Imaging of enlarged lymph node

IMAGING OF ENLARGED LYMPH NODE.

Head and Neck Imaging.Ehab Abo-Ulfotouh Helal.

Lecture Of Radio-Diagnosis.

An oval-shaped organ of the immune system.

Distributed widely throughout the body.

Linked by lymphatic vessels.

Lymph nodes act as filters for foreign particles.

Become enlarged in various conditions.

Lymph Node structures:

http://en.wikipedia.org/wiki/Immune_system

http://en.wikipedia.org/wiki/Lymph_vessel

Lymph Node structures:

Radiological anatomy:




Head and neck carcinomas are the sixth most common malignancy reported worldwide.

LN metastasis is one of the most important prognostic factors in patients with head and neck carcinoma.

The major goals of diagnostic imaging in these patients is accurate prediction of LN metastasis.

Not only for the planning of appropriate treatment but also for monitoring the treatment response.

Imaging of enlarged LN on head and neck:

Size: The size of LN

cannot be used as the sole criterion in DD.

An increase in LN size on serial examinations.

Changes in the size of malignant nodes.

Sonographic Feature of Cervical Lymph Nodes:

Nodal Borders& margins:

Metastatic nodes have sharp borders.

Due to tumor infiltration and reduced fatty deposition within LN .

Increased acoustic impedance difference between LN and the surrounding tissues.


Reactive nodes usually show un-sharp borders.

Un-sharp borders due to edema & inflammation of surrounding soft tissue.


Shape Feature: Malignant and TB

nodes round.

Reactive and normal nodes usually oval.

The L/S ratio was used to characterize this feature.


Medulla Ratio & distribution:

If the difference between 2 parts was less than 30%.

This node was considered absence of medulla.


The distances from each edge to the centroid of the medulla were measured.


Echogeneity: Homogeneous hypo-

echoic pattern with preserved echo-genic hilum mainly observed in benign nodes.

Heterogeneous and anechoic patterns with loss echogenic hilum are observed in metastatic nodes.


Normal and reactive nodes predo-minantly hypo-echoic.

Metastatic nodes

may be hypo or mixed hypo and eccenteric hyper-echoic component.


Vascular Pattern: Normal and reactive

lymph nodes tend to have central hilar vascular pattern.

club- or Y-shaped and extended from the extra-nodal area into deep portion of the node.

May be appear as apparently a-vascular lesion.


Metastatic and lympho-matous nodes usually show peripheral or mixed vascularity.

The presence of peripheral vascularity strongly suggesting of a pathologic process.


Nodal parenchyma exhibited homogeneous and low echogenicity.

Regular margin and oval or flattened in shape.

The hilum was identified as a highly echogenic structure in the central part of the node.

On power Doppler, usually hypovascular or has hilar vascular pattern.

U/S Feature of reactive LN:

Ill defined margin of enlarged LN.

Central decreased echogenicity.

Loss hilum.

On power Doppler, increase peripheral vascularity.

U/S Feature of suppurative LN:

Nodal parenchyma exhibited inhomogeneous low or mixed echogenicity.

Irregular margin with round shape.

Sharp borders.

Loss of normal hilar echogenicity.

On power Doppler sonograms, has peripheral or mixed vascular pattern.

U/S Feature of metastatic LN:

U/S Feature of metastatic LN:

CT SCAN: scanning orientation was parallel to the

Frankfurt horizontal line.

Start point at skull base down to the level of aortic arch.

3 mm in thickness.

A collimation of 3 mm, a pitch of 1:1, a matrix of 512x512, a display field of view of 23 cm, 120 kVp, and 200 mA.

CROSS-SECTIONAL IMAGING:

Was carried out after an IV bolus injection of contrast material 100 mL (2 mL/kg of body weight), at a rate of 1.0 mL/sec.

Started scanning 80 sec after the start of contrast medium injection.

Completed in 50–60 sec after the start of scanning.

The scanning period (80–140 sec after the start of contrast medium injection) was confirmed to be the time when the lymph node showed appropriate contrast enhancement against neck muscles.

CT SCAN:

A. short- and long-axis diameters of the node:

Short-axis diameter: was used as a size criterion. Average short-axis lengths of nodes at level I: 7

(reactive) and 11 mm (metastatic). Level II: 7 (reactive) and 13 mm (metastatic). Level III, VI and V: 6 (reactive) and 10 mm

(metastatic).

A long axis diameter of more than 10 mm plus a long-to-short-axis ratio of less than 1.6, suggesting metastatic node.

CT scan criteria:

CT scan criteria:

B. Assessment of changes in the internal architecture:

The presence or absence of necrosis, We considered an area of low attenuation (10–18 HU) to be evidence of nodal necrosis.

The margin, categorized as well or ill defined.

Enhancement pattern, described as homogeneous or heterogeneous .

CT scan criteria:

CT scan criteria:

Discrete, smooth and well-defined kidney or cigar shaped soft-tissue structures .

The hilum composed of fat tissue attenuation.

No necrosis.

Homogenous and uniform, enhancing criteria and attenuation.

CT feature of Non metastatic nodes:

Rounded shape with ill defined margin.

The long-to-short axis ratio decreases.

Eccentric cortical hypertrophy.

Central necrotic content.

Heterogeneous enhancing pattern.

CT feature of metastatic nodes:

Ill defined peripheral enhancing thick wall.

Intra-nodal septation.

Central hypo-dense non enhancing fluid collection.

Marked stranding of adjacent fat ?cellulitis.

CT feature of suppurative nodes:

Conventional MRI criteria used in clinical imaging studies are morphologic criteria including:

A. Maximum short axial diameter. B. Presence of necrosis and loss of LN hilum. C. Heterogeneous enhancement and peri-nodal infiltration.

A size criterion and presence of necrosis are relatively objective.

But the other criteria are less objective and dependent on the interpretation of the radiologist.

MR imaging of Benign and Malignant Nodes:

2D-Single-Shot Diffusion-Weighted Echo Planer Imaging (ss DWEPI ) has been applied to head and neck imaging.

DWEPI provides a quantitative measurement of the ADC of water protons in tissue.

ADC value can be used to differentiate malignant LNs from benign LNs.

Can be a marker for prediction and early detection of chemo-radiation therapy response.

DWEPI also can be used for the early detection of recurrence.


Axial DW images of cervical lymph nodes were obtained by using a neurovascular array coil.

The sequence was repeated for two different values of gradients (b = 500 and 1000 s/mm2).

The section thickness was 5 mm.

Was performed with a matrix of 128 /128, field of view of 24 cm, and an intersection gap of 1 mm.

To increase the signal-to-noise ratio, the sequence was repeated four times for each imaging.


Hilum Structure of the Nodes:

The hilar fat, has high-intensity area on T1WIs and a low-intensity area on fat suppressedT2WIs.

The vessels may be evident in the hilum on T1WIs and fat suppressed T2WIs.

MR Imaging analysis:

Was lost at a metastatic nodes.

Narrowed or also lost in nodal lymphomas.

Preserved hilum was noted on benign LN.


Margins of the Nodes: T1-weighted and fat suppression

imaging was good for the depiction of nodal margins.

Nodal margins blending into surrounding tissue were found in metastatic nodes.

Irregular margins were found in lymphomas.

Regular borders were found on benign nodes.


Parenchymal architecture: Metastatic nodes frequently

exhibited heterogeneous architecture of the parenchyma on T1- or fat-suppressed T2-weighted.

Metastatic nodes contained hypo to intermediately intense areas indicative of cancer cell nests and interstitial fibrous tissue.

With or without central hyper-intense areas indicative of liquefaction necrosis on fat-suppressed T2.



Basically lymphomas exhibited homogeneous

architecture.

Heterogeneous architecture of the nodal ymphomas was significantly low compared with metastatic nodes.

heterogeneity in the nodal architecture may be due to the presence of necrotic areas.

Associated with narrowed hilum and blood vessels inside, which were depicted as so-called small-vessel sign.



The ADC of metastatic nodes equal to or greater than 0.73 × 10–3 mm2/sec.

ADC of the Nodes:

On lymphoma, it had an ADC equal to or less than 0.51 × 10–3 mm2/sec.

Due to increased nuclear-to-cytoplasmic ratio and hyper-cellularity.

Reduce the extracellular matrix and the diffusion space of water protons in the extracellular and intracellular dimensions.

ADC of the Nodes:

ADC of the Nodes: The ADC of benign nodes (0.652 ± 0.101 × 10–3 mm2/sec).

PET using the radio-labeled glucose analog 18F-FDG has great importance in lymph node imaging.

PET supplies a semi-quantitative metabolic characterization of tissues that may help to predict tumor behavior.

The sensitivity and specificity of 18F-FDG PET for identification of lymph node metastases on a neck level-by-level basis were higher than those of CT/MRI.

The incorporation of functional information derived from PET has the potential factor to improve prognostic stratification and treatment planning for patients.

PET and PET/CT of the Neck Lymph Nodes:

Negative prognostic factors were noted including: A- Extra capsular spread (ECS).

B- Close or positive margins.

C- Peri-neural invasion.

D- Poor differentiation of tumor depth, and the number of metastatic neck lymph nodes.


Patients were instructed to fast for 6 h before the PET study. 18F-FDG was administered intravenously. For PET/CT scans, oral contrast was administered to

patients during the uptake time. No IV contrast material was administered for CT scans. Head to mid thigh scans were obtained for all patients. PET and CT images were acquired 50 min after the injection

of 18F-FDG. PET, CT, and fused PET/CT images were available for review

and were displayed in axial, coronal, and sagittal planes. PET data were displayed as non-corrected and attenuation-

corrected images as well as in a rotating MIP.


Area of increased 18F-FDG uptake with intensity higher than that of surrounding tissues and did not correspond to the physiologic bio-distribution of the radiotracer, were defined as positive.

18F-FDG activity only in areas of the physiologic tracer bio-distribution or no sites of increased uptake were considered negative.

The highest activity within a region of interest was measured.

The standardized uptake value (SUV) was determined as the highest activity concentration per injected dose per body weight (kg).


18F-FDG uptake was graded visually on the following 5-point scale:

0-definitely benign, no uptake.

1-probably benign, 2.3 (range, 1.4–4.0).

2-equivocal, 2.6 (range, 1.4–4.4).

3-probablymalignant, 3.5 (range, 2.1–7.9).

4-definitely malignant, 6.6 (range, 2.6–24.5).

SUV of 3.1 was used as the cutoff for positive PET results.


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Imaging of enlarged lymph node