Diagnostic Scan Research Articles

Occupational radiation dose on the hand of assisting medical staff in diagnostic CT scans.

Chronic radiation exposure increases the risk of skin damage of medical personnel engaged in radiology. However, hand dose measurements in computed tomography (CT) for diagnostic purposes have not been evaluated. The occupational radiation dose to the hands of CT assistants was herein investigated to evaluate its compliance with the equivalent dose limit for the hand (500mSv/year). The occupational doses of nine CT assistants were measured in 89 cases (April 2017-May 2018) by installing radio-photoluminescence glass dosemeters (GD-302M) (70-μm dose-equivalent conversion coefficient=0.37) on the dorsal aspect of both hands. The occupational dose to the hand was the highest with head holding (right: 1.14mSv/CT scan, left: 1.07mSv/CT scan). Considering the results for annual work, even for head holding, the hand dose of the CT-assisting personnel was insignificant. However, CT assistants should be mindful of the possibility of locally higher doses to hands.

SAT553 A Case of Metastatic Functional Papillary Thyroid Cancer in the Setting of Graves’ Disease

Abstract Disclosure: N. Manuel: None. S.J. Sternlieb: None. J. Dendy: None. Q.Z. Iqbal: None. A Case of Metastatic Functional Papillary Thyroid Cancer In the Setting of Graves’ DiseaseManuel, N., Sternlieb, S., Grissett, B., Iqbal, Q., Dendy, J. Background: Grave’s disease (GD) and papillary thyroid cancer (PTC) can be concomitant diseases. We report a rare case of metastatic PTC with concomitant GD leading to symptomatic hyperthyroidism despite total thyroidectomy. Clinical Case: A 58-year-old woman with longstanding history of thyroid nodules and left dominant nodule with benign biopsy on multiple occasions presented to her PCP with dyspnea, weight loss and globus sensation. CT of the chest was obtained revealing tracheal deviation from neck mass, mediastinal lymphadenopathy and multiple pulmonary nodules. Biopsy of lung nodule showed follicular features consistent with tumor cells of thyroid origin. She had a total thyroidectomy with central neck dissection with a final diagnosis of left sided 5 cm infiltrative follicular variant papillary thyroid carcinoma. Thyroid hormone replacement was initiated and on follow up 4 weeks later she was noted to be tachycardic at weight-based dose. At that time TSH was <0.010 uIU/mL (0.400 - 4.00), free T4 was 1.96 ng/dL (0.71 – 1.51) and Thyroglobulin was found to be 31516 ng/dL (Athyrotic <0.1). Prior to planned RAI she developed symptoms of dyspnea on exertion and edema and was sent to the ER for abnormal D. Dimer. Workup for PE was negative including CTA of the chest. A follow up visit showed further symptoms of hyperthyroidism with worsening fatigue, dyspnea, palpitations and new onset tremor. Levothyroxine dose was decreased further but 2 weeks later she returned to the ER with worsened thyroid function tests, and she was admitted for symptomatic hyperthyroidism. Levothyroxine was held and she was placed on PTU and propranolol. Given the overt symptomatic hyperthyroidism there were concerns for either Jod-Basedow phenomenon from iodine load with recent imaging or for hyperfunctioning PTC metastasis as the cause. Thyrotropin receptor antibody level was checked to further clarify and was elevated at 22 IU/L (0.00 – 1.75) consistent with GD. An I-131 diagnostic whole-body scan demonstrated small foci of right thyroid bed remnant and iodine-avid metastases involving mediastinal nodal disease as well as pulmonary and osseous metastases. She then underwent RAI therapy with 104.5 mCi I-131 without Thyrogen stimulation. Follow up whole body scan showed persistence of iodine-avid metastasis without any new foci of uptake compared to pretreatment scans. Conclusion: Although the coexistence of them is rare, GD should be put into the differential of rapidly progressive metastatic PTC especially if patient markedly hyperthyroid on lower doses of thyroid hormone. While functional thyroid carcinoma is rare, with less than 100 cases in literature, thorough investigation should be completed in order to not miss this concomitant disease process. Presentation Date: Saturday, June 17, 2023

SAT559 Challenges Involved in Managing a Paraplegic Patient with Metastatic Papillary Thyroid Cancer Requiring Radioactive Iodine Therapy

Abstract Disclosure: G. Al-Naqeeb: None. E. Munger: None. P. Veeraraghavan: None. C. Cochran: None. P. Bernaldez: None. P. Wong: None. N. Devaraj: None. T. Fisher: None. K. Lee: None. O. Owoade: None. I. Jones: None. S. Gubbi: None. J. Klubo-Gwiezdzinska: None. Background: High radioactive iodine (RAI) therapy doses utilized for treating thyroid cancer patients require a 24-48-hour radiation isolation period until the total effective dose equivalent exposure (TEDE) to the general population does not exceed 5mSv. We present a unique scenario of a paraplegic patient with metastatic papillary thyroid cancer (PTC) requiring RAI therapy and the radiation precaution strategies implemented by our team to reduce radiation exposure risk to the medical staff.A 69-year-old female with RAI-refractory tall cell-variant PTC (pT4aN1bM1; BRAF V600E pathogenic variant) with pulmonary metastases, paraplegia due to a motor vehicle accident with neurogenic bowel and bladder, was referred to our center for management of PTC. Laboratory data revealed a serum thyroglobulin of 2313 ng/mL (normal=1.6-59.9), and anatomical imaging showed numerous pulmonary nodules that had increased in size and number compared to prior imaging from 6 months ago. Due to disease progression, re-differentiation therapy with dabrafenib was initiated. After 3-months of dabrafenib therapy, a diagnostic thyroid hormone withdrawal-aided 131I scan with dosimetry revealed a significant re-induction of RAI uptake in pulmonary lesions and it was determined that therapy with an RAI dose of 200 mCi would not exceed a safe radiation exposure to the bone marrow of 200 rads. A multi-step mitigation strategy was developed based on a multidisciplinary team meeting and appropriate mock sessions. Stay times were estimated for individuals based on historical TEDE following the care of non-paralyzed patients receiving similarly prescribed activity. To minimize exposure to nursing staff, the patient’s Foley catheter was shielded with lead lining and bowels were emptied the night before RAI with a laxative. For each entry, posted safety sheets were updated with one-foot and one-meter isodose lines and on-contact exposure rates. Two nurses and one radiation safety staff member donned full personal protective equipment (PPE; full body suit, double gloves, booties, face covering) in the staging area and entered via lane one. While nursing provided direct care needs, radiation safety staff emptied the shielded catheter, organized clutter and packaged radioactive waste containers. Upon completion of duties, staff exited via lane two, removed PPE, and performed a full personnel contamination survey in the staging area. The patient successfully underwent RAI therapy with 200 mCi. Six months later the serum thyroglobulin had reduced to 48.4ng/ml with a substantial reduction in pulmonary metastatic tumor burden on imaging studies. Conclusion: Post-RAI therapy care of paralyzed patients during radiation isolation poses a unique challenge to medical staff warranting modifications in routine care practices, which can be achieved safely through optimal planning and enhanced training. Presentation Date: Saturday, June 17, 2023

Analysis and prediction of liver volume change maps derived from computational tomography scans acquired pre- and post-radiation therapy

External beam radiation therapy (EBRT) of liver cancers can cause local liver atrophy as a result of tissue damage or hypertrophy as a result of liver regeneration. Predicting those volumetric changes would enable new strategies for liver function preservation during treatment planning. However, understanding of the spatial dose/volume relationship is still limited. This study leverages the use of deep learning-based segmentation and biomechanical deformable image registration (DIR) to analyze and predict this relationship. Pre- and Post-EBRT imaging data were collected for 100 patients treated for hepatocellular carcinomas, cholangiocarcinoma or CRC with intensity-modulated radiotherapy (IMRT) with prescription doses ranging from 50 to 100 Gy delivered in 10–28 fractions. For each patient, DIR between the portal and venous (PV) phase of a diagnostic computed tomography (CT) scan acquired before radiation therapy (RT) planning, and a PV phase of a diagnostic CT scan acquired after the end of RT (on average 147 ± 36 d) was performed to calculate Jacobian maps representing volume changes in the liver. These volume change maps were used: (i): to analyze the dose/volume relationship in the whole liver and individual Couinaud’s segments; and (ii): to investigate the use of deep-learning to predict a Jacobian map solely based on the pre-RT diagnostic CT and planned dose distribution. Moderate correlations between mean equivalent dose in 2 Gy fractions (EQD2) and volume change was observed for all liver sub-regions analyzed individually with Pearson correlation r ranging from −0.36 to −067. The predicted volume change maps showed a significantly stronger voxel-wise correlation with the DIR-based volume change maps than when considering the original EQD2 distribution (0.63 ± 0.24 versus 0.55 ± 23, respectively), demonstrating the ability of the proposed approach to establish complex relationships between planned dose and liver volume response months after treatment, which represents a promising prediction tool for the development of future adaptive and personalized liver radiation therapy strategies.

Assessing the Appropriateness of Repeat MRI Scan Requests Within a Foot and Ankle Department

Category: Other Introduction/Purpose: With diagnostic resources often in great demand, it is important to ensure clinicians request investigations appropriately. Unnecessary radiological investigations are costly and delay patient care. This study aimed to assess the incidence and appropriateness of repeat MRI scans being requested in a single foot and ankle unit, to identify areas which can be improved. Methods: This was a retrospective analysis of 1322 scans between October-2019 to October-2022. We included all patients who had a diagnostic MRI scan requested after being assessed in our foot-and-ankle clinics. Assessments were made on the proportion of repeat scans, the seniority of requester, the indications put forward for the repeat scan, the modality of patient assessment (telephone vs face-to-face appointment), and the impact on patient management. A scan was considered a repeat, if the same anatomical location was scanned within a 3-year period. Scans were deemed appropriate if they were: part of a clinical trial, for tumour/infection/stress-fracture monitoring, for new trauma, pre-operative planning, following agreement in MDT discussions, or following significant changes in clinical symptoms. We expected that scans should ideally only be requested where the result is expected to influence management and that a scan should not be repeated without evidence of change in clinical symptoms (unless for monitoring). Results: Over the 3-year period, 6.5% of MRI scans performed were considered repeat scans. The average time between initial and repeat scans was 13.1±8.6months (range 1-33 months). 88% of patients had only one repeat scan. The majority(58%) of repeat scans were requested by non-senior clinicians. In total, 47/85(55%) scans were deemed appropriate. 75% of the patients in this cohort had been assessed face-to-face. Twenty of these scans were repeated for significant change in clinical symptoms and 50% meaningfully influenced management plans. Conversely, 38/85(45%) repeat scans did not have strong clinical indications. The majority(80%) of these were requested by non- senior clinicians and 50% were requested after a telephone review. From the scans requested by the non-senior clinicians, none(0%) had a meaningfully influence on patients’ management plans. Conclusion: This study highlights that although repeat MRI scans were not common, they seldom influenced patient management unless there was a meaningful change in patient symptoms. MRI scans were more likely to influence management when initiated by senior clinicians and following a face-to-face assessment. In order to streamline patient care and reduce unnecessary investigations we propose a protocol to guide the requesting of repeat scans. This protocol includes identifying significant symptomatic change, in-person review, and senior clinician or multi-disciplinary input when a repeat scan is being considered.

A deep learning segmentation method to assess dose to organs at risk during breast radiotherapy

Background and purposeContouring of organs at risk is important for studying health effects following breast radiotherapy. However, manual contouring is time-consuming and subject to variability. The purpose of this study was to develop a deep learning-based method to automatically segment multiple structures on breast radiotherapy planning computed tomography (CT) images. Materials and methodsWe used data from 118 patients, including 90 diagnostic CT scans with expert structure delineations for training and 28 breast radiotherapy planning CT images for testing. The radiotherapy CT images also had expert delineations for evaluating performance. We targeted a total of eleven organs at risk including five heart substructures. Segmentation performance was evaluated using the metrics of Dice similarity coefficient (DSC), overlap fraction, volume similarity, Hausdorff distance, mean surface distance, and dose. ResultsThe average DSC achieved on the radiotherapy planning images was 0.94 ± 0.02 for the whole heart, 0.96 ± 0.02 and 0.97 ± 0.01 for the left and right lung, 0.61 ± 0.10 for the esophagus, 0.81 ± 0.04 and 0.86 ± 0.04 for left and right atrium, 0.91 ± 0.02 and 0.84 ± 0.04 for left and right ventricle, and 0.21 ± 0.11 for the left anterior descending artery (LAD), respectively. Except for the LAD, the median difference in mean dose to these structures was small with absolute (relative) differences < 0.1 Gy (6 %). ConclusionsExcept for the LAD, our method demonstrated excellent performance and can be generalized to segment additional structures of interest.

Pilot Study of a Novel Ring Gantry-Based PET/CT Linear Accelerator in Patients with Prostate Cancer Receiving [18F]-DCFPyL for PSMA PET Imaging.

The RefleXion X1® system is a hybrid PET imaging-radiotherapy system that uses real-time positron emissions from a PET tracer to deliver biologically guided radiotherapy (BgRT). This study (NCT05470699) evaluated the hypothesis that the X1 PET imaging subsystem would be able to detect [18F]-DCFPyL PSMA PET signal sufficient to generate a deliverable BgRT plan in patients with prostate cancer. Patients with prostate cancer scheduled for a diagnostic [18F]-DCFPyL PSMA PET scan as part of standard of care were eligible. Upon completion of the diagnostic PSMA PET scan, images were transferred to the radiotherapy planning system for target identification and contouring. If at least one PET avid tumor lesion was identified, the patient was then scanned on the X1 unit. BgRT planning was performed on each X1 scanned patient. The target lesion volume, activity concentration (AC) and normalized target signal (NTS) were acquired. Successful and deliverable BgRT plans required that the target AC was ≥ 5 kBq/ml and NTS ≥ 2.7. Twenty-six patients underwent [18F]-DCFPyL PET scans (13 with rising PSA after surgery or radiotherapy, 6 with known metastases and 7 with newly diagnosed high-risk prostate cancer). Median (range) PSA was 3.40 (0.04-122). In 16 patients a PET avid tumor was identified and contoured for planning (4 lymph nodes, 5 bone, 6 prostate gland, and 1 prostate bed). In 13 patients the target lesion was visualized on the X1 PET scan, while in 3 patients the target lesion was too close to the bladder to be clearly visualized. BgRT planning was feasible and met standard of care published SBRT organ dose constraints in 8 patients (3 prostate gland, 3 bone, 2 lymph nodes). BgRT planning was not feasible in 8 patients due to insufficient AC, low NTS or proximity of the target lesion to the PET avid bladder. The accompanying table compares median (range) target volume, AC and NTS for feasible versus not feasible plans. This is the first study to investigate the feasibility of using [18F]-DCFPyL PET imaging for BgRT plan generation on the X1 system in patients with prostate cancer. Lesions that are relevant to radiotherapy of prostate cancer can be visualized including lymph node and bone metastases. A dedicated BgRT workflow with PSMA PET imaging on the X1 at 60 minutes post injection will result in higher target AC and will optimize BgRT planning. PET avid lesions < 1 cm or close to the bladder may make BgRT planning challenging. [18F]-DCFPyL-guided BgRT is technically feasible using the RefleXion X1. BgRT using targeted PET radiopharmaceuticals to biologically guide external beam radiotherapy represents a promising new dimension in radiation oncology and warrants further investigation.

Endoscopic finding versus CT nose and paranasal sinuses appearance in chronic rhinosinusitis: A comparative study

Background: Chronic rhinosinusitis (CRS) is a common disease encountered in otorhinolaryngology field, however, there is no consensus about its definitive diagnostic method. Nasal endoscopy and sinus CT scan are successfully used as diagnostic modalities. Aim: To evaluate the correlation between nasal endoscopy as compared to sinus CT in CRS diagnosis. Material and methods: A prospective randomized study, in which, 80 patients attended outpatient ENT clinic, from March 2018 to April 2019, whom met the diagnostic criteria of CRS guidelines, were recruited, and the diagnostic modalities were; nasal endoscopy using Lund-Kennedy scoring system, followed with sinus CT scan using Lund-Mackay scoring system within 1 week. Both modalities were compared, with focus on pathological findings, as well as, the specificity, sensitivity, positive predictive value and negative predictive values, in addition, to the anatomic variations data. All the above-mentioned respective parameters were statistically analyzed. Results: Nasal obstruction (92.5%), maxillary sinus (82.5%) with mucosal thicken opacity (83.75%) by CT scan, and muco- -purulent middle meatus discharge (73.75%) by nasal endoscopy. The association between diagnostic endoscopy and CT scan had P value = 0.001 by Student-t-test, and r = 0.734 by Pearson`s correlation coefficient. Diagnostic accuracy of nasal endoscopy was 95%, sensitivity was 91.6 % (95% CI 87.38–93.67%), specificity was 88.3% (95% CI 85.91–89.59%), while positive predictive value 81.7% and negative predictive value was 79.87%. Conclusion: Strong and statistical correlation between the nasal endoscopic and sinus CT findings, also between nasal obstruction symptom and nasal endoscopy, while, no significant difference on anatomical variants data.

Differential Diagnosis between Parapyelic Cyst and Pyeloureteral Junction: A Clinical Case Study

Objectives: Intra-sinus renal cysts or parapyelic cysts represent a rare form of renal cysts. They are often associated with lower back pain. Symptomatic cases can be treated with percutaneous puncture and sclerotherapy, but due to the proximity to the renal hilum, the treatment of these cysts has undergone significant changes. Thus, percutaneous treatment has become contraindicated due to the potential for complications. While laparoscopic treatment appears to be the most suitable and effective technique, open surgery still has its indications, especially for large cysts and cases where there is diagnostic uncertainty along with an associated junction abnormality, as is the case in our study. Patients and Methods: We report a case of a right parapyelic cyst revealed by acute right pyelonephritis, with a diagnostic scan suggesting pyeloureteral junction syndrome secondary to a subpyelic crossing with an 8 cm parapyelic cyst, with contrast material passing into the cyst. Due to diagnostic uncertainty and operative difficulties under laparoscopy, a right lumbotomy was performed, allowing for the resection of an 8 cm parapyelic cyst and confirming the absence of an associated junction abnormality, without intraoperative complications. Results: 450 cc of citrine yellow fluid was recovered, with a permeable junction and absence of the lower polar vessel. Postoperative evolution was favorable both medically and surgically, with removal of the urinary catheter and JJ stent on postoperative day 5. Conclusion: Surgical treatment of parapyelic cysts through lumbotomy remains of interest as an effective approach, especially in cases of diagnostic uncertainty, with low morbidity and a short convalescence period.

Dosimetric Plan Evaluation of Biology Guided Radiotherapy Using [18F]-DCFPyL PSMA Radiotracer in Patients with Prostate Cancer

The X1 system represents a cutting-edge solution in radiotherapy delivery, with its capability to perform Biology Guided Radiotherapy (BgRT). The system utilizes real-time positron emission tomography (PET) signal as biological fiducials to provide tracked dose delivery and is initially available for use with [18F]-Fluorodeoxyglucose (FDG). The aim of this research study is to assess the quality of BgRT treatment plans for prostate cancer using patients' PSMA PET images obtained on the X1 system. Sixteen patients with at least one PET-avid tumor identified on their whole-body diagnostic PSMA PET scan were selected. These patients were scanned on X1 following their diagnostic scan without additional radiotracer administration. Based on the X1 PET images, a BgRT plan was created for each patient, with the prescription dose determined by the location of treatment sites. The planning objectives of organs-at-risk (OARs) were established in accordance with the 2018 Timmerman guidelines. Target coverage objective was the dose covering 95% (D95%) of the planning target volume (PTV) to be higher than 100%. The following parameters were analyzed: PTV D95%, the minimal dose (Dmin) of gross tumor volume (GTV), plan maximum dose (Dmax), conformity index (CI), gradient index (GI), and maximum point dose (D0.03cc) to the nearest OARs. The X1 BgRT planning system also generated dose volume histogram (DVH) bounds, which model variations in BgRT delivery. The low boundary of GTV Dmin, representing the minimum GTV dose in the worst-case scenario, was recorded. BgRT plans were created for all patients, except for one where the target signal was indistinguishable from the bladder. The prescription dose was 2700 cGy or 3000 cGy in 3 fractions for lymph node lesions, 2400 cGy to 3000 cGy in 3 fractions for bone metastasis, and 4500 cGy in 5 fractions for lesions in prostate. All plans met the dose constraints for OARs as per the Timmerman guidelines. The Dmax of all plans was 129.9% ± 6.9% (mean ± standard deviation). The PTV D95% and GTV Dmin were 101.7% ± 1.0% and 111.0% ± 7.6%, respectively. The low boundary of GTV Dmin was 95.9% ± 5.8%. The CI and GI were 1.22 ± 0.11 and 9.40 ± 2.12, respectively. The D0.03cc to nearest OARs was 84.6% ± 25.4%. The estimated treatment time was 699 ± 228 seconds. This study is a pioneering effort to evaluate the quality of BgRT plans for prostate cancer patients using the [18F]-DCFPyL PSMA radiotracer. Our results showed that all BgRT plans met the planning objectives defined in the Timmerman protocol. BgRT with [18F]-DCFPyL represents a promising treatment modality for patients with prostate cancer. Further research is needed to validate this approach, including a comprehensive assessment of the dosimetric and tracking accuracy through physical measurements.

Radiomics Based Assessment of Tumor Infiltrating CD8 T-Cells Predicts Induction Systemic Therapy Response in HPV+ Oropharyngeal Cancer: Exploratory Analysis of Prospective Trials

The adaptive immune system is increasingly recognized to be important for tumor control in HPV+ oropharyngeal cancer (HPV+OPC), and pre-clinical models suggest tumor specific T-cell priming occurs in draining lymph nodes. De-escalation strategies incorporating T-cell infiltration present a novel prognostic biomarker. The purpose of this study was to examine the utility of a validated radiomics model of CD8 T-cell infiltration within the framework of 2 prospective HPV+OPC response-adaptive de-escalation trials. We hypothesized that nodal radiomics scores (RS) would be correlated with response to induction systemic therapy. Patients enrolled on 2 prospective phase II response adapted de-escalation trials for low- and high-risk HPV+OPC were included in the analysis. Patients received induction chemotherapy and chemoimmunotherapy in trials 1 and 2, respectively. Primary tumors and nodes were retrospectively delineated on diagnostic CT scans before and after induction therapy to ascertain volumetric tumor burden & response. RS were generated on pre-induction scans for both primary tumors and nodes. RS and tumor response were dichotomized using a 50% threshold (high vs low, responder vs non-responder, respectively). Linear regression was used to evaluate the correlation between % volume change in tumor burden and RS. Fisher's exact test was used to evaluate concordance between RS and tumor response. A total of 87 patients (N = 47 Trial 1, N = 40 Trial 2) were evaluable. The mean post-induction therapy reduction in primary and nodal volumetry was 80.7% and 67% respectively. Primary and nodal RS were not associated with primary (T1/T2 vs T3/T4) or nodal stage (N1-N2b vs N2c-N, p > 0.10 both). Both primary and nodal RS were correlated with % volume change, r = 0.24 (p = 0.034) and r = 0.37 (p = 0.002), respectively. The mean difference in % volume change in primary and node, using the RS, was 11.13% (p = 0.015) and 17. 69% (p = 0.004). There was no association between primary tumor RS and total lesion responder status (p = 0.312). However, there was an association between high vs low nodal RS and total lesion responder status (p = 0.005). This is the first report of a validated radiomics score of CD8-T cell infiltration in HPV+OPC to predict response to systemic therapy. While radiomics scores in both the primary and nodes were associated with percent volume response, this association was stronger in nodes. Higher nodal radiomics scores were associated with improved volume reduction in total lesion burden. This effect however was not observed in the primary tumor. CD8-T cell infiltration in nodes, but not in the primary tumor, was associated with overall tumor response after systemic induction therapy in HPV+ oropharyngeal cancer.

Deep Learning-Based Multi-Modality Segmentation of Primary Gross Tumor Volume in CT and MRI for Nasopharyngeal Carcinoma

The delineation of primary gross tumor volume (GTV) of nasopharyngeal carcinoma (NPC) is an essential step for radiotherapy planning. In clinical practice, radiation oncologists manually delineate the GTV in planning CT with the help of diagnostic MRI. This is because NPC tumors are closely adjacent to many important anatomic structures, and CT and MRI provide complementary strength to accurately determine the tumor extension boundary. Manual delineation is time-consuming with the potential registration errors between MRI and CT decreasing the delineation accuracy. In this study, we propose a fully automated GTV segmentation method based on CT and MRI by first aligning MRI to CT, and then, segmenting the GTV using a multi-modality deep learning model. We collected 104 nasopharyngeal carcinoma patients with both planning CT and diagnostic MRI scans (T1 & T2 phases). An experienced radiation oncologists manually delineated the GTV, which was further examined by another senior radiation oncologist. Then, a coarse to fine cross-modality registration from MRI to CT was conducted as follows: (1) A rigid transformation was performed on MRI to roughly align MRI to CT with similar anatomic position. (2) Then, the region of interest (RoI) on both CT and rigid-transformed MRI were cropped. (3) A leading cross-modality deformable registration algorithm, named DEEDS, was applied on the cropped MRI and CT RoIs to find an accurate local alignment. Next, using CT and registered MRI as the combined input, a multi-modality deep segmentation network based on nnUNet was trained to generate the GTV prediction. 20% patients were randomly selected as the unseen testing set to quantitatively evaluate the performance. The quantitative NPC GTV segmentation performance is summarized in Table 1. The deep segmentation model using CT alone achieved reasonable high performance with 76.6% Dice score and 1.34mm average surface distance (ASD). When both CT and registered MRI were used, the segmentation model further improved the performance by 0.9% Dice score increase and 11% relative ASD error reduction, demonstrating the complementary strength of CT and MRI in determining NPC GTV. Notably, the achieved 77.5% Dice score and 1.19mm ASD by the multimodality model is among the top performing results reported in recent automatic NPC GTV segmentation using either CT or MRI modality. We developed a fully automated multi-modal deep-learning model for NPC GTV segmentation. The developed model can segment the NPC GTV in high accuracy. With further optimization and validation, this automated model has potential to standardize the NPC GTV segmentation and significantly decrease the workload of radiation oncologists in clinical practice.

Prompt Pain Relief from Bone Metastases: Mature Results from the Virtual Simulation Program

Rapidpain relief for patients with bone metastases can be a challenge due to the lengthy and complex radiotherapy workflow. The purpose of this study was to evaluate the time (in days) between initial radiation oncology consultation and start of palliative radiation treatment after implementing an alternative virtual simulation palliative workflow. Patients meeting strict criteria were selected for virtual simulation, which included only those with painful bone metastases who were recommended palliative radiotherapy using standard AP/PA or opposed lateral fields. A recent (within 30 days) diagnostic CT scan clearly visualizing the target volume was required for treatment planning. For comparison, a reference group of 40 consecutive patients with bone metastases that underwent in-person CT simulation prior to virtual simulation implementation was reviewed. Forty-five patients were treated for painful bone metastases as part of the virtual simulation program from May 2021 to October 2022. Regarding travel distance, 23 patients lived locally (<50 miles from treatment center) and 22 patients were distant (≥50 miles from treatment center). Average time from consult to treatment for all virtual simulation patients was 3.7 days compared to 7.5 days for in-person CT simulation patients (3.8 days sooner on average, p = <0.001). For outpatient treatments, average time from consult to treatment for distant virtual simulation patients was 4.0 days compared to 8.9 days for distant in-person CT simulation patients (4.9 days sooner on average, p = 0.003). The virtual simulation program decreased the time from consult to start of treatment for patients recommended palliative radiotherapy for painful bone metastases by over 50%. This benefit was most significant for outpatients traveling ≥ 50 miles for treatment. Virtual simulation-based planning can be considered for patients anxious to proceed with radiotherapy quickly, or in underserved settings with limited transportation options to regional treatment centers.

Refining Surveillance Guidelines after SBRT for Early-Stage Lung Cancer

Stereotactic Body Radiation Therapy (SBRT) is a popular treatment for patients with early-stage non-small cell lung cancer (NSCLC). After treatment, NCCN guidelines suggest 3-6-month imaging surveillance up to year 3, every 6 months in years 3-5, and yearly after 5 years. The Delphi Consensus Study recommends annual screening in years 2-5. While patients are more likely to locally recur up to two years after treatment there remains a paucity of data on the benefit of long-term surveillance. We therefore evaluated a cohort of NSCLC patients to evaluate the utility and frequency of both short- and long-term surveillance. A total of 224 patients with early-stage NSCLC treated with SBRT between 2014-2019 at a single institution were retrospectively evaluated. Patients with nodal disease, treated with >8 fractions, or metastatic disease at time of SBRT were excluded. Any cross-sectional imaging of the chest for each patient after SBRT was reviewed for evidence of recurrence or new malignancy. Recurrence or new malignancy was defined radiographically and/or pathologically. The median scan interval (MSI) was calculated using the time between surveillance scans. The MSI between patients with or without new disease was compared by t-test. Frequency of recurrence between patients with <T2 or > = T2 disease was compared using chi squared analysis. A total of 224 patients were reviewed and 168 were included in the analysis. 919 scans were performed, 800 as scheduled surveillance scans and 119 for other indications. Median number of scans per patient was 5 (IQR 3-13), with a max of 15 scans. The MSI was 5 months (IQR 3-6) for up to 3 years after treatment, 8 months (IQR 6-12) between 3-5 years after treatment, and 12 months (IQR 11-13) ≥5 years after treatment. There was no significant difference in MSI between patients that did or did not develop new/recurrent disease. 47% of patients with <T2 had new disease compared to 63% with > = T2 tumors (p = 0.10). All 3 patients with T3 disease recurred or had new malignancy identified on 2, 7, and, 36-month scans. 67 instances of new disease were found on 521 scans (13%) during years 1-3, 12 instances on 70 scans (17%) years 3-4, and 5 found on 11 scans (45%) after 5 years. Of 84 total instances of new disease, representing 50% evaluable patients, 75 were discovered on surveillance scans compared to 9 on non-surveillance scans. The MSI for patients in this cohort aligns with published guidelines. Half of the patients developed new disease with the vast majority discovered on surveillance scans. Higher chance of new disease in larger tumors would suggest not all patients benefit from the same scan interval with some patients receiving up to 15 diagnostic scans during follow up. With patients continuing to recur >5 years after treatment, scan frequency, radiation exposure, and probability of recurrence should all be considered in comprehensive surveillance guidelines.

QUANTIFYING THE NEED FOR A BEST SUPPORTIVE CARE CLINIC

Abstract AIMS Patients newly diagnosed with high-grade primary brain tumour and poor performance status discussed in the Multidisciplinary team (MDT) may not be felt to benefit from active treatment and their uptake in clinic is poor. We aimed to explore the volume of patients not being treated in our region, their survival rates, and the reasons for the limited requests for clinical review. METHOD Data was obtained from medical records of identified patients from April 2021 to April 2022. This included demographics, presentation, diagnosis date, clinic visits, and date of death. RESULTS 78 patients were referred for suspected high-grade primary brain tumours and selected for best supportive care by the MDT. Only 73 (64% male) were diagnosed radiologically with a high-grade primary tumour and the rest were excluded. Median age was 79 years (range 74 – 84). The commonest presenting symptoms were confusion (53%), falls (29%), and dysphasia (25%). Median survival time after diagnostic scan was 67 days (range 34 – 107). Survival rates at 1, 3, 6, and 12 months were 82%, 33%, 8%, and 1%, respectively. 28 patients (38%) were seen in clinic. 13 had been provided with the option to attend by letter. The median duration from referral to clinic was 9 days (range 7 – 14). CONCLUSIONS Only a third of non-treatable patients with newly diagnosed high-grade primary brain tumours are being seen in the clinic. Communication between the MDT and the patient offering this service is poor. Longer term survivors suggest an incorrect diagnosis who may benefit from further review.

Using prostate-specific membrane antigen positron-emission tomography to guide prostate biopsies and stage men at high-risk of prostate cancer.

To assess whether a diagnostic pathway in which prostate-specific membrane antigen (PSMA) positron-emission tomography (PET)/computed tomography (CT) is used as a single imaging modality is feasible to guide targeted biopsy and to detect clinically significant prostate cancer (csPCa) in biopsy-naïve men at high-risk of disease. A total of 60 men with a prostate-specific antigen (PSA) level of 20-50 ng/mL underwent 18 F-PSMA(DCFPyL)-PET/CT prior to prostate biopsies in this prospective, non-randomised cohort study. Magnetic resonance imaging (MRI) was not performed. Using a 12-segment mapping model of the prostate, PSMA-guided targeted biopsy was performed along with systematic biopsies. The detection rate of PCa and csPCa was assessed for combined systematic and targeted biopsy, and for targeted biopsy only. csPCa was defined as a prostate biopsy with an International Society of Uropathology (ISUP) Grade Group ≥2. Lesions suspicious for PCa in the prostate gland were observed on all PSMA-PET/CTs. A total of 27/60 men (45%) already had metastatic disease on staging 18 F-PSMA(DCFPyL)-PET/CT. Combined PSMA-guided targeted and systematic biopsies detected PCa in 56/60 (93.3%) patients, with 52 of them (92.9%) having csPCa. PSMA-guided targeted biopsy, if performed as a single biopsy modality, identified PCa in 52/60 men (86.7%) and in 27/27 men (100%) men with metastases. Using the PSMA-driven single imaging modality pathway in biopsy-naïve men at high-risk of PCa, a substantial number of diagnostic MRI scans could be avoided while at the same time obtaining adequate targeting, staging, and detection of csPCa.

P16.06.A INCIDENCE, FOLLOW UP AND OUTCOME IN INCIDENTAL MENINGIOMA IN THE GOTHENBURG REGION - WHAT HAS HAPPENED IN 10 YEARS?

Abstract BACKGROUND Meningiomas constitute a large portion of brain tumors, with an often indolent natural course of disease. There a now more asymptomatic meningiomas diagnosed each year as compared to their symptomatic counterparts. With brain imaging widely available, increased findings of incidental meningiomas have emerged. There are many unique challenges to the management of incidental meningioma, where if no symptoms are present, there is a lack of evidence-based guidelines for follow-up and treatment. The aim of this study was to map the use of brain scanning, and the subsequent findings of presumed incidental meningioma between the years 2008-2009 and 2018-2019, and to study differences in follow-up, treatment, and outcome among these patients. MATERIAL AND METHODS Records of performed CT and MRI of the brain at the radiological departments at three hospital sites were retrospectively reviewed in search for patients with presumed incidental meningioma. Their medical health records were the used to study the natural course and clinical handling of these patients. RESULTS An almost identical number of patients underwent brain scanning at our three hospital sites during the two time periods (n=22 259 vs. 22 013). In 2018-2019, 25% more incidental meningiomas were diagnosed as compared to 2008-2009 (n=161 vs. 129). In the later years, patients had a higher median age (79 years vs. 73 years, p=0.03) and more often underwent brain imaging due to non-metastatic cancer (n=38 vs. 15, p=0.009). There were no differences in the indication for diagnostic scanning, nor management decision at time of diagnosis. CONCLUSION We could not show an increase in patients undergoing scanning of the brain between the two time periods studied, but with passing time it has become more common to frequently scan the brain of elder individuals, and individuals with cancer without metastases, perhaps due to improved treatment options for patients if metastatic disease was found. When an incidental meningioma was subsequently found, no differences could be seen in the clinical handling of the patients in terms of treatment or follow-up.

Suboptimal diagnostic accuracy of ultrasound and CT for compensated cirrhosis: Evidence from prospective cohort studies.

Abdominal ultrasound (US) and CT are important tools for the initial evaluation of patients with liver disease. Our study aimed to determine the accuracy of these methods for diagnosing cirrhosis. In all, 377 participants from 4 prospective cohort studies evaluating patients with various liver diseases were included. All patients were included between 2017 and 2022 and had undergone a liver biopsy as well as US and/or CT. Using the histological assessment as the gold standard, we calculated diagnostic accuracy for US and CT. Liver biopsies were evaluated by expert histopathologists and diagnostic scans by experienced radiologists. The mean age was 54 ± 14 years and 47% were female. Most patients had NAFLD (58.3%) or alcohol-associated liver disease (25.5%). The liver biopsy showed cirrhosis in 147 patients (39.0%). Eighty-three patients with cirrhosis had Child-Pugh A (56.4% of patients with cirrhosis) and 64 had Child-Pugh B/C (43.6%). Overall, the sensitivity for diagnosing cirrhosis by US was 0.71 (95% CI 0.62-0.79) and for CT 0.74 (95% CI 0.64-0.83). The specificity was high for US (0.94, 95% CI 0.90-0.97) and for CT (0.93, 95% CI 0.83-0.98). When evaluating patients with Child-Pugh A cirrhosis, sensitivity was only 0.62 (95% CI 0.49-0.74) for US and 0.60 (95% CI 0.43-0.75) for CT. For patients with Child-Pugh B/C, sensitivity was 0.83 (95% CI 0.70-0.92) for US and 0.87 (95% CI 0.74-0.95) for CT. When limiting our analysis to NAFLD (20% with cirrhosis), the sensitivity for US was 0.45 (95% CI 0.28-0.64) and specificity was 0.97 (95% CI 0.93-0.99). US and CT show moderate sensitivity and may potentially overlook compensated cirrhosis underlining the need for additional diagnostic testing.

Can CT-based gap and step-off displacement predict outcome after nonoperative treatment of acetabular fractures?

The aim of this study was to investigate the association between fracture displacement and survivorship of the native hip joint without conversion to a total hip arthroplasty (THA), and to determine predictors for conversion to THA in patients treated nonoperatively for acetabular fractures. A multicentre cross-sectional study was performed in 170 patients who were treated nonoperatively for an acetabular fracture in three level 1 trauma centres. Using the post-injury diagnostic CT scan, the maximum gap and step-off values in the weightbearing dome were digitally measured by two trauma surgeons. Native hip survival was reported using Kaplan-Meier curves. Predictors for conversion to THA were determined using Cox regression analysis. Of 170 patients, 22 (13%) subsequently received a THA. Native hip survival in patients with a step-off ≤ 2 mm, > 2 to 4 mm, or > 4 mm differed at five-year follow-up (respectively: 94% vs 70% vs 74%). Native hip survival in patients with a gap ≤ 2 mm, > 2 to 4 mm, or > 4 mm differed at five-year follow-up (respectively: 100% vs 84% vs 78%). Step-off displacement > 2 mm (> 2 to 4 mm hazard ratio (HR) 4.9, > 4 mm HR 5.6) and age > 60 years (HR 2.9) were independent predictors for conversion to THA at follow-up. Patients with minimally displaced acetabular fractures who opt for nonoperative fracture treatment may be informed that fracture displacement (e.g. gap and step-off) up to 2 mm, as measured on CT images, results in limited risk on conversion to THA. Step-off ≥ 2 mm and age > 60 years are predictors for conversion to THA and can be helpful in the shared decision-making process.

Prompt Pain Relief From Bone Metastases: The Virtual Simulation Program

Rapid pain relief for patients with bone metastases can be a challenge due to the lengthy and complex radiation therapy workflow. The purpose of this study was to evaluate the time (in days) between initial radiation oncology consultation and start of palliative radiation treatment after implementing an alternative virtual simulation palliative workflow. Patients meeting strict criteria were selected for virtual simulation, which included only those with painful bone metastases who were recommended palliative radiation therapy using standard anterior-posterior/posterior-anterior or opposed lateral fields. A recent (within 30 days) diagnostic computed tomography (CT) scan clearly visualizing the target volume was required for treatment planning. For comparison, a reference group of 40 consecutive patients with bone metastases who underwent in-person CT simulation before virtual simulation implementation was reviewed. Forty-five patients were treated for painful bone metastases as part of the virtual simulation program from May 2021 to October 2022. Regarding travel distance, 23 patients lived locally (<50 miles from the treatment center) and 22 patients were distant (≥50 miles from the treatment center). Average time from consultation to treatment for all patients undergoing virtual simulation was 3.7 days, compared with 7.5 days for patients undergoing in-person CT simulation (3.8 days sooner, on average; P ≤ .001). Before full implementation of the virtual simulation program, 5 eligible patients participated in a virtual simulation pilot from April 2021 to May 2021, in which each patient was contoured and planned on both a pre-existing diagnostic CT scan and a standard CT simulation scan. For virtual simulation-based plans, the average V90, V95, and V99 were 99.99%, 99.87%, and 96.70%. No significant planning target volume (PTV) coverage difference was found on subsequent in-person CT simulation scans. The virtual simulation program decreased the time from consultation to start of treatment by more than 50% for patients recommended palliative radiation therapy for painful bone metastases. This benefit was most significant for outpatients traveling ≥50 miles for treatment. Virtual simulation-based planning can be considered for patients anxious to proceed with radiation therapy quickly or in underserved settings with limited transportation options to regional treatment centers.