From the Guidelines

Contrast-enhanced CT of the neck is the imaging modality of choice for persistent neck lymphadenopathy.

The American College of Radiology and the American Academy of Otolaryngology-Head and Neck Surgery recommend contrast-enhanced CT or MRI for patients with a neck mass deemed at increased risk for malignancy 1.
CT has several benefits, including superior spatial resolution, lower cost, and shorter scanning time, making it a preferred initial imaging modality for a palpable nonpulsatile neck mass in an adult 1.
CT can help identify a dental source of infection, evaluate the extent of deep neck inflammation, and confirm fat-containing lesions in the neck 1.
MRI is preferred when a primary tumor of the nasopharynx is suspected or when there is cranial nerve abnormality on physical examination, but it has limitations due to motion artifact and longer scanning time 1.
Ultrasound can be used to characterize a neck mass and guide percutaneous tissue sampling, but it is best suited for evaluation of superficial tissue and may not adequately visualize the upper aerodigestive tract 1.

Dual-phase CT imaging (without and with IV contrast) is not usually necessary, and CT performed only without IV contrast may be helpful in some cases 1.
The standard neck CT or MRI should extend from the skull base to the thoracic inlet to adequately capture all structures for evaluation 1.
Imaging should reflect "as low as reasonably achievable" (ALARA) practices to minimize radiation exposure 1.

From the Research

The imaging modality of choice for persistent neck lymphadenopathy is a subject of discussion among various studies.

Ultrasound (US) is considered a useful imaging modality for the assessment of cervical lymphadenopathy, especially in developing countries due to its ease, noninvasiveness, reproducibility, and cost effectiveness 2.
US can be used as the first-line imaging tool in the diagnostic evaluation of cervical lymphadenopathy, and when combined with fine-needle aspiration (FNA), it has a high sensitivity and specificity 2.
Computed Tomography (CT) is also considered superior to other imaging modalities for detection of cervical lymphadenopathy, providing a non-invasive means of visualizing the major lymph node bearing areas in the head and neck region 3.
Magnetic Resonance Imaging (MRI) is also used for lymph node imaging, but further technical development is necessary to improve accuracy of lymph node metastases in patients with N0 neck 4.
The choice of imaging modality may depend on the specific clinical scenario and the availability of resources, but US and CT are commonly used for the assessment of cervical lymphadenopathy 5, 6.

US is effective for detection, localization, and delineation of enlarged lymph nodes, and can demonstrate infiltration of adjacent structures 6.
CT is useful for visualizing the major lymph node bearing areas and can help plan the appropriate surgical approach and/or radiation ports 3.
MRI can provide characteristics of lymph nodes, but its accuracy needs to be improved with further technical development 4.

Imaging modalities can change the operative course of patients with cervical lymphadenopathy, and can demonstrate inoperability in some cases 6.
The information obtained from imaging modalities can be used to plan the appropriate treatment approach and to follow the therapeutic response 3.