Validation of CT doses of SPECT/CT and PET/CT hybrid devices: lessons learned.

The aim of the study was to check the validity of computed tomographic (CT) doses exhibited by SPECT/CT and PET/CT hybrid devices. Dose measurements were taken from four SPECT/CT and four PET/CT cameras commercially available from different manufacturers. A calibrated ionization chamber was placed in whole-body or head phantoms for the acquisition of CT images with clinically used parameters. Computed tomography dose index (CTDIvol) values were calculated according to the IEC 60601-2-44:1999 formula. The measured CTDIvol doses were compared with those preprogrammed by the manufacturer. In the case of the whole-body phantom, the differences between the measured and displayed values varied between -31 and +24% [European document RP162 (2012) sets up the limit for acceptance criterion as ±20%]. The head phantom data showed either an agreement between -10 and +24%, or an underestimation by two-fold. The latter seemed to be because, while preprogramming the doses, the manufacturer had used the whole-body phantom instead of a proper head phantom. The results of the work demonstrate the need for individual dosimetric calibration of every single X-ray tube. Dosimetric checks should be included in the regular quality control programmes of the SPECT/CT and PET/CT devices. Special attention should be paid to head-and-neck and paediatric protocols, in which the use of a head phantom is recommended for dose calibration.

Radiopharmaceutical diagnosis of Erdheim-Chester's disease.

Erdheim-Chester's disease is a non-inherited multi-focal lipid-storing histiocytosis of unknown origin without a complete and convincing diagnostic and therapeutic protocol. We have previously suggested diagnostic methods using radioisotopes to evaluate this disseminating disease, but they are neither specific nor selective in this regard. The present hypothesis-driven paper reviewing our case proposes novel approaches involving nuclear medicine and utilizing radiopharmaceuticals to identify this potentially fatal multi-system disease.

An isotope-diagnostic approach to Erdheim-Chester's disease of the heart.

Erdheim-Chester's disease is a form of histiocytic granulomatosis afflicting the skeletal system and various inner organs. Apart from incidental findings of involvement of various structures and tissues, a complete diagnostic workup to evaluate afflicted bodily parts is not known. The authors we present several specific isotope-diagnostic techniques of a case to support the identification of this rare multisystem infiltrative disease.

Sentinel node detection in malignant melanoma patients: radiation safety considerations.

BACKGROUND: The surgical management of malignant melanoma necessitates correct sentinel lymph node localization. The highest reported sensitivities are those of lymphoscintigraphy and intraoperative gamma-probe detection combined with a vital blue dye technique. OBJECTIVE: Control of the radiation doses experienced by surgical personnel untrained in the use of unsealed radioactive materials. METHODS: Sentinel lymph nodes were localized, and biopsies were performed in 25 patients with malignant melanoma. Radiation doses during surgery were determined with energy-compensated silicon pin diode detectors and LiF thermoluminescent ring dosimeters. RESULTS: In 21 cases (24%), the measured doses were less than 1 microSv, but in 4 operations (16%), 1 to 4.5 microSv was received. The equivalent dose rate was generally less than 1 microSv/h. The finger-absorbed doses for the surgeon and the assistant surgeon were (mean+/-SD) 159+/-23 and 48+/-17 microGy per intervention, respectively. CONCLUSION: Personal dosimetric survey and limitation of the number of surgical interventions do not appear to be essential.

[The role of FDG-PET scan in the diagnosis of pancreatic carcinoma]. / Az FDG-PET-vizsgálat értéke a pancreascarcinoma diagnosztikájában.

In 22 patients with focal pancreatic lesions, the values of different diagnostic modalities were analysed for the evaluation of malignancy. The CA 19-9 level was elevated in 4/5 malignant cases (sensitivity: 80%) and in 4/15 of benign cases (specificity: 73%). Hypodensity/hypoechogeneity was considered to be the characteristic sign of malignancy during CT/ultrasound (sensitivity: 100%, specificity: 50%/47%). ERCP was found to be specific but not sensitive enough and the rate of unsuccessful investigations was relatively high (4/22). The diagnostic value of FDG-PET was found to be superior to other diagnostic modalities (sensitivity 100%, specificity 88%). In cases with focal pancreatic hypoechogenic/hypodense lesions detected by CT or US in suspicion of malignancy, the FDG-PET should be the next step in the diagnostic strategy.

The possible role of F-18 FDG positron emission tomography in the differential diagnosis of focal pancreatic lesions.

PURPOSE: To compare the diagnostic values of different methods for the differentiation of malignant from benign pancreatic lesions. METHODS: In 22 patients with focal pancreatic lesions, the carbohydrate antigen (CA) 19-9 level was measured; abdominal ultrasound (US), computed tomography (CT), endoscopic retrograde cholangiopancreatography (ERCP), and F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) were performed; and the value of these methods were analyzed for their use in cancer diagnosis. RESULTS: Malignant lesions were identified in six patients and verified by surgery or clinical follow-up. The CA 19-9 level was elevated in four of the five patients examined (sensitivity, 80%). In all six cases, US and CT revealed hypoechogenic and hypodense areas (sensitivity, 100%). In one patient, ERCP was unsuccessful but yielded true-positive results in three others (sensitivity, 60%). The sensitivity of FDG PET was 100%. Sixteen focal cases of pancreatic disease proved to be benign. The CA 19-9 level was elevated in four of them (specificity, 73%). Hypoechogenic and hypodense areas were evident on US and CT in eight patients. The specificity of CT was 50% (8 of 16 cases). The specificity of US was 47% (7 of 15 cases). The specificity of successful ERCP was 92%. Fourteen negative FDG-PET results were truly negative. In two patients, however, the PET findings proved to be falsely positive (specificity, 88%). CONCLUSIONS: FDG-PET is an effective tool to differentiate malignant from benign focal pancreatic lesions. In persons with focal pancreatic hypoechogenic or hypodense lesions detected by CT or US and an elevated CA 19-9 level, FDG PET should be the next step in the diagnostic strategy.