There are various Regulatory Bodies at the international and National level, which lay down norms for radiation protection. These are the International Commission for Radiation Protection (ICRP) the National Commission for Radiation Protection (NCRP) in America, and the Atomic Energy Regulatory Board (AERB) in India. These bodies recommend norms for permissible doses of radiation from X ray tubes and the shielding required for the walls of an X ray room. Data is also available from the work of Investigators regarding the room shielding required in a CT suite. The recommended lead equivalent in shielding apparel to be worm by radiation workers is 0.5 mm. The regulatory bodies also lay down safe dose limits for radiation workers and for the general public. The duties of the Radiation Safety Officer (RSO) are also specified by the regulatory bodies, as are the radiation surveillance and radiation safety programmers.

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Objectives: The purpose of this study is to evaluate the role of MRI as an investigative modality in white matter diseases and to document its value in early diagnosis and management. This was done by studying the MR appearances of various white matter diseases encountered in our hospital with special reference to multiple sclerosis and correlating it with the clinical presentation. In addition, the most common diseases among them were identified. Materials and Methods: Forty patients with a strong clinical suspicion of demyelinating disorder were evaluated by MRI using 0.5 Tesla (Signa Contour, GE) scanner in a prospective study period of 2 years. Images were obtained in sagittal, axial and coronal planes using SE T1, PD and T2 and FLAIR sequences. Slice thickness of 5mm, FOV of 24 x 24 and 256 x 192 matrix were used. Results: Demyelinating foci were demonstrated with a high degree of accuracy on MR as prolonged T1 and T2 relaxation times, the site of the lesion varying in different disorders. Multiple sclerosis accounted for the majority of cases (37.5 percent) followed by acute disseminated encephalomyelitis (15 percent). Other causes like infections, toxic causes, periventricular leukomalacia and leukodystrophies comprised the remainder of the cases. In multiple sclerosis, majority of the patients presented in the third decade of life with a definite female preponderance (M:F-1:2). The most common symptom and site of involvement were visual impairment (73.3 percent) and periventricular area (80 percent) respectively. Conclusion: MRI due to its excellent gray-white matter resolution is very sensitive in detecting subtle demyelination, the sensitivity being still further enhanced by FLAIR sequences. The present study concludes that MRI, in correlation with the clinical signs and symptoms is an ideal modality in early diagnosis of white matter diseases and aids in the early institution of therapy so that the curable conditions among them can be treated.

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CT Scan Paranasal sinuses has become mandatory for all patients undergoing functional endoscopic sinus surgery. It depicts the anatomical complexities of osteomeatal complex in much simpler way and acts as a roadmap for endoscopic sinus surgery. Fifty patients of chronic sinusitis were evaluated by CT Scan PNS - coronal and axial views. The anatomical variations and changes in osteomeatal complex on CT Scan were studied. In majority of patients, osteomeatal complex and anterior ethmoids were involved (88%). Agger nasi cells (40%) were the most common anatomical variations followed by concha bullosa and haller cells (16%). Apart from this deviated nasal septum was found in 44% of patients. The variations found on CT Scan were later confirmed on nasal endoscopy. All the patients then underwent endoscopic sinus surgery. This study revealed various anatomical variations which were responsible for the primary pathology of the patient.

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Objectives : Vertebral hemangiomas are benign vascular lesions occurring in spine. Though vertebral hemangiomas are frequently seen, they are rarely symptomatic. Pain is the commonest symptom. There is no agreement on single treatment modality for symptomatic lesions. Surgery, intralesional injection of absolute alcohol, methyl methacrylate injection are few methods used to treat them. Radiotherapy has been shown effective in many studies in terms of pain relief and at times in cord compression too. Results of radiotherapy in symptomatic vertebral hemangiomas treated in our centre are analyzed. Materials and methods: Six patients with symptomatic vertebral hemangiomas were treated with external radiotherapy to a dose of 36-40 Gy. Four patients had only pain as their symptom. Two patients had additional neurological deficits with paraperesis at presentation. Result in terms of pain relief was assessed at the end of RT and during follow up. Median follow up was four and half months. Results : Out of six patients, pain relief was seen in four patients who had only pain as their symptom. There was neither pain relief nor improvement in neurological deficits in remaining two patients. Conclusion : Radiotherapy is an effective and simple modality of treatment for symptomatic vertebral hemangiomas where pain is the main symptom without neurological deficits. It is non invasive and safe.

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Objectives: To distinguish between neoplastic and non-neoplastic lesions showing ring enhancement or ring like lesions in the brain in CT or MRI with the help of correlative Nuclear imaging. Material and Methods: Twenty seven patients with various ring enhancing lesions in the brain detected in CT and/ or MRI were correlated with cerebral first pass study, Planar and SPECT imaging using different radiotracers like 99m Tc-HMPAO. TI-201, 99m Tc-DTPA/GHA, 99m mTc-MIBI or Tetrofosmin Results: Nuclear scanning was helpful in distinguishing between neoplastic and non-neoplastic conditions in 42 percent of cases in this study where C T or MRI were doubtful. Conclusion: Nuclear imaging coupled with CT or MRI provides a fairly accurate diagnosis in differentiating neoplastic conditions from non-neoplastic conditions without any MR Spectroscopic or Sterotactic biopsy technique applied on the patients.

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Objective: To study the feasibility and efficacy of US guided water enema (USWE) in hydrostatic reduction of acute intussusception in children who present early. Materials and Methods: Five children with "early" intussusception were subjected to USWE reduction. Results: Of the five patients who underwent this procedure, three had complete reduction of ileo-colic intussusception and two had near-complete reduction. Conclusion: USWE for childhood intussusception is safe and may be an effective alternative method in the non-operative management of intussusception.

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Objective: To study the pulsatility index (PI), resistance index (RI) and systolic/diastolic (S/D) ratio of the "umbilical" and "uterine" arteries during pregnancy. To determine the normal range (mean + 2SD) for the various indices in our population. To also determine the statistical significance (P-value) of these values by comparing them with the abnormal indices in pregnancies that developed pregnancy-induced hypertension (PIH), and small for gestational age (SGA) babies. To determine which artery "umbilical vs. uterine" and which index PI vs. RI vs. S/D, serve as better indicators for bad maternal and perinatal outcome in PIH and SGA babies. To conclude whether a Doppler study can be an effective screening test. Materials and Methods: A total of 120 random pregnancies were screened at 20, 28 and 34 weeks of gestation. A color Doppler scanner with a carrier frequency of 3.5 MHz was used for studying the uterine and the umbilical arteries. Pregnancies with a normal outcome were used for calculating the normal range of various indices and for testing the specificity and negative predictive value (NPV) of the study. Those pregnancies with an abnormal outcome (PIH and SGA babies) were used for calculating the sensitivity and positive predictive value (PPV) of the study. Results: In normal pregnancies, the flow velocity waveforms (FVWs) showed a good diastolic flow and fall in indices as pregnancy progressed. A low diastolic flow and high indices characterized the pregnancies with abnormal outcomes. The uterine artery had a better sensitivity and specificity as compared to the umbilical artery. Among the various uterine waveform parameters, the diastolic notch had the highest sensitivity and specificity. Among the umbilical indices, the PI had the highest sensitivity and specificity. Conclusion: Doppler provides a non-invasive method of assessing the fetal and maternal circulation during pregnancy. Both uterine and umbilical arteries have a low sensitivity at 20 weeks and therefore cannot be used as a screening test.

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CT scanning is widely used in the diagnostic workup of right lower quadrant pain. While appendicitis remains the most frequent cause, a majority of patients referred for suspected appendicitis turn out to have alternative diagnoses or a normal CT study. The purpose of our pictorial essay is to present an overview of the CT findings of appendicitis and its common mimics and to highlight the features that provide clues to alternative diagnoses.

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Soft tissue masses have a varied presentation. Though all masses cannot be optimally imaged on USG, its easy availability, real-time capability, and cost-effectiveness, as well as the freedom it provides to examine in any direction, make it an automatic choice as a first-line modality. Though Doppler is an exciting modality, it has its limitations and is not always rewarding. USG is more useful for superficially located masses. The role of USG is to provide information about the extent of the mass, its nature, and its relationship to the surrounding structures. One important aim is to differentiate between a pseudotumor and a true mass lesion. Doppler can provide additional information in selected cases. USG can play a pivotal role in guiding a needle for obtaining a sample for tissue diagnosis. Benign lesions are more common than malignant ones, in day-to-day practice. As with any other musculoskeletal examination, technical expertise and a sound knowledge of musculoskeletal anatomy are important.

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Objectives : To study the usefulness and accuracy of MR cisternography as noninvasive study in the diagnosis of cerebrospinal fluid (CSF) fistula with diagnostic sinonasal endoscopy and surgical correlation. Material and Methods: Twenty four patients with clinically suspected CSF rhinorrhoea were examined for CSF fistula with MR cisternography. The MR imaging technique included 3mm thin T2 weighted coronal and sagittal sections using Fast spin echo. In addition 1.5mm thin T2 weighted coronal sections were also obtained using CISS (Constructive Interference in Steady State) sequence. MR findings were correlated with diagnostic sinonasal endoscopy and surgical findings. Results : MR cisternography demonstrated the presence of fistula in 17 patients, absence of fistula in seven patients. Out of 17 patients with fistula, the diagnosis could be confirmed in 14 patients by diagnostic sinonasal endoscopy/surgery. Out of the seven patients without fistula, there was positive correlation in six patients when they were followed up clinically and by diagnostic nasal endoscopy. However in one patient, fistula was demonstrated on CT cisternography and was confirmed on sinonasal endoscopic surgery. The accuracy, sensitivity of MR cisternography was 96, 94% respectively. Conclusion : MR cisternography is a useful and accurate noninvasive study in localizing the site and extent of CSF fistula.

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Objectives : MRI has proven to be the best imaging modality in the evaluation of pituitary tumors. Dynamic Imaging is technically a new tool, which has emerged with lot of promise in the evaluation of pituitary adenomas, particularly in accurate delineation of those microadenomas with no contour abnormality and in differentiating residual/recurrent adenoma from surrounding post operative tissue. Dynamic MR imaging is not only useful in the evaluation of pituitary microadenomas but has an equally important role in the assessment of macroadenoma as well. This study analyses and reviews the value of dynamic MR Imaging in pituitary adenomas and postoperative pituitary tumors. Materials and Methods : A prospective MR Study was undertaken in twenty-five consecutive patients with suspected pituitary adenomatous lesions. These patients were subjected to dynamic MR imaging at our Department from Jan 1997 to Dec 1998. The study was performed on a 0.5T super conducting MR imaging system with Fast Spin echo technique. Gadodiamide (0.1 mmol/Kg) was administered over sixty seconds by hand injection. Dynamic coronal images were obtained simultaneously from three different portions of the gland. Fifteen images were obtained from each of the three portions at an interval of twenty to thirty seconds between the images. Result : Dynamic MRI was performed in nineteen patients with microadenoma and six cases of macroadenoma. Dynamic MRI study was of diagnostic value in comparison with routine contrast MRI in eleven of the nineteen patients. Dynamic study did not add to the diagnosis and was merely of confirmatory value in remaining eight patients. Dynamic MRI study was used to identify the optimal time for delineation of the adenomatous tumor, by virtue view of the simultaneous differential contrast enhancement patterns between normal pituitary gland and adenoma. Further the enhancement pattern of the normal pituitary gland, the adenomatous nodule and the optimal delineation were individually assessed. This evaluation revealed the average time in seconds for onset of enhancement and the peak enhancement of normal pituitary gland were 43.1 and 111.9 seconds respectively. In comparison the pituitary adenomatous nodules exhibited an average time of 105.8 seconds for onset of enhancement and 188.1 seconds for peak enhancement. The average time in seconds for optimal tumor delineation was 93.9 seconds. Conclusion : Dynamic MR Imaging has emerged as a technically refined tool in the evaluation of pituitary adenomas. The key questions in evaluation of pituitary adenomas include the presence or absence of a tumor, the number, the location of adenoma nodule, the invasive effects on adjacent structures and the post therapy status of adenoma. Clearly, dynamic MR Imaging is the foremost imaging modality answering these vital questions in patients with pituitary adenomas.

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