Volume changes during head-and-neck radiotherapy and its impact on the parotid dose – A single-institution observational study

Aims: This study aims at assessing the volume changes that occur in the targets (gross tumor volume and planning target volume [PTV]) and the organs at risk in squamous cell carcinoma of the head and neck during radiotherapy and assessing the dose changes that occur as a result of them. Settings and Design: This was a prospective observational study in a tertiary care center after obtaining the appropriate scientific and ethics committee clearance. Subjects and Methods: Forty-five patients diagnosed with squamous cell carcinoma of the head and neck, who were treated with intensity-modulated radiotherapy in the time period from March 2018 to May 2019, were enrolled in the study. A planning computed tomography (CT) scan (CTplan) was done for all patients, followed by scans after 15 fractions (CT15) and after 25 fractions (CT25). The volume changes and the subsequent dose changes were assessed and recorded. Statistical Analysis Used: Data entry was done in MS Excel spreadsheet. The continuous variables were expressed as mean + standard deviation. The comparison of normally distributed continuous variables was done by paired t-test. Data analysis was done by SPSS (Statistical Package for the Social Sciences) version 16.0. P < 0.05 was considered statistically significant. A multivariate linear regression model was constructed to study the correlation between mean dose to the parotid glands and the other variables. All statistical modeling and analysis were done using SAS (Statistical Analysis Software) version 9.4. Results: Of the 45 patients, 25 were male and 20 were female. The majority of the patients had malignancies in the oral cavity (16) and hypopharynx (14). Most of them had Stage III/IV (AJCC v 8) disease (41). There were a 36% decrease in the PTV-high risk (PTV-HR) volume and a 6.05% decrease in the PTV-intermediate risk (PTV-IR) volume CT15. In CT25, the volume decrease in the PTV-HR and the PTV-IR was 47% and 9.06%, respectively. The parotid glands also underwent a reduction in their volume which has been quantified as 21.7% and 20.9% in the ipsilateral and contralateral parotids in CT15 and 36% and 33.6% in CT25, respectively. The D2 (dose received by 2% of the volume) and D98 (dose received by 98% of the volume) of the PTV-IR showed changes of +3.5% and –0.2% in CT15 and + 4.6% and –0.31% in CT25, respectively. The homogeneity index and conformity number of the PTV-IR changes by 0.03 and 0.08 in CT15 and by 0.04 and 0.12 in CT25, respectively. The mean dose to the ipsilateral parotid gland increased by 14% in CT15 and 19% in CT25. The mean dose to the contralateral parotid gland increased by 17% in CT15 and 25% in CT25. Conclusion: The dose to the parotid glands increases as a result of the changes that occur during the course of radiation. The changes are significant after 15 fractions of radiation. A replanning at this juncture might be considered to reduce the dose to the parotid glands

Variations in the cerebral venous anatomy and pitfalls in the diagnosis of cerebral venous sinus thrombosis: low field MR experience.

BACKGROUND: Knowledge of variations in the cerebral venous anatomy and apparent signal abnormalities seen on Magnetic resonance (MR) angiography are essential to avoid over-diagnosis of cerebral venous sinus thrombosis (CVST), while interpreting the MR angiograms. AIMS: To evaluate the variations of cerebral venous anatomy and signal abnormalities by using 3D phase contrast MR angiography performed in a 0.5 Tesla MRI scanner. MATERIALS AND METHODS: One hundred patients who underwent MR imaging and MR angiography examinations at our institution from March 2004 to February 2005, with normal MR imaging of brain were studied retrospectively. Patients with clinical suspicion of CVST and patients who underwent color doppler evaluation for suspected deep vein thrombosis were excluded. RESULTS: The superior sagittal, straight sinus and the internal cerebral veins were visualized in all patients. There was hypoplasia of the right transverse sinus in 13 patients, left transverse sinus in 35 patients, right sigmoid sinus in 6 patients and left sigmoid sinus in 19 patients. Absence of transverse sinus on left side was observed in one patient and absence of sigmoid sinus in 2 patients on left side. Flow gaps were observed in non-dominant transverse sinus, sigmoid sinus as well as transverse sigmoid sinus junctions. The occipital sinus was visualized in 17 patients. CONCLUSIONS: MR angiography done at low field strengths is also a reliable method, for assessing cerebral venous sinuses. Awareness of the normal anatomical variations of venous sinuses and apparent MR angiographic flow gaps prevent misdiagnosis of cerebral venous sinus thrombosis.

Primary lymph node gastrinoma in jejunal mesentery.

Primary gastrinomas have been reported in lymph nodes within the gastrinoma triangle. We report a 56-year-old woman with possible primary lymph node gastrinoma in the jejunal mesentery. Six months after excision of the tumor, she is asymptomatic and serum gastrin level is normal.