Optically stimulated luminescence in vivo dosimetry for radiotherapy: physical characterization and clinical measurements in (60)Co beams.

A commercial optically stimulated luminescence (OSL) dosimetry system was investigated for in vivo dosimetry in radiation therapy. Dosimetric characteristics of InLight dot dosimeters and a microStar reader (Landauer Inc.) were tested in (60)Co beams. The reading uncertainty of a single dosimeter was 0.6%. The reproducibility of a set of dosimeters after a single irradiation was 1.6%, while in repeated irradiations of the same dosimeters it was found to be 3.5%. When OSL dosimeters were optically bleached between exposures, the reproducibility of repeated measurements improved to 1.0%. Dosimeters were calibrated for the entrance dose measurements and a full set of correction factors was determined. A pilot patient study that followed phantom validation testing included more than 100 measured fields with a mean relative difference of the measured entrance dose from the expected dose of 0.8% and the standard deviation of 2.5%. In conclusion, these results demonstrate that OSL dot dosimeters represent a valid alternative to already established in vivo dosimetry systems.

Comparison of doses calculated by the Monte Carlo method and measured by LiF TLD in the buildup region for a 60Co photon beam.

This work studied the percent depth doses of (60)Co photon beams in the buildup region of a plastic phantom by LiF TLD measurements and by Monte Carlo calculations. An agreement within +/-1.5% was found between PDDs measured by TLD and calculated by the Monte Carlo method with the TLD in a plastic phantom. The dose in the plastic phantom was scored in voxels, with thickness scaled by physical and electron density. PDDs calculated by electron density scaling showed a better match with PDD(TLD)(MC); the difference is within +/-1.5% in the buildup region for square and rectangular field sizes.

Immunoscintigraphy with 99Tcm-labelled monoclonal anti-CEA BW 431/26 antibodies in patients with suspected recurrent and metastatic colorectal carcinoma: two-year follow-up.

The aim of this study was to evaluate immunoscintigraphy with BW 431/26 anti-CEA antibody in the follow-up of 15 patients with colorectal carcinoma. A whole-body scan followed by SPET imaging of the abdomen and pelvis was performed 4-6 and 20-24 h after the intravenous infusion of 0.6-1.0 mg of intact anti-CEA monoclonal BW 431/26 antibody labelled with 814-1110 MBq of 99Tcm. The HAMA response and serum CEA levels were determined. Immunoscintigraphic findings were verified by biopsy, radiologically and/or by 2 year follow-up. On an individual patient basis, immunoscintigraphy demonstrated an overall sensitivity of 83%, specificity of 100%, accuracy of 87%, positive predictive value of 100% and negative predictive value of 60%. Better results were achieved in the pelvic region than in the liver or in the extra-hepatic abdominal region. We evaluated 40 lesions; on an individual lesion basis, immuno-scintigraphy gave a sensitivity of 80% and an accuracy of 80%. SPET images detected significantly more lesions than whole-body planar images (P < 0.05). SPET at 20-24 h detected significantly more 'hot' lesions than at 4-6 h (P < 0.01). No correlation between CEA serum levels and immunoscintigraphy was observed (r = 0.376, P > 0.05). One of nine patients (11%) developed HAMA after immunoscintigraphy. We conclude that immunoscintigraphy with BW 431/26 antibody appears able to differentiate between tumour recurrence and scar tissue, and to evaluate liver metastases of colorectal carcinoma. Serum CEA levels appear not to influence the result of immunoscintigraphy and the HAMA response is minimal. A delayed SPET scan should be part of an immunoscintigraphic imaging protocol when 99Tcm-labelled BW 431/26 monoclonal antibody is used.

Bone marrow immunoscintigraphy for the detection of skeletal metastases in patients with breast cancer.

In this study, we evaluated the efficacy of bone marrow immunoscintigraphy (BMIS) for the detection of skeletal metastases in 23 patients with histologically confirmed breast cancer. All patients underwent whole-body BMIS 3-6 h after the intravenous injection of 0.20-0.33 mg of the intact anti-NCA 95 MAb BW 250/183 labelled with 259-555 MBq 99Tcm and a whole-body 99Tcm-MDP bone scan. In four patients, BMIS SPET of the lumbar spine was also performed. Serum alkaline phosphatase was determined in all patients and the level of human anti-mouse antibody (HAMA) in 16. Final diagnosis was confirmed by radiology and 2 years follow-up. Compared with the 99Tcm-MDP bone scan, BMIS demonstrated better specificity (88% vs 75%) and a better positive predictive value (92% vs 85%). There were no significant differences between BMIS and the bone scan in the detection of skeletal metastases (P > 0.05). In one patient with normal planar BMIS of the lumbar spine, SPET disclosed a metastatic lesion in the bone marrow. The correlation coefficient between BMIS and bone scan and between BMIS and serum alkaline phosphatase was r = 0.688 and r = 0.483 respectively. One patient developed a minor HAMA response after BMIS. Patients with diffuse increased activity of the skull on the bone scan had a significantly higher skull to whole body ratio on BMIS (P < 0.01). Thus BMIS can improve the specificity and positive predictive value of bone scanning in the detection of skeletal metastases, with a low HAMA response. Diffuse increased activity of the skull on bone scans could be explained by bone marrow extension. SPET scanning of the spine may improve the sensitivity of BMIS.

Radioimmunoscintigraphy--a new, specific procedure in nuclear oncology.

The purpose of this review is to describe in detail a new, specific, nuclear medicine imaging procedure in the field of oncology. Although the history of radioimmunoscintigraphy is not so short, the greatest advances in the realization of this idea have been made during the last two decades. The time has come for radioimmunoscintigraphy to became a standard procedure in the diagnosis of malignant as well as non-malignant diseases. Except some historical facts about the development of radioimmunoscintigraphy, this review also shows all the complexities of the problem which had to be resolved before a good idea was effectively realized. The authors have tried to present, to a reasonable extent, all problems in connection with the selection of radionuclides, antibodies, methods of labeling antibodies, and imaging procedure. In general, what interests medical professionals the most is the clinical application of radioimmunoscintigraphy as well as future development and improvements of this procedure as a step of radioimmunotherapy--a new kind of treatment in oncology.