imaging in solitary pulmonary nodule

1. IMAGING IN
SOLITARY PULMONARY NODULE
MODERATOR
DR .ROHIT AGARWAL
ASSISTANT PROFESSOR
MD,DNB, PDCC
PRESENTER
DR. NABA KUMAR
JR 2

2. A solitary pulmonary nodule is defined as a discrete, well
marginated,rounded opacity less than or equal to 3 cm in diameter
surrounded at least partially by lung parenchyma, does not touch
the hilum or mediastinum, and is not associated with adenopathy,
atelectasis, or pleural effusion.
Lesions larger than 3 cm are considered masses and are treated as
malignancies until proven otherwise.
DEFINATION

4.  Pulmonary nodules can be divided into solid lesions and
subsolid lesions, which can be further subdivided into part-
solid and pure ground glass nodules
Subsolid nodule (SSN):A pulmonary nodule with at least partial
ground glass appearance
Groundglass:Opacification with a higher density than the
surrounding tissue, not obscuring underlying bronchovascular
structures

5. Differentiation between benign and malignant SPNs
forms the goal of imaging. This differentiation is
important because the overall mortality associated with
lung cancer is about 85% and about 20 % of lung cancers
are discovered in the form of SPN.SPN is seen in about
0.2% of chest radiographs
IMPORTANCE

6. Primary evaluation:
 Is the lesion truly solitary?
 Is the lesion intrapulmonary?
 Is the lesion nodule?

7. Is the lesion true solitary?
 Dominant pulmonary nodule in X-ray may be associated with
smaller nodules.
 Careful search by CXR PA , lateral view & in some cases CT may
be necessary.
 Multiple pulmonary nodules of similar sizes and appearance
- usually metastasis or granuloma
- require different evaluation than solitary
lesions.

8. Is the lesion intrapulmonary?
 Intrapulmonary lesions
-discrete opacities at least moderately well marginated
by aerated lung on both frontal and lateral
radiographs
 Pleural and mediastinal lesion
- base forms obtuse angles with lung and is not
outlined by lung .

9. Spurious SPN’s
Pleural based and chest wall lesions, nipple shadow, skin
nodules like neurofibroma, artifacts may be the causes of
spurious SPNs, however oblique views, repeat radiographs
or even CT at times may help to differentiate these from a
true SPN

10. Is this a nodule?
 Discrete round or oval opacity 4-30 mm in diameter
 Linear and angular opacities are not nodules and
represent scar or areas of linear atelectasis.
 3D analysis or volumetric CT can help to differentiate
flat scar from true SPNs.

11. MALIGNANT
NEOPLASM
BENIGN
NEOPLASM
INFECTIVE NONINFECTIOUS
INFLAMMATORY
-Carcinoma
(squamous cell,
small cell,
adenocarcinoma,
bronchioloalveola
r carcinoma)
– Lymphoma
– Carcinoid
– Pulmonary
metastasis (colon,
melanoma, renal
cell, breast,
osteosarcoma)
-Hamartoma
– Chondroma
– Fibroma
-Round
pneumonia
– Abscess
– Granuloma
(fungal,
mycobacterial)
-Sarcoidosis
– Rheumatoid
arthritis
– Amyloidosis
– Wegener's
granulomatosis
DIFFERENTIAL DIAGONOSIS OF SOLITARY
PULMONARY NODULE

12. AIRWAY AND
INHALATIONAL
DISEASE
VASCULAR
LESION
CONGENITAL
LESION
IDIOPATHIC /
MISCELLANEOUS
– Mucoid
impaction
(mucous plug)
– Bronchial
atresia
– Cystic fibrosis
-Conglomerate
mass or
progressive
massive fibrosis
(e.g. silicosis)
– Lipoid
pneumonia
-Pulmonary
artery aneurysm
– Hematoma
– Infarct
– Arteriovenous
malformation
(AVM)
– Sequestration
– Bronchogenic
cyst
– Bronchial
atresia
-Amyloidosis
– Fluid filled
bulla
– Round
atelectasis

13. Clinical details
The patient’s age is also a significant distinguishing feature
(a carcinoma is only seen in <1% of patients <35 years old)
o Prior history of cancer
o Family history of lung cancer
o Occupation risks – exposure to asbestos, radon, nickel,
chromium, polycyclic hydrocarbon.
o Coexisting chronic obstructive pulmonary disease (COPD)
and emphysema
o History of TB – may indicate chance of SPN being benign.
o Travel history

14. Investigations to be done in a case of SPN
 Chest x ray
 CT scan
 MRI
 Nuclear imaging
 Biopsy
•Nodules are identifiable on the chest x-ray when they
attain 8-10 mm size.

15. Chest X-ray
 Initial examination.
 Most SPNs - incidental finding.
 Nearly 90% of newly discovered SPNs on chest
radiographs may be visible in retrospect on prior
radiographs. Previous CXR are important to study
growth pattern.
 Visualization of some nodules difficult due to
superimposed structures
 Poorer resolution than CT for calcification or size.

16. The advantages of CT over CXR
 Better size estimation (diameter from largest
cross-sectional area or volume measurement)
 Better border resolution
 Hidden areas assessment - lung apices, perihilar
regions, and costophrenic angles
 Detection of multiple nodules
 Enhancement & nodule attenuation
characterisation
 Staging of Malignancy possible
 CT can help guide needle biopsy
Cause of many SPNs will remain undetermined
after initial & thin-section CT exam.

17. SIZE
 Not a reliable discriminator
 Larger– more chance of malignancy
 Nodules approaching 3 cm in diameter are more
likely to be malignant
 Converse not true. Many pulmonary malignancy < 2
cm at time of dx (if detected by screening chest CT)
Diameter(cm) Malignancy rate(%)
<1 35
1-2 50
2-3 80
>3 97
Likelihood of malignancy related to nodule diameter

18. Shape
 Lung carcinomas tend to be irregular in shape, lobulated or
notched.
 Granulomas often are round.
 Hamartomas and metastases may be round, oval,
smooth .
 Scars or areas of atelectasis -linear or angular.
Japanese screening studies showed that a polygonal shape
and a three-dimensional ratio > 1.78 was a sign of
benignity

19. A polygonal shape means that the lesion has multiple
facets (multi-sided).A peripheral subpleural location was
also a sign of benignity in this study.The three-
dimensional ratio is measured by obtaining the maximal
transverse dimension and dividing it by the maximal
vertical dimension.A large three-dimensional ratio
indicates that the lesion is relatively flat, which is a
benign sign.
Transverse image (left) and coronal reconstruction
(right)Three-dimensional ratio = transverse dimension
: vertical dimension

20. Location
 2/3rd lung cancers occur in the upper lobe and the right upper
lobe is m.c involved.
 Adenocarcinomas -peripheral
 Squamous cell carcinomas - centrally
 Metastatic tumor - subpleural or outer third of the lung.

21. Edge Charecteristics
 Benign lesions - smooth, sharply defined edge.
 Malignant nodules - ill-defined, irregular, lobulated, or
spiculated margin. Exception- metastases and carcinoid tumors.

22.  Corona radiate /corona maligna -
spiculation associated with a nodule
or mass.
 Pleural tail sign- a thin linear
opacity is seen extending from edge
of lung nodule to pleural surface.
 Spiculated contour is more
suggestive of malignancy than a
pleural tail
Lobulated or scalloped margins -
intermediate probability
Smooth margins - more likely
benign unless metastatic in origin

23. Sharply marginated
 Granuloma
 Hamartoma
 Carcinoid tumor
 Metastasis
Spiculated (corona radiata) or pleural tail
 Adenocarcinoma Insitu
 Carcinoma
 Granuloma or focal scarring

24. Halo sign
 Halo of ground-glass opacity
surrounding nodule.
 Leukemic patients with
angio- invasive aspergillosis
halo sign represent
hemorrhage
 Adenocarcinoma or
Adenocarcinoma insitu-
lepidic tumor growth

25. Reverse halo sign/atoll sign
 Central area of ground-glass attenuation surrounded by a halo
or crescent of consolidation.
 First described in cryptogenic organizing pneumonia.
 Paracoccidioidomycosis, tuberculosis, lymphomatoid
granulomatosis, wegener granulomatosis, sarcoidosis, and
tumors after radiofrequency ablation.

27. Air Bronchograms and Pseudocavitation -
 M.C in adenocarcinomas
than in benign nodules.
 Bubble-like lucencies or
pseudocavitation may
simulate cavities and are
seen in up to 55% of
Adenocarcinoma insitu
 Caused by desmoplastic
reaction to tumor that
distorts airways.

28. CAVITATION
BENIGN
1. Thin smooth wall
2. <5 mm thickness- 95%
benign
5-15 mm- 75% benign
MALIGNANT
1. Irregular thick wall
2. > 16mm thickness
Cavitation most commonly found in :
Squammous cell ca> large cell ca> adenocarcinoma>>>small
cell ca(rare)

30. Air-crescent Sign/Air meniscus sign
 Air outlining superior aspect
of the mass results crescent-
shaped collection of air
 Gravitational shift of the
intracavity mass strongly
suggests mycetoma and
excludes carcinoma.
 D/D
Aspergilloma
Blood clot in cyst complicated
hydatid
Mucus plug in cystic
bronciectasis

31. Air-fluid level
 Benign lesion, particularly lung abscess.
 Uncommon in a cavitary carcinoma but may be seen in the
presence of hemorrhage or super infection.

32. Satellite Nodules
 Small nodules adjacent to
larger nodule or mass.
 Predict a benign lesion.
 Granulomatous diseases and
infections such as TB.
 Sarcoidosis - galaxy
sign.(presence of multiple
satellite nodule)

33. Feeding Vessel Sign
 Small pulmonary artery is
seen leading directly to a
nodule .
 Metastasis, septic emboli, and
arteriovenous fistula.

34. Calcification is an important imaging feature that can be used
to distinguish between benign and malignant SPNs.
Calcification in a Benign Nodule (Figs. A to D)
• Concentric rings of calcification (target calcification)
• Conglomerate foci of calcification involving a large part of the
nodule (popcorn calcification)
• Homogeneous calcification/uniform calcification
• Dense central (bull's eye) calcification.
CALCIFICATION

35. .
Indeterminate Calcification
Eccentric calcification may be seen in a benign lesion which
gets calcified in an eccentric fashion or when a benign
calcified lesion is engulfed by a malignant lesion.
Stippled/punctate calcification may be seen in both benign
and malignant lesions and is thus classified as
indeterminate.
Calcification in a Malignant Nodule
A malignant nodule may show calcification which is diffuse
and amorphous or psammomatous (in case of metastasis
from mucin secreting tumors from the colon or ovary) or
dystrophic (in areas of tumor necrosis).Centrally located
calcification in a spiculated SPN also suggests malignancy

38. HAMARTOMA
POP CORN CALCIFICATION

39. ATTENUATION
Ground-glass Opacity
 Nodules contain ground glass component are more likely to be
malignant.
 Partly solid lesions with ground-glass components had
a malignancy rate of 63%.
 Nonsolid - only ground-glass lesions had a malignancy
rate of 18%.
 Only solid lesions had a malignancy rate of only 7%

41. Fat
 On HRCT fat can be accurately diagnosed if low CT numbers
are seen ( -40 to -120 HU)
Causes of SPNs Containing Fat
 Hamartoma
 Lipoma
 Liposarcoma (primary or metastatic)
 Lipoid pneumonia
 Histoplasmoma
 Teratoma

42. Low (Water or Fluid) Attenuation
 Benign cystic lesions such as Congenital Cystic Adenomatoid
Malformation, or fluid- filled cyst or bulla, diagnosed on CT by
their low attenuation and very thin or invisible walls.
 Mucoid impaction - low attenuation
 Bronchogenic cysts or other cystic lesions may have a higher
attenuation because of their protein content.
 A necrotic neoplasm, conglomerate mass, or lung abscess
or infarction have low attenuation center but thick and
perceptible wall.

43. Contrast Enhancement
 Malignant nodules tend to have greater vascularity than benign
nodules.
 Contrast enhancement less than 15 HU has a very high
predictive value for benignity (99%).
After a baseline scan, 4 consecutive scans at 1 minute
interval are performed.
This applies only for nodules with the following selection
criteria:
 Nodule > 5mm
 Relatively spherical
 Homogeneous, no necrosis, fat or calcification
 No motion or beam hardening artifacts

44. An analysis of combined wash-in and wash-out characteristics
(studied at 15 minute delay) gives a more precise evaluation of the
nodule enhancement
For benign nodules:
• Wash in <25 HU
• Wash in ≥25 HU with a washout ≥31 HU
• Wash in ≥25 HU and a persistent enhancement without a washout.
For malignant nodules:
• Wash in ≥25 HU
• Washout of 5–31 HU (not more than 31 HU).

45. • The arterial supply of a nodule is via the bronchial arteries
while the washout is via the bronchial veins.
• In the case of malignancy, a retarded flow in the
intravascular and interstitial space accounts for contrast
retention.
• In the case of benign nodules, this washout takes place
through relatively straight vessels and active lymphatic
flow resulting in a significant washout.
• A persistent enhancement when seen in a benign nodule
occurs due to the presence of fibrosis in the nodule, the
fibrotic portion of the nodule retaining contrast for a long
time without washout

46. Growth and Doubling Time
 Nodule growth is also assessed by a volume doubling time (VDT)
defined as the time in which the volume of a nodule becomes
double. As the most common shape is spherical, the volume is
calculated using the equation 4πr. A 26% increase in diameter is
taken as a doubling in volume based on
VDT = [t × log 2]/log (Vt/Vo)
Where Vo is the initial volume and Vt is the volume at time t.
This formula is based on an exponential model of nodule growth,
i.e. a 5 mm nodule will reach a diameter of 20.3 mm in 12 months
if the doubling time (DT) is 60 days but will reach a diameter of only
7.1 mm in 12 months, if the doubling time is 240 days.

47.  The volume doubling time (VDT) for malignant SPNs is rarely less
than a month or more than a year (range 20–400 days).
 Nodules with a doubling time less than 20 days and more than 400
days are considered benign.
 stability of nodule size over 2 years (730 days) has been considered
to suggest benignity.
 small purely ground-glass opacity (nonsolid) nodules with
malignant histologic features may have a mean volume DT of about
2 years while it is about 6 months for the solid cancers.
 Subsolid nodules that have a higher likelihood of malignancy have a
volume doubling time between the two extremes.

48. MRI
Dynamic MR Imaging
Blood patterns and tissue perfusion have been studied by dynamic MR
imaging in liver, brain and breast.
This technique can be used to characterize SPNs as well.
Signal intensity time curves are generated following intravenous
injection of gadolinium and maximum relative enhancement ratio and
shape of enhancement can be calculated from these.
A ratio >0.15 indicates a malignant SPN, a ratio <0.80 indicates benign
lesion and ratio between 0.8 and 0.15 usually indicates active infection
These MR indices are useful for differentiating between benign and
malignant SPNs

49. Diffusion-weighted MRI Imaging
MRI has an inherent advantage in terms of tissue characterization.
Tissue contrast attained using diffusion weighted imaging (DWI) is
different from that obtained using conventional MR sequences.
In a study by Satoh, et al difference between benign and malignant
was based on a DWI scale graded from 1 to 5. These were:
1) nearly no signal intensity as seen in an almost normal lung
2) signal intensity between 1 and 3
3) Signal intensity almost equal to the spinal cord at thoracic spine
4) higher signal than spinal cord
5) much higher signal than that of the spinal cord.
A score of 3 (a nodule with signal intensity equal to that of the spinal
cord) was considered the threshold for differentiation between benign
and malignant pulmonary nodules in their study.

50. Nuclear imaging
•Scope of nuclear imaging is being increasing in evaluation of SPN.
PET & SPECT scans have been approved for use in SPN evaluation.
•Malignant cells have higher metabolic rates than normal cells;
hence their glucose uptake is higher.
•In thoracic PET scanning , 18FDG isotope is used, FDG uptake is
quantified using the standard uptake ratio (SUR) to normal
measurements of patient weight.
•PET scan in addition can detect mediastinal mets.

51. • Standard uptake value (SUV) greater than 2.5 is generally
considered as indicative of malignancy.
• False negative studies can result if nodule is smaller than 1cm in
diameter.
PET has a sensitivity and specificity of about 90% for detecting
malignant nodules which are larger than 10 mm in diameter, but
this high sensitivity and specificity is applicable to solid nodules
In the case of partly solid nodule (PSN) and ground-glass attenuation
nodule (GGAN) FDG uptake cannot be used to reliably distinguish
between benign and malignant lesions. PET has been found to
have a sensitivity as low as 10% and specificity of about 20% for
evaluating ground glass opacities.

52. Demerits of nuclear imaging
 PET scanner resolution is 7-8 mm, hence SPN smaller than 10
mm may be missed.
 Metabolically active foci (lesion e.g. granulomas, infection,
inflammation may produce false positive results.
 In high glucose of serum, FDG uptake may be decreased since
hence giving false negative results.

54. Transthoracic Needle Aspiration Biopsy (TNAB)
For a SPN with a high clinical suspicion of malignancy, surgical resection
is the best option if the lesion is operable as needle biopsy does not
alter management.
If the biopsy result is positive, resection has to be done, a negative
result does not exclude malignancy and has to be followed by resection
If there is a high clinical suspicion of malignancy as the sensitivity of
this technique is about 60% for lesions less than 2 cm in diameter .
The diagnostic yield further falls to 51% for GGO dominant lesions.Thus,
needle biopsy is usually indicated for inoperable SPN to confirm the
histology. As compared to bronchoscopy, the complication rate of TNAB
is high.
Complications include pneumothorax and hemorrhage seen in about 5–
30% of cases.

56. Management

58. Risk factors
Defining high- or low-risk is currently more difficult than it was
in the old guideline.
Previously a high-risk subject was identified based on a history
of heavy smoking, history of lung cancer in a first-degree
relative or exposure to asbestos, radon or uranium.
Now, it is aimed for to separate high-risk lesions from low-risk
ones by considering more parameters than subject
characteristics alone

61. For multiple nodules, the subsequent management is based on
suspicious nodule which may not be the largest nodule. Pure GGNs
more than 10 mm, part solid GGN with solid component larger than 5
mm, bubbly appearance of reticulation, atypical subsolid nodules with
spiculation should be interpreted with high degree of suspicion.
It has been recommended that thin CT sections of the thorax (≤1 mm)
should be performed to enable accurate characterization of the small
pulmonary nodules. Sagittal and coronal reconstruction should always
be obtained. A low radiation dose technique is recommended for follow
up CT scans with the use of dose modulation and iterative
reconstruction techniques to reduce radiation.
According to the ACR recommendations for screening CT, the CT dose
index volume (CTDI vol) should not be more than 3 mGy

62. MCQ

63. Q1.Definition of solitary pulmonary nodule include all except-
a. Relatively well-defined.
b. Surrounded at least partially by lung.
c. 3 cm or more in diameter.
d. Not associated with lymphadenopathy, atelectasis or
pneumonia.
Ref –W. Richard Webb ,Thoracic Imaging Pulmonary and
Cardiovascular Radiology , 3rd edition
 Section Two Neoplasms, Masses, and Focal Lung
Abnormalities

64. Anc -c
Q2. Feeding Vessel Sign seen in all except –
A. Metastasis,
B. Infarct
C. Arteriovenous fistula
D. Hamartoma
Ref –W. Richard Webb ,Thoracic Imaging Pulmonary and
Cardiovascular Radiology , 3rd edition(2017)
Section Two Neoplasms, Masses, and Focal Lung
Abnormalities

65. Ans - d
Q3. Calcification in lung nodule favours benign etiology -
a. Bull’s eye calcification
b.Stippled calcification
c.Ecentric calcifcation
d.Any of the above
Ref –. W. Richard Webb ,Thoracic Imaging Pulmonary and
Cardiovascular Radiology , 3rd edition(2017)
Section Two Neoplasms, Masses, and Focal Lung
Abnormalities

66. Ans -a
 Q4.Contrast opacification is a feature of-
a.Arteriovenous malformation
b.Pulmonary vein varix
c.Pulmonary artery aneurysm
d.All
Ref –W. Richard Webb ,Thoracic Imaging Pulmonary and
Cardiovascular Radiology , 3rd edition(2017)
Section Two Neoplasms, Masses, and Focal Lung
Abnormalities

67. Ans - D
 Q5. False statement regarding recent Fleischner Society
2017 guideline for incidentally detected pulmonary
nodul1es in adult patients < 35 yrs are-
1.The minimum threshold of the nodule for follow-up
has been increased to 6 mm rather than 5 mm.
2. Follow-up intervals have been given a precise time
period.
3. The guidelines for solid and semisolid nodules are
now included in one single table
4)There is specific recommendations for
multiple pulmonary nodule
Ref –Fleischner society guideline ,2017

68. ANS -B
 Q6. False statement is-
A. Small cell carcinoma rarely cavitate
B. Gravitational shift of intracavity mass suggest mycetoma
C. Metastatic tumors have a predilection for inner third of lung
D. Halo sign in bronchoalveolar carcinoma(adenocarcinoma
insitu) indicate lepidic spread of tumor.
Ref –W.Richard Webb ,THORACIC IMAGING,Pulmonary and
Cardiovascular Radiology THIRD EDITION (2017)

69. Ans -C
 Q7.Maligancy with sharp margins-
a. Carcinoid
b. Metastases
c. Both
d. None
Ref –W.RichardWebb,Thoracic Imaging Pulmonary and
Cardiovascular Radiology THIRD EDITION(2017)

70. ANS -C
 Q8. ACCORDING TO BTS Pulmonary Nodule Risk
Prediction Calculator HERDER MODEL BASED ON-
 PET-CT
 CT
 DYNAMIC MR
 BIOPSY
 Ref-BTS guideline for pulmonary nodules
,Guideline of the British Thoracic Society
Onno Mets and Robin Smithuis 2015

71. ANS -A

72. ANS- B
 Q9. most important morphological fature to differentiate
benign from malignat solitary pulmonary nodule?
A. calcification
B. cavitation
C. location
D. size
Ref- W.Richard Webb,Thoracic Imaging Pulmonary and
Cardiovascular Radiology THIRD EDITION(2017)

73. Ans -A
 Q10.False negative PET findings can be seen with all except-
A. Lesions < 10 mm in diameter
B. Carcinoid tumors
C. Adenocarcinoma
D. Infection
Ref- W.Richard Webb,Thoracic Imaging Pulmonary and
Cardiovascular Radiology THIRD EDITION(2017)

74. ANS -D

75. THANK YOU