Biodosimetry using micronucleus assay in acute partial body therapeutic irradiation.

Biological dosimetry provides information on the absorbed dose and its distribution in the body for an early assessment of irradiation consequences in exposed individuals. In this study, an effort has been made to see the applicability of biological dosimetry using micronuclei assay for dose estimation in therapeutic irradiation of cancer patients in acute high dose partial body irradiation. Dose estimation in partial body irradiations was done on the basis of Dolphin's contaminated Poisson method, using the in vitro dose response calibration curve. The equivalent whole body dose and the dose to the irradiated part of the body were estimated to be 1.8+/-0.1 Gy and 6.4+/-0.3 Gy, respectively. The estimated percentage of irradiated blood and the fraction of cells exposed were 41.5+/-1.6% and 10.4+/-0.8%, respectively. The estimated fraction of irradiated cells was comparable with the actual volume of irradiation.

Biological estimation of dose in hemi-body irradiation of cancer patients by cytogenetic analysis.

The objective of this study was to estimate equivalent whole body dose and dose to the irradiated region in hemi-body irradiation of cancer patients using chromosome aberrations and micronuclei techniques. The frequency of unstable chromosome aberrations and micronuclei was studied in peripheral blood lymphocytes of cancer patients before and after hemi-body irradiation. The mean estimated equivalent whole body dose was 3.74 +/- 0.16 Gy and 4.07 +/- 0.15 Gy from dicentrics and micronuclei frequency in lymphocytes after hemi-body irradiation. The mean dose to the irradiated region from unstable chromosome aberrations was estimated to be 6.85 +/- 0.2 Gy and 6.79 +/- 0.26 Gy using Dolphin's contaminated Poisson dispersion analysis and the Qdr method, respectively. The mean dose to the irradiated region from micronuclei frequency was 7.04 +/- 0.25 Gy by Dolphin's method. There was a slight underestimation of mean dose to the irradiated part in vivo. The percentage of irradiated blood and fraction of the cells exposed could be estimated using the contaminated Poisson method.

Comparison of contralateral breast dose for various tangential field techniques in clinical radiotherapy.

Contralateral breast (CLB) cancer is a rare but serious concern in radiotherapy. In this study, the CLB dose was measured using MOSFET dosimeter in 49 patients who underwent breast conservation surgery treated by different radiotherapy tangential field techniques, which included enhanced dynamic wedge (EDW), physical wedge, and intensity modulated radiation therapy (IMRT). The mean percent of the prescribed dose received by the contralateral areola in treatment technique using physical wedge (Cobalt), physical wedge (Linac), EDW, and IMRT were 4.27% (SD: 0.65), 3.61% (SD: 0.60), 3.38% (SD: 0.58), and 1.65% (SD: 0.24), respectively. There was a 29% CLB dose reduction at 3 cm from the medial tangential field border with IMRT compared to other wedged tangential field techniques. The study shows that the CLB dose could be reduced with IMRT or reducing or avoiding the medial wedge in conventional tangential field planning for breast cancer.

Biodosimetry using chromosome aberrations in human lymphocytes.

In vitro dose-response calibration curves for (60)Co gamma rays have been established for unstable chromosome aberrations in human peripheral blood lymphocytes. The observed dose-response data were fitted to a linear quadratic model. The calibration curve parameters were used to estimate the equivalent whole-body dose and dose to the irradiated region in partial body irradiation of cancer patients. The derived partial body doses and fractions of lymphocytes irradiated were in agreement with those estimated from the radiotherapy regimes.

Radiation dose to family members of hyperthyroidism and thyroid cancer patients treated with 131I.

The thermoluminescence dosemeter (TLD) was used for measuring radiation dose to family members of thyrotoxicosis and thyroid cancer patients treated with (131)I using CaSO(4):Dy discs. There were 45 family members of thyrotoxicosis patients, who were divided into two groups with 22 in the first and 23 in the second group. Radiation safety instructions were the same for both the groups except in the second group where the patients were advised to use a separate bed at home for the first 3 d of dose administration. An activity ranging from 185 to 500 MBq was administered to these patients. The whole-body dose to family members ranged from 0.4 to 2.4 mSv (mean 1.1 mSv) in the first group and 0-1.9 mSv (mean 0.6 mSv) in the second group. A total of 297 family members of thyroid cancer patients were studied for whole-body dose estimation. An activity ranging from 0.925 to 7.4 GBq was administered to the thyroid cancer patients. The family members were divided into three groups depending upon the mode of transport and facilities available at home to avoid close proximity with the patient. Group A with 25 family members received a dose ranging from 0 to 0.9 mSv (mean 0.4 mSv), group B with 96 family members received a dose ranging from 0 to 8.5 mSv (mean 0.8 mSv) and group C with 176 family members received a dose ranging from 0 to 5.0 mSv (mean 0.8 mSv). The thyroid monitoring was also done in 103 family members who attended the patients in isolation wards for >2 d. Thyroid dose in them ranged from 0 to 2.5 mGy (mean 0.1 mGy).

Thallium-201 versus Tc99m-glucoheptonate SPECT for evaluation of recurrent brain tumours: a within-subject comparison with pathological correlation.

BACKGROUND: Thallium-201 (Tl-201) is the most commonly used tracer for functional imaging of recurrent brain tumours. However, the physical properties of Tl-201 are not particularly suitable for this application, thus, a technetium-99 (Tc99m) labelled alternative with more favourable physical properties has been sought. The aim of this study was to compare the ability of Tl-201 and Tc99m-glucoheptonate single photon emission computed tomography (SPECT) to detect viable recurrent tumour and differentiate post-radiation gliosis. METHOD: Brain SPECT with Tl-201 and Tc99m-glucoheptonate was performed in 20 patients with malignant brain tumour in whom recurrent disease was suspected. Tracer uptake in the mass was defined as high, moderate or low and was correlated with histological verification of the lesion in all cases. RESULTS: Recurrent tumour was demonstrated in 17 patients by both Tl-201 and Tc99m-glucoheptonate SPECT and confirmed by surgical resection in all 17 patients. Three patients had no tracer uptake on either Tl-210 or Tc99m-glucoheptonate SPECT and surgical resection revealed only fibrotic tissue with areas of necrosis. Tc99m-glucoheptonate images were found to correlate more closely with the surgical findings with regard to the location of tumour margin, extent of tumour invasion and intratumoural necrosis. CONCLUSION: Tc99m-glucoheptonate brain SPECT is an accurate agent for SPECT imaging of recurrent brain tumours and may provide more information about the location of the tumour margin and its extent and intratumoural necrosis than Tl-201. Tc99m-glucoheptonate may be a viable replacement for Tl-201.

Radioiodine dose for remnant ablation in differentiated thyroid carcinoma: a randomized clinical trial in 509 patients.

Remnant ablation can be achieved by either administering an empiric fixed dose or using dosimetry-guided techniques. Because of the technical and logistic difficulties, most centers have adapted the fixed-dose or standard-dose technique for remnant ablation using (131)I. In the late 1970s, low-dose (131)I remnant ablation was introduced, and subsequently many centers confirmed the effectiveness of such therapy. However, the optimal dose (administered activity) of (131)I for remnant ablation is not yet settled. In a randomized clinical trial to find out the smallest possible effective dose for remnant ablation in cases of differentiated thyroid carcinoma, between July 1995 and January 2002, 565 patients were randomized into eight groups according to (131)I administered activity, starting at 15 mCi and increasing activity in increments of 5 mCi until 50 mCi. In the postrandomization phase, 56 patients were excluded from the study for various reasons, and final analysis was done with 509 patients. The mean age of the patients was 37.5 +/- 12.7 yr with a female to male ratio of 2.6. The surgical procedure was total/near-total thyroidectomy in 72% and subtotal or hemithyroidectomy in the rest. Histology was papillary thyroid carcinoma in 80.6% of patients and follicular thyroid carcinoma in the rest. With one dose of (131)I, remnant ablation was achieved in 59.6, 63.6, 81.4, 83.6, 79.4, 78.3, 84.4, and 81.8% of patients in the 15- to 50-mCi groups, respectively (overall ablation rate, 77.6%). The successful ablation rate was statistically different in patients receiving less than 25 mCi of (131)I compared with those receiving at least 25 mCi [63 of 102 (61.8%) vs. 332 of 407 (81.6%); P = 0.006]. However, there was no significant intergroup difference in outcome among patients receiving 25-50 mCi of (131)I. Patients with small tumor size (

Cytogenetic and molecular genetic studies on Indian patients with chronic lymphocytic leukemia.

This is the first cytogenetic and molecular genetic study to find any specific genetic abnormalities in Indian patients with chronic lymphocytic leukemia (CLL). Cytogenetic studies on 18 patients indicated that their karyotypes were relatively simple and trisomy 12 was seen on karyotype evolution in one patient. Fluorescence in situ hybridization (FISH) revealed abnormal clones of trisomy 12 in nine cases and RB gene deletion in 14 of the 29 cases analyzed. Three patients had both clones. Immunoglobulin genes were rearranged in all the cases and TCR beta in none of the 18 cases Southern blotted. BCL-1 was rearranged in one case. No rearrangement of BCL-2 gene was seen in any case. Genetic changes in Indian CLL were more similar to Western CLL than to Japanese CLL, even though India is supposed to be a low incidence area. Therefore, factors (such as HLA and other genetic markers) other than these routine parameters must be studied to explain the low incidence of CLL in India.

Case report: giant cell tumour of metacarpals: report of three cases.

Giant cell tumour of the metacarpal bone is rare. We have encountered three cases during the last 30 years. Surgical treatment is difficult in such a critical site and is always associated with functional deformities and poor cosmesis. We have successfully treated two males and one female with lesions of the 1st, 2nd and 4th metacarpal bones using a Theratron-60 telecobalt machine. The radiation dose delivered was 50-55 Gy over 4.5-5 weeks. The three patients all tolerated radiotherapy treatment well, though moderate radiation dermatitis (Grade II-III) was seen. The regression of tumour mass started after about 2 months of radiation therapy and complete regression occurred after several months. The pain subsided immediately. Long follow up of 7-11 years revealed no signs of local recurrence, distant metastasis or radiation induced malignancy. The results of radiation therapy are excellent in terms of functional integrity and cosmesis.

Optimum filtration for time-activity curves in nuclear medicine.

Insufficient filtration and over-smoothing are misleading processes in the quantification of time-activity curves. The optimum filtration requires a good knowledge of the frequency spectrum and relative amplitudes of the data and superimposed noise. Due to variations in biomedical data, it is very difficult to adjust the filter for individual cases. To overcome this problem a new method of noise reduction is proposed. In this method the time-activity curves are transformed into a low frequency (linear) curve that can be filtered heavily without significant distortion of the real data. The theory of the proposed filter and the results of its comparison with three-point filter, five-point filter and data bounding methods are presented. The comparison was performed using deconvolution analyses of simulated renograms. The results show that the proposed filter causes minimum distortion of the renogram and impulse retention function in terms of the root mean square error and the peak of the renogram. Moreover, the filter is much less sensitive to over-smoothing (number of filter iterations), the signal-to-noise ratio and the mean transit time of the renogram compared with other filters.

Radioiodine lobar ablation as an alternative to completion thyroidectomy in patients with differentiated thyroid cancer.

This study seeks to evaluate the role of radioiodine in the ablation of the remaining thyroid lobe, following a histopathological diagnosis of minimally invasive follicular carcinoma or papillary carcinoma of > or =1.5 cm size in patients undergoing hemithyroidectomy. There were 93 patients (69 females and 24 males) with an average age of 37.3+/-12.5 years (range, 16-70 years) and a mean follow-up duration of 46 months. Sixty-six of the patients had papillary cancer and remaining 27 had follicular thyroid cancer. The mean 24 h radioiodine neck uptake at the first visit was 17.2+/-7.3% (4.4-34%). In view of the large amount of thyroid tissue to be ablated, which may produce radiation induced thyroiditis, low doses of radioiodine (15-60 mCi) were administered to the patients. The patients were evaluated 6 months after radioiodine therapy with a 131I whole-body scan and 48 h radioiodine neck uptake, and a thyroglobulin assay after 4-6 weeks of levothyroxine withdrawal. The thyroid lobe was completely ablated in 53 patients (56.9%) after one dose of I and the remaining patients had partial thyroid ablation, with the mean radioiodine neck uptake being reduced to 3.1+/-2.4%. The mean first dose of 131I was 31.8+/-11.7 mCi; the estimated mean absorbed dose was 251.3+/-149.3 Gy (range, 120-790 Gy). Around 30% patients, in each of whom a remnant thyroid lobe was ablated with a single dose of radioiodine, received < or =200 Gy. The cumulative ablation rate was 92.1% after two doses of 131I. Only seven patients needed a third dose of 131I. In our cohort, 15 patients (16.1%) complained of throat discomfort and neck pain. All of them were managed with mild analgesics except three patients who needed additional oral prednisolone for 7-10 days to overcome neck oedema. We conclude that, although completion thyroidectomy remains the standard treatment after hemithyroidectomy in cases of differentiated thyroid cancer, radioiodine ablation of an intact thyroid lobe is possible and it can be achieved with much smaller doses of radioiodine than previously believed. Lobar ablation is an attractive alternative to surgery for those who refuse to undergo completion thyroidectomy or had complications during initial surgery. However, the long-term outcome in this subset of patients remains to be determined.

Estimation of thyroid mass in Graves' disease by a scintigraphic method.

scintigraphic method for the estimation of the thyroid mass in patients with Graves' disease is described. The method was first standardized using thyroid phantoms with eight different volumes ranging from 5 to 110 cm(3). The planar and single photon emission computed tomography (SPECT) images of each phantom were acquired with four different activities [3.7 MBq (100 microCi), 11.1 MBq (300 microCi), 22.2 MBq (600 microCi) and 37 MBq (1.0 mCi) of 99mTc-pertechnetate] with a 20% window symmetrically placed over the photopeak of 99mTc. The thyroid lobes were enclosed with the help of regions of interest (ROI) tools and a threshold was selected to identify the thyroid boundaries. The same threshold was used in all slices of an image. In the phantom study, a 20% threshold for planar images and a 30% threshold for SPECT were found to be optimum for measuring the thyroid volume. The volume from planar images was calculated by the formula described by Allen and Goodwin (The scintillation counter as an instrument for in-vivo determination of thyroid weight. Radiology 1952; 58: 68-79), whereas, in SPECT images, the sum of the slice areas was multiplied by the slice thickness. The estimated volume of each phantom was compared and correlated with its actual volume. After standardization of the technique with phantom studies, planar scintigraphy (with 20% threshold) in 51 patients and SPECT (with 30% and 35% threshold) in 40 patients with Graves' disease were performed to estimate the thyroid size. The thyroid size was also estimated by ultrasonography, which showed good agreement with the scintigraphic method, particularly with SPECT.