PET/CT in non-small-cell lung cancer: value of respiratory-gated PET

The use of PET in the staging of patients with NSCLC is cost-effective, mainly due to a reduction in the number of futile operations. The addition of SUVmax to pathologic tumor size identifies a subgroup of patients at highest risk for death as a result of recurrent disease after resection. Tumor staging is more accurate with PET-CT than with CT alone or with PET alone. The greatest source of error in accurate localization and quantification on PET or PET-CT in lung cancer is respiratory motion. At MSKCC respiratory-gated PET (RGPET) is used in treatment planning. The lesion in the gated image is smaller in diameter than in the ungated image. Respiratory-correlated dynamic PET (RCDPET) can be considered an alternative method to RGPET. RCDPET shows very accurate local co-registration that can be used to make an attenuation correction and obtain an SUV. Gating gives a much clearer picture resulting in more than a one-third increase in the quantification. The SUV of lung lesions must be re-evaluated based on these techniques. This development will have important implications in areas such as the liver for controlling respiratory motion, which is a major problem in terms of lesion detection. We have successfully taken the first step in an attempt to correct for respiratory motion artifacts in PET imaging of lung lesions. (Chang     

Computational neuropharmacology: dynamical approaches in drug discovery

Computational approaches that adopt dynamical models are widely accepted in basic and clinical neuroscience research as indispensable tools with which to understand normal and pathological neuronal mechanisms. Although computer-aided techniques have been used in pharmaceutical research (e.g. in structure- and ligand-based drug design), the power of dynamical models has not yet been exploited in drug discovery. We suggest that dynamical system theory and computational neuroscience--integrated with well-established, conventional molecular and electrophysiological methods--offer a broad perspective in drug discovery and in the search for novel targets and strategies for the treatment of neurological and psychiatric diseases.     

FDG-PET standardized uptake values in normal anatomical structures using iterative reconstruction segmented attenuation correction and filtered back-projection

Filtered back-projection (FBP) is the most commonly used reconstruction method for PET images, which are usually noisy. The iterative reconstruction segmented attenuation correction (IRSAC) algorithm improves image quality without reducing image resolution. The standardized uptake value (SUV) is the most clinically utilized quantitative parameter of [fluorine-18]fluoro-2-deoxy-D-glucose (FDG) accumulation. The objective of this study was to obtain a table of SUVs for several normal anatomical structures from both routinely used FBP and IRSAC reconstructed images and to compare the data obtained with both methods. Twenty whole-body PET scans performed in consecutive patients with proven or suspected non-small cell lung cancer were retrospectively analyzed. Images were processed using both IRSAC and FBP algorithms. Nonquantitative or gaussian filters were used to smooth the transmission scan when using FBP or IRSAC algorithms, respectively. A phantom study was performed to evaluate the effect of different filters on SUV. Maximum and average SUVs (SUVmax and SUVavg) were calculated in 28 normal anatomical structures and in one pathological site. The phantom study showed that the use of a nonquantitative smoothing filter in the transmission scan results in a less accurate quantification and in a 20% underestimation of the actual measurement. Most anatomical structures were identified in all patients using the IRSAC images. On average, SUVavg and SUVmax measured on IRSAC images using a gaussian filter in the transmission scan were respectively 20% and 8% higher than the SUVs calculated from conventional FBP images. Scatterplots of the data values showed an overall strong relationship between IRSAC and FBP SUVs. Individual scatterplots of each site demonstrated a weaker relationship for lower SUVs and for SUVmax than for higher SUVs and SUVavg. A set of reference values was obtained for SUVmax and SUVavg of normal anatomical structures, calculated with both IRSAC and FBP image reconstruction algorithms. The use of IRSAC and a gaussian filter for the transmission scan seems to give more accurate SUVs than are obtained from conventional FBP images using a nonquantitative filter for the transmission scan.     

Prospective assessment of primary rectal cancer response to preoperative radiation and chemotherapy using 18-fluorodeoxyglucose positron emission tomography

PURPOSE: The purpose of this prospective study was to determine the ability of fluorine-18 fluorodeoxyglucose positron emission tomography to assess extent of pathologically confirmed rectal cancer response to preoperative radiation and 5-fluorouracil-based chemotherapy. METHODS: Patients with primary rectal cancer deemed eligible for preoperative radiation and 5-fluorouracil-based chemotherapy because of a clinically bulky or tethered tumor or endorectal ultrasound evidence of T3 and/or N1 were prospectively enrolled. Positron emission tomography and CT scans were obtained before preoperative radiation and 5-fluorouracil-based chemotherapy (5,040 cGy to the pelvis and 2 cycles of bolus 5-fluorouracil with leucovorin) and repeated four to five weeks after completion of radiation and 5-fluorouracil-based chemotherapy. In addition to routine pathologic staging, detailed assessment of rectal cancer response to preoperative radiation and 5-fluorouracil-based chemotherapy was performed independently by two pathologists. Positron emission tomography parameters studied included conventional measures such as standardized uptake value (average and maximum), positron emission tomography-derived tumor volume (size), and two novel parameters: visual response score and change in total lesion glycolysis. RESULTS: Of 21 patients enrolled, prospective data (pretreatment and posttreatment positron emission tomography, and complete pathologic assessment) were available on 15 patients. All 15 demonstrated pathologic response to preoperative radiation and 5-fluorouracil-based chemotherapy. This was confirmed in 100 percent of the cases by positron emission tomography compared with 78 percent (7/9) by CT. In addition, one positron emission tomography parameter (visual response score) accurately estimated the extent of pathologic response in 60 percent (9/15) of cases compared with 22 percent (2/9) of cases with CT. CONCLUSIONS: This pilot study demonstrates that fluorine-18 fluorodeoxyglucose positron emission tomography imaging adds incremental information to the preoperative assessment of patients with rectal cancer. However, further studies in a larger series of patients are needed to verify these findings and to determine the value of fluorine-18 fluorodeoxyglucose positron emission tomography in a preoperative strategy aimed at identifying patients suitable for sphincter-preserving rectal cancer surgery.Supported in part by the Gerschel Foundation and the National Cancer Institute, R01 CA82534-01.Dr. Ruo is McEachern Fellow of the Canadian Cancer Society.     

Red marrow dosimetry for radiolabeled antibodies that bind to marrow, bone, or blood components

Hematologic toxicity limits the radioactivity that may be administered for radiolabeled antibody therapy. This work examines approaches for obtaining biodistribution data and performing dosimetry when the administered antibody is known to bind to a cellular component of blood, bone, or marrow. Marrow dosimetry in this case is more difficult because the kinetics of antibody clearance from the blood cannot be related to the marrow. Several approaches for obtaining antibody kinetics in the marrow are examined and evaluated. The absorbed fractions and S factors that should be used in performing marrow dosimetry are also examined and the effect of including greater anatomical detail is considered. The radiobiology of the red marrow is briefly reviewed. Recommendations for performing marrow dosimetry when the antibody binds to the marrow are provided.     

Early hyperbaric oxygen therapy for cerebral air embolism during atrial fibrillation ablation

Cerebral air embolism is a potentially life‐threatening complication of left‐sided ablation procedures. We present a 51‐year‐old woman with cerebral air embolism during atrial fibrillation cryoballoon ablation. Taking a deep breath while removing the dilatator was the most likely mechanism in our case. The patient was successfully treated with hyperbaric oxygen therapy at early stage and was discharged without any neurological sequelae.     

Facilitating triple rhomboid flaps for meningomyelocele defect closure using a honeycomb structure as a template

Purpose

Various reconstruction options are available for the soft-tissue coverage of meningomyelocele defects. For small defects, primary closure or local single flaps may be sufficient, while large defects require more complex reconstructive techniques. This study suggests an easy way for surgeons to close large meningomyelocele defects using triple rhomboid flaps.

Methods

The hexagonal structure of a honeycomb was considered when planning for the coverage of large meningomyelocele defects. The intact skin around the defect was imagined as multiple hexagons, which allowed us to plan triple rhomboid flaps correctly and more easily. This technique was used in seven patients with defects ranging from 7?×?5 to 12?×?8 cm in size.

Results

No major postoperative complications were seen. Minimal dehiscence was observed in two patients and healed secondarily.

Conclusions

The honeycomb modification for planning triple rhomboid flaps is an easy, practical, and memorable approach for surgeons reconstructing large meningomyelocele defects.