**3. Results**

A total number of 65 PSMA-positive tumor lesions were found in 23 patients (range 1 to 12 lesions), see Table 1 for patient characteristics. In addition, in 7 patients no lesions were found, and therefore, these were excluded. In theory, a perfect test–retest will result in identical values for the test and the retest. In daily practice, however, measurements of a lesions SUVmax in repeated acquisitions will yield results normally distributed around the true value. In tumor lesions showing an increased SUVmax from test to retest, the average increase was 16.8% ± 10.6% (SD) on standard OSEM reconstructions (33 lesions) and 22.1% ± 18.6% (SD) on BPL reconstructions (30 lesions). In tumor lesions showing a decreased SUVmax from test to retest, these values were −21.0% ± 15.2% (SD) on standard OSEM reconstructions (32 lesions) and −23.2% ± 19.7% (SD) on BPL reconstructions (35 lesions), respectively. Overall repeatability in 65 lesions was −1.5% ± 22.7% (SD) on

standard OSEM

small difference between both



 and −2.1%

reconstructions

± 29.1% (SD) on BPL

 was not

statistically

 significant.

reconstructions.

 The

reconstructions

AS = active surveillance, BT = brachytherapy, EBRT = external beam radiotherapy, ELND = extended lymph node dissection, HT = hormonal therapy, LND = lymph node dissection, RP = radical prostatectomy (open procedure), RALP = robot assisted radical prostatectomy.

> As shown in Figure 1A, overall repeatability of SUVmax had upper and lower limits of agreemen<sup>t</sup> of +42.9% and −45.9% for standard OSEM reconstructions and +55.0% and −59.1% for BPL reconstructions, respectively. For suspected local recurrence, SUVmax had a repeatability of −5.0% ± 14.4%, with upper and lower limits of agreemen<sup>t</sup> of +23.2% and −33.1% for standard OSEM reconstructions. For BPL reconstructions, SUVmax repeatability was −9.5% ± 16.8%, with upper and lower limits at +23.5% and −42.5%. See Figure 1B. For suspected lymph node metastases, SUVmax repeatability was −4.5% ± 22.8% for standard OSEM reconstructions, with upper and lower limits of +40.1% and −49.1%. For BPL reconstructions, SUVmax repeatability was −3.3% ± 30.6%, with upper and lower limits at +56.6% and −63.2%. See Figure 1C. For suspected bone metastases, SUVmax had a repeatability of +4.4% ± 26.1%, with upper and lower limits of agreemen<sup>t</sup> of +55.7% and −46.8% for standard OSEM reconstructions. For BPL reconstructions, SUVmax repeatability was +2.7% ± 32.8%, with upper and lower limits at +67.0% and −61.6%. See

Figure 1D. None of the differences between standard OSEM and BPL reconstructions were statistically significant.

**Figure 1.** *Cont*.

**Figure 1.** Repeatability results of SUVmax for both reconstructions in all lesions (65 lesions, (**A**)), local recurrences (9 lesions, (**B**)), lymph node metastases (36 lesions, (**C**)) and bone metastases (20 lesions, (**D**)).

Tumor SUVmax repeatability was dependent on lesion area, with smaller lesions exhibiting poorer repeatability on both standard OSEM and BPL reconstructions (F-test, *p* < 0.0001). See Figure 2A,B.

(**B**)

**Figure 2.** Correlation between SUVmax repeatability and lesion size for standard OSEM (**A**) and BPL reconstruction (**B**).

> Tumor absolute SUVmax was higher in BPL reconstructions than in standard OSEM reconstructions for all lesions (data not shown). The relative increase in measured SUVmax in the BPL reconstructions (as compared to standard OSEM reconstruction) was dependent on lesion size. Smaller lesions (lesion area < 200 mm2) showed a significant larger increase of SUVmax as compared to larger lesions (lesion area > 200 mm2): 44.3% ± 4.6% versus 25.5% ± 42.2% for the test scans (*p* = 0.004) and 43.5% ± 3.9% versus 18.6% ± 3.1% for the retest scans (*p* < 0.001), respectively. See Table 2.


**Table 2.** BPL SUVmax increase (relative to standard reconstruction) for smaller and larger lesions.
