L-1-11C-tyrosine PET in patients with laryngeal carcinomas: comparison of standardized uptake value and protein synthesis rate.

UNLABELLED: PET with L-1-(11)C-tyrosine (TYR) can measure and quantify increased protein synthesis in tumor tissue in vivo. For quantification of the protein synthesis rate (PSR), arterial cannulation with repeated blood sampling to obtain the plasma input function and a dynamic TYR PET study to calculate a time-activity curve are necessary. In most PET studies the standardized uptake value (SUV) method is used to quantify tumor activity. The SUV can be calculated without repeated arterial blood sampling and prolonged scanning time, as required for determination of the PSR. The relationship between PSR and SUV is largely unknown and different factors can cause wide variability in the SUV. Therefore, the comparison of the absolute quantification method (PSR) with the SUV method is obligatory to determine the possible use of noninvasive PET in head and neck oncology. METHODS: Twenty-four patients with proven squamous cell carcinomas of the larynx (T1-T4) were studied using dynamic TYR PET. The PSRs of tumor and nontumor (background) regions were determined. Four different methods were used to calculate the SUV: uncorrected SUV (SUV(BW)); and SUVs corrected for body surface area (SUV(BSA)), for lean body mass (SUV(LBM)), and for the Quetelet index (SUV(QI)). Correlations between PSR values and SUVs were calculated. RESULTS: The PSR of all tumors was significantly higher (P < 0.001) than the PSR of nontumor tissue. The correlations of SUV(BW), SUV(BSA), SUV(LBM), and SUV(QI) with the quantitative values of the PSR were high (r = 0.84-0.90). The best correlation was observed with the SUV based on the LBM (SUV(LBM)). CONCLUSION: High correlation between the quantitative values (PSR) and the SUVs offers the possibility to use noninvasive TYR PET for detection and reliable quantification of primary head and neck tumors.

Comparison of (11)C-choline and (18)F-FDG PET in primary diagnosis and staging of patients with thoracic cancer.

UNLABELLED: PET with (18)F-FDG is used for detection and staging of thoracic cancer; however, more specific PET radiopharmaceuticals would be welcome. (11)C-labeled choline (CHOL) is a new radiopharmaceutical potentially useful for tumor imaging, since it is incorporated into cell membranes as phosphatidylcholine. The aim of this study was to investigate whether (11)C-CHOL PET has advantages over (18)F-FDG PET in patients with thoracic cancer. METHODS: We evaluated 17 patients with thoracic cancer both with (11)C-CHOL PET and (18)F-FDG PET. After transmission scanning, (11)C-CHOL was injected intravenously, and whole-body scanning was started after 5 min. Immediately thereafter, (18)F-FDG was injected intravenously, followed after 90 min by interleaved attenuation-corrected whole-body scanning. Scans were performed from crown to femur. Visual and quantitative (standardized uptake value) analyses of (11)C-CHOL PET and (18)F-FDG PET were performed and compared with results of traditional staging and follow-up. RESULTS: The most prominent features of normal (11)C-CHOL distribution were high uptake in liver, renal cortex, and salivary glands. Except for some uptake in choroid plexus and pituitary gland, brain uptake was negligible. All primary thoracic tumors were detected with (11)C-CHOL PET and (18)F-FDG PET. Both (11)C-CHOL PET and (18)F-FDG PET correctly identified all 16 patients with lymph node involvement. However, in a lesion-to-lesion analysis, (11)C-CHOL PET detected only 29 of 43 metastatic lymph nodes, whereas (18)F-FDG PET detected 41 of 43. (11)C-CHOL PET detected fewer intrapulmonary and pleural metastases than (18)F-FDG PET (27/47 vs. 46/47). More brain metastases were detected with (11)C-CHOL PET (23/23) than with (18)F-FDG PET (3/23). For primary tumors, the median (range) standard uptake values of (11)C-CHOL and (18)F-FDG were 1.68 (0.98-3.22) and 4.22 (1.40-8.26), respectively (P = 0.001). CONCLUSION: (11)C-CHOL PET can be used to visualize thoracic cancers. Although detection of lymph node metastases with (11)C-CHOL PET was inferior compared with (18)F-FDG PET, the detection of brain metastases was superior.

Value of 123I-subtraction and single-photon emission computed tomography in addition to planar 99mTc-MIBI scintigraphy before parathyroid surgery.

PURPOSE: To find out if single-photon emission computed tomography (SPECT) and (123)I-subtraction can enhance the findings of (99m)Tc-methoxyisobutylisonitrile (MIBI) scintigraphy for the preoperative localization of parathyroid (PT) tumors. METHODS: Among the 111 consecutive patients who underwent preoperative planar (99m)Tc-MIBI scintigraphy for hyperparathyroidism (HPT), 64 underwent delayed SPECT, and 17 underwent (123)I-subtraction. Two independent blinded experts scored the topographical localization, diagnostic confidence, and impact of each diagnostic modality on the surgical strategy. RESULTS: For adenomas, (99m)Tc-MIBI scintigraphy had a sensitivity of 77% with a positive predictive value (PPV) of 83%. SPECT did not affect the sensitivity or PPV, but it increased the diagnostic confidence and changed the surgical strategy in 21% of the patients. (123)I-subtraction increased the sensitivity from 64% to 82%, but decreased the PPV from 88% to 82%. In hyperplastic glands, (99m)Tc-MIBI scintigraphy had a sensitivity of 47% and a PPV of 95%. When (99m)Tc-MIBI scintigraphy was combined with SPECT and (123)I-subtraction, the results were 44%/10% and 52%/92%, respectively. Both SPECT and (123)I-subtraction decreased the diagnostic confidence. CONCLUSIONS: Adding SPECT to (99m)Tc-MIBI scintigraphy improved the surgical decision for parathyroid adenomas. The addition of (123)I-subtraction was of limited value. For hyperplastic glands, (99m)Tc-MIBI scintigraphy was relatively ineffective, even with the addition of SPECT or (123)I-subtraction.

Effect of attenuation correction on the interpretation of 99mTc-sestamibi myocardial perfusion scintigraphy: the impact of 1 year's experience.

The aim of this study was to determine the yield of attenuation correction in myocardial perfusion imaging (MPI), before and after a 1-year experience period. In 48 consecutive patients referred for MPI, both non-corrected (NC) and attenuation-corrected (AC) images were analysed by three independent readers shortly after implementation of attenuation correction. The same images were re-analysed 1 year later, after having obtained experience in attenuation correction on a routine basis in >500 patients with clinical feedback. Results were compared with gold standards for ischaemia and infarction based on coronary angiography, follow-up, ultrasound and gated blood pool imaging. Sensitivity and specificity for the detection of coronary artery disease were 95% and 45% respectively for NC images and 77% and 70% respectively for AC images at first readings. After 1 year of AC experience, NC sensitivity/specificity was 100%/61%, and AC results were 89%/92%. It is concluded that attenuation correction improves the performance of MPI interpretation. With attenuation correction, specificity is increased and sensitivity is similar as compared with NC images. However, attenuation correction requires experience and is associated with a learning curve.

Carbon-11 tyrosine PET for visualization and protein synthesis rate assessment of laryngeal and hypopharyngeal carcinomas.

Accurate assessment of tumour extent and lymph node involvement in squamous cell carcinomas of the head and neck region is essential for therapy planning. Unfortunately, conventional diagnostic examination and imaging techniques, which monitor tumours on the basis of anatomical parameters, have drawbacks in clinical practice. The aim of this study was to investigate the feasibility of L-[1-(11)C]-tyrosine (TYR) positron emission tomography (PET) for visualisation of squamous cell carcinoma of the larynx and hypopharynx and quantification of tumour activity by assessment of protein synthesis rate (PSR). Dynamic TYR PET was performed on 31 patients with T1-T4 laryngeal or hypopharyngeal carcinoma before therapy. Plasma activity of TYR, (11)CO(2) and (11)C-protein levels were measured, and PSRs were calculated for primary malignancies. All 31 laryngeal and hypopharyngeal tumours were visualised as a hotspot (sensitivity 100%). The median PSR of the tumours (2.06 nmol ml(-1) min(-1); range 0.72-6.96) was significantly higher ( P<0.001) than that of non-tumour (background) tissue (0.51 nmol ml(-1) min(-1); range 0.22-0.89). L-[1-(11)C]-Tyrosine PET appears to be a potential method for visualisation of primary laryngeal and hypopharyngeal tumours. In vivo quantification of tumour activity by assessment of PSR is possible and may have a future role in the therapy planning and therapy evaluation of laryngeal and hypopharyngeal tumours.