Preoperative Detection of Local Tumor Extent in Patients with Advanced Retinoblastoma: Predictive Value of MRI and Clinical Findings. / Präoperativer Nachweis der lokalen Tumorausdehnung bei Patienten mit fortgeschrittenem Retinoblastom: prädiktiver Wert MR-tomografischer und klinischer Befunde.

OBJECTIVE: Before planned enucleation, local tumor extension in advanced retinoblastoma is routinely assessed preoperatively using high-resolution magnetic resonance imaging (MRI). The aim of our study was to analyse the predictive value of MRI and clinical characteristics for predicting tumor extent, as confirmed by histopathology postoperatively. PATIENTS AND METHODS: All consecutive patients were included who underwent primary enucleation for advanced retinoblastoma after high-resolution MRI examination in our hospital between January 2011 and December 2021. The primary study endpoint was the evaluation of the predictability of histopathological risk factors on preoperative MRI examination. The sensitivity and specificity of the MRI examination with respect to clinically relevant optic nerve infiltration and choroidal infiltration were determined. RESULTS: The mean age of the 209 included patients was 1.6 years (range 1 month to 4.7 years). MRI indicated optic nerve infiltration in 46 (22%) patients, extensive choroidal infiltration in 78 (40.2%) patients, and scleral infiltration in one patient (2.6%). Histopathological examination demonstrated postlaminar optic infiltration in 25 (12%) patients and extensive choroidal infiltration in 17 (8.1%) cases. Scleral infiltration was evident in 8 (3.8%) patients. In the final multivariate analysis, MRI findings of tumor infiltration and a preoperative intraocular pressure ≥ 20 mmHg were independently associated with histopathological evidence of clinically relevant optic nerve (p = 0.033/p = 0.011) and choroidal infiltration (p = 0.005/p = 0.029). The diagnostic accuracy of the prediction models based on the multivariate analysis for the identification of the clinically relevant optic nerve (AUC = 0.755) and choroidal infiltration (AUC = 0.798) was greater than that of purely MRI-based prediction (respectively 0.659 and 0.742). The sensitivity and specificity of MRI examination for determining histopathological risk factors in our cohort were 64% and 65% for clinically relevant optic infiltration and 87% and 64% for clinically relevant choroidal infiltration. CONCLUSION: The local tumor extent of retinoblastoma with infiltration of the optic nerve and choroid can be well estimated based on radiological and clinical characteristics before treatment initiation. The combination of clinical and radiological risk factors supports the possibility of early treatment stratification in retinoblastoma patients.

PDGF, NGF, and EGF as main contributors to tumorigenesis in high-risk retinoblastoma.

Retinoblastoma (RB) is the most common form of eye cancer experienced in childhood. Its aggressive malignancy is associated with excellent survival rates in high-income countries; however, the prognosis in third-world countries is less favorable. Early diagnosis can maximize the patient's visual outcomes and their survival rate. Therapy should be conducted in highly specialized treatment centers. Intravenous chemotherapy (IVC) in bilaterally affected children currently forms the majority of therapy. Local destructive procedures and local chemotherapies such as intra-arterial chemotherapy (IAC) or intravitreal chemotherapy can be taken into consideration depending on the extent and size of the tumor. Nonetheless, children and parents remain under constant stress, revisiting doctors for medical treatment and fearing vision loss and even enucleation of the eye. Adequate molecular patient stratification to improve targeted therapy is still lacking. This retrospective study analyzed formalin-fixed paraffin-embedded specimens from a cohort of 21 RB samples. A total of 11 of those samples showed undifferentiated retinoblastoma (URB) histopathological risk features, and the other 10 showed differentiated retinoblastoma (DRB) histopathological grading. RNA from all samples was isolated and analyzed via digital gene expression patterns. Conductors of cell survival and DNA repair were dominant in the DRB samples. In contrast, the agents responsible for cell-cycle progression and apoptosis were overexpressed in URB samples. Our work reveals the importance of molecular mechanisms within the immune system subjected to histologic subtypes of RB, providing more detailed background on their genetic behavior. This is of great interest for therapeutic strategies, such as targeted immune- and gene-based therapies, for retinoblastoma.

ADAM10 and ADAM17-Novel Players in Retinoblastoma Carcinogenesis.

A disintegrin and metalloproteinase (ADAM) family proteins, acting as sheddases, are important factors in a number of pathologies, including cancer, and have been suggested as promising therapeutic targets. The study presented focuses on the involvement of ADAM10 and ADAM17 in retinoblastoma (RB), the most common malignant intraocular childhood tumor. A significant correlation between ADAM17 expression levels and RB laterality and RB staging was observed. Levels of ADAM10 or ADAM17 regulating miRNAs miR-145, -152, and -365 were significantly downregulated in RB cell lines, and reduced miR levels with simultaneously upregulated ADAM10 and ADAM17 expression were found in RB patients. The involvement of both ADAMs analyzed in ectodomain shedding of the neuronal cell adhesion molecule L1 (L1CAM), shown to induce pro-tumorigenic effects in RB, was confirmed. Lentiviral ADAM10 and ADAM17 single or ADAM10/17 double knockdown (KD) induced caspase-dependent apoptosis and reduced cell viability, proliferation, growth, and colony formation capacity of RB cells. Moreover, differential phosphorylation of the serine/threonine kinase AKT was observed following ADAM17 KD in RB cells. Chicken chorioallantoic membrane (CAM) assays revealed that ADAM17 and ADAM10/17 depletion decreases the tumorigenic and migration potential of RB cells in vivo. Thus, ADAMs are potential novel targets for future therapeutic RB approaches.

Combination of Brachytherapy and Intravitreal Chemotherapy in the Treatment of Retinoblastoma with Vitreous Seeding.

Purpose: The aim of this study was to report the efficacy of combined intravitreal chemotherapy (IVC) and ruthenium-106 brachytherapy in retinoblastoma, either as first-line or second-line treatment, following systemic chemoreduction or intra-arterial chemotherapy. Methods: Retrospective data of 18 eyes from 18 patients treated with IVC and brachytherapy from August 2014 to December 2019 were collected. Results: The method described was our first-line therapy in 6 patients, whereas it was used as second-line treatment after chemoreduction in the remaining 12 patients. The eyes showed the following classification at initial presentation: 2 group B eyes, 3 group C eyes, and 13 group D eyes. The mean follow-up was 19.5 months (range 2-53 months). The mean patient age at brachytherapy was 34.0 months (range 15-83 months). The median prescribed dose at the tumour base and apex was 574.5 ± 306.7 Gy and 88.5 ± 12.2 Gy, respectively. The ocular retention rate was 66.7%. Six eyes had to be enucleated due to uncontrollable subretinal and recurrent vitreous seeding, tumour relapse, recurrence of a solid tumour elsewhere in the eye, and persistent vitreous bleeding with loss of tumour control. The mean number of intravitreal injections of melphalan was 5.0. Two patients received a simultaneous injection of topotecan for insufficient therapeutic response. With regard to radiogenic complications, we could observe temporary retinal and vitreous bleeding (27.8%), serous retinal detachment (44.4%), and radiogenic maculopathy and retinopathy (11.1%). None of the children showed metastatic disease during follow-up. Conclusion: Ruthenium-106 plaque therapy in combination with IVC is an effective local therapy with good tumour control rates even in advanced eyes. Overall, the analysed therapeutic approach shows an acceptable side-effect profile, especially when considering that external-beam radiation therapy and systemic polychemotherapy or at least the number of cycles needed, with their increased incidence of adverse events, can thus be avoided.

Long-Term Results after Intraocular Surgery in Treated Retinoblastoma Eyes.

Introduction: The aim of the study was to analyze the results of intraocular surgery in treated retinoblastoma eyes and to assess the long-term results with a priority on local recurrences, secondary enucleation, and metastases. Methods: Retrospective noncomparative case series. Results: From March 1964 to January 2020, 42 eyes of 40 retinoblastoma patients underwent intraocular surgery. Time interval between the last therapy and surgery was 9.5 years (mean: 114 months; median: 54.5 months). 31 eyes were treated for radiogenic cataract formation with a gain in visual acuity of 61.3%. One child developed an upper eyelid metastasis, 3 showed second primary malignancies (SPM), one a late recurrence, and 2 eyes were enucleated. Retinal surgery was performed in 17 eyes; 6 eyes were done as a combined procedure. Indications were radiogenic complications in the sense of a vitreous hemorrhage in 11 eyes and a rhegmatogenous retinal detachment in 6 eyes. 41.2% of the treated eyes had a postoperative gain in visual acuity, whereas 9.5% of the eyes could not be preserved in the long term. Regarding systemic involvement 2 patients developed late recurrences and one a SPM. Conclusion: Surgical therapy in treated retinoblastoma is necessary in isolated cases. In our series, cataract surgery was a safe procedure with a good option of a significant increase in visual acuity. As expected, vitreoretinal treated eyes showed a limited gain in visual acuity, a higher risk of late recurrences, and a lower globe retention rate. Therefore, a careful indication and individual risk-benefit analysis are mandatory.

Comparing efficacy and side effects of two systemic chemotherapy regimens for eye-preserving therapy in children with retinoblastoma.

BACKGROUND: Eye-preserving therapy in retinoblastoma comprises systemic chemotherapy, but studies analyzing the efficacy of different chemotherapy regimens are scarce. METHODS: The efficacy and side effects of two different eye-preserving chemotherapy regimens containing either vincristine, etoposide, and carboplatin (VEC) or cyclophosphamide, vincristine, etoposide, and carboplatin (CyVEC) were compared in a prospective non-interventional observational study including children diagnosed with retinoblastoma between 2013 and 2019 in Germany and Austria. Event-free eye survival (EFES) and overall eye survival (OES) of all 164 eyes treated with both regimens and risk factors were investigated. RESULTS: The EFES after VEC (2-year EFES 72.3%) was higher than after CyVEC (2-year EFES 50.4%) (plogrank  < .001). The OES did not differ significantly between the two treatment groups (plogrank  = .77; 2-year OES VEC: 82.1% vs. CyVEC: 84.8%). Advanced International Classification of Retinoblastoma (ICRB) group was prognostic for a lower EFES (plogrank  < .0001; 2-year EFES ICRB A/B/C 71.3% vs. ICRB D/E 43.0%) and OES (plogrank  < .0001; 2-year OES ICRB A/B/C 93.1% vs. ICRB D/E 61.5%). The multivariate analysis showed that age at diagnosis older than 12 months and ICRB A/B/C were associated with better EFES. No second malignancies or ototoxicities were reported after a follow-up of median 3.1 years after diagnosis of retinoblastoma (range 0.1-6.9 years). CONCLUSIONS: Despite omitting cyclophosphamide, the EFES was higher after VEC chemotherapy that contains higher doses of carboplatin compared to CyVEC. The major risk factor for enucleation was advanced ICRB tumor grouping. Randomized clinical trials on efficacy and side effects of eye-preserving chemotherapy are required to tailor treatment protocols for retinoblastoma patients.

Intraarterial Chemotherapy for Retinoblastoma - Initial Experiences of a German Reference Centre. / Intraarterielle Chemotherapie beim Retinoblastom ­ erste Erfahrungen eines deutschen Referenzzentrums.

BACKGROUND: Adequate management of retinoblastoma requires a multidisciplinary and individual approach to treatment. Intraarterial chemotherapy (IAC) is one of the most commonly used treatment modalities, and enables supraselective application of chemotherapy via the ophthalmic artery and is now established in almost all treatment centres. However, published treatment success rates are heterogeneous. There are some unanswered issues regarding sight-threatening ocular complications and the long-term occurrence of secondary malignancies and metastatic disease. The objective of the present study is to analyse the results of a German national reference centre. METHODS: Retrospective analysis of all children with an indication for at least one IAC from April 2010 to April 2020. IAC was used either as primary or recurrence therapy. Obligatory follow-up was at least 6 months. RESULTS: 137 eyes of 127 children with an indication for IAC could be included. 12 eyes with a follow-up of less than 6 months and 37 eyes in which IAC was technically not feasible were excluded. In summary, 88 eyes of 79 children were finally analysed. Mean follow-up was 38 months, ranging from 7 to 117 months. In total, 195 procedures were completed. In 30 eyes (34.1%) IAC was conducted as primary and in 58 (65.9%) as secondary therapy. There was an initial IAC treatment response in 75 eyes (85.2%) with a recurrence-free rate of 61.3%. Eye salvage rate was 68.1% with 28 enucleated eyes in total. Ocular complications were observed in 36 eyes (40.9%), with 19 eyes (21.6%) showing severe sight-threatening and 11 eyes (12.5%) presenting minor non-sight-threatening toxic reactions. During follow-up, 1 child developed a secondary malignancy, 1 child developed metastasis and 1 child died as a consequence of trilateral retinoblastoma. CONCLUSION: In summary, IAC is a potent modality for retinoblastoma treatment and has been very successful, even in advanced disease and heavily pretreated eyes. However, ocular complications should be taken in consideration, especially when the only seeing eye is treated. Long term incidences of secondary malignancies and metastatic diseases should be further investigated in prospective studies.

Eye Tumors in Childhood as First Sign of Tumor Predisposition Syndromes: Insights from an Observational Study Conducted in Germany and Austria.

Retinoblastoma and other eye tumors in childhood are rare diseases. Many eye tumors are the first signs of a genetic tumor predisposition syndrome and the affected children carry a higher risk of developing other cancers later in life. Clinical and genetic data of all children with eye tumors diagnosed between 2013-2018 in Germany and Austria were collected in a multicenter prospective observational study. In five years, 300 children were recruited into the study: 287 with retinoblastoma, 7 uveal melanoma, 3 ciliary body medulloepithelioma, 2 retinal astrocytoma, 1 meningioma of the optic nerve extending into the eye. Heritable retinoblastoma was diagnosed in 44% of children with retinoblastoma. One child with meningioma of the optic nerve extending into the eye was diagnosed with neurofibromatosis 2. No pathogenic constitutional variant in DICER1 was detected in a child with medulloepithelioma while two children did not receive genetic analysis. Because of the known association with tumor predisposition syndromes, genetic counseling should be offered to all children with eye tumors. Children with a genetic predisposition to cancer should receive a tailored surveillance including detailed history, physical examinations and, if indicated, imaging to screen for other cancer. Early detection of cancers may reduce mortality.

Feasibility of Proton Beam Therapy as a Rescue Therapy in Heavily Pre-Treated Retinoblastoma Eyes.

Despite the increased risk of subsequent primary tumors (SPTs) external beam radiation (EBRT) may be the only therapeutic option to preserve a retinoblastoma eye. Due to their physical properties, proton beam therapy (PBT) offers the possibility to use the effectiveness of EBRT in tumor treatment and to decisively reduce the treatment-related morbidity. We report our experiences of PBT as rescue therapy in a retrospectively studied cohort of 15 advanced retinoblastoma eyes as final option for eye-preserving therapy. The average age at the initiation of PBT was 35 (14-97) months, mean follow-up was 22 (2-46) months. Prior to PBT, all eyes were treated with systemic chemotherapy and a mean number of 7.1 additional treatments. Indication for PBT was non-feasibility of intra-arterial chemotherapy (IAC) in 10 eyes, tumor recurrence after IAC in another 3 eyes and diffuse infiltrating retinoblastoma in 2 eyes. Six eyes (40%) were enucleated after a mean time interval of 4.8 (1-8) months. Cataract formation was the most common complication affecting 44.4% of the preserved eyes, yet 77.8% achieved a visual acuity of >20/200. Two of the 15 children treated developed metastatic disease during follow-up, resulting in a 13.3% metastasis rate. PBT is a useful treatment modality as a rescue therapy in retinoblastoma eyes with an eye-preserving rate of 60%. As patients are at lifetime risk of SPTs consistent monitoring is mandatory.

Long-Term Clinical Results and Management following Vitrectomy in Undetected Retinoblastoma Eyes.

INTRODUCTION: Given the rarity of retinoblastoma and the consequences of accidental vitrectomy in the event of misdiagnosis, reporting on clinical experience in this area is important. OBJECTIVE: The aim of this study was to analyse the management and complications with a focus on local orbital recurrence and metastatic disease in 10 children vitrectomized in an undetected retinoblastoma eye. METHODS: This is a retrospective descriptive case series conducted in a single-centre referral university hospital. RESULTS: From October 1991 to June 2019, 10 patients with a vitrectomy in an unsuspected retinoblastoma eye were included in this study. The main preoperative diagnoses were unilateral inflammation with a suspected lymphoma, uveitis or toxocariasis in 5 cases, vitreous haemorrhage after trauma in 2 cases, and the last 3 were misdiagnosed with Coats disease, rhegmatogenous retinal detachment and congenital cataract. Mean age at surgery was 3 years, ranging from 14 months to 6 and a half years. Nine patients were suffering from unilateral retinoblastoma; these were enucleated and treated with 4-6 cycles of chemotherapy and/or radiation therapy. The sclerotomy sites were infiltrated with tumour cells in 3 cases. In 1 patient, the differential diagnosis of a malignant medulloepithelioma could not be excluded. One patient had bone marrow infiltration on initial presentation; all other patients are healthy without any signs of orbital recurrence or metastatic disease with a mean follow-up of 5.4 years. CONCLUSION: In children, intraocular tumours, including retinoblastoma and medulloepithelioma, should be ruled out before pars plana vitrectomy is performed. If no doubtless preoperative diagnosis can be established, preoperative magnetic resonance imaging is mandatory. If a vitrectomy in a retinoblastoma eye has been performed, immediate enucleation of the eye with subsequent chemotherapy and orbital radiation is effective to avoid local recurrence and systemic metastases.

[Tumors and Pseudotumors of the Retina and the Ciliary Epithelium]. / Tumoren und Pseudotumoren der Netzhaut und des Ziliarepithels.

The variety of retinal tumors ranges from harmless lesions to benign, locally destructive tumors and life-threatening diseases, and they are not always easy to distinguish from each other. The differential diagnosis includes real neoplasia, reactive inflammatory pathologies and vascular anomalies of the fundus as well. If possible, the diagnosis should be made clinically in order to avoid the danger of tumor cell spread via invasive diagnostic tools. Nevertheless, genetic analysis of the pathology is gaining more importance and adds to the precise characterization of the diagnosis. Depending on the tumor entity, therapy in a specialized center is necessary.

Bone metastasis of retinoblastoma five years after primary treatment.

PURPOSE: Histopathological, immunohistochemistry- and molecular pathology-based diagnostics to distinguish metastasis of retinoblastoma from subsequent primary malignancy in patients with heritable retinoblastoma. OBSERVATIONS: An eight year-old girl presented with tibial pain and bone lesion five years after multimodal treatment of bilateral retinoblastoma, initially clinically suspicious of osteomyelitis. Histopathological examination of bone biopsy specimen revealed a highly proliferative small blue round cell tumor mimicking Ewing's sarcoma of bone. Immunohistochemistry confirmed the diagnosis of a distant metastasis of the previous retinoblastoma. Other subsequent primary malignancies presenting as small blue round cell tumors, such as sarcomas or leukemia, were excluded by immunohistochemistry and molecular methods. CONCLUSIONS AND IMPORTANCE: In countries with early diagnosis of retinoblastoma, distant metastases of retinoblastoma are extremely rare, whereas subsequent primary malignancies are common in survivors of heritable retinoblastoma. Immunohistochemistry and molecular pathology are essential components of diagnostic pathway. In retinoblastoma patients, distant metastases including osseous lesions should be included in the differential diagnosis of small blue round cell tumors.

Histopathology of retinoblastoma eyes enucleated after intra-arterial chemotherapy.

BACKGROUND: To demonstrate histopathological findings in retinoblastoma eyes enucleated after intra-arterial chemotherapy (IAC) with special emphasis on vascular toxicity and local tumour control. METHODS: Retrospective study with a consecutive series of 23 retinoblastoma eyes enucleated after IAC where histopathological work-up was available. RESULTS: From November 2010 to June 2019 23 eyes were enucleated after the attempt of eye salvaging therapy with IAC using melphalan. IAC was the first line treatment in nine and salvage treatment in 14 eyes. Doses of melphalan ranged from 3 to 7.5 mg, whereby a strict protocol with age-appropriate dosage was not used until 2015. The mean number of treatment cycles was 1.8. The main indications for enucleation were poor treatment response or tumour progression in 14 eyes, severe vascular complications in five eyes and a total exudative retinal detachment with amaurosis in the remaining four eyes. We found active disease in 15 eyes with an indication for adjuvant chemotherapy due to high risk factors for metastases in four eyes. To date none of these patients developed metastatic disease. Concerning vascular toxicity, we detected a central retinal artery occlusion in three eyes, severe vasculitis in another three, ischaemic outer retina atrophy and choroidal ischaemia in seven eyes with one eye developing a severe proliferative retinopathy. CONCLUSION: IAC is a highly effective treatment option for advanced retinoblastoma, but the described potential risks should be kept in mind. These include severe vascular complications, as well as the possibility of persisting vital tumour cells fulfilling high-risk criteria for adjuvant chemotherapy.

Single source dual-energy computed tomography in the diagnosis of gout: Diagnostic reliability in comparison to digital radiography and conventional computed tomography of the feet.

OBJECTIVES: To investigate the diagnostic value of single-source dual-energy computed tomography (SDECT) in gouty arthritis and to compare its capability to detect urate depositions with digital radiography (DR) and conventional computed tomography (CT). METHODS: Forty-four patients who underwent SDECT volume scans of the feet for suspected gouty arthritis were retrospectively analyzed. SDECT, CT (both n=44) and DR (n=36) were scored by three blinded readers for presence of osteoarthritis, erosions, and tophi. A diagnosis was made for each imaging modality. Results were compared to the clinical diagnosis using the American College of Rheumatology (ACR) classification criteria. RESULTS: The patient population was divided into a gout (n=21) and control (n=23) group based on final clinical diagnosis. Osteoarthritis was evident in 15 joints using CT and 30 joints using DR (p=0.165). There were 134 erosions detected by CT compared to 38 erosions detected by DR (p<0.001). In total 119 tophi were detected by SDECT, compared to 85 tophi by CT (p=0.182) and 25 tophi by DR (p<0.001). SDECT had best diagnostic value for diagnosis of gout compared to DR and conventional CT (sensitivity and specificity for SDECT: 71.4% and 95.7%, CT: 71.4% and 91.3% and DR: 44.4% and 83.3%, respectively). For all three readers, Cohen's kappa for DR and conventional CT were substantial for all scoring items and ranged from 0.75 to 0.77 and 0.72-0.76, respectively. For SDECT Cohen's kappa was good to almost perfect with 0.77-0.84. CONCLUSIONS: SDECT is capable to detect uric acid depositions with good sensitivity and high specificity in feet, therefore diagnostic confidence is improved. Using SDECT, inter-reader variance can be markedly reduced for the detection of gouty tophi.

First experience with single-source dual-energy computed tomography in six patients with acute arthralgia: a feasibility experiment using joint aspiration as a reference.

OBJECTIVES: Dual-energy computed tomography (DECT) is an emerging imaging technique for examining patients with suspected gout. Single-source dual-energy CT (S-DECT) is a new way of obtaining DECT information on conventional CT scanners rather than using special dual-source CT systems. METHODS: We tested the feasibility of S-DECT (320-row CT; Aquilion ONE, Toshiba Medical Systems, Otawara, Japan) in 6 patients (5 men, 1 woman; mean age 61.3, range 48 to 69 years) with acute arthralgia and suspected gout, and compared the S-DECT findings with the results of joint aspiration. RESULTS: Three patients had a diagnosis of gouty arthritis with negatively birefringent crystals in synovial fluid, in addition to gouty tophi in S-DECT. Three patients had no detectable crystals by polarization microscopy and no tophi on DECT. Their final diagnoses were rheumatoid arthritis, activated osteoarthritis, and septic arthritis in one case each. CONCLUSION: This initial experience suggests that S-DECT might be a valuable alternative to dual-source CT. Hence, more patients may benefit from its additional diagnostic abilities in the future.

Detection and characterization of crystal suspensions using single-source dual-energy computed tomography: a phantom model of crystal arthropathies.

OBJECTIVES: The aim of this study was to perform phantom measurements to prove the feasibility of single-source dual-energy computed tomography (DECT) of the extremities using a volume scan mode. In addition, we, for the first time, wanted to determine which concentrations of monosodium urate (MSU) in gout and calcium pyrophosphate (CP) in pseudogout are needed to detect or distinguish these soft tissue depositions with DECT. MATERIALS AND METHODS: We created a hand-shaped plastic phantom assembled with a descending order of concentrations of MSU (6.25%-50%) and CP (1.56%-50%) with similar attenuation in conventional computed tomographic (CT) images. Dual-energy imaging was done on a standard 320-row CT scanner with acquisition of 2 volumes: one at 80 and the other at 135 kV. Using linear regression analysis, dual-energy gradients were calculated for MSU and CP. Thereafter, we selected a specific region of interest on the dual-energy graph to color-code MSU and CP on the images. Three blinded readers scored 10 scans of the randomly equipped phantom, corresponding to 60 samples, to determine the sensitivity and specificity of this technique. Receiver operating characteristics analysis was done to determine the diagnostic power. RESULTS: We found a dual-energy gradient for MSU of 1.020 ± 0.006 and for CP of 0.673 ± 0.001. Assessment of the randomized phantom scans indicates reliable detection of MSU at concentrations of 12.5 % or higher and that of CP at 6.25 % or higher, corresponding to deposits with mean Hounsfield unit values of 59.8 for MSU and 101.1 for CP. The sensitivity for MSU ranged from 83.3% to 97.3% at 15/90 mA (135/80 kV) and from 86.7% to 97.3% at 100/570 mA. Specificity was 96.7% to 100% in 15/90 mA and 100% in 100/570 mA of scans. However, there was inferior sensitivity for CP owing to lower concentrations. In the receiver operating characteristics analysis, the area under the curve for MSU ranged from 0.867 to 0.947 at 15/90 mA and from 0.867 to 0.919 at 100/570 mA and that for CP from 0.659 to 0.745 and from 0.718 to 0.750, respectively. CONCLUSIONS: This phantom study shows that single-source DECT allows detection and characterization of crystal deposits when present in soft tissue at relatively low concentrations. Further studies in patients have to prove its benefits in diagnostic imaging and treatment monitoring as well as its significance compared with dual-source CT systems.