ABSTRACT. The effects of a timolol maleate gel-forming solution (TMGS) on intraocular pressure (IOP), blood pressure (BP), and pupil size (PS) were evaluated in normotensive dogs. TMGS was administered once daily to six normotensive beagle dogs. TMGS administration reduced IOP and PS. The hypotensive effect persisted for 24 hr after the administration. The mean reduction in IOP was 5.3 mm Hg (P<0.01). The changes in BP and PS were not significant. These results suggest that TMGS can potentially be used in the treatments of glaucoma and ocular hypertension in dogs. KEY WORDS: canine, gellan gum, timolol.J. Vet. Med. Sci. 68(6): 631-633, 2006 Glaucoma is a painful disease and is characterized by retinal ganglion cell death, optic nerve damage that is usually associated with elevated intraocular pressure (IOP), and progressive loss of vision that could result in blindness. Glaucoma therapy aims to lower IOP in order to preserve ocular function and reduce pain [1].Timolol maleate (TM) is a nonselective beta-adrenergic that substantially reduces the volume of aqueous humor and thereby reduces IOP [1,3,20]. TM ophthalmic solution is widely used to treat glaucoma in humans and dogs. However, TM has the potential to cause systemic side effects [4, 6, 8-10, 15-17, 19, 20]. The TM gel-forming solution (TMGS) is delivered in a gellan gum solution and can be administered to the eye as a drop; this drop forms a viscous solution on contact with the ocular surface. TMGS holds TM for a longer period of time than the TM aqueous solution; consequently, TMGS is administered once daily [2,10,[12][13][14]. In this study, we evaluated the effects of TMGS on IOP, systolic and diastolic blood pressure (BP), and pupil size (PS) in normotensive beagle dogs.All animals were treated in accordance with the Association for Research in Vision and Ophthalmology Statement for the Use of Animals in Ophthalmic and Vision Research. Six clinically normal beagle dogs (two males and four females) were used in this study. Their body weights ranged from 9.7 to 13.0 kg (median weight: 12.2 kg), and their ages ranged from 4 to 11 years (median age: 8.0 years). Dogs were defined as normotensive after a complete physical and ophthalmic examination, including tonometry, slit-lamp biomicroscopy, and ophthalmoscopy; these examinations did not reveal any abnormalities. A 0.5% TMGS (Timoptol XE 0.5%, Banyu Pharmaceutical Co., Ltd., Tokyo) was used in this study. TMGS was administered in one eye (treated eye) of each dog. Once-a-day administration (9:00 AM) was continued for 7 days. The contralateral eyes (nontreated eyes) were not treated. IOP was measured using an applanation tonometer (Tono-Pen XL, Medtronic, FL, U.S.A.); BP, an oscillometric hematomanometer (BP100D, Fukuda M-E Kogyo Co., Ltd., Tokyo, Japan); and PS, a pupillometer (Mita's pupillometer, Inami, Tokyo, Japan). IOP, BP, and PS were measured before administration of TMGS; 1, 2, 4, 6, 10, and 24 hr after administration on the first day; and at 7:00 PM everyday from the second day until the en...

Recent linear accelerators can perform cone beam computed tomography to correct setup errors immediately before dose delivery. We calculated the dose distribution with setup errors acquired from cone-beam computed tomography to determine a more realistic and individual effect of setup errors. The differences in dose distribution were analyzed.The setup errors of three patients who were irradiated in the neck, esophagus, and pelvic area were obtained retrospectively. We found that the maximum dose variances for the three cases were 19.9 to 35.9%. The maximum dose variance points were relatively far from the isocenter. The volume of the 10% dose difference had widths of 1.3 to 1.85 cm around the beam edges. The V95 and mean doses at the clinical target volume were mostly unchanged. Doses around the beam edges were more varied than those around the isocenter for every case. The dose on the spinal cord located near the beam edges varied by 5 -10 % compared with the dose of the radiotherapy plan in two of the cases. We demonstrated the individual dose distributions of the cases affected by daily setup errors for all fractions.

In this study, we evaluated the image distortion of three magnetic resonance imaging (MRI) systems with magnetic field strengths of 0.4 T, 1.5 T and 3 T, during stereotactic irradiation of the brain. A quality assurance phantom for MRI image distortion in radiosurgery was used for these measurements of image distortion. Images were obtained from a 0.4-T MRI (APERTO Eterna, HITACHI), a 1.5-T MRI (Signa HDxt, GE Healthcare) and a 3-T MRI (Signa HDx 3.0 T, GE Healthcare) system. Imaging sequences for the 0.4-T and 3-T MRI were based on the 1.5-T MRI sequence used for stereotactic irradiation in the clinical setting. The same phantom was scanned using a computed tomography (CT) system (Aquilion L/B, Toshiba) as the standard. The results showed mean errors in the Z direction to be the least satisfactory of all the directions in all results. The mean error in the Z direction for 1.5-T MRI at －110 mm in the axial plane showed the largest error of 4.0 mm. The maximum errors for the 0.4-T and 3-T MRI were 1.7 mm and 2.8 mm, respectively. The errors in the plane were not uniform and did not show linearity, suggesting that simple distortion correction using outside markers is unlikely to be effective. The 0.4-T MRI showed the lowest image distortion of the three. However, other items, such as image noise, contrast and study duration need to be evaluated in MRI systems when applying frameless stereotactic irradiation.

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SummaryPurpose: In this study, we proposed and evaluated a positional accuracy assessment method with two high-resolution digital cameras for add-on six-degrees-of-freedom radiotherapy (6D) couches. Methods and Materials: Two high resolution digital cameras (D5000, Nikon Co.) were used in this accuracy assessment method. These cameras were placed on two orthogonal axes of a linear accelerator (LINAC) coordinate system and focused on the isocenter of the LINAC. Pictures of a needle that was fixed on the 6D couch were taken by the cameras during couch motions of translation and rotation of each axis. The coordinates of the needle in the pictures were obtained using manual measurement, and the coordinate error of the needle was calculated. The accuracy of a HexaPOD evo (Elekta AB, Sweden) was evaluated using this method. Results: All of the mean values of the X, Y, and Z coordinate errors in the translation tests were within ±0.1 mm. However, the standard deviation of the Z coordinate errors in the Z translation test was 0.24 mm, which is higher than the others. In the X rotation test, we found that the X coordinate of the rotational origin of the 6D couch was shifted. Conclusions: We proposed an accuracy assessment method for a 6D couch. The method was able to evaluate the accuracy of the motion of only the 6D couch and revealed the deviation of the origin of the couch rotation. This accuracy assessment method is effective for evaluating add-on 6D couch positioning.