Quantitative methods for indirect CT lymphography

The development of an indirect computed tomography lymphography protocol for sentinel lymph node detection in head and neck cancer and comparison to other sentinel lymph node mapping techniques

Identification of metastatic disease critically impacts the care and prognosis of patients with neoplasia. Multiple techniques exist for identifying the sentinel or first lymph node(s) that receive draining tumour lymph. Identification of the sentinel lymph node enables accurate tissue sampling for determination of lymphatic metastasis. The aims of this study were to develop a computed tomography (CT) protocol for identifying the sentinel lymph node in dogs with tumours of the head and neck. In addition, indirect CT lymphography was compared to lymphoscintigraphy and vital dye injection to determine which technique more reliably identified the sentinel lymph node. CT indirect lymphography using intratumoral injection of iodinated contrast identified draining lymphatic vessels in eight of 18 dogs and identified the sentinel lymph node in five of 18 dogs. CT indirect lymphography employing four-quadrant peritumoral injection of iodinated contrast identified draining lymphatic vessels in 18 of 20 dogs and identified the sentinel lymph node in 11 of 20 dogs. Vital dye injection and lymphoscintigraphy identified the sentinel lymph node in 17 of 18 and 20 of 20 dogs, respectively. Identified sentinel lymph nodes were either ipsilateral or bilateral to the primary tumour. Both CT techniques were found to be safe and simple. Peritumoral injection has the greatest promise for the detection of sentinel lymph nodes in various head and neck cancers using CT, while lymphoscintigraphy had the greatest success of the compared techniques.

Computed Tomography Lymphography With Intrapulmonary Injection of Iopamidol for Sentinel Lymph Node Localization

PURPOSE

Experimental and clinical evaluation of the potential utility of indirect computed tomographic lymphography (CT-LG) with intrapulmonary injection of iopamidol for preoperative localization of sentinel lymph node station in non-small cell lung cancer.

METHODS

CT-LG with intrapulmonary injection of 0.5 mL of undiluted iopamidol was performed in 10 dogs using a multidetector-row CT unit, followed by postmortem examination of enhanced lymph nodes in 5 of these dogs. The CT-LG with peritumoral injection of 1 mL of the contrast agent was also performed in 9 patients with non-small cell lung cancer without lymphadenopathy. At surgery, enhanced lymph nodes were resected under CT-LG guide, followed by standard lymph node dissection with macroscopic and histologic examination. A significant enhancement of lymph nodes was determined when CT attenuation value was increased with 30 Hounsfield units (HU) compared with precontrast images.

RESULTS

CT-LG visualized a total of 15 enhanced lymph nodes (on average, 1.5 nodes per animal) within 2 minutes after contrast injection in the 10 dogs, with average size of 6.7+/- 1.9 mm and average maximum CT attenuation of 149 +/- 41 HU. All the 8 enhanced nodes in 5 dogs were found in the appropriate anatomic locations in postmortem examinations. Without noticeable complications, CT-LG visualized 30 ipsilateral intrathoracic lymph nodes including 19 hilar/pulmonary and 11 mediastinal nodes in the 9 patients (on average, 2.2 hilar/pulmonary and 1.1 mediastinal nodes per patient) within 2 minutes after contrast injection, with average size of 4.7+/- 0.4 mm and average maximum CT attenuation of 134 +/- 52 HU. At surgery, all these enhanced nodes could be accurately found and resected under CT-LG guidance. Metastasis was not evident in either of these enhanced lymph nodes or the remaining distant nodes in all patients.

CONCLUSION

Quick and accurate localization of sentinel lymph node station on detailed underlying lung anatomy by using indirect CT-LG may be of value to guide selective lymph node dissection for minimally invasive surgery in non-small cell lung cancer.

A surface-modified chylomicron remnant-like emulsion for percutaneous computed tomography lymphography: synthesis and preliminary imaging findings

RATIONALE AND OBJECTIVES

To assess a surface-modified emulsion as a percutaneous CT lymphographic agent in normal dogs.

METHODS

An iodinated chylomicron remnant-like microemulsion was formulated with a mean particle size of 91.3 nm and an iodine concentration of 91 mg I/mL. Contrast material (2 mL) was injected into the subcutaneous tissues of the metatarsus and metacarpus of six normal dogs to enhance popliteal and cervical lymph nodes, respectively. CT images were acquired at 0, 15, 30, 45, 60, 240, 480, and 1440 minutes.

RESULTS

Significant lymph node enhancement occurred in as little as 15 minutes after injection and persisted at least 8 hours. Node opacification was most pronounced at 1 to 4 hours postinjection and exceeded 200 HU in some nodes (precontrast attenuation = 45 HU). Marked enhancement of popliteal efferent lymphatics and of iliac and sacral node groups also occurred indicating distribution to second order nodes. Attenuation of enhanced nodes reverted to precontrast levels by 24 hours.

CONCLUSION

The new surface-modified, chylomicron remnant-like emulsion provided marked, selective enhancement of targeted lymph nodes after subcutaneous administration. Moreover, the formulation produced significant opacification of more distant node groups from a single injection.

Eyelid lymphatics II: a search for drainage patterns in the monkey and correlations with human lymphatics

PURPOSE

To study the lymphatic drainage of the cynomolgus monkey through the use of lymphoscintigraphy.

METHODS

Lymphoscintigraphy with 500 microCi of 99mTechnetium sulfur colloid injected at specific sites around the eyelids was performed with five cynomolgus monkeys in lateral and ventral positions.

RESULTS

Lymphoscintigraphy of the monkey eyelid and periocular tissue revealed lymphatic drainage to the parotid lymph nodes from the entire upper eyelid, medial canthus, and lateral lower eyelid and drainage to the submandibular lymph nodes from the medial and central lower eyelid. In addition to draining to the parotid lymph nodes, the central upper eyelid was also seen to drain to the submandibular lymph nodes.

CONCLUSIONS

Lymphoscintigraphy of the cynomolgus monkey eyelids reveals discrete lymphatic drainage pathways for the upper and lower eyelids and a dual pathway for the central upper eyelid. Future studies will help to clarify the lymphatic drainage pathways of human eyelids.

Long-term effect of irradiation on lymph node uptake of interstitially delivered nanoparticulate contrast media

RATIONALE AND OBJECTIVES

To characterize the long-term effects of therapeutic doses of ionizing radiation on the uptake and distribution of percutaneously delivered particulate contrast media in normal lymph nodes.

METHODS

Two milliliters of an iodinated nanoparticle suspension (76 mg I/mL) was injected subcutaneously or submucosally into nine normal adult beagles. Region of interest analysis was used to estimate the volume, attenuation, and iodine concentration of opacified targeted lymph nodes and nonopacifled contralateral nodes on 24-hour postinjection CT images. All lymph nodes were then irradiated with 50 Gy in 25 fractions of 2 Gy/d. Contrast-enhanced quantitative CT was repeated 12 months after irradiation.

RESULTS

Contrast-enhanced nodes averaged 2.3+/-0.8 times the volume of nonenhanced contralateral nodes before irradiation. The mean attenuation of contrast-enhanced nodes increased to 305 to 380 Hounsfield units from a pre-enhancement value of approximately 25 Hounsfield units. Opacified node volumes after irradiation averaged 61% to 86% of preirradiation volumes but were generally not statistically different. Contrast uptake assessed by average attenuation and iodine concentration decreased significantly by an average of 17% to 22% after irradiation and was significantly less than preirradiation uptake. Qualitatively, irradiated nodes generally appeared smaller than nonirradiated nodes, but the distribution pattern of contrast media did not appear to be appreciably altered.

CONCLUSIONS

Lymph node irradiation resulted in only minimal decreases in contrast media uptake and node volume at 12 months. These effects presumably would not appreciably alter the potential clinical value of indirect lymphography for evaluating patients undergoing radiation therapy.

Lymph node uptake of interstitially delivered particulate contrast media before and after irradiation in dogs

RATIONALE AND OBJECTIVES

The authors' purpose was to assess the effects of ionizing radiation on the uptake and distribution of interstitially delivered particulate contrast medium in normal lymph nodes in dogs.

MATERIALS AND METHODS

Two milliliters of an iodinated nanoparticle suspension (NC 67722 Sterile Suspension, 76 mg of iodine per milliliter) was injected subcutaneously or submucosally into nine normal adult beagle dogs. Targeted lymph node groups were evaluated with computed tomography (CT). Region-of-interest analysis was used to estimate volume, attenuation, and iodine concentration of the opacified nodes and nonopacified contralateral nodes on CT images obtained before and 24 hours after the injection. All right-sided and some left-sided lymph nodes were irradiated with 50 Gy in 25 fractions of 2 Gy per day, beginning 28-35 days after the CT examination. Contrast medium administration and quantitative CT imaging were performed again 3 months after irradiation.

RESULTS

Contrast material uptake resulted in a twofold increase in node volume before irradiation (P < .0001). Mean attenuation of contrast-enhanced nodes increased to 230-330 HU from a precontrast enhancement value of 36.5 HU. After irradiation, opacified node volumes decreased to approximately 25%-50% of their preirradiation volumes (P < .02). Contrast material uptake decreased 10%-15% after irradiation but was not significantly less than preirradiation uptake. Qualitatively, no substantial difference in contrast material distribution existed between irradiated and nonirradiated nodes.

CONCLUSION

An elective irradiation dose decreased lymph node size, but the imaging characteristics of opacification were not otherwise appreciably altered 3 months after irradiation.