Combined SPECT/CT improves detection of initial bone invasion and determination of resection margins in squamous cell carcinoma of the head and neck compared to conventional imaging modalities.

PURPOSE: Knowledge of the presence and extent of bone infiltration is crucial for planning the resection of potential bone-infiltrating squamous cell carcinomas of the head and neck (HNSCC). Routinely, plain-film radiography, multislice computed tomography (MSCT) and magnetic resonance imaging (MRI) are used for preoperative staging, but they show relatively high rates of false-positive and false-negative findings. Scintigraphy with (99m)Tc-bisphosphonate has the ability to show increased metabolic bone activity. If combined with anatomical imaging (e.g. (SPECT)/CT), it facilitates the precise localization of malignant bone lesions. The aim of this study was to analyse the indications and advantages of SPECT/CT compared with standard imaging modalities and histology with regard to specificity and sensitivity METHODS: A longitudinally evaluated group of 30 patients with biopsy-proven HNSCC adjacent to the mandible underwent (99m)Tc-bisphosphonate SPECT/CT, MRI, MSCT and conventional radiography before partial or rim resection of the mandible was performed. Bone infiltration was first evaluated with plain films, MSCT and MRI. In a second reading, SPECT/CT data were taken into account. The results (region and certainty of bone invasion) were evaluated among the different imaging modalities and finally compared with histological specimens from surgical resection as the standard of reference. For a better evaluation of the hybrid property of SPECT/CT, a retrospectively evaluated group of 20 additional patients with tumour locations similar to those of the longitudinally examined SPECT/CT group underwent SPECT, MSCT and MRI. To assess the influence of dental foci on the specificity of the imaging modalities, all patients were separated into two subgroups depending on the presence or absence of teeth in the area of potential tumour-bone contact. RESULTS: Histologically proven bone infiltration was found in 17 patients (57 %) when analysed by conventional imaging modalities. SPECT/CT data revealed bone infiltration in two additional patients (7 %), who both showed discrete cortical bone erosion not visible by MSCT or MRI. There were no false-positive or false-negative findings on SPECT/CT. The quality criteria for detecting bone involvement in HNSCC by SPECT/CT were as follows: sensitivity 100 % (lower 95 % confidence interval limit 80 %), specificity 100 % (75 %), positive predictive value 100 % (80 %) and negative predictive value 100 % (75 %). Corresponding data for MRI were 95 % (76 %), 94 % (73 %), 95 % (76 %) and 94 % (73 %), and for MSCT were 89 % (71 %), 100 % (85 %), 100 % (86 %) and 88 % (69 %). In the retrospective evaluation SPECT showed results similar to SPECT/CT. CONCLUSION: Hybrid SPECT/CT has a high specificity as it can provide additional information about the existence and local extent of malignant bone infiltration of the mandible. Although the sensitivity of conventional SPECT is similar to that of SPECT/CT, the latter provides a much better delineation of the local tumour-bone contact area. Based on this information, surgical intervention of the rim versus partial resection can be planned and performed more precisely. Patient outcome can be improved by avoiding undertreatment and unnecessary or overextended bone resections.

Respiratory gated [18F]FDG PET/CT for target volume delineation in stereotactic radiation treatment of liver metastases.

PURPOSE: The use of 4D-[(18)F]fluorodeoxyglucose (FDG) PET/CT in combination with respiratory gated magnet resonance imaging (MRI) in target volume definition for stereotactic radiation of liver metastases was investigated. METHODS AND MATERIALS: A total of 18 patients received respiration gated FDG-PET/CT and MRI. Data were fused using a rigid co-registration algorithm. The quality of the co-registration was rated on a scale from 1 (excellent) to 5 (poor) for co-registration of MRI with gated PET and ungated PET. Gross tumor volume (GTV) was delineated in CT (GTV (CT)), MRI (GTV(MRI)), and PET (GTV(PET)). MRI- and PET-based GTVs were defined by three observers each. Interobserver variability was calculated for all patients as well as for subgroups with and without previous treatment of liver metastases. All GTVs were compared for all patients and separately for patients with previous local therapy. In addition, a semiautomatic segmentation algorithm was applied on the PET images. RESULTS: Co-registration between MR and PET images was rated with 3.3 in average when non-gated PET was used and improved significantly (p < 0.01) to 2.1 using gated PET. The average GTV(CT) was 51.5 ml, GTV(MRI) 51.8 ml, and the average GTV(PET) 48.1 ml. Volumes delineated in MRI were 9.9% larger compared to those delineated in CT. Volumes delineated in PET were 13.8% larger than in MRI. The differences between the GTVs were more pronounced in patients with previous treatment. The GTVs defined in MRI showed an interobserver variability of 47.9% (84.1% with previous treatment and 26.2% without previous treatment). The PET-defined GTVs showed an interobserver variability of 21% regardless of previous treatment. Semiautomatic segmentation did not provide satisfying results. CONCLUSION: FDG-PET can distinguish vital tumor tissue and scar tissue, and therefore alters the GTV especially in patients with previous local treatment. In addition, it reduces the interobserver variability significantly compared to MRI. However, respiratory gated PET is necessary for good co-registration of PET and MRI.

NMR-based discovery of lead inhibitors that block DNA binding of the human papillomavirus E2 protein.

The E2 protein is required for the replication of human papillomaviruses (HPVs), which are responsible for anogenital warts and cervical carcinomas. Using an NMR-based screen, we tested compounds for binding to the DNA-binding domain of the HPV-E2 protein. Three classes of compounds were identified which bound to two distinct sites on the protein. Biphenyl and biphenyl ether compounds containing a carboxylic acid bind to a site near the DNA recognition helix and inhibit the binding of E2 to DNA. Benzophenone-containing compounds which lack a carboxylic acid group bind to the beta-barrel formed by the dimer interface and exhibit negligible effects on the binding of E2 to DNA. Structure-activity relationships from the biphenyl and biphenyl ether compounds were combined to produce a compound [5-(3'-(3",5"-dichlorophenoxy)-phenyl)-2,4-pentadienoic acid] with an IC50 value of approximately 10 microM. This compound represents a useful lead for the development of antiviral agents that interfere with HPV replication and further illustrates the usefulness of the SAR by NMR method in the drug discovery process.

Novel inhibitors of Erm methyltransferases from NMR and parallel synthesis.

The Erm family of methyltransferases confers resistance to the macrolide-lincosamide-streptogramin type B (MLS) antibiotics through the methylation of 23S ribosomal RNA. Upon the methylation of RNA, the MLS antibiotics lose their ability to bind to the ribosome and exhibit their antibiotic activity. Using an NMR-based screen, we identified a series of triazine-containing compounds that bind weakly to ErmAM. These initial lead compounds were optimized by the parallel synthesis of a large number of analogues, resulting in compounds which inhibit the Erm-mediated methylation of rRNA in the low micromolar range. NMR and X-ray structures of enzyme/inhibitor complexes reveal that the inhibitors bind to the S-adenosylmethionine binding site on the Erm protein. These compounds represent novel methyltransferase inhibitors that serve as new leads for the reversal of Erm-mediated MLS antibiotic resistance.

Impact of specific training in detecting osteoporotic vertebral fractures on routine chest radiographs.

PURPOSE: Vertebral fractures are the most common complication of osteoporosis. Routine chest radiographs are a potential screening method, but a significant under-reporting has been described previously. The purpose of this study was to evaluate the effect of a specific training on the detection rate of vertebral fractures of a radiology resident. MATERIALS AND METHODS: 936 routine lateral chest radiographs of postmenopausal women were evaluated by a radiology resident (R1) during clinical routine. After the evaluation of 470 radiographs (pre-training group), R1 underwent a specific training based on the teaching initiative of the IOF/ESSR. Afterwards the remaining 466 radiographs were evaluated (post-training group). As a standard of reference, all radiographs were reviewed by two radiologists in consensus (R2 + 3). A semi-quantitative method (spinal fracture index, SFI) was used to assess vertebral fractures. RESULTS: Kappa-values as statistical measure of agreement between R1 and R2 + 3 for the detection of vertebral fractures (Genant Severity > 0) increased from κ = 0.311 (95 % CI: 0.217 - 0.405; "fair agreement") in the pre-training group to κ = 0,882 (95 % CI: 0,835 - 0,929; "almost perfect agreement") in the post-training group. Similar results were observed for severe fractures (Genant Severity > 1). Especially fractures with Genant Severity 1 were not detected by R1 before training. CONCLUSION: A brief training is essential to increase the awareness of radiologists to correctly report osteoporotic vertebral fractures and may help to initiate appropriate therapy in patients with vertebral fractures.

Global and regional reproducibility of T2 relaxation time measurements in human patellar cartilage.

Seven T2 maps (multiecho (ME) sequence: 3000 ms, eight echoes with 13.2 ms of echo spacing, 20 sections) and T1-weighted (T1-w) fast low-angle shot (FLASH-water excitation (WE)) data sets from four imaging sessions (right patellae of 10 healthy volunteers) were obtained. A segmentation of cartilage (WE sequence) was overlaid on the ME data and T2 values were calculated for total cartilage, three layers, three facets (global), and 240 ROIs (regional). Reproducibility (precision error) was calculated as the root mean square average (RMSA) of the individual coefficients of variation (COVs, %) and standard deviations (SDs, ms) for intra- and intersession reproducibility. The precision error was 3-7% and 6-29% for global and regional T2, respectively. There was no difference between intra- and intersession reproducibility, but there was worse reproducibility in the superficial layers compared to the deeper layers. Peripheral ROI reproducibility (mean=13%) was worse than in the central portions (mean=11%), but omission of the periphery did not positively affect the globally calculated T2 reproducibility. The precision errors were small compared to reported changes in diseased cartilage, suggesting good discriminatory power of the technique. Our data provide a first estimate of global and regional reproducibility errors of T2 in healthy cartilage, and may serve as a basis for sample size calculations and aid study designs for longitudinal and cross-sectional trials in osteoarthritis (OA).

Molecular structure of three mutations at the maize sugary1 locus and their allele-specific phenotypic effects.

Starch production in all plants examined is altered by mutations of isoamylase-type starch-debranching enzymes (DBE), although how these proteins affect glucan polymer assembly is not understood. Various allelic mutations in the maize (Zea mays) gene sugary1 (su1), which codes for an isoamylase-type DBE, condition distinct kernel phenotypes. This study characterized the recessive mutations su1-Ref, su1-R4582::Mu1, and su1-st, regarding their molecular basis, chemical phenotypes, and effects on starch metabolizing enzymes. The su1-Ref allele results in two specific amino acid substitutions without affecting the Su1 mRNA level. The su1-R4582::Mu1 mutation is a null allele that abolishes transcript accumulation. The su1-st mutation results from insertion of a novel transposon-like sequence, designated Toad, which causes alternative pre-mRNA splicing. Three su1-st mutant transcripts are produced, one that is nonfunctional and two that code for modified SU1 polypeptides. The su1-st mutation is dominant to the null allele su1-R4582::Mu1, but recessive to su1-Ref, suggestive of complex effects involving quaternary structure of the SU1 enzyme. All three su1- alleles severely reduce or eliminate isoamylase-type DBE activity, although su1-st kernels accumulate less phytoglycogen and Suc than su1-Ref or su1-R4582::Mu1 mutants. The chain length distribution of residual amylopectin is significantly altered by su1-Ref and su1-R4582::Mu1, whereas su1-st has modest effects. These results, together with su1 allele-specific effects on other starch- metabolizing enzymes detected in zymograms, suggest that total DBE catalytic activity is the not the sole determinant of Su1 function and that specific interactions between SU1 and other components of the starch biosynthetic system are required.