Purpose: The purpose of this study was to evaluate the feasibility and diagnostic performance of stress myocardial perfusion imaging (MPI) using a first-generation dual-source photon-counting CT (PCCT) scanner by comparison with reference standards.
Materials and methods: Consecutive patients referred for coronary CT angiography (CCTA) with concomitant stress MPI using PCCT scanner and at least one functional reference test within one month were included. Static PCCT-MPI with regadenoson (Rapiscan, GE Healthcare) was acquired 12 s after the intravenous administration of 40 mL of iodinated contrast material and paired with myocardial delayed enhancement imaging. Reference tests for ischemia included stress cardiac magnetic resonance imaging, stress echocardiography, single-photon emission computed tomography, or invasive coronary angiography. Diagnostic performance was evaluated using sensitivity, specificity, accuracy, areas under receiver operating characteristic curve analysis (AUC) as well as Youden index-derived thresholds.
Results: Forty-one patients were included. There were 28 men and 13 women with a median age of 62 years (Q1, 57; Q3, 70; range: 18-85 years). Of these, 35 patients (85 %) had obstructive coronary artery disease (CAD) on CCTA. PCCT-MPI identified myocardial hypoperfusion in 18 patients (44 %) with a median dose-length product of 97 mGy.cm (Q1, 76.8; Q3, 155.8). Visual assessment yielded 100 % sensitivity (95 % confidence interval [CI]: 81-100 %) and 96 % specificity (95 % CI: 78-100 %), with an AUC of 0.98 (95 % CI: 0.93-1.00) for the diagnosis of ischemic and infarcted myocardium. An optimal defect-to-remote iodine ratio cutoff of 0.79 showed 98 % accuracy (95 % CI: 87-100 %) and an AUC of 0.99 (95 % CI: 0.98-1.00 %). Integration of PCCT-MPI with CCTA could have obviated additional functional testing or invasive angiography in up to 50 % of patients with obstructive CAD.
Conclusion: Stress static PCCT-MPI is feasible and demonstrates excellent diagnostic accuracy for detecting myocardial ischemia. Defect-to-remote iodine ratio from spectral imaging further enhances performance, establishing PCCT as a comprehensive imaging modality that unifies anatomic and functional coronary assessment at a reasonable radiation dose, within a single examination.
Purpose: The purpose of this prospective study was to evaluate the diagnostic performance of dual-energy computed tomography (DECT) using a dual-layer detector scanner in assessing the pathological response of peritoneal metastases (PMs) from non-mucinous colorectal cancer to neoadjuvant chemotherapy (NAC).
Materials and methods: Consecutive patients with PMs from non-mucinous colorectal cancer who underwent preoperative DECT using a dual-layer detector scanner before cytoreductive surgery were prospectively included. Virtual monoenergetic images at 40 keV (VMI40kev), VMIs at 100 keV (VMI100kev), VMI slope (VMIslope), iodine concentration (IC), normalized iodine concentration with aorta (nICaorta) and liver (nICliver), effective Z atomic number (Zeff), and extracellular volume fraction (ECVf) were evaluated on PMs by two radiologists. Pathological response of PM was classified using the peritoneal regression grading score (PRGS), and classified as either good (complete response or major histological regression - PRGS ½) or poor (minor or no histological response - PRGS ¾) responses. DECT variables of PMs with good responses were compared to those of PMs with poor responses using independent-sample t-tests. Receiver operating characteristic curves were built to estimate the capabilities of the different DECT variables in differentiating between PMs with good responses (PRGS ½) and those with poor responses (PRGS ¾). Intra-class correlation coefficients analyses were performed to estimate interobserver variability in DECT variable measurements.
Results: Forty-four patients (22 men median age, 62 years; age range: 35-78 years) with 77 PM were included from September 1st 2023 to July 1st 2025. Thirty-nine out of 77 PMs (51 %) exhibited good response (PRGS ½) and 38 PMs (49 %) exhibited poor response (PRGS ¾). VMI40kev, VMIslope, IC, nICaorta, nICliver, ECVf were significantly greater in PRGS ¾ PMs by comparison with PRGS ½ (P < 0.05). The best AUC values to distinguish between good and poor pathological response of PMs were obtained with nICaorta (AUC, 0.74: 95 % confidence interval [CI]: 0.63-0.85) and ECVf (AUC, 0.74; 95 % CI: 0.63-0.84). ICC was > 0.8 for most DECT variables.
Conclusion: DECT using a dual-layer detector scanner provides promising biomarkers for predicting pathological response in non-mucinous PM after chemotherapy.

