[Nuclear medical diagnostics for liver tumors]. / Nuklearmedizinische Diagnostik von Lebertumoren.

Standard nuclear medical procedures, such as functional, blood-pool and colloid scintigraphy, play a minor role in the routine workup of liver tumors. However, these techniques are capable of assessing specific organ functions and frequently allow the diagnosis of unclear liver lesions. The sensitivity of scintigraphic procedures can be increased using tomographic imaging (SPECT), the specificity with the introduction of hybrid scanners such as SPECT/CT. Whole body positron emission tomography with 18F-fluoro-deoxy-glucose (FDG) in combination with CT scanning (PET/CT) represents one of the most sensitive imaging modalities for the detection of hepatic metastases and extrahepatic tumor manifestations. For the staging and follow-up of colorectal cancer, FDG-PET/CT represents a standard imaging modality. Metastases from neuroendocrine tumors can be detected using PET and specific tracers such as [68Ga]DOTATOC and [18F]DOPA. Molecular imaging with PET allows the quantification of metabolic processes which can be used for the assessment of an early response to treatment.

Radio-guided surgery for persistent differentiated papillary thyroid cancer: case presentations and review of the literature.

BACKGROUND AND AIMS: Persistent differentiated papillary thyroid cancer following radical locoregional surgery with metastases is an indication for limited reoperation or radioiodine therapy. Following injection of radioiodine, radio-guided surgery with application of an intraoperative gamma probe offers detection of metastases not seen by conventional imaging and control of completeness of resection. PATIENTS/METHODS: We demonstrate four patients with locoregional metastases, two of them with additional distant metastases of papillary thyroid cancer following radical neck surgery. Postoperative radioiodine scans demonstrated persistent ipsilateral or contralateral cervical and mediastinal lymph node and isolated rib metastases. RESULTS: Radio-guided surgery (RGS) leads to complete clearance of persistent lymph node metastases by limited recurrent neck surgery, resection of metastases not seen by conventional imaging and control of complete mediastinal lymph node dissection. Post-RGS scans allowed early diagnosis of occult diffuse or nodal pulmonary metastases in two patients. At last follow-up, 23 to 48 months following RGS and radioiodine therapy, there was no evidence of disease. CONCLUSIONS: Radio-guided surgery is an additive surgical technique with low morbidity in selected patients with persistent thyroid cancer individualizing tumor therapy options in multimode oncological therapy.

[Scintigraphic procedures in internal medicine--indications, limits, possibilities]. / Szintigraphische Verfahren in der Inneren Medizin -- Indikationen, Grenzen, Möglichkeiten.

Scintigraphy continues to play an important diagnostic role in internal medicine. Many diagnostic questions can only be answered with scintigraphic methods. The application of specific radiopharmaceutical tracers offers the unique possibility to visualize ongoing functional changes, associated with diseases concerning internal medicine. The diagnostic potential of modern scintigraphic procedures such as PET for internal medicine is not yet sufficiently used and will continue to grow with hybrid systems, such as PET-CT and SPECT-CT.

PET imaging of somatostatin receptors: design, synthesis and preclinical evaluation of a novel 18F-labelled, carbohydrated analogue of octreotide.

Because of the excellent nuclear properties of fluorine-18 and the growing interest in somatostatin receptor (sst) scintigraphy with PET, a novel carbohydrated (18)F-labelled sst ligand was developed and preclinically evaluated. Synthesis of N(alpha)-(1-deoxy- D-fructosyl)- N(epsilon)-(2-[(18)F]fluoropropionyl)-Lys(0)-Tyr(3)-octreotate ([(18)F]FP-Gluc-TOCA) was completed in approximately 3 h (20%-30% yield). [(19)F]FP-Gluc-TOCA showed no affinity to hsst1 and hsst3, moderate affinity to hsst4 (IC(50): 437+/-84 n M) and hsst5 (IC(50): 123+/-8.8 n M) and very high affinity to hsst2 (IC(50): 2.8+/-0.4 n M). As a result of carbohydration, lipophilicity of [(18)F]FP-Gluc-TOCA was found to be low (lg P(OW)=-1.70+/-0.02). In mice, the tracer was rapidly cleared via renal excretion (kidneys: 8.69%+/-1.09%ID/g) and showed low uptake in liver (0.72%+/-0.14%ID/g) and intestine (1.88%+/-0.52%ID/g) and high tumour uptake (13.54%+/-1.47%ID/g) (all data at 1 h p.i.). Tumour to non-tumour ratios at 60 min p.i. reached 25, 19, 7, 1.6 and 56 for blood, liver, intestine, kidney and muscle, respectively. A similar biodistribution pattern was observed in pancreatic tumour-bearing rats. Tumour uptake in rats was reduced to 36% and 18% of control (30 and 60 min) by co-injection of 500 microg Tyr(3)-octreotide, demonstrating sst-specific uptake. In a first [(18)F]FP-Gluc-TOCA-PET study of a patient with a metastatic carcinoid in the liver the tracer showed superior pharmacokinetics, e.g. rapid urinary excretion and low uptake in liver, kidney and spleen. Multiple liver lesions (SUVs ranging from 21.4 to 38.0) and previously unknown focal uptake in the abdomen (SUV 10.0) were clearly visible. This is the first report on PET imaging using an (18)F-labelled sst binding peptide; it indicates that [(18)F]FP-Gluc-TOCA offers excellent imaging characteristics and allows sst imaging with high tumour to non-tumour contrast.

Prediction of response to preoperative chemotherapy in adenocarcinomas of the esophagogastric junction by metabolic imaging.

PURPOSE: Preoperative chemotherapy in patients with gastroesophageal cancer is hampered by the lack of reliable predictors of tumor response. This study evaluates whether positron emission tomography (PET) using fluorine-18 fluorodeoxyglucose (FDG) may predict response early in the course of therapy. PATIENTS AND METHODS: Forty consecutive patients with locally advanced adenocarcinomas of the esophagogastric junction were studied by FDG-PET at baseline and 14 days after initiation of cisplatin-based polychemotherapy. Clinical response (reduction of tumor length and wall thickness by > 50%) was evaluated after 3 months of therapy using endoscopy and standard imaging techniques. Patients with potentially resectable tumors underwent surgery, and tumor regression was assessed histopathologically. RESULTS: The reduction of tumor FDG uptake (mean +/- 1 SD) after 14 days of therapy was significantly different between responding (-54% +/- 17%) and nonresponding tumors (-15% +/- 21%). Optimal differentiation was achieved by a cutoff value of 35% reduction of initial FDG uptake. Applying this cutoff value as a criterion for a metabolic response predicted clinical response with a sensitivity and specificity of 93% (14 of 15 patients) and 95% (21 of 22), respectively. Histopathologically complete or subtotal tumor regression was achieved in 53% (eight of 15) of the patients with a metabolic response but only in 5% (one of 22) of the patients without a metabolic response. Patients without a metabolic response were also characterized by significantly shorter time to progression/recurrence (P =.01) and shorter overall survival (P =.04). CONCLUSION: PET imaging may differentiate responding and nonresponding tumors early in the course of therapy. By avoiding ineffective and potentially harmful treatment, this may markedly facilitate the use of preoperative therapy, especially in patients with potentially resectable tumors.