M. Westhofen

pO(2) Polarography versus positron emission tomography ([(18)F] fluoromisonidazole, [(18)F]-2-fluoro-2'-deoxyglucose). An appraisal of radiotherapeutically relevant hypoxia.

Background and Purpose:The aim of the present study was to validate ([18F] fluoromisonidazole (FMISO) and [18F]-2-fluoro-2’-deoxyglucose (FDG) positron emission tomography (PET) for determination of radiotherapeutically relevant hypoxia by the gold standard for measuring tissue oxygenation in human tumors, the computerized polarographic needle electrode system (pO2 histography).Patients and Methods:Up to now, a total of 16 patients with a metastatic neck lymph node from a primary squamous carcinoma of the head and neck underwent pO2 and PET measurements. Tumor tissue pO2 was measured with polarographic needle electrodes using a pO2 histograph (Eppendorf®). Under CT control, the needle electrode was placed in the tumor without general or local anesthesia. To assess the biological and clinical relevance of oxygenation measurement, the relative frequency of pO2 readings, with values ≤ 2.5, ≤ 5.0, and ≤ 10.0 mmHg, as well as mean and median pO2 were recorded.All PET studies were carried out using an ECAT EXACT 922/47® scanner with an axial field of view of 16.2 cm. FMISO PET consisted of one static scan of the relevant region, performed 120 min after intravenous administration. The acquisition and reconstruction parameters were as follows: 15-min emission scanning and 4-min transmission scanning with 68Ge rod sources. FDG PET of the lymph node metastasis was performed 68 ± 11 min after intravenous administration, applying the whole-body tool with 8-min emission scanning and 4-min transmission scanning per bed position.Results:In order to detect possible relations between the different relevant polarographically measured parameters of tumor hypoxia and FMISO PET data-based oxygenation values, the Pearson correlation coefficient was calculated. Average (r > 0.5) to high correlation (r > 0.7) was found between tumor-to-muscle ratio of FMISO after 2 h and parameters of hypoxic fraction (pO2 readings with values ≤ 2.5, ≤ 5.0, and ≤ 10.0 mmHg as well as mean and median). No correlations could be shown between FDG PET parameters and polarographically determined tumor oxygenation status.Conclusion:Summarizing the FMISO uptake represents a global value for macroscopic tumor parts. As a noninvasive measurement this method seems highly feasible to evaluate the state of oxygenation in subjacent tumors.Hintergrund und Ziel:Ziel dieser Untersuchung war die Validierung von [18F]-Fluormisonidazol-(FMISO-) und [18F]-Fluordeoxyglucose-( FDG-)Positronenemissionstomographie (PET) zur Erfassung der strahlentherapeutisch relevanten Hypoxie durch das computergestützte polarographische Nadelelektrodensystem (pO2-Histographie), das den Goldstandard zur Festlegung der Gewebeoxygenierung in menschlichen Tumoren darstellt.Patienten und Methodik:Bis jetzt wurden bei insgesamt 16 Patienten mit metastatisch befallenen Halslymphknoten eines Plattenepithelkarzinoms der Kopf-Hals-Region pO2- und PET-Messungen durchgeführt. Der pO2 des Tumorgewebes wurde mit Hilfe polarographischer Feinnadelelektroden eines pO2-Histographen (Eppendorf®) gemessen. Die Nadelelektrode wurde CT-gesteuert ohne Lokalanästhesie positioniert. Als Grad für die biologische und klinische Relevanz wurden die relative Häufigkeit der pO2-Messwerte ≤ 2,5, ≤ 5,0 und ≤ 10,0 mmHg sowie der Mittelwert und der Median dokumentiert.Die PET-Untersuchungen wurden an einem Vollring-Tomographen (ECAT EXACT 922/47®; Siemens/CTI) durchgeführt. Die FMISO-PET erfolgte als statische Aufnahme der relevanten Region 120 min p.i. Folgende Akquisitions- und Rekonstruktionsparameter wurden verwendet: 15-minütige Emissionsmessung und 4-minütige Transmissionsmessung mit Hilfe von 68Ge-Stabquellen. Die FDG-PET der metastatisch befallenen Halslymphknoten wurde 68 ± 11 min p.i. unter Verwendung eines Ganzkörperprotokolls mit einer Emissionsmessung von 8 min und einer Transmissionsmessung von 4 min pro Bettposition durchgeführt.Ergebnisse:Um mögliche Korrelationen zwischen den verschiedenen relevanten, polarographisch gemessenen Parametern der Tumorhypoxie und den mittels FMISO-PET gewonnenen Messdaten zu detektieren, wurde der Pearson-Korrelationskoeffizient berechnet. Es zeigte sich eine mittlere (r > 0,5) bis hohe Korrelation (r > 0,7) zwischen dem Tumor/Muskel-Quotienten der FMISO-Aufnahme 2 h p. i. und den verschiedenen Hypoxieparametern (pO2-Messwerte ≤ 2,5, ≤ 5,0, ≤ 10,0 mmHg sowie Mittelwert und Median der pO2-Messwerte). Keine Korrelation konnte zwischen den FDG-PET-Parametern und dem polarographisch bestimmten Tumoroxygenierungsstatus aufgezeigt werden.Schlussfolgerung:Die mit PET gemessene FMISO-Aufnahme gibt einen globalisierten Messwert für makroskopische Anteile des Tumors wieder. Aufgrund des nichtinvasiven Charakters scheint diese Methode besonders geeignet, den Oxygenierungsstatus bei tiefer liegenden Tumoren zu erfassen.

T2-weighted turbo spin-echo images, maximum-intensity projections, and three-dimensional volume-rendering for delineation of pathologies and anatomic details of the inner ear.

Purpose:The aim of the current study was to compare 3-dimensional T2-weighted turbo spin-echo (TSE) axial slices, maximum-intensity projections (MIPs), and volume-rendered images with respect to the delineation of pathologic findings and anatomic structures of the inner ear. Each of the compared image types was available at 2 different resolutions. Materials and Methods:In 64 patients, 3-dimensional T2-TSE images were acquired with a matrix of 128 × 100 and 230 × 230 (field-of-view 90 × 90 mm2). Direct axial images, MIPs, and volume-rendered images from the 2 datasets were evaluated in terms of the delineation of pathologic findings and anatomic structures. Analysis was performed by 2 radiologists in consensus. Results:Though axial images acquired with a matrix of 230 × 230 showed more anatomic details than images acquired with a matrix of 128 × 100, pathologic findings (33 in total) were assessable with the same confidence on images of either resolution. Pathologies completely surrounded by fluid were best assessed on axial slices. The delineation of pathologies not embedded in a fluid was almost equally good in axial slices, MIPs, or 3-dimensional volume-rendered images. Conclusion:Reading the axial images cannot be replaced by viewing postprocessed reconstructions for initial diagnosis, because only some of the pathologies can be delineated on MIPs and volume reconstructions. However, reconstructions can be valuable for assessing the extent of pathologies and their spatial relation to the anatomic structures.

Ergebnisse der prätherapeutischen Lymphknotendiagnostik bei Kopf-Hals-Tumoren - Klinische Wertigkeit der 18FDG-Positronen- Emissions-Tomographie (PET)1 -

Background: Histological studies demonstrate that there is a high percentage of occult nodal metastasis in head and neck malignomas. Patients with positive lymph nodes have a comparatively worse prognosis. A neck dissection is required in these cases. By demonstrating morphological abnormalities, imaging procedures like ultrasound, computer tomography (CT), and magnetic resonance imaging (MRI) can provide important initial informations about possible malignant alteration of the lymph nodes. Positron emission tomography (PET) allows functional metabolic imaging of a suspected tumor site. The aim of this study was a comparative evaluation of different diagnostic procedures with special emphasis on the value of PET in the pretherapeutic diagnosis of nodal spread in head and neck cancer. Patients and Methods: Forty patients (28 male and 12 female) with a suspected malignoma in the head and neck region underwent clinical examination including palpation of the neck sides, ultrasound, CT, and PET to detect a nodal spread of the malignancy. Fifty neck dissections were performed in 28 patients. Lymph node biopsies were performed in the remaining patients. The results of the diagnostic procedures were compared to the histology and the clinical course of the patients. The mean follow-up period was 12.5 months. Results. A nodal metastasis was verified in 35% of all cases. Sensitivity of all imaging procedures including PET was 82%. Palpation had a sensitivity of only 61%. Specificity was 85% for ultrasound, 94% for CT and palpation, and 87% for PET. PET produced false negative results in 13.4% of all cases. Inflammation was detected in these cases. The positive predictive value was marginally better for PET than for ultrasound (77% vs. 75%). It proved to be lower than the values for palpation (86%) and CT (88%). Negative predictive value was 90-91% for all imaging procedures. Conclusion: In the primary diagnosis of nodal alterations in the head and neck region, a PET scan has the same diagnostic value as ultrasound or CT. By imaging the metabolism of a suspected nodal metastasis, PET can help to improve the assessment of regions was uncertain anatomic features. To avoid false positive results, acute and chronic inflammatory alterations have to be ruled out before the PET imaging.

Ergebnisse der prätherapeutischen Lymphknotendiagnostik bei Kopf-Hals-Tumoren

Background: Histological studies demonstrate that there is a high percentage of occult nodal metastasis in head and neck malignomas. Patients with positive lymph nodes have a comparatively worse prognosis. A neck dissection is required in these cases. By demonstrating morphological abnormalities, imaging procedures like ultrasound, computer tomography (CT), and magnetic resonance imaging (MRI) can provide important initial informations about possible malignant alteration of the lymph nodes. Positron emission tomography (PET) allows functional metabolic imaging of a suspected tumor site. The aim of this study was a comparative evaluation of different diagnostic procedures with special emphasis on the value of PET in the pretherapeutic diagnosis of nodal spread in head and neck cancer. Patients and Methods: Forty patients (28 male and 12 female) with a suspected malignoma in the head and neck region underwent clinical examination including palpation of the neck sides, ultrasound, CT, and PET to detect a nodal spread of the malignancy. Fifty neck dissections were performed in 28 patients. Lymph node biopsies were performed in the remaining patients. The results of the diagnostic procedures were compared to the histology and the clinical course of the patients. The mean follow-up period was 12.5 months. Results. A nodal metastasis was verified in 35% of all cases. Sensitivity of all imaging procedures including PET was 82%. Palpation had a sensitivity of only 61%. Specificity was 85% for ultrasound, 94% for CT and palpation, and 87% for PET. PET produced false negative results in 13.4% of all cases. Inflammation was detected in these cases. The positive predictive value was marginally better for PET than for ultrasound (77% vs. 75%). It proved to be lower than the values for palpation (86%) and CT (88%). Negative predictive value was 90-91% for all imaging procedures. Conclusion: In the primary diagnosis of nodal alterations in the head and neck region, a PET scan has the same diagnostic value as ultrasound or CT. By imaging the metabolism of a suspected nodal metastasis, PET can help to improve the assessment of regions was uncertain anatomic features. To avoid false positive results, acute and chronic inflammatory alterations have to be ruled out before the PET imaging.