Computed tomography (CT) and magnetic resonance imaging (MRI) can play an important role in preoperative and post-treatment assessment of thyroid malignancy. The radiologist should be aware of the pathological behavior of thyroid carcinoma, and the characteristic imaging appearance of the primary tumor and metastases. This review describes the approach to imaging thyroid cancer on CT and MRI for four common scenarios: detection of the incidental thyroid nodule, evaluation of thyroid metastases, presurgical imaging for invasive disease, and evaluation for recurrence in the post-treatment neck.
SUMMARY:This clinical report describes the enhancement characteristics of hypersecreting parathyroid lesions on dual-phase neck CT. We retrospectively analyzed the enhancement characteristics of 5 pathologically confirmed PTH-secreting lesions on dual-phase CT examinations. Attenuation values were measured for PTH-secreting lesions, vascular structures (CCA and IJV), and soft tissue structures (thyroid gland, jugulodigastric lymph node, and submandibular gland). From the attenuation values, "relative enhancement washout percentage" and "tissue-vascular ratio" were calculated and compared. All lesions decreased in attenuation from arterial to venous phase, while the mean attenuation values of other soft tissue structures increased. A high relative enhancement washout percentage was correlated with parathyroid lesions (P Ͻ .006). The tissue-CCA ratio and tissue-IJV ratio for PTHsecreting lesions in the arterial phase were statistically significantly higher compared with soft tissue structures (P Ͻ .05). If these results are validated in future larger studies, noncontrast and delayed venous phases of 4D-CT could be eliminated to markedly reduce radiation exposure.ABBREVIATIONS: CCA ϭ common carotid artery; HU ϭ Hounsfield units; IJV ϭ internal jugular vein; PTH ϭ parathyroid hormone; ROC ϭ receiver operating characteristic curve M ost cases of primary hyperparathyroidism are due to benign parathyroid adenomas and parathyroid hyperplasia. These lesions are sometimes difficult to identify at surgery and on imaging due to variations in number and location of abnormal parathyroid glands, with multiglandular hyperplasia and multiglandular adenomas occurring in up to 14% of cases.1,2 Ectopic parathyroid adenomas and ectopic parathyroid hyperplasia account for 20 -25% of cases.3,4 Initial work-up in a patient with primary hyperparathyroidism usually consists of sonography or technetium (Tc)99m sestamibi scintigraphy with or without SPECT imaging. When these tests are negative, second-tier imaging investigations, such as 4D-CT and MR imaging of the neck, can be helpful in preoperative planning.The original description of 4D-CT includes image sets in 3 planes (axial, coronal, and sagittal).5 The "fourth" dimension of 4D-CT is the perfusion information derived from noncontrast, arterial, and venous phase imaging. Since this paper was published, different institutions have produced modified protocols. Some have interpreted "4D" as a 4-phase neck CT with precontrast and 3 postcontrast phases of neck imaging.
6-9Others image with precontrast and single postcontrast neck phases, 10 or postcontrast arterial and venous phases only.
11Because of these multiple phases of imaging, 4D-CT has been criticized for its high radiation dose. To reduce radiation dose, but still obtain perfusion information that might allow detection of parathyroid lesions, we have modified the protocol at our institution to dual-phase scanning with only arterial and venous phase imaging. The aim of this clinical report is to describe the enhancement characte...
The ED for the CTF-guided ESI was almost half that of conventional fluoroscopy because of the shorter fluoroscopy time. However, the overall radiation dose for CTF-guided ESIs can be up to four times higher when a full diagnostic lumbar CT scan is performed as part of the procedure. Radiation dose reduction for CTF-guided ESI is best achieved by minimizing the dose from the preliminary planning lumbar spine CT scan.
Both organ-based dose modulation and thyroid shields significantly reduce the thyroid organ dose without degradation of subjective image quality compared with automatic tube current modulation. Organ-based dose modulation has the additional benefit of dose reduction to the ocular lens.
ObjectCerebrospinal fluid leaks due to unrecognized durotomy during spinal surgery are often managed with a second surgery for dural closure. CT-guided percutaneous patching targeted to the dural defect offers an alternative to surgery since it can be performed in a minimally invasive fashion without the need for general anesthesia. This case series describes the authors' experience using targeted CT-guided percutaneous patching to repair incidental durotomies incurred during spinal surgery.MethodsThis investigation is a retrospective case series involving patients who underwent CT-guided percutaneous patching of surgical incidental durotomies and were referred between January 2007 and June 2013. Their presenting clinical history, myelographic findings, and clinical outcomes, including the need for eventual surgical duraplasty, were reviewed.ResultsNine cases were identified, including 7 durotomies incurred during lumbar discectomy, one due to a medial transpedicular screw breach, and one incurred during vertebrectomy for spinal osteosarcoma. All patients who had favorable outcomes with percutaneous intervention alone had 2 common features: dural defect of 4 mm or smaller and absence of a pseudomeningocele. Patients with CSF leaks complicated by pseudomeningocele and those with a dural defect of 6 mm or more all required eventual surgical management.ConclusionsThe authors' results suggest that findings on CT myelography may help predict which patients with postsurgical durotomy can be treated with percutaneous intervention. In particular, CT-guided patching may be more likely to be successful in those patients with dural defects of less than 5 mm and without pseudomeningocele. In patients with larger dural defects or pseudomeningoceles, percutaneous blood patching alone is unlikely to be successful.
Reducing the voltage from 120 to 80 kVp for neck CT can result in greater than 50% reduction in the absorbed organ dose to the bone marrow of the cervical spine and mandible without impairment in subjective image quality.
The unexpected visualization of the normal or pathologic uterus has been reported in the radionuclide imaging literature. Occasionally, this may create a diagnostic dilemma during interpretation of Tc-99m RBC scans, bone scans, or renal scans and additional imaging modalities are usually necessary to further define the abnormality. We report an interesting case of fibroid uterus identified as an intense, heterogeneous, and persistent vascular pelvic mass during a Tc-99m RBC scan in a patient with concomitant active lower gastrointestinal hemorrhage.
The aim is to describe the technique of preoperative CT-guided hookwire localization of small, but suspicious, cervical lymph nodes. We present 3 patients who underwent the procedure for nonpalpable cervical nodes detected on PET/CT prior to complete surgical resection of the nodes. The details of the radiological procedure, surgical outcomes, and pathologic results are described. The mean intervention time for preoperative hookwire localization was 9 minutes (range 7-14 minutes). There were no complications. All surgeons felt that the lengths of the surgical skin incision and operative times were reduced because of localization. The pathologic diagnoses were 2 benign nodes and 1 case of metastatic ovarian carcinoma. In conclusion, preoperative CT-guided hookwire localization is a useful technique for guiding surgical excision, especially when cervical nodes are small and deep in location.
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