Mini Gamma Camera Research Articles

Research and manufacture of the mini gamma camera using multi-anode photo multiplier tube (Ma-PMT)

Gamma camera is an imaging technique that captures gamma radiation emitting from the radiation sources. In this paper, the authors built a Mini-Gamma camera system using a micro photomultiplier tube (µPMT) H12700, signal processing circuit, and control software as self-designed products. The Gamma camera system includes four parts: collimator, scintillator NaI(Tl), µPMT, processing, and controller boards. The electronic system had preamplifiers used to convert negative signals from the µPMT to positive signals, integrators used to sharpen the signal from the preamplifier, and an amplifier circuit to amplify the signal from the preamplifier, a position detection circuit to detect the location of radiation interaction in the crystal. All circuits in the Mini-Gamma camera system are optimized to achieve the best projection image quality. In this paper, the lab-built Mini-Gamma Camera has an energy resolution of 45% at 60 keV gamma rays, the affected field of the camera is 42×48.5 mm2, and the spatial resolution of the image is around 1 mm.

Radioisotopic purity and imaging properties of cyclotron-produced 99mTc using direct 100Mo(p,2n) reaction

Evaluation of the radioisotopic purity of technetium-99m (99mTc) produced in GBq amounts by proton bombardment of enriched molibdenum-100 (100Mo) metallic targets at low proton energies (i.e. within 15–20 MeV) is conducted. This energy range was chosen since it is easily achievable by many conventional medical cyclotrons already available in the nuclear medicine departments of hospitals. The main motivation for such a study is in the framework of the research activities at the international level that have been conducted over the last few years to develop alternative production routes for the most widespread radioisotope used in medical imaging. The analysis of technetium isotopes and isomeric states (9xTc) present in the pertechnetate saline Na99mTcO4 solutions, obtained after the extraction/purification procedure, reveals radionuclidic purity levels basically in compliance with the limits recently issued by European Pharmacopoeia 9.3 (2018 Sodium pertechnetate (99mTc) injection 4801–3). Moreover, the impact of 9xTc contaminant nuclides on the final image quality is thoroughly evaluated, analyzing the emitted high-energy gamma rays and their influence on the image quality. The spatial resolution of images from cyclotron-produced 99mTc acquired with a mini-gamma camera was determined and compared with that obtained using technetium-99m solutions eluted from standard 99Mo/99mTc generators. The effect of the increased image background contribution due to Compton-scattered higher-energy gamma rays (Eγ > 200 keV), which could cause image-contrast deterioration, was also studied. It is concluded that, due to the high radionuclidic purity of cyclotron-produced 99mTc using 100Mo(p,2n)99mTc reaction at a proton beam energy in the range 15.7–19.4 MeV, the resulting image properties are well comparable with those from the generator-eluted 99mTc.

Abstract ID: 247 Patient specific scatter reduction in SIRT gamma camera images

Clinical Bremsstrahlung imaging with gamma cameras or SPECT scanners, for example used in selective internal radiation therapy (SIRT) [1], suffers from low contrast due to a continuous spectrum and a high amount of scatter. Information about the scattering of the radionuclide within the patient's body can be obtained from Monte-Carlo simulations and subsequently being used to improve image quality. An MAA-acquisition (CT+SPECT) of a HCC patient with a unifocal uptake in the right liver lobe is segmented (lesion) and loaded into the MC simulation framework GATE [2]. The voxelized lesion is used as Y90 source (1.5 GBq, 'fastY90' [3] is used yielding a speedup of 2.3×), the CT dataset is used for attenuation by converting HUs into corresponding materials. A mini gamma camera (Crystal Photonics, Germany) with a LEHR collimator and 4 × 4 cm2 detector size is positioned close to liver on the patient's skin, pointing towards the lesion. A simulation (60 s acquisition time) is performed on a cluster with 512 cores (2.2-2.5 Ghz each). The total number of counts, the energy spectrum and the order of scattered particles within each geometric volume are obtained from the ROOT output. Particles that have not scattered at all are defined as primary events. Scattering is only calculated within the phantom. The simulation took 172 min on the cluster with input data voxel size of 1 × 1 × 3.75 mm3. The number of emitted particles is 7.6 M with 600 k detected counts (∼8% ratio). 13.3% of the detected particles are primary events. Additionally, scatter of multiple orders has been observed (41%, 24% and 13% and 8% for the first four orders). The energy-spectrum of the simulated 2D gamma camera image can be analyzed and used to correct the actual image acquired of that specific patient to achieve improved image quality and subsequently also dosimetry.

Flexible mini gamma camera reconstructions of extended sources using step and shoot and list mode.

Hand- and robot-guided mini gamma cameras have been introduced for the acquisition of single-photon emission computed tomography (SPECT) images. Less cumbersome than whole-body scanners, they allow for a fast acquisition of the radioactivity distribution, for example, to differentiate cancerous from hormonally hyperactive lesions inside the thyroid. This work compares acquisition protocols and reconstruction algorithms in an attempt to identify the most suitable approach for fast acquisition and efficient image reconstruction, suitable for localization of extended sources, such as lesions inside the thyroid. Our setup consists of a mini gamma camera with precise tracking information provided by a robotic arm, which also provides reproducible positioning for our experiments. Based on a realistic phantom of the thyroid including hot and cold nodules as well as background radioactivity, the authors compare "step and shoot" (SAS) and continuous data (CD) acquisition protocols in combination with two different statistical reconstruction methods: maximum-likelihood expectation-maximization (ML-EM) for time-integrated count values and list-mode expectation-maximization (LM-EM) for individually detected gamma rays. In addition, the authors simulate lower uptake values by statistically subsampling the experimental data in order to study the behavior of their approach without changing other aspects of the acquired data. All compared methods yield suitable results, resolving the hot nodules and the cold nodule from the background. However, the CD acquisition is twice as fast as the SAS acquisition, while yielding better coverage of the thyroid phantom, resulting in qualitatively more accurate reconstructions of the isthmus between the lobes. For CD acquisitions, the LM-EM reconstruction method is preferable, as it yields comparable image quality to ML-EM at significantly higher speeds, on average by an order of magnitude. This work identifies CD acquisition protocols combined with LM-EM reconstruction as a prime candidate for the wider introduction of SPECT imaging with flexible mini gamma cameras in the clinical practice.

Use of radioguided surgery in the surgical treatment of osteoid osteoma

Osteoid osteoma is the third most common benign bone tumor and complete surgical resection is definitive treatment. There are a limited number of publications on the use of radioguided surgery in this type of lesion. To assess the utility of radioguided surgery in our environment as a method of surgical treatment of this tumor. We retrospectively evaluated 12 patients (2 women and 10 men, age range 9-44 years) with clinical and radiological suspicion of osteoid osteoma. Bone scintigraphy showed foci of pathology uptake compatible with suspected lesion in the femur (4 cases), tibia (3), vertebral column (3), humerus (1) and talus (1). Subsequently patients underwent surgical treatment by radioguided surgery after injection of a dose of (99m)Tc-hydroxy diphosphonate. The nidus was removed using gamma probe and mini gamma camera, considering the technique to be completed when its counts decreased to the levels of the surrounding bone counts. Lesions were located in all patients (12 of 12), and were confirmed histologically in 8 of them, including an osteoblastoma. The cure rate was 100%, based on the disappearance of pain after a minimum follow-up of 6 months. Use of radioguided surgery in the surgical treatment of osteoid osteoma showed satisfactory results, with 100% efficiency in both lesion location and outcome of treatment and without major postoperative complications.

The use of radioguided surgery in the resection of osteoid osteoma

ObjectiveOsteoid osteoma is the third most common benign bone tumor and complete surgical resection is definitive treatment. There are a limited number of publications on the use of radioguided surgery in this type of lesion.To assess the utility of radioguided surgery in our environment as a method of surgical treatment of this tumor. Material and methodsWe retrospectively evaluated 12 patients (2 women and 10 men, age range 9–44 years) with clinical and radiological suspicion of osteoid osteoma. Bone scintigraphy showed foci of pathology uptake compatible with suspected lesion in the femur (4 cases), tibia (3), vertebral column (3), humerus (1) and talus (1). Subsequently patients underwent surgical treatment by radioguided surgery after injection of a dose of 99mTc-hydroxy diphosphonate. The nidus was removed using gamma probe and mini gamma camera, considering the technique to be completed when its counts decreased to the levels of the surrounding bone counts. ResultsLesions were located in all patients (12 of 12), and were confirmed histologically in eight of them, including an osteoblastoma. The cure rate was 100%, based on the disappearance of pain after a minimum follow-up of 6 months. ConclusionUse of radioguided surgery in the surgical treatment of osteoid osteoma showed satisfactory results, with 100% efficiency in both lesion location and outcome of treatment and without major postoperative complications.

Mini gamma camera “sentinela 102” in post-neoadjuvant chemotherapy (NAC) for guiding surgical treatment in locally advanced breast cancer (LABC) patients

Mini gamma camera “sentinela 102” in post-neoadjuvant chemotherapy (NAC) for guiding surgical treatment in locally advanced breast cancer (LABC) patients

Radioguided Parathyroidectomy with Portable Mini Gamma-Camera for the Treatment of Primary Hyperparathyroidism.

Background. A proper localisation of pathological parathyroid glands is essential for a minimally invasive approach in the surgical treatment of primary hyperparathyroidism (PHP). The recent introduction of portable mini gamma-cameras (pMGCs) enabled intraoperative scintigraphic scanning. The aim of our study is to evaluate the efficacy of this new method and compare it with the preoperative localisation surveys. Methods. 20 patients were studied; they were evaluated preoperatively by neck ultrasound and 99mmTc-sestaMIBI-scintigraphy and intraoperatively with the pMGC IP Guardian 2. The results obtained from the three evaluations were compared. Results. The pMGC presented a sensitivity of 95%, a specificity of 98.89%, and a diagnostic accuracy of 98.18%, which were higher than those of preoperative ultrasound (sensitivity 55%; specificity 95%; diagnostic accuracy 87%) and scintigraphy with 99mmTc-sestaMIBI (sensitivity 73.68%; specificity 96.05%; diagnostic accuracy 91.58%). Conclusions. The pMGC can be used effectively as an intraoperative method to find the correct location of the pathological parathyroid glands. The pMGC is more reliable than the currently used preoperative and intraoperative localisation techniques.

FhSPECT-US guided needle biopsy of sentinel lymph nodes in the axilla: is it feasible?

Until now, core needle biopsy of the axillary sentinel lymph nodes in early stage breast cancer patients is not possible, due to the lack of a proper combination of functional and anatomical information. In this work we present the first fully 3D freehand SPECT--ultrasound fusion, combining the advantages of both modalities. By using spatial positioning either with optical or with electromagnetic tracking for the ultrasound probe, and a mini gamma camera as radiation detector for freehand SPECT reconstructions, we investigate the capability of the introduced multi-model imaging system, where we compare both 3D freehand SPECT and 3D ultrasound to ground truth for a realistic breast mimicking phantom and further analyze the effect of tissue deformation by ultrasound. Finally, we also show its application in a real clinical setting.

The Intraoperative Mini Gamma Camera in Primary Hyperparathyroidism Surgery

Introduction and objectivesThe evolution of primary hyperparathyroidism surgical treatment has been improved after the arrival of new techniques that allow for better parathyroid gland tracking. A mini gamma camera has recently been developed that makes it possible to take intraoperative parathyroid gammagraphies.The objective of this study was to evaluate the utility of this technique. MethodWe prospectively studied 29 patients with primary hyperparathyroidism, comparing the diagnostic effectiveness of the MGP with the results obtained with preoperative techniques (ultrasound scan plus Tc99m-sestamibi gammagraphy). ResultsThe sensitivity and specificity of the mini gamma camera were superior to those of the preoperative techniques, applied to the lateral neck as well as to the face of the neck (lateral: 89.6% sensitivity and 96.15% specificity compared to 79.31% and 92.59% respectively; and neck face: sensitivity and specificity 83.33% and 90.91% against 48.39% and 72.73%). ConclusionsThe portable mini gamma camera accurately tracks pathologic parathyroid glands. In that sense, it could be useful when considering a radio-guided surgery with minimal parathyroid invasion.

La minigammacámara intraoperatoria en la cirugía del hiperparatiroidismo primario

Introduction and objectivesThe evolution of primary hyperparathyroidism surgical treatment has been improved by the arrival of new techniques that allow for better parathyroid gland tracking. A mini gamma camera has recently been developed that makes it possible to take intraoperative parathyroid gammagraphies.The objective of this study was to evaluate the utility of this technique. MethodWe prospectively studied 29 patients with primary hyperparathyroidism, comparing the diagnostic effectiveness of the MGP with the results obtained with preoperative techniques (ultrasound scan plus Tc99m-sestamibi gammagraphy). ResultsThe sensitivity and specificity of the mini gamma camera was superior to those of the preoperative techniques, applied to the lateral neck as well as to the face of the neck (lateral: 89.6% sensitivity and 96.15% specificity compared to 79.31% and 92.59% respectively; and neck face: sensitivity and specificity 83.33% and 90.91% against 48.39% and 72.73%). ConclusionsThe portable mini gamma camera accurately tracks pathologic parathyroid glands. In that sense, it could be useful when considering a radio-guided surgery with minimal parathyroid invasion.

A Hybrid Camera for simultaneous imaging of gamma and optical photons

We present a new concept for a medical imaging system, the Hybrid Mini Gamma Camera (HMGC). This combines an optical and a gamma-ray camera in a co-aligned configuration that offers high spatial resolution multi-modality imaging for superimposition of a scintigraphic image on an optical image. This configuration provides visual identification of the sites of localisation of radioactivity that would be especially suited to medical imaging. An extension of the new concept using two hybrid cameras (The StereoScope) offers the potential for stereoscopic imaging with depth estimation for a gamma emitting source.

Image Synthesis Using a Mini Gamma Camera and Stereo Optical Cameras

We have previously developed a method that combines a mini gamma camera with an optical camera to synthesize the two kinds of images and help surgeons to easily identify sentinel lymph nodes on the gastric surface in cancer resection surgery. Since we assumed in this method that the object surface is flat, its application was limited. In this article, we extend this method so as to estimate the three-dimensional shape of the object from stereo optical cameras. A prototype system with a mini gamma camera and two optical cameras was constructed and a preliminary experiment with a rigid machine-made phantom was performed. From comparison with results obtained by the previous method, we confirmed the effectiveness of using the three-dimensional shape.

Feasibility of sentinel node detection in renal cell carcinoma: a pilot study

Lymphatic drainage from renal cell carcinoma is unpredictable and the therapeutic benefit and extent of lymph node dissection are controversial. We evaluated the feasibility of intratumoural injection of a radiolabelled tracer to image and sample draining lymph nodes in clinically non-metastatic renal cell carcinoma. Eight patients with cT1-2 cN0 cM0 (<6 cm) renal cell carcinoma prospectively received percutaneous intratumoural injections of (99m)Tc-nanocolloid under ultrasound guidance (0.4 ml, 225 MBq at one to four intratumoural locations depending on tumour size). Lymphoscintigraphy was performed 20 min, 2 h and 4 h after injection. After the delayed images a hybrid SPECT/CT was performed. SPECT was fused with CT to determine the anatomical localization of the sentinel node. Surgery with sampling was performed the following day using a gamma probe and a portable mini gamma camera. Eight patients, seven with right-sided renal cell carcinoma, were included with a mean age of 55 years (range: 45-77). The mean tumour size was 4 cm (range: 3.5-6 cm). Six patients had sentinel nodes on scintigraphy (two retrocaval, four interaortocaval, including one hilar) with one extraretroperitoneal location along the internal mammary chain. All nodes could be mapped and sampled. In two patients no drainage was visualized. Renal cell carcinomas were of clear cell subtype with no lymph node metastases. Sentinel node identification using preoperative and intraoperative imaging to locate and sample the sentinel node at surgery in renal cell carcinoma is feasible. Sentinel node biopsy may clarify the pattern of lymphatic drainage and extent of lymphatic spread which may have diagnostic and therapeutic implications.

Spinal osteoblastoma resection with radioguided surgery

Osteoblastoma is an uncommon primary neoplasm of the bone, with histological manifestations similar to an osteoid osteoma. Approximately 40% of these tumors are located in the spine, usually involving the posterior structures. This location may be associated with scoliosis and neurologic manifestations. Diagnostic imaging includes simple x-ray, CT scan, MRI and radionuclide studies. Bone scintigraphy demonstrates increased radiotracer accumulation. The standard treatment consists of open intralesional resection. Nevertheless, localization of nidus may be difficult and bone resection may be limited due to the proximity of the neural structures. We present the case of a patient with a spinal osteoblastoma in whom the use of radioguided surgery was performed with a gamma probe and mini gamma camera. This technique made it possible to accurately locate the tumor and perform effective removal of the nidus.

Extirpación de un osteoblastoma vertebral mediante cirugía radiodirigida

Osteoblastoma is an uncommon primary neoplasm of the bone, with histological manifestations similar to osteoid osteoma. Approximately 40% of them are located in the spine, usually involving the posterior structures. This location may be associated with scoliosis and neurologic manifestations. Diagnostic imaging includes simple X-ray, CT scan, MRI and radionuclide studies. Bone scintigraphy demonstrates an increased radiotracer accumulation. The standard treatment consists of open intralesional resection. Nevertheless, localization of nidus may be difficult and bone resection may be limited due to the proximity of the neural structures. We present the case of a patient with a spinal osteoblastoma in whom the use of radioguided surgery was performed through gamma probe and mini gamma camera. This technique made it possible to accurately locate the tumor and perform an effective removal of the nidus.

Thyroid Cancer Imaging In Vivo by Targeting the Anti-Apoptotic Molecule Galectin-3

BackgroundThe prevalence of thyroid nodules increases with age, average 4–7% for the U.S.A. adult population, but it is much higher (19–67%) when sub-clinical nodules are considered. About 90% of these lesions are benign and a reliable approach to their preoperative characterization is necessary. Unfortunately conventional thyroid scintigraphy does not allow the distinction among benign and malignant thyroid proliferations but it provides only functional information (cold or hot nodules).The expression of the anti-apoptotic molecule galectin-3 is restricted to cancer cells and this feature has potential diagnostic and therapeutic implications. We show here the possibility to obtain thyroid cancer imaging in vivo by targeting galectin-3.MethodsThe galectin-3 based thyroid immuno-scintigraphy uses as radiotracer a specific 99mTc-radiolabeled mAb. A position-sensitive high-resolution mini-gamma camera was used as imaging capture device. Human galectin-3 positive thyroid cancer xenografts (ARO) and galectin-3 knockout tumors were used as targets in different experiments in vivo. 38 mice with tumor mass of about 1 gm were injected in the tail vein with 100 µCi of 99mTc-labeled mAb to galectin-3 (30 µg protein/in 100 µl saline solution). Tumor images were acquired at 1 hr, 3 hrs, 6 hrs, 9 hrs and 24 hrs post injection by using the mini-gamma camera.FindingsResults from different consecutive experiments show an optimal visualization of thyroid cancer xenografts between 6 and 9 hours from injection of the radiotracer. Galectin-3 negative tumors were not detected at all. At 6 hrs post-injection galectin-3 expressing tumors were correctly visualized, while the whole-body activity had essentially cleared.ConclusionsThese results demonstrate the possibility to distinguish preoperatively benign from malignant thyroid nodules by using a specific galectin-3 radio-immunotargeting. In vivo imaging of thyroid cancer may allow a better selection of patients referred to surgery. The possibility to apply this method for imaging and treatment of other galectin-3 expressing tumors is also discussed.

An operative gamma camera for sentinel lymph node procedure in case of breast cancer

Large field of view gamma cameras are widely used to perform lymphoscintigraphy in thesentinel lymph nodes (SLN) procedure in case of breast cancer. However, they are not specified for thisapplication and their sizes do not enable their use in the operative room to control the excision of the allSLN. We present the results obtained with a prototype of a new mini gamma camera developed especiallyfor the operative lymphoscintigraphy of the axillary area in case of breast cancer. This prototype iscomposed of 10 mm thick parallel lead collimator, a 2 mm thick GSO:Ce inorganic scintillating crystalfrom Hitachi and a Hamamatsu H8500 flat panel multianode (64 channels) photomultiplier tube(MAPMT) equipped with a dedicated electronics. Its actual field of view is 50 × 50mm2. The gammainteraction position in the GSO scintillating plate is obtained by calculating the center of gravity of thefired MAPMT channels. The measurements performed with this prototype demonstrate the usefulness ofthis mini gamma camera for the pre, per and post-operative identification of SLN's and how itscomplementary role with an intraoperative handheld gamma probe enables to improve the efficiency ofthis practice. A 100 × 100mm2 field of view camera designated to cover the entire axillary area is underinvestigation.

Precise Localization of Sentinel Lymph Nodes and Estimation of Their Depth Using a Prototype Intraoperative Mini -Camera in Patients with Breast Cancer

The aim of this study was to evaluate the ability of a prototype intraoperative mini gamma-camera, the CarolIReS, with a 50 x 50 mm field of view, to precisely localize sentinel lymph nodes (SLNs) and to determine their depth in a series of patients with infiltrative breast cancer requiring SLN excision. With the use of phantoms, the broadness of the signal of an acquired projection was shown to linearly depend on its distance from the collimator. A preclinical ex vivo study of 25 excised SLNs demonstrated that SLN size did not influence depth estimation. The minimum activity threshold for successful use of the proposed method was determined. After a preoperative radioisotope injection and lymphoscintigraphy, the SLN was localized in a series of 11 patients using both the mini gamma-camera and a gamma-probe. During surgery, a ruler was used to measure the depth of all SLNs before their excision. Using the measured linear dependence of image broadness, we found that the expected SLN anatomic depth was compatible with its measured depth during surgery. This study showed that the mini gamma-camera efficiently estimated the location of SLNs in 3 dimensions.

Performance tests of two portable mini gamma cameras for medical applications

We have developed two prototypes of portable gamma cameras for medical applications based on a previous prototype designed and tested by our group. These cameras use a CsI(Na) continuous scintillation crystal coupled to the new flat-panel-type multianode position-sensitive photomultiplier tube, H8500 from Hamamatsu Photonics. One of the prototypes, mainly intended for intrasurgical use, has a field of view of 44 x 44 mm2, and weighs 1.2 kg. Its intrinsic resolution is better than 1.5 mm and its energy resolution is about 13% at 140 keV. The second prototype, mainly intended for osteological, renal, mammary, and endocrine (thyroid, parathyroid, and suprarenal) scintigraphies, weighs a total of 2 kg. Its average spatial resolution is 2 mm; it has a field of view of 95 x 95 mm2, with an energy resolution of about 15% at 140 keV. The main advantages of these gamma camera prototypes with respect to those previously reported in the literature are high portability and low weight, with no significant loss of sensitivity and spatial resolution. All the electronic components are packed inside the mini gamma cameras, and no external electronic devices are required. The cameras are only connected through the universal serial bus port to a portable PC. In this paper, we present the design of the cameras and describe the procedures that have led us to choose their configuration together with the most important performance features of the cameras. For one of the prototypes, clinical tests on melanoma patients are presented and images are compared with those obtained with a conventional camera.