Automatic segmentation of whole-body bone scintigrams as a preprocessing step for computer assisted diagnostics

Bone scintigraphy or whole-body bone scan is one of the most common diagnostic procedures in nuclear medicine used in the last 25 years. Pathological conditions, technically poor quality images and artifacts necessitate that algorithms use su±cient background knowledge of anatomy and spatial relations of bones in order to work satisfactorily. We present a robust knowledge based methodology for detecting reference points of the main skeletal regions that simultaneously processes anterior and posterior whole-body bone scintigrams. Expert knowledge is represented as a set of parameterized rules which are used to support standard image processing algorithms. Our study includes 467 consecutive, non-selected scintigrams, which is to our knowledge the largest number of images ever used in such studies. Automatic analysis of whole-body bone scans using our knowledge based segmentation algorithm gives more accurate and reliable results than previous studies. Obtained reference points are used for automatic segmentation of the skeleton, which is used for automatic (machine learning) or manual (expert physicians) diagnostics. Preliminary experiments show that an expert system based on machine learning closely mimics the results of expert physicians

Comparison of three radiolabelled peptide analogues for CCK-2 receptor scintigraphy in medullary thyroid carcinoma

Purpose: Cholecystokinin 2 (CCK-2) receptor overexpression has been demonstrated in a high percentage of medullary thyroid carcinomas (MTC). Analogous to somatostatin receptors, CCK-2 receptors might be viable targets for radionuclide scintigraphy and/or radionuclide therapy. Several CCK-2 receptor-binding radiopeptides have been developed, and some have been carried through into clinical studies. However, these studies are mostly limited and difficult to compare. The aim of this study was to evaluate the diagnostic and therapeutic potential of three promising CCK-2 receptor-binding radiopeptides in patients with MTC. Methods: 111In-DOTA-(D)Asp-Tyr-Nle-Gly-Trp-Nle- Asp-Phe-NH2 (111In-DOTA-CCK), a CCK analogue, and the gastrin-based ligands 99mTc-N4-Gly-(D)Glu-(Glu) 5-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2 (99mTc- demogastrin 2) and 111In-DOTA-(D)Glu-Ala-Tyr-Gly-Trp-Met-Asp-Phe- NH2 (111In-DOTA-MG11) were each administered to the same group of six patients. Planar images made at 3-5, 7 and 24 h p.i. were used for comparison of tumour visualisation and renal uptake. Results: 99mTc-demogastrin 2 scintigraphy visualised all known lesions and new lesions in four of six patients. 111In-DOTA-CCK and 111In-DOTA-MG11 on the other hand missed several lesions; tumour uptake of these two radiopharmaceuticals was quite low. Comparison of retention of renal activity showed no major differences between the three radiopeptides. Conclusion: 99mTc-demogastrin 2 scintigraphy appeared most promising as a diagnostic tool in patients with MTC. Further studies are required to evaluate its value in patient management. Direct comparisons of the compounds studied strongly suggests that 111In-DOTA-CCK and 111In-DOTA-MG11 have less potential as imaging agents than 99mTc-demogastrin 2. These DOTA-linked compounds are considered unlikely to be useful for radionuclide therapy because of low tumour uptake

Comparison of three radiolabelled peptide analogues for CCK-2 receptor scintigraphy in medullary thyroid carcinoma

Cholecystokinin 2 (CCK-2) receptor overexpression has been demonstrated in a high percentage of medullary thyroid carcinomas (MTC). Analogous to somatostatin receptors, CCK-2 receptors might be viable targets for radionuclide scintigraphy and/or radionuclide therapy. Several CCK-2 receptor-binding radiopeptides have been developed, and some have been carried through into clinical studies. However, these studies are mostly limited and difficult to compare. The aim of this study was to evaluate the diagnostic and therapeutic potential of three promising CCK-2 receptor-binding radiopeptides in patients with MTC. In-111-DOTA-(D)Asp-Tyr-Nle-Gly-Trp-Nle-Asp-Phe-NH2 (In-111-DOTA-CCK), a CCK analogue, and the gastrin-based ligands Tc-99m-N-4-Gly-(D)Glu-(Glu)(5)-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2 (Tc-99m-demogastrin 2) and In-111-DOTA-(D)Glu-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2 (In-111-DOTA-MG11) were each administered to the same group of six patients. Planar images made at 3-5, 7 and 24 h p.i. were used for comparison of tumour visualisation and renal uptake. Tc-99m-demogastrin 2 scintigraphy visualised all known lesions and new lesions in four of six patients. In-111-DOTA-CCK and In-111-DOTA-MG11 on the other hand missed several lesions; tumour uptake of these two radiopharmaceuticals was quite low. Comparison of retention of renal activity showed no major differences between the three radiopeptides. Tc-99m-demogastrin 2 scintigraphy appeared most promising as a diagnostic tool in patients with MTC. Further studies are required to evaluate its value in patient management. Direct comparisons of the compounds studied strongly suggests that In-111-DOTA-CCK and In-111-DOTA-MG11 have less potential as imaging agents than Tc-99m-demogastrin 2. These DOTA-linked compounds are considered unlikely to be useful for radionuclide therapy because of low tumour uptake

Computerized segmentation of whole-body bone scintigrams and its use in automated diagnostics

Bone scintigraphy or whole-body bone scan is one of the most common diagnostic procedures in nuclear medicine used in the last 25 years. Pathological conditions, technically poor image resolution and artifacts necessitate that algorithms use su±cient background knowledge of anatomy and spatial relations of bones in order to work satisfactorily. A robust knowledge based methodology for detecting reference points of the main skeletal regions that is simultaneously applied on anterior and posterior whole-body bone scintigrams is presented. Expert knowledge is represented as a set of parameterized rules which are used to support standard image processing algorithms. Our study includes 467 consecutive, non-selected scintigrams, which is, to our knowledge the largest number of images ever used in such studies. Automatic analysis of whole-body bone scans using our segmentation algorithm gives more accurate and reliable results than previous studies. Obtained reference points are used for automatic segmentation of the skeleton, which is applied to automatic (machine learning) or manual (expert physicians) diagnostics. Preliminary experiments show that an expert system based on machine learning closely mimics the results of expert physicians

Somatostatin receptor scintigraphy with [111In-DTPA-d-Phe1]- and [123I-Tyr3]-octreotide: the Rotterdam experience with more than 1000 patients

Various tumours, classically specified as either neuroendocrine or non-neuroendocrine, contain high numbers of somatostatin receptors, which enable in vivo localization of the primary tumour and its metastases by scintigraphy with the radiolabelled somatostatin analogue octreotide. In addition granulomas and autoimmune processes can be visualized because of local accumulation of somatostatin receptor-positive activated mononuclear leucocytes. In many instances a positive scintigram predicts a favourable response to treatment with octreotide. It is tempting to speculate that octreotide labelled with an appropriate radionuclide might be used in cancer therapy. The successful application of radiolabelled octreotide in scintigraphy indicates the possible usefulness of other radiolabelled peptides, either native peptides or derivatives of these, in, for example, nuclear oncology. The small size of these peptides, e.g. bombesin and substance P, is of the utmost importance for a relatively fast blood clearance, thus leading to low background radioactivity. In this way peptides are powerful alternatives to (fragments of) monoclonal antibodies, the application of which to scintigraphic localization of specific cell surface antigen-bearing tumours is plagued by slow blood clearance and, hence, high background levels