Use Of Gamma Probe Research Articles

Simulation study of the effect of the geometrical parameters on the performance of a beta probe

Abstract An intraoperative probe is a small tool used to identify, locate, and dissect pathological lesions during surgery and confirm their removal. The most common type of probe is the gamma probe, which detects gamma-emitting sources. Despite the successful use of gamma probes in clinics, their application can be limited when the background radiation from healthy tissue nearby or the injection site is high. In these cases, the use of beta probes that detect beta-emitting radiotracers would be beneficial. The shorter range of beta radiation compared to gamma radiation would result in improved detection efficacy when background radiation is significant. In this simulation study, we examined how geometrical parameters may impact the performance of a beta probe. Our results showed that the source depth inside the phantom and detector size affected the performance of the beta probe. We also proposed and evaluated two designs of beta probes capable of adjusting their performance.

MP61-15 SKILL-ASSESSMENT DURING ROBOT-ASSISTED RADIOGUIDED SURGERY - USING ARTIFICIAL INTELLIGENCE TO EXTRACT KINEMATIC METRICS OF DROP-IN GAMMA PROBE USE

You have accessJournal of UrologyCME1 Apr 2023MP61-15 SKILL-ASSESSMENT DURING ROBOT-ASSISTED RADIOGUIDED SURGERY - USING ARTIFICIAL INTELLIGENCE TO EXTRACT KINEMATIC METRICS OF DROP-IN GAMMA PROBE USE Samaneh Azargoshasb, Hilda A De Barros, Daphne D.D. Rietbergen, Paolo Dell'oglio, Pim J Van Leeuwen, Christian Wagner, Tobias Maurer, Henk G. Van der poel, Matthias N. Van Oosterom, and Fijs W. B. Van Leeuwen Samaneh AzargoshasbSamaneh Azargoshasb More articles by this author , Hilda A De BarrosHilda A De Barros More articles by this author , Daphne D.D. RietbergenDaphne D.D. Rietbergen More articles by this author , Paolo Dell'oglioPaolo Dell'oglio More articles by this author , Pim J Van LeeuwenPim J Van Leeuwen More articles by this author , Christian WagnerChristian Wagner More articles by this author , Tobias MaurerTobias Maurer More articles by this author , Henk G. Van der poelHenk G. Van der poel More articles by this author , Matthias N. Van OosteromMatthias N. Van Oosterom More articles by this author , and Fijs W. B. Van LeeuwenFijs W. B. Van Leeuwen More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003319.15AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Radioguided prostate cancer (PCa) surgery has been greatly facilitated by the introduction of the steerable DROP-IN gamma probe technology. Reported indications include sentinel node (SN) resections and prostate-specific membrane antigen (PSMA)-targeted resections. Both make use of 99mTc-labeled imaging vectors. As result of the targeting mechanisms used the signal- and background intensities in these procedures, however, differ substantially. To study how this reflects on the surgical decision-making process we used computer-vision strategies to compare DROP-IN gamma probe use during SN- and PSMA-targeted surgeries. METHODS: A DROP-IN gamma probe was applied during 45 robot-assisted PCa surgeries from 2018 to 2021 at single tertiary care referral centre: SN resections [n=25; primary surgery; intraprostatic injection of indocyanine green (ICG)-99mTc-nanocolloid (∼200MBq, 5-6h prior to surgery)], PSMA-targeted resections [n=20; salvage surgery; intravenous injection of 99mTc-PSMA I&S (∼550MBq, 16-22h prior to surgery)}. Preoperative imaging-roadmaps were created using SPECT/CT and PET/CT imaging. Using custom tracking algorithms, based on a neural network architecture, the DROP-IN probe trajectories were extracted from endoscopic videos. Trajectories were then processed to extract key kinematic performance metrics. To allow for skill-assessment, the metrics were incorporated in decision-making and dexterity scores. RESULTS: The nodal signal intensities in PSMA- vs SN-targeted resections were 550 vs. 1200 counts in preoperative SPECT-CT scans (p=0.098) and 150 vs 1050 counts/s with regard to intraoperative probe readouts (p<0.001). Due to the relatively high background signals observed during PSMA tracing a 2-fold reduction in the intraoperative signal to background ratio (SBR) (1.8 vs. 3.6; p<0.001) was observed in this setting. Kinematic analysis revealed significant differences in a number of metrics, e.g., target identification time (368 sec per PSMA lesion vs. 75 sec per SLN; p<0.001), number of probe pick-ups (5 vs. 1; p<0.001), and reduction in dexterity (281-fold; p<0.001) and decision-making scores (3.9-fold; p<0.001) during PSMA-targeted resections. CONCLUSIONS: DROP-IN technology facilitates robotic radioguided surgery in SN and PSMA-targeted resections. However, a profound performance difference was observed in favour of SN-targeted resections. In particular, the SBR<2 as found mostly in PSMA-targeted resections directly converted to a decline in dexterity and decision-making. These findings might be related to limited previously experience in PSMA-targeted surgery. Source of Funding: This research was supported by an NWO-TTW-VICI grant (TTW 16141) and with hardware by Eurorad S.A. and Intuitive Inc. © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e858 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Samaneh Azargoshasb More articles by this author Hilda A De Barros More articles by this author Daphne D.D. Rietbergen More articles by this author Paolo Dell'oglio More articles by this author Pim J Van Leeuwen More articles by this author Christian Wagner More articles by this author Tobias Maurer More articles by this author Henk G. Van der poel More articles by this author Matthias N. Van Oosterom More articles by this author Fijs W. B. Van Leeuwen More articles by this author Expand All Advertisement PDF downloadLoading ...

Skill-assessment during robot-assisted radioguided surgery - using artificial intelligence to extract kinematic metrics of DROP-IN gamma probe use

Skill-assessment during robot-assisted radioguided surgery - using artificial intelligence to extract kinematic metrics of DROP-IN gamma probe use

Role of Lymphoscintigraphy and SPECT-CT in Sentinel Lymph Node Detection in Early Stage Squamous Cell Carcinoma of Oral Cavity: Our Experience

Objective: A multidisciplinary team trial in a tertiary care centre in patients with early stage squamous cell carcinoma of oral cavity to review the established role of advanced imaging modalities like lymphoscintigraphy and SPECT-CT in sentinel lymph node identification and to layout our experience in performing this modality. Methods: A prospective, case control study of diagnosed cases of T1/T2 N0 squamous cell carcinoma of oral cavity undertaken from December 2016 to January 2018 at our institution of which the patients in study group underwent SLNB guided neck dissection and the patients in control group underwent Elective Neck Dissection. We compared both the groups in terms of the operating time, the post-operative histopathology, the diagnostic accuracy and the outcomes which were statistically analysed. Also we studied and analysed the efficacy of static and dynamic lymphoscintigraphy followed by SPECT-CT in identifying sentinel lymph node areas in neck and intra-operative gamma probe use to precisely locate the sentinel nodes. Results: Out of 40 patients, 20 each in study and control groups were included. The SLN identification rate was 100% with combined SPECT-CT and gamma probe use whereas it was 70% with imaging alone. The sensitivity, specificity, positive predictive value and negative predictive value of SLNB and END were 80% , 56.58%, 9.61%, 98% and 78.5 %, 73.48% ,10.67% , 98.8 % respectively. The operating time was less in the SLNB group with statistically significant difference between the two groups. Conclusion: High SLN identification rate with combined use of SPECT-CT and gamma probe and high NPV render SLNB as a reliable modality in the management of early stage oral cavity cancers in a centre with a multidisciplinary team set up and appropriate facilities.

Role of gamma probe-assisted intraoperative sentinel lymph node evaluation in predicting axillary breast cancer metastasis after neoadjuvant chemotherapy.

Intraoperative sentinel lymph node biopsy is a universally accepted technique to identify patients who are candidates for axillary lymph node dissection during breast cancer surgery. However, there is controversy over its use in patients who underwent preoperative neoadjuvant chemotherapy. This study aimed to examine the diagnostic value of gamma probe-assisted intraoperative sentinel lymph node examination with frozen section in breast cancer patients who had undergone preoperative neoadjuvant chemotherapy. This retrospective study included 94 tumors diagnosed with stage IIA, IIB or IIIA invasive breast cancer with locoregional lymph node metastasis who underwent surgical treatment after neoadjuvant chemotherapy. Intraoperatively, axillary sentinel lymph node sampling was done using radioactive colloid and gamma probe and materials were examined with frozen section method. Patients with positive sentinel nodes underwent axillary resection. Histopathological examination of all surgical samples was done postoperatively. In 87 of 94 tumors (92.6%), a sentinel lymph node could be identified using the method. The sensitivity, specificity and accuracy of the method for predicting axillary macro metastasis were 85.7, 86.5 and 86.2%, respectively, with 5.7% false negative rate. Sentinel lymph node identification using preoperative scintigraphy and intraoperative use of gamma probe seems to be a feasible and efficient method in terms of differentiating patients that require axillary lymph node dissection during breast cancer surgery, even when they have received neoadjuvant chemotherapy. Further large prospective studies allowing subgroup analyses are warranted.

Implementation of Protocol for Image-Guided Resection of Non-Palpable Breast Cancer Tumors

Background: The use of gamma probes and Tc-99m colloids for radioguided occult-lesion localization (ROLL) is replacing guidewire localization in breast cancer in Europe. However, ROLL could be further improved by adding intraoperative SPECT imaging to assess tumor margins.

Directional probe for radio-guided surgery: A pilot study.

The sentinel lymph node (SLN) biopsy technique has highly evolved during the last 20 yr. Consequently, the intraoperative use of Gamma Probes (GPs) for SLN mapping is increased. This preliminary study evaluates a novel directional GP prototype. This proof-of-concept prototype is designed to identify the direction of radiopharmaceuticals uptakes, by combining the information from multiple detectors. The purpose of this work is to develop a tool able to effectively guide the surgeon reducing the surgery time. The proposed prototype consists of three CsI(Tl) scintillation crystals, each coupled with an S10931 silicon photomultiplier (Hamamatsu Photonics K.K., Hamamatsu, JP). The three detectors lie on the same plane with an angle of 30° between them. The central detector is placed as in a common GP, so it can be used to pinpoint the target tissue. Meanwhile, the lateral sensors provide a broader view of the surgical field. A dedicated data acquisition system digitizes and processes the signals from the front-end electronics. Finally, an embedded system, based on ARM processor, calculates and displays the acquired count rates. In order to assess the prototype behavior, the isosensitivity curves for the three detectors were measured. Meanwhile, for the central one, the main quality criteria measurements were also performed (i.e., sensitivity, radial sensitivity, and spatial resolution). For the central detector, the measured sensitivity at the tip of the probe is better than 5 cps/kBq. The full width at half maximum (FWHM) of the radial sensitivity is less than 30° and the FWHM of the lateral sensitivity (spatial resolution) is about 7.2 mm. The central detector measured isosensitivity distribution shows a narrow profile in agreement with the spatial resolution measured. On the contrary, the two lateral detectors exhibit widespread isosensitivity distributions that mean a larger field of view. The system had shown satisfactory performance and reliability, meeting the minimal requirements of gamma probe systems. The prototype presented in this paper allows a rapid localization by the use of the whole system, while the sole central detector can be used to pinpoint the target source. This device, unlike common GPs, allows localizing simultaneously different areas of radiopharmaceuticals uptake, thus precisely guiding the surgeon to the region of interest. These preliminary results encourage to develop a further prototype for intraoperative validation.

Is there an additional benefit of Tc-99m-PSMA-guided gamma probe use for salvage lymph node dissection in recurrent prostate cancer.

e591 Background: PSMA-PET/CT is the most sensitive diagnostic tool in biochemical recurrent prostate cancer to detect minimal metastatic disease. However, it may be difficult to localize small PSMA-positive lymph nodes intraoperatively. Therefore, it was the aim to investigate whether preoperative Tc-99m-PSMA targeting may improve intraoperative tumor localization by use of a gamma probe. Methods: In 13 Patients Ga-68-PSMA-PET/CT identified iliac lymph nodes in patients suitable for salvage lymph node dissection. On the day before operation a mean activity of 480 MBq Tc-99m-PSMA was injected and gamma camera scintigraphy + SPECT was performed 4-5 hours after tracer application. About 24 hours after tracer application a salvage lymph node dissection was performed on the side of initial suspicious lymph node metastases. Sensitivity, specifity, pos and neg. predictive values were calulated for PSMA-PET/CT and gamma probe use to analyse the additional use. Results: In 9 / 13 patients PSMA-positive metastatic lymph nodes were identified in Ga-68 PSMA-PET/CT. A total of 156 lymph nodes were removed with 14 lymph nodes in 9 patients being positive in histopathologic examination. Sensitivity, specifity, pos and neg. predictive values for PSMA PET/CT and gamma probe were 85% and 79%, 99% and 100%, 85% and 100% and 99% and 98% respectively. In one patient only gamma probe use identified a pathologic lymph node. Conclusions: Gamma probe guided salvage lymph node dissection in PSA recurrent prostate cancer is feasible and had a high concordance with PSMA-PET/CT. However, the additional diagnostic benefit is limited compared to PSMA-PET/CT because in only one patient (7%) a positive lymph node could be identified with the use of the gamma probe outside the standard operative area in salvage lymph node dissection.

The Added Value of a Single-photon Emission Computed Tomography-Computed Tomography in Sentinel Lymph Node Mapping in Patients with Breast Cancer and Malignant Melanoma.

Single-photon emission computed tomography-computed tomography (SPECT-CT) allows for physiological and anatomical co-registration in sentinel lymph node (SLN) mapping and offers additional benefits over conventional planar imaging. However, the clinical relevance when considering added costs and radiation burden of these reported benefits remains somewhat uncertain. This study aimed to evaluate the possible added value of SPECT-CT and intra-operative gamma-probe use over planar imaging alone in the South African setting. 80 patients with breast cancer or malignant melanoma underwent both planar and SPECT-CT imaging for SLN mapping. We assessed and compared the number of nodes detected on each study, false positive and negative findings, changes in surgical approach and or patient management. In all cases where a sentinel node was identified, SPECT-CT was more accurate anatomically. There was a significant change in surgical approach in 30 cases - breast cancer (n = 13; P 0.001) and malignant melanoma (n = 17; P 0.0002). In 4 cases a node not identified on planar imaging was seen on SPECT-CT. In 16 cases additional echelon nodes were identified. False positives were excluded by SPECT-CT in 12 cases. The addition of SPECT-CT and use of intra-operative gamma-probe to planar imaging offers important benefits in patients who present with breast cancer and melanoma. These benefits include increased nodal detection, elimination of false positives and negatives and improved anatomical localization that ultimately aids and expedites surgical management. This has been demonstrated in the context of industrialized country previously and has now also been confirmed in the setting of a emerging-market nation.

New technologies in thyroid cancer surgery

Several new technologies have advanced the practice of thyroid surgery in recent years, with some centers implementing substantial changes in the way thyroid surgery is performed. As many thyroid cancers are diagnosed at an early stage the treatment is quite effective, and the prognosis is good for most patients with differentiated thyroid cancer. With excellent long term survival, advancements in the treatment of patients with thyroid cancers are focusing on reducing complications of surgery, improving quality-of-life and delivering care in a cost-effective way. The LigaSure electrothermal bipolar vessel sealing system and Harmonic scalpel have been designed to aid in dissection with less thermal spread than conventional electrocautery. Alternative access approaches to the thyroid allow for improved cosmetic outcomes and potentially improve the view of the surgical field. The intraoperative use of gamma-probe for the localization of metastases and sentinel lymph nodes are being increasingly reported on. Surgeon performed ultrasound is promoted for improving the detection of disease, and intraoperative nerve monitoring is now widespread, aiding in laryngeal nerve detection and protection. The assay of parathyroid hormone is also in common use for predicting patients at risk for developing postoperative hypocalcemia. This article reviews the current literature on new technologies for thyroid surgery and discusses some of the implications for the future of this field of surgery.

Sentinel node biopsy for oral and oropharyngeal squamous cell carcinoma in the previously treated neck

In patients with early stage oral or oropharyngeal squamous cell carcinoma (OSCC) sentinel node biopsy (SNB) is a reliable method to detect occult disease in the neck. However, patients with a history of surgery or radiotherapy in the neck may have aberrant lymphatic drainage caused by disruption of lymphatic channels. Therefore, treatment of the same levels at risk as in the primary setting may not be appropriate. The aim of our prospective observational study was to evaluate the clinical application of SNB in previously treated OSCC. Between 2003 and 2010 twenty-two patients were included. Lymph node mapping consisted of preoperative lymphoscintigraphy, SPECT/CT, intraoperative use of gamma-probe and patent blue. Endpoints were the sentinel node (SN) detection rate, unexpected lymphatic drainage patterns, negative predictive value and regional tumor control. 4/22 (18%) Patients were previously treated only on the contralateral site. The SN detection rate was 100% and unexpected drainage was found in 1/4 patients. The other 18 patients had ipsi- or bilateral previous neck treatment and a SN detection rate of 83%. The upstaging rate was 7% and 67% had unexpected lymphatic drainage patterns. The median follow-up was 22 months. Regional tumor control and negative predictive value were 100%. SNB in previously treated OSCC patients is feasible. SN detection is reliable and regional tumor control after staging by SNB is excellent. Moreover, SNB renders an assessment of the individual lymphatic drainage pattern, compensating for a potential variability after previous treatment of the neck.

Our initial experiences related to gamma probe use in completion thyroidectomy

In this study twenty two differentiated thyroid carcinoma (DTC) case performed completion thyroidectomy between June 2008 and October 2010 in Gaziantep University Medical Faculty Hospital were examined prospectively and surgical results of gamma probe were observed. Patients who had less then total thyroidectomy in their first operations with DTC pathology reports, went through gamma probe supported completion thyroidectomy, gamma probe efficiency was examined. In preoperative period, mean TSH value was identified as 1.48 mIU/l. 0.1mCi liquid I-131 was given to the patients after minimum 2 hours of starvation period one day before the day of surgery. All the areas where there was a signal over the background values were resected out from thyroid channel. While mean background radiation value was 24.04 cps (2-49) and mean basal radiation value of thyroid lodge was 753.09 cps (29-5156), after resection mean radiation value of thyroid lodge was measured as 13.4 cps (1-47). Postoperative TSH blood level before suppression therapy was measured as 52.86 mIU/l average. In post operative period all patients' (100%) thyroglobulin levels decreased. In the operations supported by gamma probe, we did not observe any increase in complication rates compared to literature. These results suggest that completion total thyroidectomy with gamma probe makes post operative treatment and follow up easier by providing more efficient surgical resection, and also completion thyroidectomy with gamma probe is the most efficient method in avoiding recurrences.

PET/CT imaging of clear cell renal cell carcinoma with 124I labeled chimeric antibody

Clear cell renal cell carcinoma (ccRCC) presents problems for urologists in diagnosis, treatment selection, intraoperative surgical margin analysis, and long term monitoring. In this paper we describe the development of a radiolabeled antibody specific to ccRCC (124I-cG250) and its potential to help urologists manage each of these problems. We believe 124I-cG250, in conjunction with perioperative Positron emission tomography/computed tomography imaging and intraoperative handheld gamma probe use, has the potential to diagnose ccRCC, aid in determining a proper course of treatment (operative or otherwise), confirm complete resection of malignant tissue in real time, and monitor patients post-operatively.

In Vivo Characterisation of Parathyroid Lesions by Use of Gamma Probe: Comparison with Ex Vivo Count Method and Frozen Section Results

In this study we hypothesized that if timing of gamma probe-guided parathyroidectomy were individualized according to an optimal-time-to-surgery technique, in vivo characterization of parathyroid lesions would be possible. We compared our findings with an ex vivo counting method ("20% rule") and frozen section results. Thirty-five patients who were referred for surgical treatment of hyperparathyroidism were studied. Maximum parathyroid to thyroid sestamibi uptake ratio (UR(max)) was measured by use of preoperative dynamic scintigraphy. The interval between sestamibi injection and UR(max) was defined as the optimal time to surgery. On the day of surgery, the patients received the same dose of sestamibi and were taken to the operating room at UR(max) as determined by preoperative scintigraphy. Intraoperative in vivo gamma probe counts from parathyroid lesions were compared with in vivo contralateral background thyroid counts (in vivo/Bkg) and to ex vivo parathyroid counts relative to postexcision background of the adjacent normal tissue (ex vivo/Bkg). A total of 70 excised lesions were evaluated. In vivo/Bkg counts obtained from parathyroid adenoma were significantly different from parathyroid hyperplasia (z = -3.093, P = 0.002) and other lesions (z = -3.958, P = 0.0001). By receiver operating characteristic curve (ROC) analysis, we found the cutoff value for the in vivo/Bkg counts ratio to be 103% to differentiate parathyroid adenoma from hyperplasia with a sensitivity, specificity, and accuracy of 82.5, 65, and 74.4%, respectively. On the other hand, sensitivity, specificity, and accuracy of the ex vivo/Bkg method to differentiate parathyroid adenoma from hyperplasia with a cutoff value of 34.7 was found to be 70.8%, 60%, and 65.9%, respectively. The difference between the accuracy of these 2 tests was not significant statistically (P = 0.137). Sensitivity of frozen section to differentiate parathyroid adenoma and hyperplasia was 76.2% and 33.3%, respectively. Patient-specific optimal protocol for timing of sestamibi injection together with in vivo/Bkg method is a useful alternative method in guiding the surgeon to differentiate parathyroid adenoma from parathyroid hyperplasia and other tissues and may help surgeons' decisions during the operation. Combined use of in vivo/Bkg and ex vivo/Bkg methods may give more accurate results than frozen section.

Surgical therapy of penis carcinoma

Primary therapy of penile cancer (carcinoma in situ/T1 tumors) consists of circumcision, microsurgical excision, application of 5-fluorouracil cream, radiation, or laser treatment. In cases of larger T1 tumors or T2 and distal T3 tumors, partial penectomy with a 2-cm margin of clearance is mandatory. Secondary therapy includes inguinal lymphadenectomy 4-6 weeks after primary treatment and antibiotic prophylaxis. Independent prognostic factors for the presence of lymph node metastases are T stage and grading. Only patients with noninvasive G1 or G2 tumors and nonpalpable inguinal lymph nodes are candidates for surveillance with careful follow-up. Inguinal lymphadenectomy is performed in a radical or modified (Catalona) manner. Sentinel biopsy (Cabanas) may regain importance with the use of gamma probes. Complication rates of inguinal lymphadenectomy correlate to the extent of the procedure and must be weighed against the possibility of cure with lymphadenectomy. In cases of inguinal lymph node metastasis, removal of the iliac lymph nodes (one- or two-step procedure) is necessary.

Biopsia selectiva del ganglio centinela en el melanoma mediante localización con linfogammagrafía preoperatoria y sonda de detección gamma intraoperatoria

The experience in detection of sentinel lymph node in melanoma using preoperative scintigraphy and intraoperative gamma probe is referred. We studied 60 patients with stage I-II melanoma who underwent sentinel lymph node biopsy performed using 99m-Tc-labelled sulphur colloid as radioactive tracer. A preoperative scintigraphy was performed and intraoperative gamma probe was used to localize the sentinel node in all cases. Scintigraphy results, effectiveness of intraoperative detection (technical efficacy), pathological results, and follow-up have been studied. Preoperative detection was 98.3% and the mean basin detected was 1.17. There were multiple basins especially when melanomas were on the trunk. Technical efficacy was 98.4% and intraoperative detection was more difficult in parotid gland region. HMB-45 immunohistochemical staining was essential in pathological studies, in whom 10% were positives. Lymphadenectomy could be avoided in 90% of the patients. Recurrences were not detected during follow-up and metastases were found only in non biopsied cases. Sentinel node biopsy morbidity was significative lesser than that of lymphadenectomy. Preoperative scintigraphy and intraoperative gamma probe use to localize sentinel node in melanoma have a high efficacy. They can reveal multiple basins and they allow a more selective surgical approach and a minimal dissection.

Invited commentary: Can we reliably differentiate normal from abnormal parathyroid glands? (In the operating room? Eventually?)

Surgery 2000;128:1102.

Use of surgical gamma probe for the detection of lymph node metastases in differentiated thyroid cancer.

Patients with differentiated thyroid cancer (DTC) after total or near-total thyroidectomy require 131I therapy. After surgery the persistence of lymph node metastases in our series of patients was frequent (30%). Such patients are preferentially treated with radioiodine and shifted to surgical reintervention when the nodal lesions persist after two 131I treatments. Use of an intraoperative radioactive probe (C-TraK) to allow a more radical surgical approach in thyroid cancer patients submitted to surgery for lymph node metastases. After adequate withdrawal of L-thyroxine suppressive therapy six patients were given high 131I doses followed by post-therapy WBS which demonstrated cervical activity in 5 patients and peri-jugular activity in 1. Surgery with the help of a gamma probe allowed to detect and remove all metastatic nodes. After excision all surgical specimens showed higher radioactive counts with respect to the background. The post-surgical scan showed the disappearance of all areas of 131I uptake. Histology confirmed the presence of metastatic lesions from papillary thyroid cancer. We conclude that the use of a gamma probe can be successful in patients with metastatic neck lesions resistant to 131I treatment, particularly in patients with nonpalpable lesions.

Single-dose isotope injection for both preoperative lymphoscintigraphy and intraoperative sentinel lymph node identification in melanoma patients.

For patients with melanoma the 'sentinel' lymph node biopsy technique, although simple in concept, has the potential to provide misleading information if great care is not taken to ensure accurate sentinel node (SN) identification. The method initially reported involved lymphatic mapping by injection of blue dye around the primary melanoma site. Preoperative lymphoscintigraphy was subsequently shown to improve both the speed and accuracy of SN identification. More recently, intraoperative use of a hand-held gamma probe has been recommended, and it is likely that maximum reliability of SN biopsy will be achieved if all three manoeuvres are undertaken. As originally described, use of a gamma probe intraoperatively followed injection of tracer a short time before the surgical procedure. We report a simpler method of confirming SN identity with a gamma probe, using residual activity in the node following lymphoscintigraphy the previous day. In 21 patients close concordance with preoperative lymphoscintigram results and intraoperative findings after blue dye injection confirmed the reliability of the technique. Avoiding the need for repeat isotope administration on the day of surgery simplifies logistics, reduces costs, minimizes inconvenience and radiation dose for patients, and eliminates potential health and safety problems for operating theatre staff.