MRI of the head and neck

Neuroradiology back to the future: head and neck imaging

SUMMARY

Imaging of the head and neck was initially described within the first year after Roentgen's discovery of the x-ray and was used to localize foreign bodies in the head and neck area, including the orbital, laryngeal, and esophageal regions. Subsequently, x-rays were used to evaluate the air-filled paranasal sinuses, the pneumatized temporal bone, and the upper aerodigestive tract. Special views for evaluating these structures were developed by early investigators. As contrast agents were developed, a variety of invasive procedures were developed to assess the structures of the head and neck. CT and MR imaging were applied to the extracranial head and neck slightly later than the brain and spine; these modalities revolutionized head and neck radiology, finally allowing assessment of the deeper structures of this complex anatomic region.

A review for solitary plasmacytoma of bone and extramedullary plasmacytoma

Solitary plasmacytoma (SP) is characterized by a mass of neoplastic monoclonal plasma cells in either bone (SBP) or soft tissue without evidence of systemic disease attributing to myeloma. Biopsy confirmation of a monoclonal plasma cell infiltration from a single site is required for diagnosis. The common presentation of SBP is in the axial skeleton, whereas the extramedullary plasmacytoma (EMP) is usually seen in the head and neck. The ratio of SP seen at males to females is 2 : 1 and the median age of patients is 55 years. The incidence rate of SP in black race is approximately 30% higher than the white race. Incidence rate increases exponentially by advancing age. SBP has a significant higher risk for progression to myeloma, and the choice of treatment is radiotherapy (RT) that is applied with curative intent at min. 4000 cGy. By only RT application, long-term disease-free survival (DFS) is possible for approximately 30% of patients with SBP and 65% of patients with EMP.

Magnetic resonance imaging versus clinical palpation in evaluating cervical metastasis from head and neck cancer

We prospectively compared the value of MRI and clinical palpation for detecting cervical metastases in patients with primary cancer of the head and neck. Sixty patients with squamous cell carcinoma of the upper aerodigestive tract were evaluated with MRI and clinical palpation before undergoing a total of 81 neck dissections. The results of preoperative clinical palpation and MRI were compared with the histopathologic outcome. The sensitivity and specificity were 75.6% and 97.5%, respectively, for clinical palpation and 73.2% and 95%, respectively, for MRI. The rate of occult cervical metastasis was 24% with clinical palpation and 26.8% with MRI. The use of MRI did not improve the rate of early detection of occult metastasis, nor did it improve the detection of extracapsular spread. Our findings show that we could not depend on palpation or MRI alone to determine the need for elective neck dissection. However, MRI can be used to improve the preoperative grading of cervical lymph nodes. In selected cases, this may direct surgeons to convert the treatment plan to choose a more conservative neck dissection or, after sentinel node sampling and frozen-section control, to convert the treatment to a more radical dissection.

MRI of nasopharyngeal carcinoma with emphasis on relationship to radiotherapy

MRI has been used increasingly in the evaluation of nasopharyngeal carcinoma (NPC) because of its good tissue contrast and multiplanar capacity. Although there are some controversies in assessing skull base invasion and cervical metastatic adenopathy, recent reports demonstrate that MRI is currently better than or as good as CT in defining the extent of NPC. During follow-up of patients with NPC after radiotherapy, MRI is also more effective than CT in demonstrating tumor recurrence and in detecting postradiation complications. However, the difficulty of using MRI to detect early mucosal recurrence and to differentiate postradiation tissue changes from local tumor recurrence should be recognized. This paper reviews the literature regarding MRI of NPC related to radiotherapy, with special emphasis on treatment planning, recurrence assessment, and complication detection.

Efficacy and safety of gadopentetate dimeglumine in the evaluation of patients with a suspected tumor of the extracranial head and neck

The clinical efficacy and safety of gadopentetate dimeglumine as a paramagnetic contrast agent for magnetic resonance (MR) imaging of the extracranial head and neck was evaluated in a multicenter trial involving 60 patients. Patients with signs and/or symptoms of a tumor in the nasopharynx, oropharynx, hypopharynx, larynx, or neck were studied. T1-weighted images were obtained before and after injection of gadopentetate dimeglumine, 0.1 mmol/kg, at a rate of 10 mL/min. No lesions were seen on the pre- or postinjection images of five of the 60 patients. Postinjection lesion enhancement was present in 53 of the remaining 55 (96%) patients. The absence of postinjection lesion enhancement in one of the two remaining patients was useful information. Postinjection impressions differed from preinjection diagnosis in 22 of 60 (37%) patients. Additional information was obtained from postinjection relative to preinjection images in 38 of 60 (63%) patients. Four adverse experiences were reported in three of 60 (5%) patients. Two mild (chest wall pain and headache) and one moderate (nausea) adverse experiences were considered by the authors to be unrelated to the studied drug. One severe adverse experience was reported. This patient had a seizure, considered by the investigator to be remotely related to the study drug and attributed to the abrupt withdrawal of anticonvulsant medications. The data indicate that gadopentetate dimeglumine is safe and efficacious in the evaluation of patients with extracranial head and neck lesions.

Computed tomography (CT) and magnetic resonance imaging (MRI) in T-stage evaluation of oral and oropharyngeal carcinomas

174 CT and 32 MRI investigations were carried out on patients with carcinomas of the mouth and oropharynx. The methods were compared and their value in predicting the pre-therapeutic T-staging studied. The combination of CT and clinical examination was able to improve the T-staging considerably compared with clinical examination alone. MRI was superior to CT in delineating the tumour margins in 78% of patients. T1-weighted and gradient echo sequences after intravenous gadolinium injection were particularly useful. Nevertheless, T-staging based on clinical and CT-findings was changed in only 5% of patients by MRI. MRI is especially useful in T1 tumours and in cancer of the base of the tongue. MRI should also be used instead of CT were dental fillings obscure the region of interest. If there are good MRI facilities and an experienced team available MRI can be used before CT.

Correlation of clinical, surgical, pathologic, and MR fat suppression results for head and neck cancer

Magnetic resonance (MR) imaging provides superior soft tissue delineation of head and neck tumors compared to previous radiologic studies. Further refinements using fat suppression and gadolinium (Gd-DTPA) enhancement have added to these improved images. We performed MR studies of 16 patients with head and neck tumors with detailed clinical, surgical, and pathologic information. MR studies included standard spin-echo T1-weighted images (T1WI) with and without fat suppression and T2-weighted images (T2WI) with fat suppression. Gadolinium was also administered with fat suppression. Conventional and paired fat suppression MR images were compared by a grading system. Post-Gd-DTPA fat suppression T1WI, and T2WI with fat suppression, showed superior sensitivity for tumor delineation when compared to conventional T1WI. Fat suppression T2WI was the best technique to delineate squamous cell carcinoma both in the primary site and regional lymph nodes. Clinical, surgical, and pathologic results correlated perfectly with imaging findings. These refinements in MR imaging represent a significant advance in the radiologic evaluation of head and neck tumors.

Magnetic resonance imaging of canine salivary glands after ductal ligation and stimulation by pilocarpine

We performed magnetic resonance imaging in six dogs after submandibular ductal ligation on one side, followed by secretory stimulation with intraperitoneal injection of pilocarpine (5 mg/kg). On the images obtained after ductal ligation but before stimulation, there was no significant change in signal intensity on either side. After injection of pilocarpine the signal intensity of the ligated gland increased significantly (p less than 0.01) in T2-weighted images and nonsignificantly in inversion recovery images, and remained constant in T1-weighted images. Significant (p less than 0.01) volume increases of the glands after ligation and stimulation were measured for the T1, T2, and inversion recovery protocols. These findings likely reflect the retention of saliva caused by pilocarpine stimulation and the absence of drainage through the obstructed duct. The results indicate that the T2-weighted images obtained after pilocarpine stimulation may be useful for studying patients with disturbance of major salivary gland function and may provide an objective basis for the noninvasive diagnosis of unilateral stenosis.

Magnetic resonance imaging and computed tomography in pediatric head and neck masses

Fifty-three magnetic resonance imaging (MRI) and 25 computed tomography (CT) studies of 53 head and neck masses in pediatric patients were reviewed retrospectively. All lesions had pathologic proof except for 2 metastatic and 2 recurrent lesions, which only had prior pathologic confirmation at their primary sites. These included 12 malignant tumors, 23 benign tumors, 6 inflammatory masses, and 12 congenital lesions. The MRI performance ranged predominantly from good to excellent in detection of the lesion and the extent of involvement and in contrast to the surrounding tissue; when CT comparison was available, MRI proved to be equal to or better than it in detection of these factors and in preoperative diagnosis. Our results suggest that MRI should be the method of choice for the initial evaluation of the pediatric head and neck region, especially in those patients requiring multiple examinations. However, CT and MRI should be used conjunctively in complicated cases, especially those possibly involving lesions with calcifications or bony involvement.

Data extrapolation for truncation artifact removal

Clinicians typically obtain high-resolution clinical MR images in an effort to avoid the truncation artifacts that often arise in Fourier transform reconstruction of limited data. A method for reducing these artifacts in MR images, at the reconstruction stage, would allow for reduced imaging times, through the collection of fewer phase encode steps and increased signal-to-noise ratios, through increased pixel size. The approach to reducing truncation artifacts in MR images is developed and a simple algorithm is presented which significantly reduces truncation artifacts in images with as few as 96 phase encode steps. The algorithm is compared with a more sophisticated method of reconstructing truncation-free images and is shown to be equivalently effective. Three clinical examples are shown illustrating the success of the method.

Magnetic resonance imaging of nasopharyngeal and paranasal sinus melanoma

Malignant melanoma of the nasopharynx and paranasal sinuses is relatively rare. We retrospectively reviewed the magnetic resonance appearance of five cases and correlated this with the histopathological appearance. In all cases, the magnetic resonance (MR) images clearly demonstrated the precise anatomic extent of the tumor and were sensitive in assessing intracranial extension and invasion into surrounding structures, including the skull base. Three cases were reviewed for histopathological evidence of melanin, hemosiderin, and acute hemorrhage. One case was reviewed for melanin and hemorrhage only. The findings in this series suggest that melanoma of the nasopharynx and paranasal sinuses have extremely variable amounts of paramagnetic substances, both melanin and products of hemorrhage. T1 shortening appears to be more often a reflection of the paramagnetic effects associated with products of hemorrhage rather than the presence of melanin.