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Biomedical subjects

L A Loevner

Publications and source records attributed to L A Loevner.

At least 19 recordsLinked to original sources
PubMed2001

The dose distribution of medium energy electron boosts to the laryngectomy stoma.

An en face, medium energy electron boost of approximately 10 Gy is often given to stomal and peristomal tissues. Because the boost is considered a simple treatment, CT-based treatment planning is rarely used. Further, the results of such a plan might be inaccurate, as the complex dose distribution surrounding the stoma air cavity is poorly modeled by many treatment planning systems. We constructed three phantoms-two with a central vertical cavity to mimic the size and shape of the stoma and proximal trachea and one with a cavity inclined at 45 degrees to the horizontal to better simulate anatomy. These were used to investigate the dose distribution surrounding the stoma. In all cases, the entrance to the stoma opening was centered in a field defined by a 7-cm circular cutout and the phantom was irradiated at a source-surface distance (SSD) of 100 cm with either vertically incident 9- or 12-MeV electrons. Film measurements were made at a range of depths below and lateral to the cavity. For the vertical cavity phantoms, diode measurements were performed and isodose plans using CT scans of the phantoms were generated on a modern treatment planning system. For these two phantoms, the combined effects of lateral scatter from surrounding material and reduced equivalent thickness for electrons which pass directly through the cavity increases the dose within a centimeter of the bottom of cavity by as much as 50% for 9 MeV and 70% for 12 MeV. In material at the shallower ("superior") end of the inclined cavity, a 40-50% overdose was noted. The dose increase is geometry dependent and is not predicted by the available treatment planning system. The potential of such a dose increase to affect normal tissues such as the neopharynx should be considered.

Electrons↗
PubMed2001

Mycotic aneurysm and cerebral infarction resulting from fungal sinusitis: imaging and pathologic correlation.

SUMMARY: A 73-year-old man was admitted with invasive aspergillus of the sphenoid sinus. Endoscopic debridement of the sphenoid sinus was complicated by rupture of a mycotic cavernous carotid artery aneurysm with severe epistaxis. The aneurysm was closed emergently by endovascular coil placement. Subsequently, the mycotic aneurysm extended intradurally and caused fatal subarachnoid hemorrhage. The radiologic-pathologic data illustrate the mechanism of fungal mycotic aneurysm formation and growth. This case emphasizes the need for rapid diagnosis of potential fungal involvement of the central nervous system and suggests the necessity for aggressive treatment once fungal cerebrovascular involvement is identified.

Aged↗
PubMed2000

Preoperative imaging to predict orbital invasion by tumor.

BACKGROUND: Our purpose was to examine the accuracy of preoperative imaging in assessing tumor invasion of the orbit and nasolacrimal system. METHODS: Nineteen preoperative CT and 17 preoperative MR images from patients at risk for orbital invasion were retrospectively reviewed. Invasion was corroborated by pathologic and intraoperative assessment. RESULTS: Tumor adjacent to the periorbita was the most sensitive predictor of orbital invasion (90%) for both CT and MRI. Extraocular muscle involvement on MRI (100%) and orbital fat obliteration (80% MRI, 86% CT) had the highest positive predictive values of the criteria evaluated. Extraocular muscle displacement and enhancement were less accurate (<65%) predictors. No one criterion was >79% accurate in predicting orbital invasion. Six or more positive criteria predicted invasion with 67% sensitivity and 80% specificity (accuracy, 72%). CT was more accurate than MRI in seven of nine criteria. Invasion of the nasolacrimal system was predicted accurately (89%). CONCLUSIONS: Although preoperative imaging can aid in surgical planning, it should not replace intraoperative assessment in ambiguous cases of orbital invasion.

Adipose Tissue↗
PubMed2000

Prevalence of unsuspected acoustic neuroma found by magnetic resonance imaging.

OBJECTIVES: Acoustic neuromas (ANs) comprise 6% of intracranial tumors. Population and autopsy studies have widely divergent estimates of AN incidence. With widespread use of MRI, asymptomatic ANs will be identified, which should improve estimates of the prevalence of this tumor. METHODS: The reports of all brain MRI scans during a 5-year period were retrospectively searched for the diagnosis of AN. MRIs obtained because of a suspicion of AN were discarded, leaving only the unsuspected ANs. RESULTS: A total of 24, 246 MRI studies were performed during this time period. Seventeen patients had unsuspected ANs. Eight tumors were smaller than 1 cm, 6 were between 1 and 2 cm, and 3 were 2 cm or larger. For all MRI scans, we found 7.0 unsuspected ANs per 10,000 brain MRI studies (0. 07%). CONCLUSION: The true prevalence of AN is likely greater than the 10 per million per year previously reported. This implies that there may be a larger number of asymptomatic ANs than previously suspected.

Adult↗
PubMed2000

The lateral osteotomy in rhinoplasty: clinical and radiographic rationale for osteotome selection.

A preferred osteotome for endonasal osteotomy would facilitate reliable, complete osteotomies with minimal soft-tissue trauma. In this report, a radiographic evaluation of the bony lateral nasal wall thickness along the track of a high-low-high osteotomy was undertaken to guide the determination of appropriate osteotome size. Bone window axial computed tomographic scans were evaluated in 56 patients with a mean age of 48 years (range, 19 to 86 years). The average thickness along the site of lateral osteotomy was determined to be 2.47 mm (standard deviation, 0.47) in male patients and 2.29 mm (standard deviation, 0.40) in female patients. On the basis of these data, clinical evaluation of prototype 3- and 2.5-mm low-profile guarded osteotomes was undertaken in comparison with a "standard" 4-mm low-profile guarded osteotome to assess both their reliability and the degree of intranasal trauma, as reflected by intranasal mucosal tears. Although 2- and 3-mm unguarded osteotomes are time-tested, they may be reliable only in the hands of the most experienced surgeons. Therefore, a low-profile guard was included in the osteotome design to allow the surgeon to engage the bone securely and minimize the risk of slippage. Forty patients underwent rhinoplasty, for a total of 80 lateral osteotomies; the mean age of the patients was 38 (range, 16 to 75). In all cases, lateral osteotomies were accomplished with one pass. The 4-mm osteotome causes intranasal mucosal tears in 95 percent of osteotomies, the 3-mm osteotome in 34 percent, and the 2.5-mm in 4 percent. Early postoperative edema and ecchymosis were comparable among the groups. One patient, who underwent osteotomies with a 4-mm osteotome, had excessive postoperative narrowing, possibly due to his wearing of eyeglasses earlier than directed. This report suggests that proper selection of osteotome and attention to proper surgical technique results in a reliable, minimally traumatic lateral osteotomy through the endonasal approach. The 2.5-mm osteotome was reliable and the least traumatic to soft tissue of the osteotomes evaluated.

Adult↗
PubMed2000

Posttransplantation lymphoproliferative disorder of the head and neck: imaging features in seven adults.

PURPOSE: To determine the cross-sectional imaging findings of posttransplantation lymphoproliferative disorder (PTLD) of the head and neck. MATERIALS AND METHODS: Computed tomographic (CT) scans (n = 6) and magnetic resonance (MR) images (n = 2) in seven patients with histopathologically proved PTLD of the Waldeyer (lymphoid) ring or cervical lymph nodes were retrospectively reviewed for abnormalities. RESULTS: The interval between transplantation and PTLD onset was 3.5-108 months (mean, 30 months). All patients had imaging abnormalities involving the Waldeyer ring, and focal 2.0-4. 5-cm masses were present in six patients (unilateral oropharyngeal tonsil in two, bilateral oropharyngeal tonsils in one, nasopharyngeal adenoids in three, unilateral pharyngeal tonsil and ipsilateral nasopharynx in one). In three patients, the mass was centrally low attenuating at CT or isointense to fluid at MR imaging, with enhancing solid peripheral lymphoid tissue. Three patients also had nodal findings: one with a 7-cm low-attenuating nodal mass in the right neck and two with numerous bilateral lymph nodes (mostly normal sized) in the anterior and posterior cervical lymph chains. One patient also had a small mass in the upper mediastinum. CONCLUSION: In the setting of organ transplantation, findings of masses in the Waldeyer ring or an excessive number of cervical nodes should increase the index of suspicion of PTLD.

Adenoids↗
PubMed2000

Nuchal fibroma: a clinicopathological review.

Nuchal fibroma, or collagenosis nuchae, is a benign soft tissue tumor that arises from the posterior cervical subcutaneous tissue, with a predilection for the interscapular and paraspinal regions. Because of its benign clinical course and its close histopathologic similarity to other benign head and neck lesions, this lesion may be misdiagnosed and underreported. The purpose of this paper is to review the histopathologic and radiologic findings unique to nuchal fibroma, and compare and contrast it to the other soft tissue neoplasms within the clinical differential diagnosis. These include several benign (elastofibroma, lipoma, fibrolipoma, nodular fasciitis) and rare malignant entities (fibrosarcoma, liposarcoma, fibromatosis).

Adult↗
PubMed2000

Extensive intracranial xanthoma associated with type II hyperlipidemia.

Xanthomas are associated with a spectrum of medical conditions, most commonly disorders of lipid storage and lipid metabolism. They occur primarily in the subcutaneous tissues, especially along the Achilles tendon and the extensor tendons of the hands. Intracranial xanthomas are extremely rare. We present a case of an extensive xanthoma of the temporal bone in a patient with hyperlipidemia.

Adult↗
PubMed2000

MR imaging for predicting neoplastic invasion of the cervical esophagus.

BACKGROUND AND PURPOSE: Esophageal invasion (EI) by head and neck neoplasm has important prognostic and surgical management implications. Our purpose was to determine the accuracy of MR imaging for predicting neoplastic cervical esophageal invasion. METHODS: MR scans of the neck obtained from 22 patients with periesophageal masses were retrospectively reviewed independently and by consensus by two experienced head and neck radiologists who were unaware of surgical findings. The patients were selected from clinical, radiologic, or pathologic reports suggesting EI. The following imaging criteria for EI were evaluated: effacement of periesophageal fat planes, circumferential mass, paraesophageal lymph nodes, luminal size, wall thickening, increased T2 wall signal, and wall enhancement. There were eight patients with EI and 14 patients without EI, as confirmed by surgical findings or pathologic examination. RESULTS: The consensus criteria with the best sensitivities were any wall thickening (100%), effaced fat plane (100%), and any T2 wall signal abnormality (100%). The criteria with the best specificities were circumferential mass greater than 270 (100%) or 180 degrees (93%) and focal T2 wall signal abnormality (86%). The overall kappa value for the two readers for all criteria was 0.57 (moderate agreement). CONCLUSION: A circumferential mass or focal T2 signal abnormality on the esophageal wall suggests the presence of EI. An intact fat plane, absence of wall thickening, and no T2 wall signal abnormalities imply that the esophagus is not invaded.

Adult↗
PubMed1999

Imaging features of posterior fossa neoplasms in children and adults.

Masses in the posterior fossa may be divided into extra-axial and intra-axial lesions. Because of its multiplanar capabilities, improved soft-tissue resolution and contrast, and the absence of scanning artifacts related to the osseous skull base, which are frequently present on CT, MRI is the imaging modality of choice in evaluating lesions arising in the posterior fossa. It is the best means of critically localizing lesions and determining the extent of disease. Analysis of the signal characteristics of a lesion on multiple different imaging sequences (T1-weighted, T2-weighted, and enhanced images) may provide information about the tissue constituents within a mass/neoplasm, such as the presence of cellularity, necrosis, and hemorrhage. MRI is also useful in guiding localization for brain tumor biopsies and assists in planning radiation therapy. However, CT also plays an important role. CT is frequently the first imaging study performed in patients with posterior fossa masses who often present with nausea, vomitting, ataxia, and other signs of increased intracranial pressure. It is a quick, available, and relatively inexpensive study to assess neurological emergencies including hydrocephalus, hemorrhage, and herniation syndromes. In addition, it frequently provides complimentary information, such as the presence of calcification or bony remodeling (osteosclerosis or osteolysis), which MRI is less sensitive in detecting.

Adult↗
PubMed1999

Superficial siderosis of the CNS associated with multiple cavernous malformations.

Superficial siderosis of the CNS due to chronic, recurrent subarachnoid hemorrhage is an uncommon and potentially debilitating disorder. The classic clinical manifestation is progressive bilateral sensorineural hearing loss (SNHL), although ataxia and pyramidal signs also are observed frequently. Cavernous malformations rarely present with subarachnoid hemorrhage. We describe an unusual case of a young patient who presented with progressive, bilateral SNHL who was found to have superficial CNS siderosis associated with multiple cavernous malformations.

Adult↗
PubMed1998

Neoplastic fixation to the prevertebral compartment by squamous cell carcinoma of the head and neck.

OBJECTIVE: The purpose of this study was to determine the accuracy of MR imaging in determining fixation of squamous cell carcinomas to the prevertebral space. MATERIALS AND METHODS: MR images of 15 patients with large pharyngeal carcinoma (n = 13) or laryngeal carcinomas with pharyngeal extension (n = 2) were retrospectively reviewed independently by two head and neck radiologists who were unaware of the surgical findings. MR images were evaluated for four criteria in the prevertebral longus muscle complex: muscle concavity, irregular tumor-muscle interface, T2 hyperintensity, and enhancement. All patients underwent panendoscopy where fixation or mobility of the tumor relative to the prevertebral fascia was assessed by manual manipulation. Tumors in six patients were fixed to the prevertebral space and inoperable. In nine patients whose tumors were not fixed, open neck explorations were performed and tumors were resected in seven patients. MR findings were compared with panendoscopy in all patients and with intraoperative assessment in nine patients. RESULTS: Eleven of 15 patients had at least two of the MR imaging criteria present. None of the MR findings were both sensitive and specific for tumor fixation. Although muscle concavity and enhancement each had a sensitivity of 88%, both criteria suffered from low specificity (14% and 29%, respectively). An irregular tumor-muscle interface and muscle T2 hyperintensity were criteria that suffered from both low sensitivity and specificity. Accuracy of the imaging criteria independently ranged from 53% to 60%. CONCLUSION: Although abnormal muscle contour, T2 hyperintensity, and enhancement are frequently present in neck carcinomas that are fixed to the prevertebral space, these findings may also be present in patients in whom the tumor is mobile and resectable. MR imaging may not be able to differentiate between neoplastic fixation and nonneoplastic changes in the prevertebral space.

Adipose Tissue↗
PubMed1998

Spontaneous thrombosis of a basilar artery traumatic aneurysm in a child.

Traumatic aneurysms are rare and occur most commonly in young adults; however, the relative frequency in the pediatric population is high, owing to the low prevalence of congenital saccular aneurysms in children. Traumatic aneurysms typically involve the anterior circulation, and spontaneous thrombosis is uncommon; hence, surgery is usually necessary. We present a case of a posttraumatic aneurysm in a child that occurred after a fall from a large height and that spontaneously thrombosed.

Accidental Falls↗