Comprehensive Monte Carlo study of patient doses from cone-beam CT imaging in radiotherapy.

Accurate knowledge of ionizing radiation dose from cone-beam CT (CBCT) imaging in radiotherapy is important to allow concomitant risks to be estimated and for justification of imaging exposures. This study uses a Monte Carlo CBCT model to calculate imaging dose for a wide range of imaging protocols for male and female patients. The Elekta XVI CBCT system was modeled using GATE and simulated doses were validated against measurements in a water tank and thorax phantom. Imaging dose was simulated in the male and female ICRP voxel phantoms for a variety of anatomical sites and imager settings (different collimators, filters, full and partial rotation). The resulting dose distributions were used to calculate effective doses for each scan protocol. The Monte Carlo simulated doses agree with validation measurements within 5% and 10% for water tank and thorax phantom respectively. Effective dose for head CBCT scans was generally lower for scans centred on the pituitary than the larynx (0.03 mSv versus 0.06 mSv for male ICRP phantom). Pelvis CBCT scan effective dose was higher for the female than male phantom (5.11 mSv versus 2.80 mSv for M15 collimator scan), principally due to the higher dose received by gonads for the female scan. Medium field of view thorax scan effective doses ranged from 1.38-3.19 mSv depending on scan length and phantom sex. Effective dose for half rotation thorax scans with offset isocentre varied by almost a factor of three depending on laterality of the isocentre, patient sex and imaged field length. The CBCT imaging doses simulated here reveal large variations in dose depending on imaging isocentre location, patient sex and partial rotation angles. This information may be used to estimate risks from CBCT and to optimize CBCT imaging protocols.

Maturation profile and fecundity of the exotic Oreochromis niloticus in the River Yamuna, India.

The knowledge on the reproductive biology of fish Oreochromis niloticus (Linnaeus, 1758) in riverine condition is meagre in the Indian sub-continent which is necessary for the development of an appropriate fishery management protocols for the rivers. In this context, the gonadal maturation profile and fecundity of 0. niloticus was studied. Mature, spawning and spent females recorded in almost all the months of the year evidenced multiple and prolonged breeding behaviour. An overall sex ratio (M/F) of 1: 1.08 observed was statistically non-significant from expected 1:1 ratio (chi2=6.994219, p=0.8642) indicating that males and females were statistically equal in number. The absolute fecundity ranged from 1192 to 4760 with mean of 2590 eggs from ovary weighing between 1.91 g to 28.89 g. Monthly changes in gonado-somatic index (GSI) revealed that fish bred throughout the year except in July and August, but at peak between October-November and March-June. Size at first maturity of male was estimated as 229.6 mm with confidence limit of 235.9 and 223.6 mm and for female as 238.1 mm with confidence limit of 244.7 and 231.7 mm, respectively.

Optical phase extractions based on reassigned continuous wavelet transform with application to simultaneous displacement and velocity measurement.

Instantaneous frequency extraction of a highly nonstationary optical interferometric fringe signal using continuous wavelet transform with Morlet wavelet often fails in the neighborhood of the null phase gradient. The present work reports that the optimal selection of the central frequency and time variance of the Morlet wavelet reduces the spread of wavelet energy to its adjacent bins, and the reassignment technique further sharpens the energy density and enhances accuracy of the extracted instantaneous frequency of the fringe signal. The developed algorithm is applied to a sinusoidal frequency-modulated fringe signal for which the mean square error percentage in normalized instantaneous frequency is determined to be 0.0032 Hz, which is significantly less than 0.0507 Hz obtained with a conventional continuous wavelet transform. Results are also compared with the existing phase stepping technique and found to be more accurate and free from any ripple like nonlinear error for sinusoidal fringe signals. The proposed technique is applied to a fringe signal obtained with a Michelson interferometer, generating displacement profiles that show advantages over those produced by the phase stepping technique. The applicability of the proposed technique is further extended to an arbitrary phase signal.

Surgery for recurrent lower lip carcinoma.

A 38 year old gentleman presented with recurrent squamous cell carcinoma of lower lip. He had earlier undergone previous surgeries and radiotherapy. At the time that he presented in KMCTH his lower lip area was much scarred and the tongue was shrunk and unavailable for vermilion reconstruction. This case report is an account of the various treatment carried out to reconstruct the lip. It was done with co-operation of the ENT department.

Accuracy of radiotherapy dose calculations based on cone-beam CT: comparison of deformable registration and image correction based methods.

Radiotherapy dose calculations based on cone-beam CT (CBCT) images can be inaccurate due to unreliable Hounsfield units (HU) in the CBCT. Deformable image registration of planning CT images to CBCT, and direct correction of CBCT image values are two methods proposed to allow heterogeneity corrected dose calculations based on CBCT. In this paper we compare the accuracy and robustness of these two approaches. CBCT images for 44 patients were used including pelvis, lung and head & neck sites. CBCT HU were corrected using a 'shading correction' algorithm and via deformable registration of planning CT to CBCT using either Elastix or Niftyreg. Radiotherapy dose distributions were re-calculated with heterogeneity correction based on the corrected CBCT and several relevant dose metrics for target and OAR volumes were calculated. Accuracy of CBCT based dose metrics was determined using an 'override ratio' method where the ratio of the dose metric to that calculated on a bulk-density assigned version of the same image is assumed to be constant for each patient, allowing comparison to the patient's planning CT as a gold standard. Similar performance is achieved by shading corrected CBCT and both deformable registration algorithms, with mean and standard deviation of dose metric error less than 1% for all sites studied. For lung images, use of deformed CT leads to slightly larger standard deviation of dose metric error than shading corrected CBCT with more dose metric errors greater than 2% observed (7% versus 1%).

VISAR signal analysis with an emphasis on ellipse fitting.

A method based on ellipse fitting for analysis of VISAR (Velocity Interferometer System for Any Reflector) signals has been described. The errors introduced on the free surface velocity history due to common measurement imperfections in the amplitude and phase angle of the VISAR signal has been investigated and a remedy to mitigate this using a proper ellipse fitting technique has been presented. Performance comparison among various ellipse fitting techniques based on empirical evidence is carried out, and the geometric fitting technique of the Gauss Newton algorithm with initial conditions from the Bookstein algebraic fitting method is proposed. The new method provides better result in terms of accuracy than existing techniques. The method is especially useful when a fractional fringe signal is present which is quite common in VISAR based measurements. The applicability of the ellipse fitting technique is first theoretically justified, and then numerical simulation of ellipse fitting is carried out. Finally, the proposed method is validated by applying it for the analysis of VISAR signals recorded in the shock wave experiment conducted on the Al-2024T4 target material. The results of present analysis display a good agreement with the data available from other sources.

Mandibular reconstruction.

One of the most difficult problem in reconstructive surgery is the replacement of lost bone from trauma, tumour, infection or congenital anomaly. This is a case report of a 20 year old male who had suffered a blast injury of his lower jaw. From his first admission in the Plastic unit of Bir Hospital on Feb 19, 2003, he had undergone multiple operations until Nov 2003. This is a description of a follow up surgery done in Kathmandu Medical College (KMC), Sinamangal. Difficulties encountered and options available have also been discussed.

Retrospective study on early outcome of acute burn injuries treated at Nepal Cleft and Burn Centre of Public Health Concern Trust-Nepal.

BACKGROUND: Nepal Cleft & Burn Center, Kirtipur Hospital, Kathmandu has been providing the acute burn care since 2013 with 10 ICU beds, 32 general beds and two operating rooms. This study analyses the demographics of and early outcome in the acute burn patients. METHODS: This is a descriptive retrospective study of the clinical data of acute burn patients admitted from January 1 to December 31, 2014. RESULTS: There were 78 patients from 3 months to 88 years of age with a median age of 29 years. Forty six (58.9%) were females and 32 (41.1%) were males. Most of the injuries (n=57; 73%) occurred inside the house. Flame burn was the commonest mode of injury (n= 48, 61.6%). Only eleven (14.1%) patients arrived on the same day of the injury. The time elapsed was from 1 to 67 days with a median of 5 days. Only two (2.5%) patients had poured water for more than 20 minutes. Range of total body surface area (TBSA) involved was 1% to 70% with a median of 12%. Range of hospital stay was 1 to 105 days with a median of 17 days. Sixty (76.9%) patients underwent 102 surgical operations. Twenty six (33.3%) patients needed blood transfusion. A total of 15 (19.2%) patients died. None survived a burn injury of more than 40% TBSA. CONCLUSIONS: Treatment of acute burn is very challenging with high mortality rate. A lot of effort is needed to change the present standard of care. Awareness programs on First Aid treatment of burn injuries together with the preventive programs focused on high risk population such as females and children in a large scale needs to be organized as soon as possible.

Shock Hugoniot of osmium up to 800 GPa from first principles calculations.

First principles total energy calculations on hcp, ω (a three atom simple hexagonal), ß (bcc) and fcc phases of osmium have been performed as a function of hydrostatic compression employing the FP-LAPW method. The comparison of total energies of these phases up to a maximum compression V/V(0) = 0.58 (pressure∼700 GPa) shows that the hcp structure remains stable up to this compression. The 300 K isotherm is determined after adding finite temperature thermal contributions to the total energy calculated as a function of volume at 0 K. From the theoretically determined isotherm, we have derived the shock Hugoniot of this metal and determined the shock parameters C(0) and s to be 4.48 km s(-1) and 1.32, respectively. Employing the theoretically calculated Gruneisen parameter in the differential form of the Lindemann melting rule, we have determined the variation of melting point of the osmium with pressure. The theoretically derived melting curve and the temperature rise along the Hugoniot predict the shock melting of osmium at ∼447 GPa with a corresponding temperature of ∼9203 K.

Xeroderma pigmentosa--a disfiguring disease.

Xeroderma pigmentosa is a rare inherited autosomal recessive disease with the inability to repair DNA damage caused by UV light. Recognized in the late 1800 by Maritz Kaposi it has been reported world wide and in all races with an over prevalence of 1-4 per million population. Kunwar et al. Those affected are extremely sensitive to the UV portion of the light and have a 2000-fold increased risk of skin cancer in the sun exposed skin. Basal cell carcinoma is the most commonly associated carcinoma followed by Squamous cell carcinoma and Melanoma. The pigmentation on the face and the rest of the body can be horribly disfiguring. The recurring cancer occurring on the face and repeated surgical treatment for the ulcerations have important social and psychological implications not encountered with other cancers. We report two cases of BCC and melanoma. The first case is of BCC of the face in a teenaged girl coexisting with xeroderma pigmentosa. The second case presented with melanoma of the scalp in a 10 year old female child. The details of these cases are presented and the management.