Deep Few-view High-resolution Photon-counting Extremity CT at Halved Dose for a Clinical Trial.

The latest X-ray photon-counting computed tomography (PCCT) for extremity allows multi-energy high-resolution (HR) imaging for tissue characterization and material decomposition. However, both radiation dose and imaging speed need improvement for contrast-enhanced and other studies. Despite the success of deep learning methods for 2D few-view reconstruction, applying them to HR volumetric reconstruction of extremity scans for clinical diagnosis has been limited due to GPU memory constraints, training data scarcity, and domain gap issues. In this paper, we propose a deep learning-based approach for PCCT image reconstruction at halved dose and doubled speed in a New Zealand clinical trial. Particularly, we present a patch-based volumetric refinement network to alleviate the GPU memory limitation, train network with synthetic data, and use model-based iterative refinement to bridge the gap between synthetic and real-world data. The simulation and phantom experiments demonstrate consistently improved results under different acquisition conditions on both in- and off-domain structures using a fixed network. The image quality of 8 patients from the clinical trial are evaluated by three radiologists in comparison with the standard image reconstruction with a full-view dataset. It is shown that our proposed approach is essentially identical to or better than the clinical benchmark in terms of diagnostic image quality scores. Our approach has a great potential to improve the safety and efficiency of PCCT without compromising image quality.

99mTc-Sestamibi SPECT/CT and histopathological features of oncocytic renal neoplasia.

BACKGROUND: 99mTc-Sestamibi Single Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) contributes to the non-invasive differentiation of renal oncocytoma (RO) from renal cell carcinoma (RCC) by characterising renal tumours as Sestamibi positive or Sestamibi negative regarding their 99mTc-Sestamibi uptake compared to the non-tumoral renal parenchyma. PURPOSE: To determine whether 99mTc- Sestamibi uptake in renal tumour and the non-tumoral renal parenchyma measured using Standard Uptake Value (SUV) SPECT, has a beneficial role in differentiating RO from RCC. MATERIAL AND METHODS: Fifty-seven renal tumours from 52 patients were evaluated. In addition to visual evaluation of 99mTc-Sestamibi uptake, SUVmax measurements were performed in the renal tumour and the ipsilateral non-tumoral renal parenchyma. Analysis of the area under the receiver operating characteristic curve identified an optimal cut-off value for detecting RO, based on the relative ratio of 99mTc- Sestamibi uptake. RESULTS: Semiquantitative evaluation of 99mTc-Sestamibi uptake did not improve the performance of 99mTc- Sestamibi SPECT/CT in detecting RO. 99mTc- Sestamibi SPECT/CT identifies a group of mostly indolent Sestamibi-positive tumours with low malignant potential containing RO, Low-Grade Oncocytic Tumours, Hybrid Oncocytic Tumours, and a subset of chromophobe RCCs. CONCLUSION: The imaging limitations for accurate differentiation of Sestamibi-positive renal tumours mirror the recognised diagnostic complexities of the histopathologic evaluation of oncocytic neoplasia. Patients with Sestamibi-positive renal tumours could be better suited for biopsy and follow-up, according to the current active surveillance protocols.

99mTc-HMPAO-WBC SPECT/CT versus 18F-FDG-WBC PET/CT in chronic prosthetic joint infection: a pilot study.

PURPOSE: The aim of this study was to compare 99mTc-HMPAO-WBC-SPECT/CT combined with 99mTc-nanocollloid SPECT/CT and 18F-FDG-WBC-PET/CT combined with 99mTc-Nanocollloid SPECT/CT for the diagnosis and treatment evaluation of chronic prosthetic joint infection (PJI). METHODS: Patients with suspected chronic PJI were examined with 99mTc-HMPAO-WBC SPECT/CT, 18F-FDG-WBC PET/CT, and 99mTc-nanocolloid SPECT/CT (to visualize bone marrow). The location and patterns of uptake were noted and compared between the two leukocyte examinations. Both leukocyte examinations were evaluated visually for infection. The PET examinations were also evaluated semiquantitatively. Chronic PJI was verified clinically by microbial culture and successfully treated PJI was confirmed by 12 months symptom-free follow-up after cessation of antibiotics. RESULTS: Nineteen patients were included with 10 hip prostheses and nine knee prostheses. Fourteen were diagnosed with chronic PJI and five with successfully treated PJI. The sensitivity of visual evaluation of 99mTc-WBC-HMPAO SPECT/CT for all joints was 0.31 and for 18F-FDG-WBC PET/CT 0.38. The specificity was 0.80 and 0.83, respectively. All patients with a true-positive SPECT examination had a false-negative PET examination and vice versa. Semiquantitative evaluation of the hips gave an area under the curve of 0.905 using the iliac crest as the background. Semiquantitative evaluation of the knees did not produce significant results. CONCLUSION: This pilot study showed no difference in the sensitivity or specificity of 99mTc-HMPAO-WBC SPECT/CT and 18F-FDG-WBC PET/CT when combined with 99mTc-nanocollloid SPECT/CT in the diagnosis or treatment evaluation of suspected late chronic PJI.

Comparison of Regularized Reconstruction and Ordered Subset Expectation Maximization Reconstruction in the Diagnostics of Prostate Cancer Using Digital Time-of-Flight 68Ga-PSMA-11 PET/CT Imaging.

In prostate cancer, the early detection of distant spread has been shown to be of importance. Prostate-specific membrane antigen (PSMA)-binding radionuclides in positron emission tomography (PET) is a promising method for precise disease staging. PET diagnostics depend on image reconstruction techniques, and ordered subset expectation maximization (OSEM) is the established standard. Block sequential regularized expectation maximization (BSREM) is a more recent reconstruction algorithm and may produce fewer equivocal findings and better lesion detection. METHODS: 68Ga PSMA-11 PET/CT scans of patients with de novo or suspected recurrent prostate cancer were retrospectively reformatted using both the OSEM and BSREM algorithms. The lesions were counted and categorized by three radiologists. The intra-class correlation (ICC) and Cohen's kappa for the inter-rater reliability were calculated. RESULTS: Sixty-one patients were reviewed. BSREM identified slightly fewer lesions overall and fewer equivocal findings. ICC was excellent with regards to definitive lymph nodes and bone metastasis identification and poor with regards to equivocal metastasis irrespective of the reconstruction algorithm. The median Cohen's kappa were 0.66, 0.74, 0.61 and 0.43 for OSEM and 0.61, 0.63, 0.66 and 0.53 for BSREM, with respect to the tumor, local lymph nodes, metastatic lymph nodes and bone metastasis detection, respectively. CONCLUSIONS: BSREM in the setting of 68Ga PMSA PET staging or restaging is comparable to OSEM.

Preoperative detection of sentinel lymph nodes with hybrid SPECT/computed tomography imaging may improve the accuracy of sentinel lymph node biopsies in patients with early stages of cancer of the oesophagus or gastro-oesophageal junction.

OBJECTIVES: The aim of this study was to investigate the sentinel lymph node biopsy (SLNB) method in patients with cancer of the oesophagus or gastro-oesophageal junction (GOJ) guided by preoperative hybrid single-photon emission tomography/computed tomography (SPECT/CT) lymphoscintigraphy. METHODS: Thirty-nine patients with stage T1-T3, any N-stage, M0 cancer of the oesophagus or GOJ planned for curatively intended esophagectomy underwent preoperative SPECT/CT lymphoscintigraphy following endoscopically guided submucosal injection of radiocolloid and intraoperative radio-guided SLNB using a hand-held gamma scintillation device. RESULTS: The detection rate in preoperative SPECT/CT imaging was 88%. The median number of detected SLN stations in preoperative imaging was 1 (range 0-4). At least one suspected SLN was identified in all intraoperative SLNP procedures. In six cases, no lymph nodes were identified in the SLNB. In six cases, the SLNB was false negative. The sensitivity for successful SLNB procedures was 20%, the specificity was 100% and the accuracy was 75%. CONCLUSIONS: Preoperative SLN mapping using SPECT/CT yields a high number of detected SLN stations compared to previous studies using planar imaging. The accuracy of the SLNB method in patients with predominantly ≥T3-stage tumours and with a history of previous neoadjuvant treatment is poor, and the method is not recommended in these patient groups.

Comparison of acquisition protocols for ventilation/perfusion SPECT-a Monte Carlo study.

One of the most commonly used imaging techniques for diagnosing pulmonary embolism (PE) is ventilation/perfusion (V/P) scintigraphy. The aim of this study was to evaluate the performance of the currently used imaging protocols for V/P single photon emission computed tomography (V/P SPECT) at two nuclear medicine department sites and to investigate the effect of altering important protocol parameters. The Monte Carlo technique was used to simulate 4D digital phantoms with perfusion defects. Six imaging protocols were included in the study and a total of 72 digital patients were simulated. Six dually trained radiologists/nuclear medicine physicians reviewed the images and reported all perfusion mismatch findings. The radiologists also visually graded the image quality. No statistically significant differences in diagnostic performance were found between the studied protocols, but visual grading analysis pointed out one protocol as significantly superior to four of the other protocols. Considering the study results, we have decided to harmonize our clinical protocols for imaging patients with suspected PE. The administered Technegas and macro aggregated albumin activities have been altered, a low energy all purpose collimator is used instead of a low energy high resolution collimator and the acquisition times have been lowered.

18F FDG-PET/CT evaluation of histological response after neoadjuvant treatment in patients with cancer of the esophagus or gastroesophageal junction.

BACKGROUND: In most parts of the world, curatively intended treatment for esophageal cancer includes neoadjuvant therapy, either with chemoradiotherapy or chemotherapy alone, followed by esophagectomy. Currently 18F-FDG positron emission tomography/computed tomography (PET/CT) is used for preoperative disease staging, but is not well established in the evaluation of neoadjuvant treatment. PURPOSE: To evaluate changes in PET parameters in relation to the histological primary tumor response in the surgical specimen in patients randomized to neoadjuvant chemoradiotherapy or chemotherapy. MATERIAL AND METHODS: Patients were randomized between either neoadjuvant chemotherapy or chemoradiotherapy followed by esophagectomy.18F-FDG PET/CT exams were conducted at baseline and following neoadjuvant treatment. Standardized uptake ratio (SUR) values were measured in the primary tumor and compared as regards histological responders and non-responders as well as different treatment arms. RESULTS: Seventy-nine patients were enrolled and 51 were available for analysis. A significant rate of SUR reduction was observed ( P = 0.02) in the primary tumor in histological responders compared to non-responders. Changes in SUR were significantly greater in responders following chemoradiotherapy ( P = 0.02), but not following chemotherapy alone ( P = 0.49). There was no statistically significant difference in SUR in patients with a complete histological response compared to those with a subtotal response. CONCLUSION: Our results are similar to those of previous studies and show that changes in the rate of SUR can be used reliably to differentiate histological responders from non-responders after neoadjuvant treatment with either chemoradiotherapy or chemotherapy. Limitations of current PET technology are likely to restrict the possibility of accurately ruling out limited residual disease.

"Sentinel lymph node imaging with sequential SPECT/CT lymphoscintigraphy before and after neoadjuvant chemoradiotherapy in patients with cancer of the oesophagus or gastro-oesophageal junction - a pilot study".

BACKGROUND: In current best practise, curatively intended treatment for oesophageal cancer usually consists of neoadjuvant chemo-radiotherapy (nCRT) or perioperative chemotherapy, and oesophagectomy. Sentinel Lymph Node Biopsy (SLNB) has the potential to identify patients without lymph node metastases and thus improve the staging accuracy and influence treatment. The impact of neoadjuvant treatment on the lymphatic drainage of oesophageal cancers and subsequently the SLNB procedure in this tumour type has previously not been well studied. PURPOSE: To evaluate changes in lymphatic drainage patterns of the tumour in patients with cancer of the oesophagus or gastro-oesophageal junction (GOJ) using Sentinel Lymph Node (SLN) hybrid SPECT/CT lymphoscintigraphy before and after nCRT. METHODS: Patients with clinical stage T2-T3, any N-stage, M0 cancer of the oesophagus or GOJ underwent endoscopically guided peri-/intratumoral injection of radio-colloid followed by hybrid SPECT/CT lymphoscintigraphy prior to, and once again following, nCRT. SPECT/CT images were evaluated to number and location of SLNs and compared between the two examinations. RESULTS: Ten patients were included in this pilot trial. SPECT/CT lymphoscintigraphy was performed in twenty procedures. The same Sentinel Lymph Node station before and after nCRT was observed in one single patient. In two patients, no SLN was detected before nCRT. In three patients no SLN was detected following nCRT. In four patients, the SLN stations were not the same station at baseline compared to follow-up examination. CONCLUSIONS: The reproducibility SLN detection in patients with cancer of the oesophagus/GOJ following nCRT was very poor. nCRT appears to alter lymphatic drainage patterns and thus may affect detection of SLNs and potentially also the accuracy of an SLNB in these patients. On the basis of these initial results, we abort further patient recruitment in our institution. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry (ANZCTR). Identifier ACTRN12618001433291 . Date registered: 27/08/2018. Retrospectively registered.

Impact of previous surgery on sentinel lymph node mapping: Hybrid SPECT/CT before and after a unilateral diagnostic breast excision.

BACKGROUND: Earlier studies have shown conflicting results regarding the accuracy of sentinel lymph node biopsy after previous breast surgery, especially after a surgical biopsy. PURPOSE: To compare lymph drainage patterns before and after a diagnostic unilateral surgical biopsy using the exact anatomical localisation of sentinel lymph nodes defined by SPECT/CT. MATERIAL AND METHODS: Thirty-seven women planned for unilateral surgical excision of an unsuspicious breast lesion were prospectively examined between September 2011 and January 2015. Hybrid SPECT/CT lymphoscintigraphy of the thorax and neck region with bilateral subareolar injections of 99mTc-Nanocoll was performed one week before and six weeks after surgery. The non-operated side served as a control. The primary outcome measure was the concordance between pre- and postoperative number and localisation of sentinel lymph nodes. RESULTS: Sentinel lymph node detection rate with SPECT/CT on operated sides was 91.9 per cent (34 of 37 procedures), to be compared with a detection rate of 93.7 per cent on all non-operated sides (104 of 111 procedures, P = 0.771). Partial or total concordance regarding the localisation and number of sentinel lymph nodes was 85.7 per cent (30 out of 35) on operated and 88.9 per cent (32 out of 36 patients) on non-operated breast sides (P = 0.735). CONCLUSION: Breast surgery slightly decreased the concordance between pre- and postoperative sentinel lymph nodes, but this finding was not statistically significant. Our results thus support that it is feasible to perform a sentinel lymph node biopsy after previous breast excisional surgery with an acceptable level of safety.