Brief histories of medical physics in Asia-Oceania.

The history of medical physics in Asia-Oceania goes back to the late nineteenth century when X-ray imaging was introduced, although medical physicists were not appointed until much later. Medical physics developed very quickly in some countries, but in others the socio-economic situation as such prevented it being established for many years. In others, the political situation and war has impeded its development. In many countries their medical physics history has not been well recorded and there is a danger that it will be lost to future generations. In this paper, brief histories of the development of medical physics in most countries in Asia-Oceania are presented by a large number of authors to serve as a record. The histories are necessarily brief; otherwise the paper would quickly turn into a book of hundreds of pages. The emphasis in each history as recorded here varies as the focus and culture of the countries as well as the length of their histories varies considerably.

Radical radiotherapy for carcinoma cervix--preliminary experience with the microSelectron high dose rate machine.

Radiotherapy for uterine cervix carcinoma is an accepted treatment for all stages of invasive malignancy. The radiation modality is usually a combination of brachytherapy and external beam therapy for all except the most extensive tumours (stage IV--FIGO). Satisfactory results have been obtained in the Singapore General Hospital using low dose-rate radium applications in combination with cobalt teletherapy. Five year actuarial survival rates of 86.7% were obtained for FIGO stage I, 65.0% for stage II, 41.4% for stage III, 4.9% for stage IV with an overall rate of 54.0% for all stages. Corresponding 10-year rates were: 79.6%, 60.2%, 35.2%, 0% and 48.2%. Preliminary results of primary radiotherapy in 36 patients with cervical carcinoma treated by high dose-rate brachytherapy (microSelectron HDR) combined with 6MVP photons from a Siemens linear accelerator are presented. The patients were registered at the Mount Elizabeth Oncology Centre from November 1989 to December 1990 inclusive. The morbidity from high dose-rate therapy appears lower (9.1% for vaginal stenosis, 6.1% for non-severe proctitis) than for the radium series (4.1% and 20.8%) although the major complication rate appears similar (3% vs 2.8% respectively). The total failure rate is also lower at 19.4% for the HDR patients compared to 33.5% for the radium group. However, these rates are not strictly comparable as the HDR series consists of a small number of patients with limited follow-up. In the light of the data indicating acceptable morbidity with significant rate of early failure, the HDR brachytherapy doses have been increased whilst keeping within the limits set by other centres.

Bone scintigraphy in nasopharyngeal carcinoma.

One hundred and forty-three patients (Group 1) with histologically proven nasopharyngeal-carcinoma (NPC) had bone scintigraphy with 99Tcm methylenediphosphonate (MDP) or dihydroxypropanediphosphonate (DPD) within 2 months of the initial diagnosis. A further 162 patients (Group 2) had bone scans during the course of follow-up if there were symptoms of bone pain or evidence of metastases at other sites. Twenty-three per cent (33/143) of the newly diagnosed NPC patients (Group 1) had evidence of bone metastases. Of these 143 patients, 101 were T0-T2, 16 were T3 and 25 were T4. Thirty-six patients had no neck nodes (NO), 44 were N1, 25 N2 and 38 N3. Of the 162 patients in Group 2, 96 (59%) had a positive bone scan. The commonest sites for bony metastases from NPC were the spine, ribs, pelvis and lower limbs in order of frequency. There is a highly significant association with the nodal stage but no association with the UICC T staging which is not adequate in nasopharyngeal carcinoma. In our part of the world, bone metastases from NPC are a common cause of an abnormal bone scan.

Significance of tissue polypeptide antigen (TPA) levels in nasopharyngeal cancer.

Serum levels of tissue polypeptide antigen (TPA) were measured in 233 patients at the time of initial diagnosis of nasopharyngeal carcinoma (NPC). Staging of NPC was done using Ho's recommendations together with computerised tomography (CT) of skull findings. The upper limit of normal serum TPA levels in our population was noted to be 112 U/1. In 126 patients with N0 and N1 lymph node staging, the mean level of TPA was 90 U/1 +/- 9 (standard error of mean, sem), while in 107 patients with N2 and N3 nodal disease the mean was 193 U/1 +/- 25.6 (p less than 0.001). Similarly, in 162 patients with T1 and T2 disease, the average TPA level was 119 +/- 13.4 while in 71 patients with T3 disease, the mean TPA was 179 U/1 +/- 29.8 (p less than 0.03). Of 200 patients without metastases, the mean TPA level was 112 +/- 12 U/l whereas in 33 patients with known metastases in liver, lung, bone or brain, the mean TPA level was 290 +/- 51 (p less than 0.001) with liver metastases producing the highest levels. The present study indicates rising values of TPA with advancing nodal and tumour stage in NPC, with high values in metastatic disease. There is a highly significant correlation between nodal stage and TPA levels. TPA is a useful marker in the staging and follow-up of NPC patients.

99Tcm-(tin) colloid scans in the evaluation of renal transplant rejection.

Technetium-99m-(tin) colloid uptake in renal transplants was quantified to evaluate rejection. A dynamic acquisition following i.v. injection of 110 MBq of this radiopharmaceutical enabled quantification of 15 to 20 min transplant uptake (PU), in terms of percentage of an injected dose after allowing for attenuation in the patient. An uptake ratio (UR) i.e. the ratio of 15 to 20 min uptake over the 0 to 5 min uptake was also derived. Normal values were obtained in 20 stable functioning transplants (normal PU less than or equal to 1%, normal UR less than or equal to 0.7). In 66 patients, PU and UR were compared with clinical, biochemical, histological and radiological, evidence of rejection. A sensitivity of 70% and specificity of 85% was obtained for this 99Tcm-(tin) colloid study in the diagnosis of renal transplant rejection.

Radionuclide measurement of liquid and solid gastric emptying in normal subjects in Singapore.

Scintigraphic methods for liquid and solid gastric emptying were utilised to study normal patterns in 21 volunteers. Of these, 19 had solid emptying studies and 14 had liquid emptying studies. The liquid study lasted 1/2 hour, while the solid study was for 1 hour. The gastric emptying half-time (T 1/2), as well as percentage retention at 15 minutes (liquids), and at 60 minutes (for solids) were noted. The time-activity curves were also corrected for tissue attenuation. Results indicated normal average liquid emptying T 1/2 to be 14.2 minutes, while that for solids was 116 minutes.

Estimation of glomerular filtration rate in children using 99m-technetium DTPA. A comparison with 51-chromium EDTA clearance.

The usefulness of radionuclide imaging studies with 99m-technetium diethylenetriaminepentaacetic acid (Tc-DTPA) for quantitating the glomerular filtration rate (GFR) in children was studied. This was compared to the conventional methods for measuring GFR using 51-chromium-EDTA clearance (Cr-EDTA), creatinine clearance and a height/plasma creatinine formula. In the 22 children studied, the correlation coefficient between renal uptake of DTPA and Cr-EDTA was 0.90 (p less than 0.001). In contrast, there was a poorer correlation between Cr-EDTA and creatinine clearance (r = 0.69) or the derived GFR using height/creatinine formula (r = 0.83). The regression line between Tc-DTPA uptake and Cr-EDTA clearance was used to derive a formula for calculating the predicted GFR. This was tested in 10 additional children, and the correlation between the predicted GFR and measured GFR (using Cr-EDTA clearance studies) was 0.92 (p less than 0.001). Quantitative estimation of the GFR during renal imaging studies is a feasible and convenient method of assessing renal function.