Accuracy evaluation of fusion of CT, MR, and spect images using commercially available software packages (SRS PLATO and IFS).

PURPOSE: A problem for clinicians is to mentally integrate information from multiple diagnostic sources, such as computed tomography (CT), magnetic resonance (MR), and single photon emission computed tomography (SPECT), whose images give anatomic and metabolic information. METHODS AND MATERIALS: To combine this different imaging procedure information, and to overlay correspondent slices, we used commercially available software packages (SRS PLATO and IFS). The algorithms utilize a fiducial-based coordinate system (or frame) with 3 N-shaped markers, which allows coordinate transformation of a clinical examination data set (9 spots for each transaxial section) to a stereotactic coordinate system. The N-shaped markers were filled with fluids visible in each modality (gadolinium for MR, calcium chloride for CT, and 99mTc for SPECT). The frame is relocatable, in the different acquisition modalities, by means of a head holder to which a face mask is fixed so as to immobilize the patient. Position errors due to the algorithms were obtained by evaluating the stereotactic coordinates of five sources detectable in each modality. RESULTS: SPECT and MR position errors due to the algorithms were evaluated with respect to CT: deltax was < or = 0.9 mm for MR and < or = 1.4 mm for SPECT, deltay was < or = 1 mm and < or = 3 mm for MR and SPECT, respectively. Maximal differences in distance between estimated and actual fiducial centers (geometric mismatch) were in the order of the pixel size (0.8 mm for CT, 1.4 mm for MR, and 1.8 mm for SPECT). In an attempt to distinguish necrosis from residual disease, the image fusion protocol was studied in 35 primary or metastatic brain tumor patients. CONCLUSIONS: The image fusion technique has a good degree of accuracy as well as the potential to improve the specificity of tissue identification and the precision of the subsequent treatment planning.

Scintigraphic detection of melanoma metastases with a radiolabeled benzamide ([iodine-123]-(S)-IBZM).

UNLABELLED: Iodine-123-(S)-2-hydroxy-3-iodo-6-methoxy-N-[(1-ethyl-2-pyrrolidinyl) methyl] benzamide ([123I]-(S)-IBZM) is a radiolabeled benzamide usually employed to study neuropsychiatric disorders, such as schizophrenia and Parkinson's disease. The ectodermic origin of melanocytes and the presence of melanin in the substantia nigra are the theoretic basis of the experimental use of this class of tracers for melanoma imaging. METHODS: Eleven patients with proven metastatic melanoma entered the study. Whole-body and planar scintigrams were performed 2, 4 and 24 hr after intravenous injection of a mean tracer activity of 205 MBq. The dosimetric evaluation was performed by the Medical Internal Radiation Dose Committee method. RESULTS: The [123I]-(S)-IBZM scans allowed the detection of all six cutaneous lesions, five of six superficial pathologic lymph nodes, four of five pulmonary and one of two hepatic metastases. The maximum tumor-to-background ratio was 2.6 in planar images. The hepatobiliary excretion of the tracer may limit detection of intra-abdominal lesions. Dosimetry is similar to data for nononcologic patients. CONCLUSION: Although it is unclear if the mechanism of radiopharmaceutical uptake in melanoma is due to binding to membrane receptors or due to interactions with intracellular structures, radiolabeled benzamide is a promising tracer to detect melanoma.

Increased survival in brain metastatic patients treated with stereotactic radiotherapy, omega three fatty acids and bioflavonoids.

Stereotactic radiotherapy represents a method to effectively treat brain metastases with high precision and with high doses. Few acute toxicities are associated with stereotactic radiotherapy, however delayed reactions may occur and after six months, 20% of patients can develop radionecrosis. To avoid this adverse effect, in patients with metastases localized in critical brain areas, a supplementation of Omega three fatty acids and bioflavonoids has been used. At the end of 1997, we initiated a series of retrospective studies to test the efficacy of stereotactic radiotherapy on 405 patients, and the prognostic importance on survival of various variables among which this type of supplementation. From the comparison of various survival curves with the Cox multivariate analysis, it emerged that the patients using this supplementation had a decreased risk ratio and an improvement in survival time. A decreased number of radionecrosis was noted. We suggest their use as radioprotectors.

Dosimetric verification of a commercial 3D treatment planning system for conformal radiotherapy with a dynamic multileaf collimator.

The dosimetric accuracy of a 3D treatment planning system (TPS) for conformal radiotherapy with a computer-assisted dynamic multileaf collimator (DMLC) was evaluated. The DMLC and the TPS have been developed for clinical applications where dynamic fields not greater than 10 x 10 cm2 and multiple non-coplanar arcs are required. Dosimetric verifications were performed by simulating conformal treatments of irregularly shaped targets using several arcs of irradiation with 6 MV x-rays and a spherical-shaped, tissue-simulating phantom. The accuracy of the delivered dose at the isocentre was verified using an ionization chamber placed in the centre of the phantom. Isodose distributions in the axial and sagittal planes passing through the centre of the phantom were measured using double-layer radiochromic films. Measured dose at the isocentre as well as isodose distributions were compared to those calculated by the TPS. The maximum percentage difference between measured and prescribed dose was less than 2.5% for all the simulated treatment plans. The mean (+/-SD) displacement between measured and calculated isodoses was, in the axial planes, 1.0 +/- 0.6 mm, 1.2 +/- 0.7 mm and 1.5 +/- 1.1 mm for 80%, 50% and 20% isodose curves, respectively, whereas in the sagittal planes it was 2.0 +/- 1.2 mm and 2.2 +/- 2 mm for 80% and 50% isodose curves, respectively. The results indicate that the accuracy of the 3D treatment planning system used with the DMLC is reasonably acceptable in clinical applications which require treatments with several non-coplanar arcs and small dynamic fields.

Clinical role of technetium-99m sestamibi single-photon emission tomography in evaluating pretreated patients with brain tumours.

One of the main problems regarding the follow-up of patients with brain tumours treated with radiotherapy is the distinction between radiation necrosis and tumour relapse. In many cases computed tomography (CT) scan is unable to distinguish between the two. We assessed the usefulness of brain single-photon emission tomography (SPET) with technetium-99m-sestamibi in cases where CT scan was not conclusive. The absence of tracer uptake in normal brain, the sharp uptake in neoplastic tissue, and the favourable physical properties of technetium make the scintigraphic method particularly accurate. We therefore propose the association of CT scan with 99mTc-sestamibi brain SPET in the follow-up of patients in whom a distinction between radiation necrosis and active disease is needed for an adequate therapeutic decision.