CT of the Chest

CT of the ChestCT of the Chest

Dorith Shaham, M.D.

Department of Radiology

Hadassah Medical Center

Indications for Chest CTIndications for Chest CT

• To evaluate abnormalities shown on CXR

• To demonstrate or exclude a suspected CXR abnormality

• To demonstrate an abnormality in a patient with a normal CXR

Types of Chest CTTypes of Chest CT

• Standard chest CT– Without IV contrast– With IV contrast

• CT-angiography– PCTA (r/o PE)– Coronary CTA

• HRCT• CT-guided intervention

– Biopsy– Pleural drainage

• Low-dose CT

IV contrastIV contrast

• Not used for pulmonary parenchimal abnormalities– Inherent high contrast

• Always used for CT-angiography• May be used for evaluation of

– Mediastinum – Hilum– Pleura

Metastatic Lung Ca Metastatic Lung Ca (Adenocarcinoma)(Adenocarcinoma)

Rt. Hilar mass and small pleural effusionRt. Hilar mass and small pleural effusion

Without IV contrast

Anterior Mediastinal Mass : Anterior Mediastinal Mass : Germ cell tumorGerm cell tumor

Without IV contrast With IV contrast

Chest CT Chest CT with IV contrastwith IV contrast

SVC syndrome

ThrombusVenous collaterals

CT-AngiographyCT-Angiography

Pulmonary Embolism:Pulmonary Embolism:Imaging ModalitiesImaging Modalities

• Chest X-ray

• V/Q scan

• Computed tomographyComputed tomography– Helical (spiral) CTHelical (spiral) CT

• MRI

• Pulmonary angiography: the “gold standard”

69- year old female with 69- year old female with shortness of breathshortness of breath

Ventilation-perfusion (V/Q) scanVentilation-perfusion (V/Q) scan

• Perfusion scan: distribution of blood flow– Macroaggregated human serum albumin (10-100

micron) labeled with Tc-99m

• Ventilation scan: distribution of alveolar ventilation– Radioactive inert gas: X-133

• V/Q mismatchV/Q mismatch: abnormal perfusion and normal ventilation

Interpretation of V/Q scanningInterpretation of V/Q scanning

• Probability stratification approach (based on the assumption that the only reason for performing a V/Q scan is to diagnose PE):– High probability– Intermediate probability/ indeterminate– Low probability– Normal

Prospective Investigation of Pulmonary Prospective Investigation of Pulmonary Embolism DiagnosisEmbolism Diagnosis (PIOPED) (PIOPED)

• Multi-institutional study conducted in the mid-80’s,

• Purpose: to determine the sensitivity and specificity of V/Q scan compared with pulmonary angiogram

• 933 patients with suspected PE – 931 had V/Q scan

– 755 had pulmonary angiography

• Study patients were followed clinically for 1 Y

PIOPED STUDYPIOPED STUDY

• High sensitivity of V/Q scan:

98% of patients with PE had abnormal scans (low, intermediate or high probability)

• Low specificity: 10%

• Non-diagnostic V/Q scans: 72%

CTPACTPA

• Direct visualization of clot

• Imaging of associated findings– Pulmonary infarction– Pleural effusion

• Imaging of alternative diagnosis

Pulmonary EmbolismPulmonary Embolism

Pulmonary Embolism Pulmonary Embolism with Infarctionwith Infarction

Atelectasis

Infarction

Pulmonary EmbolismPulmonary Embolism

Combined PCTA/CTVCombined PCTA/CTV

• No additional contrast injection

• Rapid examination

• Imaging of portions of the deep venous system that are inadequately imaged by Duplex (pelvic veins, adductor canal)

HL: Massive PE

HL: Bilateral DVT

PIOPED IIPIOPED II

• To determine the sensitivity, specificity, positive/negative predictive value of spiral CT for the diagnosis of PE.

• Reference for PE: various combinations of– V/P scan– Venous U/S– Pulmonary angiography– Contrast venography

PIOPED IIPIOPED II

• 824 patients with suspected PE

• CTPA alone:– Sensitivity: 83%– Specificity: 96%– PPV: 96% (concordant high/low clinical probability),

92% (intermediate clinical probability)

PIOPED IIPIOPED II

• Combined CTPA + CTV:– Sensitivity: 90%– Specificity: 95%

• Additional testing is necessary when clinical probability is inconsistent with imaging results

N Engl J Med 2006;354:2317-27

15-year old male with chest pain15-year old male with chest pain

Intramural hematoma

Pericardial effusion

Small right pleural effusion

Collateral blood flow

Coarctation of the aorta with enlarged internal mammary arteries

CT Coronary AngiographyCT Coronary Angiography

High Resolution CT (HRCT)High Resolution CT (HRCT)

HRCT: HRCT: TechniqueTechnique

• Narrow slice width

• “Bone” reconstruction algorithm

• Small field of view

HRCT: Ground glass opacityHRCT: Ground glass opacity

HRCTChest CT

HRCT: scanning protocolsHRCT: scanning protocols

• 1-mm slices every 10-mm/ Contiguous 1-mm slices

• Supine/ Prone

• Full inspiration/ Expiration

HRCT: patterns of lung diseaseHRCT: patterns of lung disease

• Reticular and short linear

• Nodular

• Increased lung opacity (“ground glass”)

• Decreased lung density– Cysts– Emphysema– Bronchiectasis

CT vs. HRCTCT vs. HRCT

Multiple tiny perilymphatic nodulesSarcoidosis

HRCT: BronchiectasisHRCT: Bronchiectasis

CT-guided Needle BiopsyCT-guided Needle Biopsy

IndicationsIndications

• Evaluation of – Solitary pulmonary nodule– Multiple pulmonary nodules– Mediastinal/hilar masses/lymphadenopathy– Chest wall masses

• Retrieval of organisms from infectious lung lesions

• Staging of tumors (lung cancer, extrathoracic)

ContraindicationsContraindications

• An uncooperative patient

• Bleeding diathesis– INR>1.3– Platelet count<50,000 mm3

• Severe underlying lung disease– emphysema

• Intractable cough

Image GuidanceImage Guidance

• CT• Fluoroscopy

– visualization in 2 projections

• Ultrasound– chest wall– pleura– anterior mediastinum– lung periphery

Advantages of CT-guided BiopsyAdvantages of CT-guided Biopsy

• Needle path that avoids– aerated lung– fissures– large vessels– bullae– vital cardiovascular structures

• Differentiation of necrotic vs. viable portions of tumor– I.V. contrast

Biopsy NeedlesBiopsy Needles::Westcott and TurnerWestcott and Turner

Biopsy Needles:Biopsy Needles: Cutting Spring-AcivatedCutting Spring-Acivated

Lung Biopsy: SPNLung Biopsy: SPN(Squamous cell ca.)(Squamous cell ca.)

Lung Biopsy: Lung Biopsy: Multiple nodulesMultiple nodules((Alveolar soft part sarcoma)Alveolar soft part sarcoma)

Rib Biopsy: Multiple myelomaRib Biopsy: Multiple myeloma

Cytologic SpecimenCytologic Specimen

CT-guided biopsy: ComplicationsCT-guided biopsy: Complications

• Pneumothorax

• Hemorrhage

Drainage of Intrathoracic Drainage of Intrathoracic CollectionsCollections

IndicationsIndications

• Malignant pleural effusion

• Empyema/ parapneumonic effusions

• Lung abscess

Contraindications (relative) Contraindications (relative)

• Clotting deficiency– INR < 1.5– Thrombocytopenia (< 50,000 cells/ml)– Anticoagulation therapy

Catheter PlacementCatheter Placement

• One step (trocar)

• Seldinger technique

Drainage Catheters: Drainage Catheters: One Step

Drainage CathetersDrainage Catheters: Seldinger technique

Drainage of Empyema: PostpartumDrainage of Empyema: Postpartum

Low-dose CT: Lung cancer Low-dose CT: Lung cancer screeningscreening

Baseline Findings- ELCAPBaseline Findings- ELCAP

• Low dose CT greatly increases the likelihood of detection of NCN and early lung cancer compared with chest radiography– NCN:NCN: 3 times as commonly– Malignant tumors:Malignant tumors: 4 times as commonly– Stage I tumors:Stage I tumors: 6 times as commonly

Henschke et al, Lancet 1999; 354:99-105

Low-dose CTLow-dose CT

Low-dose CT: Lung cancerLow-dose CT: Lung cancer

Low-dose CT and HRCTLow-dose CT and HRCT

1 year later

HRCT 3 months later: HRCT 3 months later: Lung cancerLung cancer

I-ELCAP results I-ELCAP results ((N Engl J Med 2006;355:1763-71)N Engl J Med 2006;355:1763-71)

• 31,567 asymptomatic persons at risk for lung cancer screened using low-dose CT (1993-2005)

• Stage I lung cancer diagnosed in 412/484 (85%)

• 10-year survival in stage I lung cancer– Overall: 88%– Surgical resection in 1 month: 92%

National Lung Screening Trial (NLST)National Lung Screening Trial (NLST) ( (N Engl J Med 2011;365:395-409)N Engl J Med 2011;365:395-409)

• Started in 2002• >53,000 current and former heavy smokers, ages 55

to 74• compared the effects of two screening procedures for

lung cancer – – low-dose helical computed tomography (CT) – standard chest X-ray

• 20% fewer lung cancer deaths among trial participants screened with low-dose helical CT– Lung cancer deaths in CT-screened: 354, in CXR

screened: 442 (p=0.0041)