacent to primary tumor – 2 or more LN adjacent to each other but at diff. LN stations → PDG-PET not able to resolve them separately – Normal size nodes with microscopic foci of tumor Assessment of Distant Metastasis Assessment – Able to detect 94% distant mets – Superior in detection of distant mets c/w other modalities – FDG-PET relatively insensitive for cerebral mets Reason: High Background caused by normal cerebral FDG uptake [CT/MRI considered superior] – Osseous mets: Bone scintigraphy vs FDG-PET – Sensitivity 90% 90% – Specifity 66% 98% Adrenal mets: for indeterminate lesions Adrenal – Sensitivity 80% and Specificity 80% Hepatic mets Hepatic – Able to detect unsuspected hepatic mets – Characterizes the hepatic abnormalities identified on CT Management Change Management – Several studies have reported an overall management change between 24-40% Cost effectiveness Cost – Major potential for cost saving is via Minimizing invasive staging of mediastinum Minimizing Avoidance of inappropriate Sx in those with inoperable locally invasive or metastatic disease FDG-PET is most cost effective when performed on pts. With CT negative for nodal metastases with Bx to confirm PET positive results Current clinical algorithm for use of FDG-PET in staging of NSCLC PET Surgery Negative No malignant Proven or presumed NSCLC operable or equivocally operable on CT Nodes PET positive in mediastinum Mediastinoscopy Nodes No surgerychemotherapy radiotherapy Biopsy negative for metastatic malignancy PET positive for distant metastases Malignant Surgery (if mediastinum negative) Biopsy Biopsy positive for metastatic malignancy Palliation Test performance of PET and CT for Test mediastinal staging in pts. With NSCLC Meta analysis Meta 39 studies 39 1959 pts 1959 Mediastinal staging CT FDG-PET Mediastinal – Sensitivity – Specificity 61% 79% 85% 90% PET more sensitive & less specific where CT PET showed enlarged nodes [100% & 78%] than when CT showed no LNE [82% & 93%] Conclusion – FDG PET more accurate than CT for Med. Staging Ann. Intern. Med. 2003; 139: 879-92 Utility of Tc99m Depreotide C/W FDG-PET & Utility surgical staging in NSCLC Kahn D et al 166 pts Detection of malignant disease PET Tc99m depreotide – Sensitivity – Specificity 96% 71% 94% 51% FDG-PET correctly stage 55% of pts C/W Tc99m FDG depreotide (45%) Conclusion – Sensitivity equal for both modalities – Specificity superior for PET Chest 2004; 125: 494-501 Utility of PET in staging potentially operable Utility NSCLC Reed C et al 303 pts, 22 institutions underwent PET after 303 routine staging Detection of PET CT N1 42% 13% N2/N3 58% 32% NPV for Med. node – 87% NPV Mets identified in 6.3% Mets Conclusion: Conclusion: – PET prevents non-therapeutic thoracotomies – +ve finding confirmed by mediastinoscopy – Mets require confirmation by biopsy J Thorac Cardiovasc Surg 2003; 126: 1943-51 Delayed FDG-PET scan for Diff. between Delayed malignant and Benign lesions Nakamoto Y et al 47 pts suspected pancreatic Ca – PET scan 47 Malignant Benign 27 20 SUV at 2hrs. ↑22 lesions ↓17 lesions SUV cut off of 2.5 – 1 false –ve, 7 false +ve Dx accuracy – 83% Delayed FDG-PET scan at 2hrs post inj. May Delayed help diff. between benign and malignant lesions Cancer 2000; 89: 2547-54 Cancer Detection of Recurrent disease Detection – Sensitivity : – Specificity : 97-100% 61.5-100% False positive results – Radiation pneumonitis [preferable – wait for 6mths Atleast – 3mths after completion of RT before performing PET scan False positive uptake declines with time False ↓ ∴ Some role of repeating PET scan if false +ve suspected [curvilinear uptake S/o false +ve] PET IN NON-MALIGNANT PET THORACIC DISORDERS Pnemoconiosis FDG-PET studies revealed ↑ uptake ↑ uptake d/t infl. Cell – macrophages fibroblasts Specific radiotracer that localizes to fibroblasts Specific and not in infl. Cell: 18F-fluoroproline Fluoroproline – PET studies → ↑ uptake in early Fluoroproline fibrosis Infection/Inflammation Infection/Inflammation Infl. Cells at site of infl./inf. show ↑ FDG uptake Infl. Cells show lower level of FDG uptake C/W Infl malignant cells ↑ uptake is d/t – ↑ GLUT expression – Cytokines & growth factor ↑ affinity of GLUT to FDG Sensitivity: 92%, Specificity: 100% in infl./inf. Sensitivity: lesions AIDS AIDS – Major role of PET imaging – Identify correct location for further inv. Bx, Aspiration, or other modalities – Sensitivity & specificity of PET in localizing lesions in AIDS pts. 92% & 94% respectively FUO FUO – – – Useful tool in this setting Identifies lesions responsible for fever in >50% of pts. FDG-PET compares favourably with Ga67 studies in PUO evaluation – FDG-PET may replace Ga67 as it gives quicker results Sarcoidosis Sarcoidosis – Useful in Mx of Pts with sarcoidosis – CXR Ab. (N) ↑ACE levels with (N) PET → may remain well without t/t – Not useful in Dx as findings may be confused with lymphoma Monitoring disease process and response Monitoring to therapy – FDG-PET useful for this purpose in TB/Aspergillosis Alveolar echinococcosis /MAI Role in pleural disease Role Useful in Dx & Staging of malignant mesothelioma Useful Useful to determine whether there is malignant transformation of reactive pleural disease More accurate than CT to identify extent of disease, More stage of disease in mediastinum, detect occult extra thoracic metastasis FDG-PET can be use to diff. benign from malignant Pl. FDG thickening and for Dx & staging of mesothelioma Study can identify other focal area of metastasis or even primary in pts. with malignant Pl. effusion with unknown primary tumor Alternate diagnostic method to invasive tests in Alternate suspected malignant Pl. effusion esp. in pts. with equivocal findings on CT/Negative finding on pl. cytology after thoracocentesis ...
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