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Pearls and pitfalls of radionuclide imaging of the lymphatic system. Part 1: sentinel node lymphoscintigraphy in malignant melanoma

Department of Radiology, John Radcliffe Hospital, Headley Way, Headington, Oxford OX3 9DU, UK

View larger version (132K): [in this window] [in a new window]   Figure 1. Lymphatic vessel drainage. Image from a 31-year-old male with a left anterior abdominal wall melanoma showing two prominent lymphatic vessels draining to a solitary left axillary sentinel node. Also note the hepatic uptake and a second echelon node within the axilla (arrow). The outline of the patient's body is obtained by using a 57Cobalt flood source to provide a transmission image.

View larger version (85K): [in this window] [in a new window]   Figure 2. Solitary sentinel node. Early(5 min) (a) frontal and (b) lateral images from a sentinel node scintigram in a 39-year-old female with a cutaneous malignant melanoma on the left shoulder demonstrating lymphatic drainage to a solitary left axillary sentinel node (arrows).

View larger version (59K): [in this window] [in a new window]   Figure 3. Multiple sentinel nodes.(a) Frontal image from a 43-year-old female with a central anterior abdominal wall melanoma demonstrating lymphatic drainage to bilateral axillary sentinel nodes, a secondary left axillary node is also noted (thin arrow). (b) Frontal image from a 35-year-old male with a melanoma on the left side of the trunk showing bilateral axillary sentinel nodes, the right sided node is more conspicuous on this image due to careful windowing, but could easily be overlooked. A lead shield has been used to avoid obscuration of a regional node by scatter from the injection site (thick arrow). The dome of the liver is seen in the lower portion of the image.

View larger version (81K): [in this window] [in a new window]   Figure 4. Drainage to interval nodes.(a) Frontal image from a 56-year-old male with a melanoma on the right wrist demonstrating tracer uptake in a right epitrochlear node (arrow) and multiple right axillary nodes. The liver is seen in the lower portion of the image. Both the epitrochlear and sentinel axillary node were marked. (b) Early (5 min) and (c) delayed (30 min) prone images from a 27-year-old female with a right posterior chest wall melanoma show an unusual sentinel node on the posterior chest wall (b) (thin arrow) and subsequent uptake of tracer within a right axillary sentinel node (c). A lead shield was used to cover the injection site (thick arrows in (b) and (c)).

View larger version (87K): [in this window] [in a new window]   Figure 5. Importance of delayed imaging.(a) Early and (b) late frontal images from a 47-year-old male with a left anterior chest wall melanoma showing bilateral axillary sentinel nodes; the right is much more conspicuous on (b) the delayed (1 h) image and could easily have been missed. Lead shields have been placed over the injection site in the images (arrows).

View larger version (89K): [in this window] [in a new window]   Figure 6. Importance of additional imaging planes– obscuration by injection site. Frontal and lateral images from a 39-year-old male with a melanoma in the left cervical region. (a) The sentinel node is completely obscured by the injection site on the frontal image, but is clearly identified on (b) the lateral view (arrow). A lead shield has been placed over the injection site in (a) (arrow).

View larger version (75K): [in this window] [in a new window]   Figure 7. Importance of additional imaging planes– overlapping nodes. Frontal and lateral images from a 53-year-old female with a melanoma on the left posterior chest wall. (a) A solitary left axillary sentinel node (arrow) and two second echelon nodes are demonstrated on the frontal view. (b) The lateral image reveals that there are actually two sentinel nodes which are superimposed on the frontal view.

View larger version (110K): [in this window] [in a new window]   Figure 8. Skin contamination with radiotracer.(a) Frontal image showing bilateral axillary sentinel nodes in a 32-year-old male with an upper anterior chest wall melanoma, the image is degraded by multiple focal areas of increased tracer uptake over the right side of the scalp due to contamination. A lead shield has been placed over the injection site (arrow). (b) Frontal image from a 41-year-old female with a left chest wall melanoma showing a left axillary sentinel node and an area of abnormal uptake in the midline at the root of the neck which could represent a further node (arrow). (c) Following skin washing a repeat frontal image confirms that this area of abnormal update was due to skin contamination and not a node.

View larger version (122K): [in this window] [in a new window]   Figure 9. Multiple nodes– secondary nodes versus multiple sentinel nodes. (a) Frontal image from a 26-year-old female with a melanoma on the right calf (injection site not shown) demonstrating nodal uptake in three right inguinal nodes. The right thigh lymphatic vessel drains directly into the lowest node (arrow) which is the sentinel node. Lymph subsequently drains to the two further nodes and these are therefore secondary nodes and need not be marked. (b) Frontal image from a 46-year-old male with a left calf melanoma (injection site not demonstrated) showing two separate lymphatic vessels (arrows) draining into two left inguinal nodes, which are therefore both sentinel nodes and should both be marked for sampling.

View larger version (56K): [in this window] [in a new window]   Figure 10. Lymphatic pooling mimicking nodes. Early(5 min) and delayed (30 min) images from a 39-year-old male with a right sided chest wall melanoma. (a) Early frontal image showing apparent drainage to two right axillary sentinel nodes. (b) Delayed frontal image showing that one of the apparent nodes has disappeared; the appearance on the early image was due to lymphatic pooling. If the delayed images had not been performed, this may have been marked erroneously as an additional sentinel node.