John A. Arrington

MRI: Stability of three supervised segmentation techniques

Supervised segmentation methods from three families of pattern recognition techniques were used to segment multispectral MRI data. Studied were the maximum likelihood method (MLM), k-nearest neighbors (k-NN), and a back-propagation artificial neural net (ANN). Performance was measured in terms of execution speed, and stability for the selection of training data, namely, region of interest (ROI) selection, and interslice and interpatient classifications. MLM proved to have the smallest execution times, but demonstrated the least stability. k-NN showed the best stability for training data selection. To evaluate the segmentation techniques, multispectral images were used of normal volunteers and patients with gliomas, the latter with and without MR contrast material. All measures applied indicated that k-NN provides the best results.

MRI of soft tissue tumors

Magnetic resonance imaging (MRI) is the only noninvasive method of defining a soft tissue tumor. The extent of the tumor and the question of involvement or noninvolvement of various adjacent tissues and structures can be determined. This information, determination of lymphatic and distant metastatic spread, is invaluable for staging and management of the disease. Whether or not the tumor type can be reliably determined, or even whether the malignant or benign nature of the tumor can be ascertained on MRI examination, is open to question. Review of the literature indicates proponents on both sides of the issue. This review illustrates the imaging features that are relevant to suggesting a histologic diagnosis, and the pitfalls that are encountered in trying to determine the malignancy or benignity of a lesion. The clinical significance of these determinations is also discussed.

Computer tomographically guided discography as a determinant of normal disc level before fusion

Computer tomographically guided discography was used as a reproducible reliable method of determining the internal architecture and integrity of intervertebral discs before spinal fusion operation. One hundred disc levels were studied in 60 prospective patients with 54 [54%) of levels proving abnormal. Twenty-nine levels (29% of total levels) demonstrated complete anular tears, and 25 (25% of total) showed incomplete radial tears of the anulus, often multiple, indicative of degenerative change. In each of these cases, one level higher had to be studied and was subsequently found to be normal and would, therefore, support a fusion.Computer tomographically guided discography was used as a reproducible and reliable method of determining the internal architecture and integrity of intervertebral discs before spinal fusion operation. One hundred disc levels were studied in 60 prospective patients with 54 (54%) of levels proving abnormal. Twenty-nine levels (29% of total levels) demonstrated complete anular tears, and 25 (25% of total) showed incomplete radial tears of the anulus, often multiple, indicative of degenerative change. In each of these cases, one level higher had to be studied and was subsequently found to be normal and would, therefore, support a fusion.

Outcomes targeting the PD-1/PD-L1 axis in conjunction with stereotactic radiation for patients with non-small cell lung cancer brain metastases.

Anti-PD-1/PD-L1 therapies have demonstrated activity in patients with advanced stage non-small cell lung cancer (NSCLC). However, little is known about the safety and feasibility of patients receiving anti-PD-1/PD-L1 therapy and stereotactic radiation for the treatment of brain metastases. Data were analyzed retrospectively from NSCLC patients treated with stereotactic radiation either before, during or after anti-PD-1/PD-L1 therapy with nivolumab (anti-PD-1) or durvalumab (anti-PD-L1). Seventeen patients treated with stereotactic radiosurgery (SRS) or fractionated stereotactic radiation therapy (FSRT) to 49 brain metastases over 21 sessions were identified. Radiation was administered prior to, during and after anti-PD-1/PD-L1 therapy in 22 lesions (45%), 13 lesions (27%), and 14 lesions (29%), respectively. The 6 months Kaplan–Meier (KM) distant brain control rate was 48% following stereotactic radiation. Six and 12 month KM rates of OS from the date of stereotactic radiation and the date of cranial metastases diagnosis were 48/41% and 81/51%, respectively. The 6 month rate of distant brain control following stereotactic radiation for patients treated with stereotactic radiation during or prior to anti-PD-1/PD-L1 therapy was 57% compared to 0% among patients who received anti-PD-1/PD-L1 therapy before stereotactic radiation (p = 0.05). A Karnofsky Performance Status (KPS) of <90 was found to be predictive of worse OS following radiation treatment on both univariate and multivariate analyses (MVA, p = 0.01). In our series, stereotactic radiation to NSCLC brain metastases was well tolerated in patients who received anti-PD-1/PD-L1 therapy. Prospective evaluation to determine how these two modalities can be used synergistically to improve distant brain control and OS is warranted.

Anterior approach for CT-guided biopsy of skull base and parapharyngeal space lesions

At our institution we use an anterior approach to biopsy of the parapharyngeal space or skull base lesions because it provides more direct access than the traditional lateral approach through the mandibular notch. The anterior approach follows a course lateral to the alveolar ridge of the maxilla and lateral pterygoid plate, and inferior to the zygomatic process of the maxilla. Biopsy was performed on 15 patients with either a skull base or a parapharyngeal space mass, none of which could be palpated externally or through the oral cavity by the ear, nose, and throat surgeon. In 12 patients the needle biopsy correlated with the surgical pathology. Three needle biopsies were nondiagnostic.

Magnetic resonance angiography of vascular lesions causing neuro-ophthalmic deficits☆

Magnetic resonance angiography (MRA) is a noninvasive, rapidly evolving technique for imaging the intra- and extracranial carotid and vertebrobasilar circulations. It may in some circumstances obviate conventional angiography and the accompanying risks associated with catheterization and contrast injection. MRA exploits the different physical properties between moving protons and stationary tissue to yield flow sensitive data in the form of anatomic images or velocity and flow measurements. Since patients with various vascular disorders may present exclusively with ophthalmologic signs and symptoms, it is expected that MRA will become more frequently utilized by ophthalmologists. The exact role of MRA in the workup of vascular disorders remains to be more precisely defined, pending the performance of additional well-controlled standardized studies. At present, MRA is utilized to complement the conventional spin-echo studies of patients with arterial and venous occlusion, vascular malformations, intracranial aneurysms, and neoplastic vascular invasion. With further refinements, it is expected that MRA will become a standard diagnostic tool for the evaluation of patients with vascular disorders.

Unsupervised fuzzy segmentation of 3D magnetic resonance brain images

Unsupervised fuzzy methods are proposed for segmentation of 3D Magnetic Resonance images of the brain. Fuzzy c-means (FCM) has shown promising results for segmentation of single slices. FCM has been investigated for volume segmentations, both by combining results of single slices and by segmenting the full volume. Different strategies and initializations have been tried. In particular, two approaches have been used: (1) a method by which, iteratively, the furthest sample is split off to form a new cluster center, and (2) the traditional FCM in which the membership grade matrix is initialized in some way. Results have been compared with volume segmentations by k-means and with two supervised methods, k-nearest neighbors and region growing. Results of individual segmentations are presented as well as comparisons on the application of the different methods to a number of tumor patient data sets.

AUTOMATED QUANTIFICATION OF BRAIN MAGNETIC RESONANCE IMAGE HYPERINTENSITIES USING HYBRID CLUSTERING AND KNOWLEDGE-BASED METHODS

Previous computerized methods of hyperintensity identification in brain magnetic resonance images (MRI) either rely heavily on human intervention or on simple thresholding techniques. Such methods can lead to considerable variation in the quantification of brain hyperintensities depending upon image parameters such as contrast. This paper describes an automated, knowledge‐guided method of hyperintensity detection in brain MRI that addresses problems associated with human subjectivity and thresholding techniques. This method, which we call knowledge‐guided hyperintensity detection (KGHID), uses encoded knowledge of brain anatomy and MRI characteristics of individual tissues to reclassify pixels from an initial unsupervised segmentation. With this encoded knowledge, KGHID discriminates lesions embedded within the white matter, hyperintense lesions of the basal ganglia and the periventricular ring. The method is designed for high sensitivity detection and monitoring of subtle lesions in patients with neurodegenerative diseases.

Renal cell carcinoma presenting as a masseteric space mass

Abstract We present an unusual case of renal cell carcinoma metastatic to the masseter muscle. Whereas metastasis of renal cell carcinoma to the head and neck in itself is common, metastasis to skeletal muscle is quite infrequent. Although the presence of metastasis in renal cell carcinoma implies an overall worse prognosis, surgical extirpation as well as management of the primary lesion is still advisable in the hope of achieving long-term survival. Renal cell carcinoma metastasis must always be included in the differential diagnosis of clear cell neoplasms of the head and neck.

Multimodal Imaging of Head and Neck Squamous Cell Carcinoma.

BACKGROUND The role of imaging in the staging, treatment planning, and ongoing surveillance of patients with head and neck squamous cell carcinoma (HNSCC) continues to evolve. Changes in patient demographics, treatment paradigms, and technology present opportunities and challenges for the management of HNSCC. METHODS The general indications and usage of standard and multimodal cross-sectional imaging in the evaluation and management of HNSCC are reviewed, with an emphasis on incorporating them into treatment pathways. Emerging imaging technologies and methods with a potential near-term impact on HNSCC are discussed. RESULTS In general, the complex, multidisciplinary approach to the treatment of advanced HNSCC requires multimodal imaging for adequate treatment planning and follow up. Early-stage disease can often be managed with clinical and endoscopic examinations and a single, cross-sectional imaging modality (eg, computed tomography, magnetic resonance imaging). CONCLUSIONS Although generalized treatment pathways and guidelines do exist, the literature is rapidly advancing and new radiotracers and evaluation methods are expected to alter both imaging and treatment recommendations in the years to come.