Optimized time-resolved 3D contrast-enhanced MRA at 3T: appreciating the feasibility of assessing cervical paragangliomas

The use of 4-dimensional magnetic resonance angiography as a noninvasive procedure to diagnose subclavian steal syndrome in a dog

CASE DESCRIPTION

A 5-year-old 4.1-kg (9.0-lb) spayed female Toy Poodle was referred because of a 6-month history of sporadic signs of neck pain.

CLINICAL FINDINGS

Diagnostic imaging with MRI and CT revealed a dilated radicular artery connecting the right and left vertebral arteries and causing mild compression of the spinal cord. The left subclavian artery caudal to the origin of the left vertebral artery was absent. Subclavian steal syndrome (SSS) was suspected.

TREATMENT AND OUTCOME

The owner declined surgical treatment; thus, the dog was treated conservatively with glucocorticoids and analgesics. Eight months later, the dog's clinical signs were unchanged but palliated with the administration of glucocorticoids and analgesics, and 4-dimensional (4-D) magnetic resonance angiography (MRA) revealed that the left vertebral artery received blood supply from the right vertebral artery through the dilated radicular artery and that the left vertebral artery caudal to this site had retrograde flow and drained into the left subclavian artery, confirming the diagnosis of SSS. The owner again declined surgery, and conservative treatment continued. The dog's condition was unchanged at the last follow-up communication 11 months after 4-D MRA.

CLINICAL RELEVANCE

Subclavian steal syndrome is an extremely rare condition in dogs, and our findings suggested that 4-D MRA could be used to definitively diagnose SSS in dogs.

Quantitative biomarkers allow the diagnosis of head and neck paraganglioma on multiparametric MRI

PURPOSE

The aim of this study is to identify quantitative MR biomarkers in head and neck paragangliomas.

METHODS

The study was approved by an institutional review board. A retrospective review of patients with head and neck paragangliomas (HNPGL) evaluated by time-resolved MRA sequences between 2009 and 2019 was performed. A control group investigated during the same period was analyzed, including nerve sheath tumors and metastatic lymph nodes from squamous cell carcinomas or undifferentiated nasopharyngeal cancer (UCNT). A gold standard was obtained for all cases. Semi-quantitative parameters of enhancement were extracted from time-intensity curves on time-resolved MRA sequences and diffusion weighted imaging/DWI was assessed for each lesion.

RESULTS

Sixty head and neck paragangliomas (HNPGLs) were included from 50 patients. The control group consisted of 30 parapharyngeal space lesions (27 patients), which included nerve sheath tumors (n = 12) and metastatic lymph nodes (n = 18) from squamous cell carcinomas or UCNT. PGLs showed a shorter time-to-peak value compared to other groups, measured at 25.0 +/- 29 sec. The wash-in and wash-out ratios were also significantly higher for PGLs, respectively measured at 5.34 ± 2.99 (p < 0,001) and 1.24 ± 0.80 (p < 0.001). On DWI sequences, the mean ADC value for PGLs (1.17 ± 0.19 10^-3 mm2/s) was significantly different than the other tumor groups (p < 0.001). HNPGLs were clearly distinguishable from other tumors on classification with regression tree based on TTP and ADC values. These distinct group features were also consistent on principal component analysis.

CONCLUSION

Our study identifies a multiparametric signature for disease subtyping, providing a strong impetus for switching from qualitative to quantitative analysis of deep soft-tissue tumors of the neck.

Diagnostic Investigation of Lesions Associated with Succinate Dehydrogenase Defects

The mitochondrial enzyme succinate dehydrogenase (SDH) acts as a tumor suppressor. Biallelic inactivation of one of the genes encoding for SDH subunits (collectively named SDHx) leads to complete loss of the protein function and the development of diverse group of tumors. Pheochromocytomas-paragangliomas are the prime example of hereditary tumors caused by SDH deficiency. In this review, we discuss the roles of imaging examinations, and illustrate new insights into genotype-imaging phenotype relationships.

Recent advances in 3D time-resolved contrast-enhanced MR angiography

Contrast-enhanced magnetic resonance angiography (CE-MRA) was first introduced for clinical studies approximately 20 years ago. Early work provided 3-4 mm spatial resolution with acquisition times in the 30-second range. Since that time there has been continuing effort to provide improved spatial resolution with reduced acquisition time, allowing high resolution 3D time-resolved studies. The purpose of this work is to describe how this has been accomplished. Specific technical enablers have been: improved gradients allowing reduced repetition times, improved k-space sampling and reconstruction methods, parallel acquisition, particularly in two directions, and improved and higher count receiver coil arrays. These have collectively made high-resolution time-resolved studies readily available for many anatomic regions. Depending on the application, ∼1 mm isotropic resolution is now possible with frame times of several seconds. Clinical applications of time-resolved CE-MRA are briefly reviewed.

Different imaging techniques in the head and neck: Assets and drawbacks

In this review, the gold standard imaging techniques for the head and neck and the latest upcoming techniques are presented, by comparing computed tomography (CT), magnetic resonance imaging and positron emission tomography-CT, as well as ultrasound, depending on the examined area. The advantages and disadvantages of each examination protocol are presented. This article illustrates the connection between the imaging technique and the examined area. Therefore, the head and neck area is divided into different sections such as bony structures, nervous system, mucous membranes and squamous epithelium, glandular tissue, and lymphatic tissue and vessels. Finally, the latest techniques in the field of head and neck imaging such as multidetector CT, dual-energy CT, flash CT, magnetic resonance angiography, spectroscopy, and diffusion tensor tractography using 3 tesla magnetic resonance are discussed.