Biomedical subjects

K Sidhu

Publications and source records attributed to K Sidhu.

9 recordsLinked to original sources

PubMed2002

Effect of respiratory gating on reducing lung motion artifacts in PET imaging of lung cancer.

Positron emission tomography (PET) has shown an increase in both sensitivity and specificity over computed tomography (CT) in lung cancer. However, motion artifacts in the 18F fluorodioxydoglucose (FDG) PET images caused by respiration persists to be an important factor in degrading PET image quality and quantification. Motion artifacts lead to two major effects: First, it affects the accuracy of quantitation, producing a reduction of the measured standard uptake value (SUV). Second, the apparent lesion volume is overestimated. Both impact upon the usage of PET images for radiation treatment planning. The first affects the visibility, or contrast, of the lesion. The second results in an increase in the planning target volume, and consequently a greater radiation dose to the normal tissues. One way to compensate for this effect is by applying a multiple-frame capture technique. The PET data are then acquired in synchronization with the respiratory motion. Reduction in smearing due to gating was investigated in both phantoms and patient studies. Phantom studies showed a dependence of the reduction in smearing on the lesion size, the motion amplitude, and the number of bins used for data acquisition. These studies also showed an improvement in the target-to-background ratio, and a more accurate measurement of the SUV. When applied to one patient, respiratory gating showed a 28% reduction in the total lesion volume, and a 56.5% increase in the SUV. This study was conducted as a proof of principle that a gating technique can effectively reduce motion artifacts in PET image acquisition.

Algorithms↗

PubMed2002

Cone-beam CT with megavoltage beams and an amorphous silicon electronic portal imaging device: potential for verification of radiotherapy of lung cancer.

We investigate the potential of megavoltage (MV) cone-beam CT with an amorphous silicon electronic portal imaging device (EPID) as a tool for patient position verification and tumor/organ motion studies in radiation treatment of lung tumors. We acquire 25 to 200 projection images using a 22 x 29 cm EPID. The acquisition is automatic and requires 7 minutes for 100 projections; it can be synchronized with respiratory gating. From these images, volumetric reconstruction is accomplished with a filtered backprojection in the cone-beam geometry. Several important prereconstruction image corrections, such as detector sag, must be applied. Tests with a contrast phantom indicate that differences in electron density of 2% can be detected with 100 projections, 200 cGy total dose. The contrast-to-noise ratio improves as the number of projections is increased. With 50 projections (100 cGy), high contrast objects are visible, and as few as 25 projections yield images with discernible features. We identify a technique of acquiring projection images with conformal beam apertures, shaped by a multileaf collimator, to reduce the dose to surrounding normal tissue. Tests of this technique on an anthropomorphic phantom demonstrate that a gross tumor volume in the lung can be accurately localized in three dimensions with scans using 88 monitor units. As such, conformal megavoltage cone-beam CT can provide three-dimensional imaging of lung tumors and may be used, for example, in verifying respiratory gated treatments.

Algorithms↗

PubMed2000

Complete paraplegia as a result of regional anesthesia.

Complications after spinal or epidural anesthesia are rare. We report 2 cases of postoperative, complete paraplegia after regional anesthesia in orthopaedic patients not on anticoagulants. The paralysis was likely the result of spinal cord compression secondary to an epidural hematoma in 1 case and subdural hematoma in 1 case. A review of the literature regarding complications of regional anesthesia is presented. Regional anesthesia should be administered with caution and in selected patients.

Aged↗

PubMed1995

Transient neonatal myasthenia gravis and pyloric stenosis.

The case report describes the occurrence of hypertrophic pyloric stenosis in a premature infant with neonatal myasthenia gravis. The infant presented for pyloromyotomy on the nineteenth day of life. Diagnosis of myasthenia gravis was made based on maternal history and clinical findings of poor muscle tone, weak suck, and weak cry. The anesthetic management is discussed with reference to the problems of newborn myasthenia gravis and pyloric stenosis as they relate to anesthetic drugs and techniques.

Anesthesia↗

PubMed1994