Biomedical subjects

R P Kivisaari

Publications and source records attributed to R P Kivisaari.

4 recordsLinked to original sources

PubMed2001

Estimation or quantification of tumour volume? CT study on irregular phantoms.

PURPOSE: To compare radiologists' subjective size estimation to computerised volume quantification of tumour-like phantoms in spiral CT. MATERIAL AND METHODS: Eight tubular phantoms with the inside irregularly covered with silicone (8.7-31.6 ml) were imaged. The phantoms were pairwise compared to analyse the differences in silicone volumes. The observers, 2 radiologists and 2 residents, used both subjective image analysis (2 sessions) and computerised volume quantification (1 session). Accuracy and observer agreement of both methods were calculated. RESULTS: Subjective size estimation was correct in 51% (mean weighted kappa, Kqw=0.73). Using four observers' mean value (Kqw=0.81) or median value (Kqw=0.77) slightly improved the results. Average intra-observer agreement was better than average interobserver agreement. In computerised volume quantification 70% of all classifications were correct (mean Kqw=0.85). The results were moderate even when every second or fourth slice were measured. CONCLUSION: Subjective size estimation of irregular tumours should be repeatedly performed by the same observer, or by using the mean or median estimate of several observers. Computer-based methods are even more reliable and their use is especially recommended for film readers with limited radiological experience. Only every fourth slice may be measured without a major loss of measurement accuracy.

Humans↗

PubMed2000

Basal brain injury in aneurysm surgery.

OBJECTIVE: The goal of this study was to determine the frequency of lesions in the basal frontotemporal area that were related to surgical damage to the brain tissue. METHODS: A prospective series of 101 patients with ruptured intracranial aneurysms were examined with high-field magnetic resonance imaging, 2 to 6 years (mean, 3.3 yr) after early surgery. RESULTS: Lesions in the basal frontotemporal region, on the side of the pterional approach, were observed for 36 patients. These lesions were not visible in computed tomographic scans obtained pre- or postoperatively or 3 months after subarachnoid hemorrhage. Patients with ruptured aneurysms in the anterior communicating artery exhibited fewer of these lesions than did patients with aneurysms in the internal carotid artery or middle cerebral artery; this difference was not statistically significant. The age of the patient, the duration and depth of hypotension, the amount of blood or ventricular enlargement in pre- and postoperative computed tomographic scans, and the incidence and severity of angiographic vasospasm in pre- and postoperative angiograms did not predict the existence of these lesions. The clinical conditions of the patients, as assessed using the Glasgow Outcome Scale, at 3 months after surgery and at the time of magnetic resonance imaging did not predict the existence of these lesions. Nine of the 10 patients who underwent surgical treatment of unruptured aneurysms on the contralateral side exhibited no signs of tissue damage. CONCLUSION: Surgical treatment of ruptured intracranial aneurysms seems to cause damage in the basal frontotemporal region in one-third of patients. The significance of these lesions remains unclear.

Adult↗

PubMed1997

Optimising imaging parameters in experimental spiral CT.

PURPOSE: This in vitro study was conducted to analyse lesion detection and relative radiation exposure in different CT techniques. MATERIAL AND METHODS: We used a plastic phantom (12 x 8 x 2 cm) containing holes filled with air or fluid of varying densities to simulate lesions. This was imaged with Siemens Somatom Plus S and GE High Speed Advantage units. We varied table feeds (3 and 6 mm/s in Siemens and 3 and 4.5 mm/s in GE) and increments (2 mm and 4 mm) while keeping collimation at 3 mm. The SmartScan program of GE and the reformatting algorithm of Siemens were also analysed. To evaluate the different methods, the phantom lesions were counted by 3 observers. Radiation exposures associated with each technique were also measured. RESULTS: The images reformatted to a coronal direction were significantly inferior (p < 0.01) to those in other techniques. The use of SmartScan did not influence lesion detection, nor did changes in pitch or increment. Spiral and non-spiral techniques proved to be equal. Radiation exposure was lowest when a greater pitch or the SmartScan program was used. CONCLUSION: Radiation exposure in CT can be limited without significantly impairing the image quality by using low-dose techniques. Reformatting to a coronal direction should be used with care as it debases the image quality.

Humans↗

PubMedDate not supplied

MR imaging after aneurysmal subarachnoid hemorrhage and surgery: a long-term follow-up study.

BACKGROUND AND PURPOSE: We assumed that patients with surgically treated aneurysmal subarachnoid hemorrhage (SAH) might have more lesions than those revealed by CT that could be visible on MR images. METHODS: We conducted a retrospective study of a series of 147 patients with aneurysmal SAH who were treated surgically within 3 days of the onset of SAH. One hundred four patients (mean age, 48.8 years) underwent MR imaging studies 2.1 to 5.6 years (mean, 3.3 years) postoperatively. RESULTS: Eighty-four (81%) patients presented a total of 152 areas of increased signal intensity on T2-weighted images, consistent with infarction; 48% of the patients had lesions in the frontal lobes. CT performed 3 months postoperatively revealed hypodense areas on the scans of only 57% of the patients and showed lesions in the frontal lobes of only 16% of the patients. CONCLUSION: Patients who undergo early surgery for aneurysmal SAH have more lesions than are revealed by CT. The difference is remarkable, especially in the frontal lobes.

Adolescent↗