Table 1 Imaging technologies based on drug delivery systems (DDSs)

LSG and SPECT/CT

Injecting a tracer containing a radioactive isotope into the interstitial tissues and using external detectioninstr-ument (SPECT) to track and image it

99mTc-labeled nanocolloid DDSs (99mTc-sulphur colloid, 99mTc-nanocolloidal albumin, 99mTc antimony trisulfide colloid, 99mTc-etarfolatide, etc.)

The short half-life and poor contrast of the 99mTc complex are improved;

Helping in the early detection of SLN;

Guiding lymph node biopsy effectively;

Reducing the occurrence of postoperative sequelae, etc

[147, 149,150,151]

PET/CT

Tumor tissues exhibit abnormally increased glucose uptake. PET/CT utilizes radiolabeled glucose analogs as tracers to image the lesion tissue based on this characteristic of malignant tumors

68 Ga-labeled targeted PSMA-DDS;

124I-labeled antibody against LYVE-1 DDS

Increasing the sensitivity and accuracy of diagnosis and reducing the

occurrence of misdiagnosis and missed diagnosis;

Improving the targeting of imaging agents to lymph nodes, etc

[167, 168]

MRI

MRI uses strong magnetic fields and radio waves to create detailed images of the body's internal structures. The magnetic field aligns the body's protons, and the radio waves cause them to emit signals which are detected and analyzed to create images

Gd₂O₃PCD coated DDS;

USPIO DDSs

Reducing Gd deposition and cytotoxicity;

Pharmacokinetics and biocompatibility are satisfactory;

Having higher diagnostic specificity and sensitivity, etc

[171, 172, 174]

NIR fluorescence imaging

NIR fluorescence imaging technology is used to visualize lymph nodes. It involves injecting a fluorescent dye and exciting its fluorescent properties using a detector to create contrast agent visualization

PLGA-ICG DDSs;

γ-PGA-ICG DDSs;

PEG coated ICG-DDSs;

Metal nanoclusters DDSs

Good retention rate and stability in vivo;

Having a stronger NIR fluorescence signal than ICG;

Increasing the molecular weight to reduce clearance by blood;

Serviceable tissue penetration and lower interference signals from endogenous substances, etc

[111, 180, 188, 190]

US/PA imaging

US imaging is based on the principle of sound wave reflection, collecting the reflected sound wave from the tissue organs and converting them into images. PA imaging uses laser-generated light pulses to generate acoustic waves in the body's tissues which are detected and analyzed to create images

Carbon NP DDS;

Cu-neodecanoate DDS

Satisfactory SLN imaging capability, imaging depth, signal noise, ratio and tissue contrast, etc

[194,195,196]

Multimodality imaging

Combining different lymph node imaging technologies

GC-AuNCs/ICG DDS (PA/Fluorescence imaging);

Nanoprobes DDSs (PA/Fluorescence imaging);

Iron oxide-ATF DDS (NIR/PA/MR I)

To compensate for the limitations of different technologies, take advantage of each technology. Explore the potential of lymph node imaging technology based on DDSs

[198,199,200,201]