This document discusses the imaging and characterization of solitary pulmonary nodules (SPNs). It defines an SPN and lists potential benign and malignant causes. Key imaging features that can help differentiate benign from malignant SPNs are described, including size, shape, edge characteristics, internal textures like calcification, fat and cavitation. The roles of CT, MRI, PET and other modalities are outlined. Determining the growth rate over time and performing biopsies are important for indeterminate nodules. Common benign entities like granulomas, hamartomas and infarcts are shown as examples.

1. IMAGING OF SOLITARY
PULMONARY NODULE
PRESENTOR : DR.NAVNI

2. DEFINITION
• A solitary pulmonary nodule (SPN) is a round
or oval opacity smallerthan 3 cm in diameter
that is completely surrounded by pulmonary
parenchyma and is not associated with
lymphadenopathy, atelectasis, or pneumonia.

3. D/D OF SPN
• MALIGNANT NEOPLASMS
A. CARCINOMA
B. LYMPHOMA
C. LYMPHOPROLIFERATIVE DISEASES
D. SOLITARY METASTATIC NEOPLASM
(MELANOMA,OSTEOSARCOMA,PROSTATE,
COLON,BREAST,RCC,TESTICULAR CARCINOMA)
E. BRONCHIAL CARCINOID
F. SARCOMA

4. • BENIGN NEOPLASM AND NEOPLASM LIKE
CONDITION
A. HAMARTOMA
B. ENDOMETRIOMA
C. MESENCHYMAL TUMOR

5. • INFECTIVE CAUSES
A. GRANULOMA
B. MYCETOMA
C. ASPERGILLOMA
D. ECHINOCOCCUS/HYDATID CYST
E. FOCAL ROUND PNEUMONIA
F. LUNG ABSCESS

6. • INFLAMMATORY
A. RHEUMATOID NODULES
B. SARCOIDOSIS
C. WEGENERS GRANULOMATOSIS

7. • AIRWAY AND INHALATIONAL DISEASE
A. MUCOID IMPACTION
B. BRONCHIAL ATRESIA
C. CYSTIC FIBROSIS
D. PROGRESSIVE MASSIVE FIBROSIS
E. LIPOID PNEUMONIA

8. • VASCULAR LESIONS
A. HEMATOMA
B. INFARCTION
C. PULMONARY ARTERY ANEURYSM
D. PULMONARY VEIN VARIX
E. ARTERIOVENOUS FISTULA
F. SEPTIC EMBOLISM

9. • CONGENITAL
A. BRONCHOGENIC CYST
B. CCAM
C. INTRAPULMONARY LYMPH NODE
D. SEQUESTRATION

10. • IDIOPATHIC/MISCELLANEOUS
A. AMYLOIDOSIS
B. FLUID FILLED BULLA
C. ROUND ATELECTASIS

11. SPURIOUS LESIONS ON CXR
• NIPPLE SHADOW
• PLEURAL BASED LESIONS
• CHEST WALL LESIONS
• SKIN NODULES
• ARTIFACTS DUE TO CLOTHING
• SCREEN ARTIFACTS
Benign granuloma and primary bronchogenic
carcinomas account for 80% of cases of SPN

12. IMAGING OF SPN
• CHEST RADIOGRAPH
• CT SCAN
• MRI
• FDG-PET / SPECT

13. MORPHOLOGICAL CHARACTERISTICS
OF SPN
1. SIZE
Size less than 9mm : difficult to appreciate on
CXR but readily seen on CT
DIAMETER MALIGNANCY RATE
<1 CM 35 %
1-2 CM 50%
2-3CM 80%
>3CM 97%

14. 2.SHAPE
CARCINOMAS : IRREGULAR/LOBULATED/NOTCHED
Lobulation occurs in 25% of benign nodules.
BENIGN : ROUND/OVAL/SMOOTH
(SCARS/AREAS OF ATELECTASIS MAY APPEAR
LINEAR OR ANGULAR)

15. 3.LOCATION
• CENTRAL TUMORS : SMALL CELL CA,
SQUAMOUS CELL CA
• PERIPHERAL TUMORS : ADENO CA, LARGE
CELL CA
• METASTASIS USUALLY BASAL AND
SUBPLEURAL
• BENIGN LESIONS ARE EQUALLY DISTRIBUTED
THROUGHOUT THE LUNG

16. 4.EDGE
• MALIGNANT :
IRREGULAR/SPICULATED/LOBULATED
( radial extension of the tumor cells along the
lymphatics, small airways or blood vessels)
• BENIGN : SMOOTH/SHARP
Metastases and carcinoid tumors have sharp,
smooth edges
21% of well defined nodules are malignant

17. IRREGULAR MARGINS IN BAC

18. LOBULATED MARGINS

19. • CORONA
RADIATA/CORONA
MALIGNA
Presence of spiculation
associated with a
nodule or a mass :
fine,linear strands
extending outward due
to fibrosis surrounding
the tumor/desmoplastic
reaction

20. • PLEURAL TAIL
Carcinomas have a thin
linear opacity extending
from the edge of a lung
nodule to the pleural
surface : due to fibrosis
Can be seen in benign
lesions too

21. • HALO SIGN
Halo of ground glass opacity surrounding a
nodule
Seen in leukemic patients with invasive
aspergillosis due to haemorrage, BAC due to
lepidic spread of tumor, wegeners
granulomatosis, tuberculoma

22. INTERNAL CHARACTERISTICS OF SPN
1. CALCIFICATION
BENIGN NODULES

23. • HOMOGENOUS/UNIFORM/DIFFUSE/SOLID
• DENSE CENTRAL/BULLS EYE
• CONCENTRIC RINGS/LAMINATED/TARGET : Tb,
fungal granulomas
• POPCORN : Hamartomas, cartilage tumors

24. CENTRAL CALCIFICATION

25. DIFFUSE,SOLID: GRANULOMA CONCENTRIC/TARGET

26. POPCORN CALCIFICATION

27. CALCIFICATION: MALIGNANCY
• DYSTROPHIC : in areas of necrosis
• DIFFUSE / AMORPHOUS
• PSAMMOMATOUS : metastases from mucin secreting tumors such
as colon , ovarian cancers
• CENTRAL CALCIFICATION IN SPICULATED SPN
• STIPPLED/PUNCTATE : due to engulfment of previous calcified
lesion
• ECCENTRIC DENSE : carcinoids, metastatic osteosarcoma,
chondrosarcoma

28. Eccentric dense calcification in
right lower lobe carcinoid
Amorphous calcification in non
small cell ca lung

29. 2. FAT
HAMARTOMA
LIPIOD PNEUMONIA
METASTATIC LIPOSARCOMA

30. AREA OF FAT ATTENUATION IN
NODULE : HAMARTOMA

31. 3. CAVITATION
• LESION WITH WALL THICKNESS
< 4 mm -LIKELY BENIGN
> 16 mm- LIKELY MALIGNANT
4-16 MM – INDETERMINATE
• IRREGULAR – LIKELY MALIGNANT
• THIN SMOOTH – LIKELY BENIGN

32. Benign cavitation Malignant cavitation

33. 4. PSEUDOCAVITATION
• Desmoplastic reaction to the tumor distorts
the airway causing narrowing and/or
irregularity of the small bronchi in relation to
the tumor
• Seen as cystic glandular spaces within the
mass

34. 5. AIR CRESCENT SIGN
• Aspergilloma
• Blood clot in a cyst
• Complicated hydatid
disease
• Ca arising in a cyst
• Rasmussen aneurysm
• Mucus plug in cystic
bronchiectasis
• Pulmonary gangrene

35. 7. AIR FLUID LEVEL
Usually seen in benign lesions like lung abscess,
infected cyst or cavity
Intracavitary hemorrhage in cavitary carcinoma

36. 8. SATELLITE NODULES
Small nodules adjacent to
larger nodule or mass
Predictor of benign disease like
granulomatous diseases
Galaxy sign : satellite nodules
in sarcoidosis
Presence of satellite nodules in
lung tumors is considered as
locally advanced tumor

37. 9. FEEDING VESSEL SIGN
Small pulmonary artery
leading directly to a
nodule
Seen in AVF,
hematogenous
metastasis, infarct

38. 10. POSITIVE BRONCHUS SIGN
• A pulmonary lesion that directly abuts,
narrows or occludes bronchial lumen is more
likely to be malignant
• Also seen in tuberculoma, pulmonary infarcts,
Inflammatory masses
• This sign helps in whether transbronchial or
trans thoracic biopsy helps in histological
diagnosis

39. POSITIVE BRONCHUS SIGN

40. CONTRAST ENHANCEMENT
• NODULE ENHANCEMENT < 15 HU - S/O
BENIGN LESION
• NODULE ENHANCEMENT > 15 HU – S/O
MALIGNANT LESION
• SENSITIVITY - 95 -100%
• SPECIFICITY -70 -93 %

41. 15 MIN DELAY
• Malignant nodules:
wash-in of >25 HU
washout of 5-31 HU
• Benign nodules:
wash-in of < 25 H
wash-in of >25 HU in combination with a washout
of > 31 HU
wash-in of > 25 HU and persistent enhancement
withoutwashout

42. • The vascular supply of most malignant pulmonary
nodules is from the bronchial arterial system.
Washout in the malignant nodules takes place via
the bronchial veins. In the washout phase from
the interstitial space, a near absence or
substantial reduction of lymphatic flow is noted
in malignant nodules. The retarded flow in the
intravascular and interstitial spaces accounts for
the retention of contrast medium in malignant
nodules.

43. • In benign nodules, the outflow of contrast
medium( washout) through the intravascular
space in inflammatory processes takes place
through relatively straight vessels with normal
configuration and washout of contrast
medium from the interstital space is
accelerated by active lymphatic flow.
Persistent enhancement is seen in some cases
due to abundant degree of fibrosis as contrast
remains in fibrotic portion for long time.

44. • Net enhancement of > 25 HU
• Washout of 5-31 HU

45. • FALSE NEGATIVE
Central necrosis
Mucin producing tumors

46. GROWTH RATE ASSESSMENT
• Volume doubling time is the time required for a lesion
to double its volume
VDT = t * log2
log Vt/Vo
t= time difference
Vt= volume at time t
Vo= initial volume
1 VDT = 26% increase in the diameter of the nodule

47. • Absence of growth over at least 2 yrs period :
reliable Indicator of benignity
• DT less than 1 month – Infection, infarction,
lymphoma
• DT 1 -18 months : bronchial carcinoma
• DT more than 18 months : Granuloma,
Hamartoma, Bronchial carcinoids
• Doubling time for adeno , undifferentiated ,
Squamous cell CA is 7.3 , 4.1 , 4.2 months
respectively.

48. • Slowest growing BACs have VDT of more than
3 years
• Mets from testicular tumors and sarcomas
have VDT of less than a month

49. COMPUTER AIDED DIAGNOSIS
• Integrated computer system that supports nodule
identification, analysis of nodule size,
morphology and textural analysis of internal
structure of nodule by analysis of high resolution
CT data.
• The CAD system recognizes opacity lesions
surrounded by lung parenchymal attenuation as
nodules. Therefore, nodules in the subpleural,
fissural and costophrenic angle areas might be
missed.

50. • Not helpful to pick up lesions less than 4mm
• Cannot replace the radiologist ; only
supporting tool

51. ROLE OF DUAL ENERGY CT IN SPN
• DECT can decompose enhanced structures
into soft tissue and iodine
• Allows for differentiation of calcification from
enhancing tissue by subtraction of iodine
component
• By single scanning after iodine injection, we
can measure the degree of enhancement
without an additional non enhanced CT

52. ROLE OF CONTRAST ENHANCED
DYNAMIC MRI IN SPN
• Dynamic contrast-enhanced MRI is helpful in
differentiating benign from malignant solitary
pulmonary nodules
• Absence of significant enhancement is a
strong predictor that a lesion is benign.
• Presence of rim enhancement –granuloma ,
network or rim enhancement –hamartoma
• Presence of homogeneous/heterogenous
enhancement : malignancy

53. Network enhancement : hamartoma

54. • Primary lung cancers, time atmaximum
enhancement ratio was 4 minutes or less
• For all tuberculomas and hamartomas, time at
maximum enhancement ratio was greater
than 4 minutes or gradual enhancement
occurred without a peaktime

55. Maximum relative enhancement ratio of
• >0.15 is the adopted threshold for a positive
differentiation between malignant and benign
SPN ( >0.15 = malignant )
• 0.80 is the adopted threshold between
malignant and infective SPN ( <0.80 =
Malignant )

56. • Dynamic MRI has been used to assess tumor
vascularity (microvesselcounts) and
interstitium (degree of elastic and collagen
fibers)

57. ROLE OF DW-MRI IN SPN
SCALE ( study by Satoh et al )
1. Nearly no signal intensity
2. Signal intensity between 1 and 3
3. Signal intensity almost equal to the spinal cord
at thorasic spine
4. Higher signal than spinal cord
SCORE OF 3 IS THRESHOLD FOR DIFFERENTIATING
BENIGN AND MALIGNANT NODULES

58. Disadvantages of MRI
• Poor resolution
• Cardiac and respiratory motion artifacts
• Difficulty in detecting lesion < 1 cm lesion
• Not useful in peripheral SPN due to signal loss

59. ROLE OF FDG-PET
• Malignant cells have upregulated metabolisms and
proliferate rapidly.This results in marked uptake of
FDG
• False negative results due to - Carcinoids , BAC ,
Adeno with BAC component , SPN < 10 mm
• False positive results are due to –Active TB ,
Histoplasmosis , Rhematoid nodules ,Aspergillosis ,
wegeners granulomatosis
• Possibility of malignancy with negative FDG-PET is
<5%

60. Axial CT Axial PET

61. FOLLOW UP ( fleischner society and
American family physicians )

63. ROLE OF SPECT IN SPN
• The diagnostic ability of 201Thallium SPECT
has been reported, with sensitivity, specificity,
and accuracy of 85to 100%, 90 to 100%, and
85 to 100%, respectively.
• Diagnostic accuracy for the pulmonary
nodules over 2 cm in size between 201Tl
SPECT and FDG-PET is almost the same.

64. THALLIUM SPECT IN SPN

65. INDETERMINATE SPN
• Transthoracic needle aspiration biopsy for
peripheral nodules
• Fibreoptic bronchoscopy with transbronchial
biopsy for endobronchial lesions
• Video assisted thoracic surgery

66. SOME COMMON BENIGN SPN

67. GRANULOMA
• Commonest are Tuberculomas
• Single , 1-3 cm in diameter , well defined ,
smooth , regular outline
• Commonest location close to pleural surface
• Calcification - laminar , fleck like ,concentric,
• Cavitation – rare
• Satellite lesions sometimes seen
• Commonly seen in upper lobes

68. Granuloma

69. PULMONARY HAMARTOMA
• Benign pulmonary mass containing connective tissue ,
cartilage , fat , smooth muscle , marrow , and bone
• Most common location – periphery of the lung
• X ray chest – spherical ,lobulated , well defined nodule
• Popcorn like calcification
• Fat density within the mass is a diagnostic feature

71. AVM
• X ray – well circumscribed lesion with lobulated
outline
• X ray/CT - Feeding vessels and draining vein can be
seen
• It can be confirmed on CT
• PULMONARY ANGIOGRAPHY RARELY INDICATED

72. AVM
Lobulated,well marginated
nodule in the lower lobe
Feeding artery (arrow) and an
enlarged draining vein (arrowhead).

73. Nidus of malformation
Pulmonary angiogram helps confirm
arteriovenous malformation. Note the early
draining vein (arrows)

74. ROUND PNEUMONIA
• Inflammatory pseudotumour
• Some times pneumonic
consolidation assumes a shape
And density similar to
pulmonary neoplasm
• Careful study reveals irregular
margin and air bronchogram
• Common in children
• May persists after recovery
from infection

75. INFARCT
• poorly marginated
nodule peripherally in
the lower lobe

76. VANISHING TUMOR
• Sharply marginated
collection of pleural fluid
contained either within
an interlobar pulmonary
fissure or in a subpleural
location adjacent to a
fissure
• Can occur on minor
fissure , oblique fissure
• Most of them are < 4 cms

77. BRONCHIAL CARCINOID
• Typical triad –
Well defined ,round lobulated , lesion
At the bifurcation
Eccentric calcification

78. Nodule with eccentric
calcifications (arrow) obstructing
the posterior segmental
bronchus of the right upper lobe.
High-resolution CT scan shows a
well-defined, round, partially
endobronchial nodule (arrow) in the
lateral subsegmental branch of the
anterior segmental bronchus of the
left upper lobe.

79. On a contrast-enhanced CT scan
(mediastinal windowing), the
nodule demonstrates marked
contrast enhancement and
mimics a vascular structure
On a contrast-enhanced CT scan
(mediastinal windowing), the
nodule demonstrates marked
contrast enhancement and mimics a
vascular structure

80. ROUND ATELECTASIS
• FOLDED LUNG
• Chronic atelectasis that resembles mass
• X ray and ct – Peripherily located , wedge shaped opacity
• Based against focally thickened pleura , commonly at lung base
• Crow feet / comet tail of vesssels sweeping into the margin of this opacity
• A rapidly forming pleural effusion produces an adjacent area of passive atelectasis
• A groove of visceral pleura may infold into the area of atelectasis and come to
surround a part of it

81. • Conventional
tomographic scan of the
chest in a lateral
projection shows a large
subpleural mass
(arrowhead) in the right
lower lobe of the lung. A
curvilinear opacity
(arrow), the comet tail
sign, arises from the
inferior pole of the mass
and courses toward the
hilum.

82. BIBLIOGRAPHY
• LEARNING RADIOLOGY
• Evaluation of solitary pulmonary nodule :RADIOGRAPHICS
• TEXTBOOK OF RADIOLOGY AND IMAGING BY DAVID SUTTON
• DIAGNOSTIC RADIOLOGY BY MANORAMA BERRY
• Evaluation of solitary pulmonary nodule detected during computed
tomography examination : POLISH JOURNAL OF RADIOLOGY
• Evaluation of the Solitary Pulmonary Nodule : AMERICAN FAMILY
PHYSICIANS
• Solitary pulmonary nodule: A diagnostic algorithm in the light of current
imaging technique : AVICENNA JOURNAL OF RADIOLOGY
• Usefulness of the CAD System for Detecting Pulmonary Nodule in Real
Clinical Practice: KOREAN JOURNAL OF RADIOLOGY
• Dynamic MRI of Solitary Pulmonary Nodules: Comparison of Enhancement
Patterns of Malignant and Benign Small Peripheral Lung Lesions: AJR

83. THANK YOU
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