Radioactive seed localisation of non-palpable lymph nodes - A feasibility study.

BACKGROUND: Radioactive seed localisation (RSL) is a preoperative localisation method using a small titanium seed containing iodine-125. The method is increasingly applied for localising non-palpable lesions in the treatment of breast cancer. We believe that RSL has the potential to be used in various surgical specialties. The aim of this feasibility study was to test RSL as a preoperative localisation of non-palpable lymph nodes. METHODS: Between November 24, 2015 and October 26, 2016, 15 patients with suspicious lymph nodes on imaging were included in the study. The lymph nodes were located in the axillary region (n = 9), the head and neck region (n = 5) and the inguinal region (n = 1). The seeds were placed in the centre of the lymph node, in the capsule or just outside the capsule guided by ultrasound. During surgery, incision and localisation of the lymph nodes were performed based on the auditory signal of the gamma probe. After excision, lymph nodes including iodine seeds were sent for pathologic examination and the seeds were returned to the Department of Nuclear Medicine. RESULTS: The non-palpable lymph nodes were all successfully marked using ultrasound. The lymph nodes were successfully localised and excised during surgery, and the procedure was performed without complications in the majority of the cases. CONCLUSION: Localisation of suspicious non-palpable lymph nodes using RSL is feasible. RSL may ease the surgical procedure, minimise trauma to the surrounding tissue and ultimately benefit the patient. Future prospective studies are necessary to determine the further use of RSL within different surgical specialties.

Colloid volume loading does not mitigate decreases in central blood volume during simulated haemorrhage while heat stressed.

Heat stress results in profound reductions in the capacity to withstand a simulated haemorrhagic challenge; however, this capacity is normalized if the individual is volume loaded prior to the challenge. The present study tested the hypothesis that volume loading during passive heat stress attenuates the reduction in regional blood volumes during a simulated haemorrhagic challenge imposed via lower-body negative pressure (LBNP). Seven subjects underwent 30 mmHg LBNP while normothermic, during passive heat stress (increased internal temperature ∼1◦C), and while continuing to be heated after intravenous colloid volume loading (11 ml kg⁻¹). Relative changes in torso and regional blood volumes were determined by gamma camera imaging with technetium-99m labelled erythrocytes. Heat stress reduced blood volume in all regions (ranging from 7 to 16%), while subsequent volume loading returned those values to normothermic levels. While normothermic,LBNP reduced blood volume in all regions (torso: 22 ± 8%; heart: 18 ± 6%; spleen: 15 ± 8%). During LBNP while heat stressed, the reductions in blood volume in each region were markedly greater when compared to LBNP while normothermic (torso: 73 ± 2%; heart: 72 ± 3%; spleen: 72 ± 5%, all P<0.001 relative to normothermia). Volume loading during heat stress did not alter the extent of the reduction in these blood volumes to LBNP relative to heat stress alone (torso: 73 ± 1%; heart: 72 ± 2%; spleen: 74 ± 3%, all P>0.05 relative to heat stress alone). These data suggest that blood volume loading during passive heat stress (via 11 ml kg⁻¹ of a colloid solution) normalizes regional blood volumes in the torso, but does not mitigate the reduction in central blood volume during a simulated haemorrhagic challenge combined with heat stress.

Radiation exposure to surgical staff during F-18-FDG-guided cancer surgery.

PURPOSE: High-energy gamma probes have recently become commercially available, developed for (18)F-FDG probe-guided surgery. The radiation received by the staff in the operating room might limit the use of it, but has never been determined. We therefore wanted to measure the absorbed staff doses at operations where patients had received a preoperative injection of (18)F-FDG. METHODS: Thirty-four patients with different cancers (breast cancer, melanoma, gastrointestinal cancers, respectively) were operated. At every operation the surgeon was monitored with a TLD tablet on his finger of the operating hand and a TLD tablet on the abdomen. The surgeon and anaesthesiologist were also monitored using electronic dosimeters placed in the trousers lining at 25 operations. RESULTS: The dose rate to the surgeon's abdominal wall varied between 7.5-13.2 microSv/h, depending on tumour location. The doses to the anaesthesiologists and the finger doses to the surgeon were much lower. About 350-400 MBq, i.e. ca. eight times higher activities than those used in the present study are supposed to be necessary for guiding surgery. It can be calculated from the body doses measured that a surgeon can perform between 150-260 h of surgery without exceeding permissible limits for professional workers. CONCLUSIONS: The radiation load to the operating staff will generally be so small that it does not present any limitation for FDG-guided surgery. However, it is recommended to monitor the surgical staff considering that the surgeon may be exposed to other radiation sources, and since the staff often includes women of child-bearing age.

Radiation doses to staff involved in sentinel node operations for breast cancer.

BACKGROUND: The use of radioactive compounds for sentinel node biopsy is now a generally accepted part of the surgical treatment of breast cancer and melanoma, with the risk of radiation exposure to the operating team. The aim of this investigation was to study the levels of this exposure in relation to the permissible radiation dose limits. METHODS: The radiation exposure to the hands and bodies of the operating surgeons (the 'risk persons') was measured by thermoluminescent dosimeters in 79 operations and to the pathologists handling the specimens in 17 cases. Radioactivity and dose rate measurement from tumours and breast specimens were also performed. RESULTS: During an operation the mean skin dose (+/-SD) to the thermoluminescent dosimeters placed at the hand and the abdominal wall were 0.04 +/- 0.04 mSv (79 operations) and 0.01 +/- 0.02 mSv (67 operations) respectively. For the pathologist, the mean hand dose per operation was below the detection limit (17 operations). Correlation between the measured dose rate and the radioactive content of the tumours was 0.998. CONCLUSIONS: The radiation exposure to the staff involved in sentinel node (SN) biopsy for breast cancer using radioactive labelled tracers will be considerably below the permissible limits, even with high numbers of SN biopsy procedures. Pregnant staff members should participate in <100 SN operations.

PET/CT with intravenous contrast can be used for PET attenuation correction in cancer patients.

PURPOSE: If the CT scan of a combined PET/CT study is performed as a full diagnostic quality CT scan including intravenous (IV) contrast agent, the quality of the joint PET/CT procedure is improved and a separate diagnostic CT scan can be avoided. CT with IV contrast can be used for PET attenuation correction, but this may result in a bias in the attenuation factors. The clinical significance of this bias has not been established. Our aim was to perform a prospective clinical study where each patient had CT performed with and without IV contrast agent to establish whether PET/CT with IV contrast can be used for PET attenuation without reducing the clinical value of the PET scan. METHODS: A uniform phantom study was used to document that the PET acquisition itself is not significantly influenced by the presence of IV contrast medium. Then, 19 patients referred to PET/CT with IV contrast underwent CT scans without, and then with contrast agent, followed by an 18F-fluorodeoxyglucose whole-body PET scan. The CT examinations were performed with identical parameters on a GE Discovery LS scanner. The PET data were reconstructed with attenuation correction based on the two CT data sets. A global comparison of standard uptake value (SUV) was performed, and SUVs in tumour, in non-tumour tissue and in the subclavian vein were calculated. Clinical evaluation of the number and location of lesions on all PET/CT scans was performed twice, blinded and in a different random order, by two independent nuclear medicine specialists. RESULTS: In all patients, the measured global SUV of PET images based on CT with IV contrast agent was higher than the global activity using non-contrast correction. The overall increase in the mean SUV (for two different conversion tables tested) was 4.5+/-2.3% and 1.6+/-0.5%, respectively. In 11/19 patients, focal uptake was identified corresponding to malignant tumours. Eight out of 11 tumours showed an increased SUVmax (2.9+/-3.1%) on the PET images reconstructed using IV contrast. The clinical evaluation performed by the two specialists comparing contrast and non-contrast CT attenuated PET images showed weighted kappa values of 0.92 (doctor A) and 0.82 (doctor B). No contrast-introduced artefacts were found. CONCLUSION: This study demonstrates that CT scans with IV contrast agent can be used for attenuation correction of the PET data in combined modality PET/CT scanning, without changing the clinical diagnostic interpretation.