Biomedical subjects

Barbara Kaser-Hotz

Publications and source records attributed to Barbara Kaser-Hotz.

30 records · Page 2Linked to original sources

PubMedDate not supplied

Assessment of a radiotherapy patient immobilization device using single plane port radiographs and a remote computed tomography scanner.

Radiation treatment requires a precise procedure for interfraction repositioning of the patient. The purpose of this study was to determine the accuracy of our fixation device in treatment position and to evaluate the setup accuracy with two different methods. The positioning data of 19 canine patients with tumors in the head region (oral, nasal, cerebral) treated with photon or proton irradiation were included in this study. The patients were immobilized by means of an individualized fixation device. Focus was set upon interfraction displacement with systematic and random components. In one method, treatment position was evaluated using single plane port radiographs and megavoltage x-rays. In the other method, two orthogonal CT-topograms were acquired to evaluate the precision of positioning of the patient in the immobilization device. Systematic and random displacements were calculated and presented as mean values with corresponding 95% confidence intervals. In spite of a difference between both methods, the positioning seemed to be accurate within the expected range. It seems that a safety margin of 3.7 mm would be enough for both methods to take into account systematic and random position variability in the fixation device, thereby preventing geometric inaccuracies of treatment delivery. The reported immobilization protocol provides accurate patient immobilization for photon and conformal proton radiation therapy.

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PubMedDate not supplied

Computed tomography-guided fine-needle aspiration and tissue-core biopsy of bone lesions in small animals.

In humans, free-hand computed tomography (CT)-guided biopsy is an accurate method to obtain a tissue sample. There are only a few reports of this technique in veterinary medicine. In the present study, 21 dogs and two cats underwent a free-hand CT-guided tissue-core biopsy (17 animals) or fine-needle aspiration (six animals) of a bone lesion. Two out of 17 tissue-core samples were also cultured. All 17 tissue-core biopsy samples were diagnostic (accuracy of 100%). Five out of six aspirates were diagnostic (accuracy of 83.3%). The overall accuracy was 95.7%. In one aspirate, cytologic quality was insufficient containing only blood. No major complications were encountered. Fourteen neoplastic, two infectious and six benign lesions were diagnosed. CT examination after intravenous contrast medium added useful information to avoid large vessels and to biopsy-viable tissue. Free-hand CT-guided tissue-core biopsy and aspiration appears to be a safe and very accurate procedure for use in the diagnosis of bone-associated diseases in small animals.

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PubMedDate not supplied

Preliminary study of plasma vascular endothelial growth factor (VEGF) during low- and high-dose radiation therapy of dogs with spontaneous tumors.

High plasma vascular endothelial growth factor (VEGF) concentrations are associated with radiation resistance and poor prognosis. After an exposure to ionizing radiation in cell culture an early phase and a late phase of increased VEGF have been documented. The activation was dependent on the radiation dose. Therefore, the purpose of this study was to measure baseline plasma VEGF and changes in VEGF over the course of fractionated radiation therapy in dogs with spontaneous tumors. Dogs with tumors had a significantly higher pretreatment plasma VEGF than did dogs without tumors. Immediately after irradiation no increased plasma VEGF was observed. Over the course of radiation therapy there was an increased plasma VEGF in dogs treated with low doses per fraction/high total dose, whereas plasma VEGF remained stable in dogs irradiated with high doses per fraction/low total dose. The regulatory mechanisms are very complex, and therefore the value of plasma VEGF measurements as an indirect marker of angiogenesis induced by radiotherapy is limited.

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PubMedDate not supplied

Radiographic, ultrasonographic, and computed tomographic appearance of alveolar echinococcosis in dogs.

Alveolar echinococcosis is a rare metacestodal infection of humans and domestic animals with Echinococcus multilocularis and predominantly affects the liver. In humans, diagnosis is based on serology, ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI), techniques that have not yet been validated for the diagnosis of alveolar echinococcosis in dogs. Therefore, the purpose of this retrospective study was to describe the radiographic, ultrasonographic, and CT appearance of canine alveolar echinococcosis. Eleven dogs with confirmed alveolar echinococcosis (PCR or histology from biopsy material of metacestode tissue) diagnosed between 1995 and 2003 were included in the study. The age of the dogs at initial presentation ranged from 7 months to 10.5 years. Abdominal radiographs were made in nine animals, abdominal ultrasonography was performed in 10 dogs, and two CT studies in one dog, respectively. The history, clinical presentation, and laboratory findings for the 11 dogs were unspecific, the most frequent clinical finding being nonpainful progressive abdominal distention. All radiographed dogs had large liver masses; they contained small mineralizations in five. The most frequent ultrasonographic finding was multiple large cavitary masses with or without wall mineralizations. Seven animals received surgical and subsequent medical therapy with albendazole (10mg/kg) and all went into clinical remission. This study reviewed for the first time imaging findings associated with alveolar echinococcosis. The disease has to be included in the list of differential diagnoses in dogs with large, cavitary liver masses, particularly when mineralization is noted.

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PubMedDate not supplied

Palliative irradiation of Scottish Fold osteochondrodysplasia.

This report describes palliative irradiation as treatment for Scottish Fold osteochondrodysplasia. A 3-year-old female spayed Scottish Fold cat suffering from osteochondrodysplasia was referred to the Veterinary Teaching Hospital, University of Zurich. Based on the breed, history, clinical signs, radiographic findings, and the histologic diagnosis of a biopsy specimen, Scottish Fold osteochondrodysplasia was confirmed. To control the exostoses leading to inflammatory processes and pain, radiotherapy was initiated as palliative treatment. This was successful in relieving the clinical signs within a few weeks. The short- and long-term results after radiotherapy are presented and discussed with a comparable human disease, the plantar heel spur, which also responds well to radiotherapy.

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PubMedDate not supplied

Measurement of tumor hypoxia in spontaneous canine sarcomas.

We used positron emission tomography (PET) with [18F]fluoromisonidazole ([18F]FMISO) to study tumor hypoxia in six dogs with spontaneous sarcomas. The tumors were regarded as hypoxic if [18F]FMISO uptake exceeded normal tissue radioactivity by 40% (tumor/muscle ratio > 1.4) or if kinetic analysis indicated a positive [18F]FMISO tissue influx rate (Ki > 0) by a Patlak plot. Using these criteria, we found hypoxia in a fibrosarcoma grade II, an undifferentiated sarcoma, and an ostoeosarcoma, but not in a fibrosarcoma grade I, another osteosarcoma, and a myxosarcoma. In three animals, the tumor oxygen partial pressure (pO2) was also measured invasively using Eppendorf needle electrodes. In these cases, the Eppendorf measurements were confirmed by the [18F]FMISO PET results. In addition, [15O]H2O PET was performed in four dogs in order to assess tumor perfusion. Comparisons of the [18F]FMISO with [15O]H2O PET images in two cases showed that tumor hypoxia occurred in the tumor center with low perfusion, whereas perfusion was heterogeneous in a nonhypoxic tumor.

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PubMedDate not supplied

Irradiation of brain tumors in dogs with neurologic disease.

Radiation therapy is the treatment of choice for many primary canine brain tumors. The radiation dose tolerated by surrounding healthy brain tissue can be a limiting factor for radiation treatment and total dose as well as fractionation schedules, and volume effects may play a role in the outcome of patients undergoing radiation therapy. The purpose of this retrospective study was to evaluate the efficacy of radiation therapy in dogs with brain tumors that showed signs of neurologic disease. Forty-six dogs with brain tumors were included in the analysis. In 34 dogs, computer-generated treatment plans were available, and dose-volume data could be obtained. The totally prescribed radiation therapy doses ranged from 35 to 52.5 Gy (mean = 40.9 [SD +/- 2.91) applied in 2.5- to 4-Gy fractions (mean = 3.2). The median overall survival time calculated for deaths attributable to worsening of neurologic signs was 1,174 days (95% confidence interval [CI], 693-1,655 days). Assuming that all deaths were due to disease or treatment consequences, the median survival time was 699 days (95% CI, 589-809 days). No prognostic clinical factors such as the location or size of the tumor or neurologic signs at presentation were identified. With computerized treatment planning and accurate positioning, high doses of radiation (> 80% of the total dose) could be limited to mean relative brain volumes of 35.3% (+/- 12.6). These small volumes may decrease the probability of severe late effects such as infarction or necrosis. In this study, very few immediate or early delayed adverse effects and no late effects were noted, and quality of life was good to excellent.

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PubMedDate not supplied

Ki67 reactivity in nasal and periocular squamous cell carcinomas in cats treated with electron beam radiation therapy.

Squamous cell carcinomas of sparsely haired skin are relatively common tumors in cats, and these tumors likely exhibit a rapid growth rate. Thus, we evaluated response and duration of response in relation to the Ki67 proliferative reactivity in such tumors. Seventeen cats with confirmed squamous cell carcinomas and treated with an accelerated, hypofractionated electron beam radiation protocol were included in the study. For all of them histologic grading, Ki67 reactivity, response, and disease-free interval (DFI) were evaluated. Response to therapy was excellent (94% complete response rate) with a median DFI of 414 days. Only moderate acute and few long-term adverse effects were seen. Cats with tumors with a low Ki67 reactivity had markedly shorter DFIs than cats with tumors with high Ki67 reactivity. We concluded that an accelerated, hypofractionated electron beam radiation therapy protocol is well suited for feline squamous cell carcinomas. The protocol appears especially efficacious in tumors with a high Ki67 reactivity.

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PubMedDate not supplied

Ultrasound guided, pre-radiation oxygen measurements using polarographic oxygen needle electrodes in spontaneous canine soft tissue sarcomas.

BACKGROUND: Poor tumour oxygenation is associated with radiation resistance. The recording of pre-treatment oxygenation status has been shown to be of prognostic relevance. MATERIAL AND METHODS: Eleven dogs with spontaneously arising soft tissue sarcomas were included in this study. Oxygen partial pressure measurements (pO2) were performed with the Eppendorf method. RESULTS: The mean of median pO2 was 9.6 mmHg (range: 0.1-30 mmHg). Four of the nine dogs included in the statistical analysis showed a median pO2 < or = 2.5 mmHg. The natural logarithm of the hypoxic subvolume correlated with the hypoxic fraction < or = 2.5 mmHg (p = 0.0712) and < or 5 mmHg (p = 0.0988). Mean corpuscular hemoglobin (MCH) and mean corpuscular volume (MCV) correlated significantly to several oxygen parameters. CONCLUSION: Hypoxia exists in spontaneous canine soft tissue sarcomas and the dog can be used as a reliable model for repeated oxygenation measurements. Ultrasonography assures reliability of needle placement.

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PubMedDate not supplied

Plasma vascular endothelial growth factor (VEGF) measured in seventy dogs with spontaneously occurring tumours.

BACKGROUND: Vascular endothelial growth factor (VEGF) acts specifically on endothelial cells mediating tumour neovascularisation and initiating tumour growth and metastasis. In humans, high VEGF levels are correlated with poorer prognosis but in dogs minimal information on plasma VEGF is available. Therefore, we analysed plasma VEGF in a variety of spontaneous canine tumours. MATERIALS AND METHODS: Plasma from seventy dogs with various spontaneous tumours was taken prior to radiation therapy. A human VEGF ELISA was used for analysis. RESULTS: Mean plasma VEGF was 7.2+/-7.8 pg/ml. Mean plasma VEGF level varied among different tumour types with the highest level in oral melanomas (12.4 pg/ml). In patients with sarcomas of soft tissue or bone origin, plasma VEGF levels increased significantly with decreasing haemoglobin concentration (p =0.013). CONCLUSION: Canine plasma VEGF levels depend on tumour histology, with higher levels found in more aggressive tumours. The negative correlation between plasma VEGF and haemoglobin (hb) is most probably due to tissue hypoxia seen in anaemic animals.

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PubMedDate not supplied

Palliative radiotherapy with electrons of appendicular osteosarcoma in 54 dogs.

Radiotherapy is effective for the palliation of pain associated with primary and metastatic bony neoplasia in dogs and humans, but no standard treatment protocol has been established. The goal of this study was to evaluate a 3 x 8 Gy and a 4 x 6 Gy protocol using electrons with a betatron or linear accelerator for the treatment of appendicular osteosarcoma in 54 dogs. Thirty-three dogs received chemotherapy consisting of carboplatin IV concurrently with radiotherapy. Eighty-three % (n = 45) of the dogs experienced pain relief during or following treatment. The median duration of pain relief from treatment start was 53 days. In conclusion, both protocols are effective for palliation of clinical signs of canine appendicular osteosarcoma. The outcome reported here is similar to the results of other studies using Co photons. The use of chemotherapy did not improve the response to radiotherapy.

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PubMedDate not supplied

Efficacy of radiation therapy for the treatment of macroscopic canine oral soft tissue sarcoma.

This retrospective study evaluated the efficacy of radiotherapy used alone in macroscopic oral soft tissue sarcoma. Thirty-one dogs qualified for the study. Twenty dogs received curative radiotherapy (median total dose: 52.5 Gy) and eleven dogs were treated palliatively (3 x 8 Gy or 5 x 6 Gy). The time-to-progression for the curatively-treated dogs was 333 days versus 180 days for the palliatively-treated dogs (p=0.134). The overall survival was 331 days for the curative group and 310 days for the palliative group (p =0.2292). The results of this study suggest that radiation therapy is useful in the treatment of oral soft tissue sarcoma.

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